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Development of fiber optic sensor based on laser Raman spectroscopy
Vidhu Shekhar Tiwari
Laser Raman Spectroscopy (LRS) has received worldwide acknowledgement as a powerful molecular 'finger print' technique. The Raman spectrum of sample contains useful information such as molecular identity, composition, constituent's concentration ratio etc. These information are manifested in the Raman spectrum in band heights, peak wavelength, band areas etc. The basis of quantitative analysis in Raman spectroscopy lies in the measurement
Laser tweezers Raman spectroscopy of single cells
NASA Astrophysics Data System (ADS)
Chen, De
Raman scattering is an inelastic collision between the vibrating molecules inside the sample and the incident photons. During this process, energy exchange takes place between the photon and the scattering molecule. By measuring the energy change of the photon, the molecular vibration mode can be probed. The vibrational spectrum contains valuable information about the disposition of atomic nuclei and chemical bonds within a molecule, the chemical compositions and the interactions between the molecule and its surroundings. In this dissertation, laser tweezers Raman spectroscopy (LTRS) technique is applied for the analysis of biological cells and human cells at single cell level. In LTRS, an individual cell is trapped in aqueous medium with laser tweezers, and Raman scattering spectra from the trapped cell are recorded in real-time. The Raman spectra of these cells can be used to reveal the dynamical processes of cell growth, cell response to environment changes, and can be used as the finger print for the identification of a bacterial cell species. Several biophysical experiments were carried out using LTRS: (1) the dynamic germination process of individual spores of Bacillus thuringiensis was detected via Ca-DPA, a spore-specific biomarker molecule; (2) inactivation and killing of Bacillus subtilis spores by microwave irradiation and wet heat were studied at single cell level; (3) the heat shock activation process of single B. subtilis spores were analyzed, in which the reversible transition from glass-like state at low temperature to liquid-like state at high temperature in spore was revealed at the molecular level; (4) the kinetic processes of bacterial cell lysis of E. coli by lysozyme and by temperature induction of lambda phage were detected real-time; (5) the fixation and rehydration of human platelets were quantitatively evaluated and characterized with Raman spectroscopy method, which provided a rapid way to quantify the quality of freeze-dried therapeutic platelet products for long term preservation; (6) LTRS based depolarized Raman spectroscopy was developed and used to do bacterial cell identification of similar species. From these experiments, several new findings and conclusions have been obtained. (1) single spore dynamic germination was measured for the first time. The result showed the time-to-germinate of a single spore was stochastic and could be discrete. (2) the thermal nature of spore killing in solution by microwaves was identified, Spores killed directly by microwaves showed death marker in Raman spectrum; (3) The Ca-DPA inside the spore core of a spore would undergo a structure modification during heat shock, which was related to the spores' state transition from a glass-like to a rubbery-like state, this structure modification during heat shock was reversible; (4) the kinetic molecular processes of E. coli cell lysis by lysozyme and by temperature induction of bacterial phage were recorded for the first time. The different cellular processes of the lysis were revealed based on the two different mechanisms; (5) LTRS technique was successfully applied to characterize human platelet fixation; a major procedure for long term preservation of therapeutic human platelet products; (6) A depolarization laser tweezers Raman spectroscopy (DLTRS) technique was developed to enhance the ability to discriminate similar bacterial species.
Tunable Laser Resonance Raman Spectroscopy of Bacteriorhodopsin
Aaron Lewis; John Spoonhower; Roberto A. Bogomolni; Richard H. Lozier; Walther Stoeckenius
Bacteriorhodopsin is a rhodopsin-like protein found in the cell membrane of Halobacterium halobium. It shows an absorption maximum at 570 nm and, in the light, undergoes cyclic spectral changes which include a relatively long-lived complex absorbing maximally at 412 nm. Excitation profiles have been obtained with several laser frequencies for two vibrations in the resonance Raman spectrum of bacteriorhodopsin. The
Fiber-Optic Laser Raman Spectroscopy Sensor
Ziegler, K.E.
The Defense Programs Plant Directed Research and Development Program sponsored the optimization and interface of a fiber-optic Raman sensor as a complementary technique to mass spectrometry currently used in the Tritium Facility for measuring hydrogen isotopes. This sensor will provide real-time feedback while reducing the sample load for off-line gas analysis by the Tritium mass spectrometers. The compact Raman system incorporates a 488 nanometer laser system, spectrometer and detector along with a 20-foot fiber-optic probe. The analysis of gas mixtures of protium and deuterium at various compositions and total pressures ranging form 11 to 5000 torr showed good signal to noise ratios using very short integration times (15 seconds). The detection limits for protium and deuterium ranged from 0.5 percent to 0.8 percent. This probe will be demonstrated in-line in the new HT TCAP (hydrogen-tritium thermal cycling absorption process) cold runs.
A time-resolved 128128 SPAD camera for laser Raman spectroscopy
Rossman. George R.
A time-resolved 128ū128 SPAD camera for laser Raman spectroscopy SPIE Conference, Paper 8374 of Technology, Pasadena, California, USA Abstract In continuous wave (CW) Raman spectroscopy, significant charge coupled devices (iCCDs) or streak cameras. Thus, time- resolved Raman spectroscopy has not been
Optimizing the Laser-Pulse Configuration for Coherent Raman Spectroscopy
NASA Astrophysics Data System (ADS)
Pestov, Dmitry; Murawski, Robert K.; Ariunbold, Gombojav O.; Wang, Xi; Zhi, Miaochan; Sokolov, Alexei V.; Sautenkov, Vladimir A.; Rostovtsev, Yuri V.; Dogariu, Arthur; Huang, Yu; Scully, Marlan O.
We introduce a hybrid technique that combines the robustness of frequency-resolved coherent anti-Stokes Raman scattering (CARS) with the advantages of time-resolved CARS spectroscopy. Instantaneous coherent broadband excitation of several characteristic molecular vibrations and the subsequent probing of these vibrations by an optimally shaped time-delayed narrowband laser pulse help to suppress the nonresonant background and to retrieve the species-specific signal. We used this technique for coherent Raman spectroscopy of sodium dipicolinate powder, which is similar to calcium dipicolinate (a marker molecule for bacterial endospores, such as Bacillus subtilis and Bacillus anthracis), and we demonstrated a rapid and highly specific detection scheme that works even in the presence of multiple scattering.
Optimizing the laser-pulse configuration for coherent Raman spectroscopy.
Pestov, Dmitry; Murawski, Robert K; Ariunbold, Gombojav O; Wang, Xi; Zhi, Miaochan; Sokolov, Alexei V; Sautenkov, Vladimir A; Rostovtsev, Yuri V; Dogariu, Arthur; Huang, Yu; Scully, Marlan O
We introduce a hybrid technique that combines the robustness of frequency-resolved coherent anti-Stokes Raman scattering (CARS) with the advantages of time-resolved CARS spectroscopy. Instantaneous coherent broadband excitation of several characteristic molecular vibrations and the subsequent probing of these vibrations by an optimally shaped time-delayed narrowband laser pulse help to suppress the nonresonant background and to retrieve the species-specific signal. We used this technique for coherent Raman spectroscopy of sodium dipicolinate powder, which is similar to calcium dipicolinate (a marker molecule for bacterial endospores, such as Bacillus subtilis and Bacillus anthracis), and we demonstrated a rapid and highly specific detection scheme that works even in the presence of multiple scattering. PMID:17431177
Laser Raman Spectroscopy in studies of corrosion and electrocatalysis
Melendres, C.A.
Laser Raman Spectroscopy (LRS) has become an important tool for the in-situ structural study of electrochemical systems and processes in recent years. Following a brief introduction of the experimental techniques involved in applying LRS to electrochemical systems, we survey the literature for examples of studies in the inhibition of electrode reactions by surface films (e.g., corrosion and passivation phenomena) as well as the acceleration of reactions by electro-sorbates (electrocatalysis). We deal mostly with both normal and resonance Raman effects on fairly thick surface films in contrast to surface-enhanced Raman investigations of monolayer adsorbates, which is covered in another lecture. Laser Raman spectroelectrochemical studies of corrosion and film formation on such metals as Pb, Ag, Fe, Ni, Co, Cr, Au, stainless steel, etc. in various solution conditions are discussed. Further extension of the technique to studies in high-temperature and high-pressure aqueous environments is demonstrated. Results of studies of the structure of corrosion inhibitors are also presented. As applications of the LRS technique in the area of electrocatalysis, we cite studies of the structure of transition metal macrocyclic compounds, i.e., phthalocyanines and porphyrins, used for catalysis of the oxygen reduction reaction. 104 refs., 20 figs.
Femtosecond laser induced nanostructuring for surface enhanced Raman spectroscopy
NASA Astrophysics Data System (ADS)
Messaoudi, H.; Das, S. K.; Lange, J.; Heinrich, F.; Schrader, S.; Frohme, M.; Grunwald, R.
The formation of periodical nanostructures with femtosecond laser pulses was used to create highly efficient substrates for surface-enhanced Raman spectroscopy (SERS). We report about the structuring of silver and copper substrates and their application to the SERS of DNA (herring sperm) and protein molecules (egg albumen). The maximum enhancement factors were found on Ag substrates processed with the second harmonic generation (SHG) of a 1-kHz Ti:sapphire laser and structure periods near the SHG wavelength. In the case of copper, however, the highest enhancement was obtained with long-period ripples induced with at fundamental wavelength. This is explained by an additional significant influence of nanoparticles on the surface. Nanostructured areas in the range of 1.25 mm2 were obtained in 10 s. The surfaces were characterized by scanning electron microscopy, Fast Fourier Transform and Raman spectroscopy. Moreover, the role of the chemical modification of the metal structures is addressed. Thin oxide layers resulting from working in atmosphere which improve the biocompatibility were indicated by vibration spectra. It is expected that the detailed study of the mechanisms of laser-induced nanostructure formation will stimulate further applications of functionalized surfaces like photocatalysis, selective chemistry and nano-biology.
Characterization of Phyllosilicates by LIBS and Laser Raman Spectroscopy
NASA Astrophysics Data System (ADS)
Wang, A.; Sobron, P.
NIR spectral signatures of phyllosilicates were recognized on Mars with wide distributions from orbit by OMEGA (on Mars Express orbiter) and CRISM (on Mars Reconnaissance Orbiter) observations. On the ground, geochemical and spectral features related to phyllosilicates were identified in rocks at two locations on Columbia Hill at Gusev crater using the data obtained by the Mars Exploration Rover (MER) Spirit. Furthermore, Opportunity rover is currently approaching the Cap of York at Endeavour crater on Meridiani Planum, where the signatures of phyllosilicates (and hydrous sulfates) were seen by CRISM. Laser-Induced Breakdown spectroscopy (LIBS) and Laser Raman spectroscopy will be used for the first time in rover missions in ChemCam on the NASA-MSL (Mars Science Laboratory) and in RLS on the ESA-ExoMars, respectively. As demonstrated by our previous studies, they are very powerful tools for characterizing the geochemistry and mineralogy aspects of the secondary minerals from aqueous alterations, especially hydrous sulfates. This study investigates the potential of LIBS and Raman spectroscopy for identifying and characterizing a variety of phyllosilicates, especially clays. Clay standards from the Clay Mineral Society were used. The LIBS measurements were made in a Planetary Environment and Analysis Chamber (PEACh) under Mars atmospheric pressure and composition, using 1064 nm as the excitation laser wavelength, same as ChemCam. The Raman measurements were made in ordinary laboratory environment using 532 nm as the excitation wavelength, same as RLS. The LIBS data were processed using custom automated software. We performed quantitative analysis of the spectra in order to evaluate the effectiveness of our method in: (a) discriminating between phyllosilicates and other silicates; (b) classifying different types of phyllosilicates (i.e., serpentine, chlorites, clays); and (c) correlating the LIBS-derived elemental abundances with the real chemical compositions of phyllosilicates. At this stage, we concentrated on investigating the LIBS peak area ratios of the Si and H emissions at 390.5 and 656.3 nm, respectively. The results from the first set study are encouraging, and we will be able to support the ChemCam investigation on MSL to classify rocks at distances. As for molecular characterization, we found that examining the Raman spectral patterns and spectral peak positions allows to: (1) classify di-octahedral and tri-octahedral phyllosilicates using the position of Si-O-Si peaks near 700 cm-1; (2) identify a variety of phyllosilicates and clays using H2O/OH peaks in 3000-4000 cm-1 and the fundamental vibration modes of polymerized SiO4 in 1150-200 cm-1; (3) characterize the Fe content in phlogopite-biotite-lepidomelane series using the relative intensities of two Raman peaks near 360 cm-1 and 550 cm-1. These results imply that laser spectroscopy (LIBS and Raman) will be powerful tools for identify, classify, and characterize phyllosilicates on Mars.
Joint analyses by laser-induced breakdown spectroscopy (LIBS) and Raman spectroscopy at stand-off distances
Roger C. Wiens; Shiv K. Sharma; Justin Thompson; Anupam Misra; Paul G. Lucey
Raman spectroscopy and laser-induced breakdown spectroscopy (LIBS) of solid samples have both been shown to be feasible with sample-to-instrument distances of many meters. The two techniques are very useful together, as the combination of elemental compositions from LIBS and molecular vibrational information from Raman spectroscopy strongly complement each other. Remote LIBS and Raman spectroscopy spectra were taken together on a
NEW MICROSCOPIC LASER-COUPLED SPECTROSCOPY INSTRUMENT COMBINING RAMAN, LIBS, AND FLUORESCENCE FOR PLANETARY SURFACE MINERALOGY. J. Blacksberg1
Rossman. George R.
NEW MICROSCOPIC LASER-COUPLED SPECTROSCOPY INSTRUMENT COMBINING RAMAN, LIBS, AND FLUORESCENCE (LIBS, Raman) have been the subject of increasing attention and development [e.g., 1, 2, 3] because simultaneously collect spectra from Raman, Laser Induced Breakdown Spectroscopy (LIBS), and fluorescence
Rayleigh rejection filters for 193-nm ArF laser Raman spectroscopy
NASA Technical Reports Server (NTRS)
Mckenzie, Robert L.
Selected organic absorbers and their solvents are evaluated as spectral filters for the rejection of 193-nm Rayleigh light associated with the use of an ArF excimer laser for Raman spectroscopy. A simply constructed filter cell filled with 0.5 percent acetone in water and an optical path of 7 mm is shown effectively to eliminate stray Rayleigh light underlying the Raman spectrum from air while transmitting 60 percent of the Raman light scattered by O2.
Laser Raman spectroscopy ¢ a powerful tool for in situ studies of catalytic materials
Helmut Kn÷zinger; Gerhard Mestl
Advantages and limitations of laser Raman spectroscopy (LRS) as an in situ vibrational spectroscopy for the study of catalytic\\u000a materials and surfaces under working conditions are discussed. Measurements can be carried out at temperatures as high as\\u000a 1200 K in controlled atmospheres. Modern instrumentation permits time resolutions in the sub?second regime for materials with\\u000a high Raman cross sections. Transient studies
Practical aspects of quantitative laser Raman microprobe spectroscopy for the study of fluid inclusions
J. D. Pasteris; B. Wopenka; J. C. Seitz
This paper is addressed to both geologists who use laser Raman microprobe (LRM) spectroscopy to analyze fluid inclusions and to those who want to evaluate analyses done by this technique. Emphasis is on how to obtain quantitative analyses of fluid inclusions. The authors discuss the basic method of fluid inclusion analysis by LRM spectroscopy and the levels of accuracy and
Shifted excitation Raman difference spectroscopy using a dual-wavelength DBR diode laser at 785 nm
NASA Astrophysics Data System (ADS)
Maiwald, M.; Eppich, B.; Fricke, J.; Ginolas, A.; Bugge, F.; Klehr, A.; Sumpf, B.; Erbert, G.; Trõnkle, G.
The application of shifted excitation Raman difference spectroscopy (SERDS) using a dual wavelength distributed Bragg reflector (DBR) diode laser at 785 nm will be presented. Both excitation wavelengths necessary for SERDS provide an optical power of more than 160 mW in continuous wave operation. Raman experiments are carried out and demonstrate the suitability of the excitation light source for SERDS. Moreover, a dual-wavelength master-oscillator power amplifier diode laser system is presented. The diode laser system reaches optical powers larger 750 mW while the spectral properties of the dual-wavelength laser remain unchanged.
Dual-wavelength Raman spectroscopy approach for studying fluid-phase equilibria using a single laser.
Kiefer, Johannes
A novel Raman spectroscopy setup for the investigation of multiphase fluid mixtures is proposed. The total output of a frequency-doubled Nd:YAG laser is separated into a strong 532 nm beam for generating Raman signals in the vapor phase and the weak residual of the fundamental 1064 nm radiation to be utilized as laser source for Raman scattering in the liquid phase. This approach will provide sufficient signal intensity from the gas (despite low density) for determination of mixture composition and at the same time it facilitates recording high-resolution spectra from the liquid in order to allow studying molecular physics phenomena together with concentration measurements. PMID:20537237
Tunable excitation source for coherent Raman spectroscopy based on a single fiber laser
NASA Astrophysics Data System (ADS)
Adany, Peter; Arnett, David C.; Johnson, Carey K.; Hui, Rongqing
We demonstrate a wavelength tunable optical excitation source for coherent Raman scattering (CRS) spectroscopy based on a single femtosecond fiber laser. Electrically controlled wavelength tuning of Stokes optical pulses was achieved with soliton self frequency shift in an optical fiber, and linear frequency chirping was applied to both the pump and the Stokes waves to significantly improve the spectral resolution. The coherent anti-Stokes Raman scattering (CARS) spectrum of cyclohexane was measured and vibrational resonant Raman peaks separated by 70 cm-1 were clearly resolved. Single laser-based tunable excitation may greatly simplify CRS measurements and extend the practicality of CRS microscopy.
Laser Raman Spectroscopy Of Gap Vibration Of Se Impurity In Natural Mineral Cinnabar From Various Mines
NASA Astrophysics Data System (ADS)
Gotoshia, Sergo V.; Gotoshia, Lamara V.
Natural minerals ?-HgS from various mines have been studied by laser Raman-spectroscopy and resonance Raman-spectroscopy. The crystals differ from each other in the content of selenium impurities included in samples from different mines. Based on Raman spectra and factor-group analyze the classification the first order phonons and then the comparison the results with the results from other works are carried out. The Raman spectra analysis of minerals from various mines show the presence of selenium impurity gap vibration at 203 cm-1 and 226 cm-1 frequencies respectively. On the statistical basis of the Raman measurements, one can conclude that the frequencies of impurities of ?-HgS generally may be used for identifying mines. Low resonance has been fixed as well in impure minerals at spectral band frequency 203 cm-1 characterizing vibrationgap of isomorphic Se impurity in cinnabar.
Laser Raman spectroscopy and its applications Ś especially in structural phase transitions
H. D. Bist
The usefulness of Raman spectroscopy as a powerful non-contact, nondestructive analytical tool has been well-demonstrated.\\u000a A birdÆs eye-view of various techniques used for the study of various types of structural phase transitions is given. A few\\u000a modern applications of laser Raman spectroscopic studies have been mentioned. Thermal variations near critical transition\\u000a region in the position, halfwidths, intensities and shapes of
Gerrard, D.L.; Bowley, H.J.
The period of this review is from late 1985 to late 1987. During this time over 6000 papers have been published in the scientific literature dealing with many applications of Raman spectroscopy and extending its use to new areas of study. This article covers only those papers that are relevant to the analytical chemist and this necessitates a highly selective approach. There are some areas that have been the subject of many papers with relatively few being of analytical interest. In such cases the reader is referred to appropriate reviews which are detailed in this section.
Secondary Structure ofHistones and DNA in Chromatin Abstract. Laser Raman spectroscopy indicates that the inner histones which are
Olins, Ada L.
Secondary Structure ofHistones and DNA in Chromatin Abstract. Laser Raman spectroscopy indicates, and characterized by various physical methods (2). Here we report the laser Raman spectra of these v, preparations and of chromatin, and identify the conformational structures of the constituent DNA and histone mole- cules. Laser
Rapid shifted excitation Raman difference spectroscopy with a distributed feedback diode laser emitting at 785 nm
NASA Astrophysics Data System (ADS)
Maiwald, M.; Erbert, G.; Klehr, A.; Kronfeldt, H.-D.; Schmidt, H.; Sumpf, B.; Trõnkle, G.
A distributed feedback (DFB) laser diode emitting at 785 nm was tested and applied as a light source for shifted excitation Raman difference spectroscopy (SERDS). Due to the physical properties of the laser diode, it was possible to shift the emission wavelength by 8 cm-1 (0.5 nm) required for our SERDS measurements by simply changing the injection current. The internal grating ensured single mode operation at both wavelength with the frequency stability of ▒0.06 cm-1 (0.004 nm) required for high resolution Raman spectroscopic applications. The shifted spectra were used for calculating enhanced Raman spectra being obscured by a strong scattering background. A 16 dB (?38 fold) improvement of the signal-to-background noise S»/?B was demonstrated using blackboard chalk as a sample. The tunable DFB laser is a versatile excitation source for SERDS, which could be used in any dispersive Raman system to subtract fluorescence contributions and scattering background.
Simultaneous Raman and laser-induced breakdown spectroscopy by a single setup
NASA Astrophysics Data System (ADS)
Matroodi, F.; Tavassoli, S. H.
A new experimental configuration is introduced for simultaneous recording of Raman and laser-induced breakdown spectroscopy (LIBS) in a single spectrum. A laser pulse is divided into two beams by a Glan-Taylor prism. By focusing one beam to the sample surface, micro-plasma is created and LIBS signal is emitted. The other beam is directed to the same point of the sample, but does not focused. The scattered light due to the second laser beam is mixed with the plasma emission and is recorded in a single spectrum. Atomic and molecular spectra of some minerals and chemical samples are recorded by the mentioned setup. Due to the high-plasma quenching in liquids, LIBS signals are not detected for organic liquid samples, instead a strong stimulated Raman signal is appeared, and as a result, an overlay of ordinary Raman with stimulated Raman is observed.
Raman spectroscopy study of laser-shocked tatb-based explosives
NASA Astrophysics Data System (ADS)
Hebert, Philippe; Bouyer, Viviane; Doucet, Michel; Rideau, Joļl; Terzulli, Louis-Pierre
We have developed a nanosecond single-shot Raman spectroscopy experiment to study the initiation and decomposition mechanisms of heterogeneous solid explosives under shock compression. The laser-driven flyer plate technique was used to generate shock waves on TATB-based explosives samples. Photon Doppler Velocimetry (PDV) measurements were performed to estimate the generated shock pressures. The first Raman spectra obtained under shock compression are presented here. The shifts observed for the different Raman peaks are consistent with those observed under static pressure.
Improved temperature precision in rotational coherent anti-Stokes Raman spectroscopy with a modeless dye laser
NASA Astrophysics Data System (ADS)
Vestin, Fredrik; Afzelius, Mikael; Bengtsson, Per-Erik
Single-shot thermometry with dual-broadband rotational coherent anti-Stokes Raman spectroscopy that employs amplified spontaneous emission from a broadband modeless dye laser has been examined. Evaluation of single-shot spectra of air, N2, and O2 showed an improved temperature precision at room temperature compared with the precision obtained with a conventional dye laser. A comparison was also made between the use of single-mode and multimode Nd:YAG lasers as sources for narrowband radiation, and in all cases the single-mode Nd:YAG laser resulted in higher precision. The experimental results are compared with theoretical predictions.
Improved temperature precision in rotational coherent anti-stokes raman spectroscopy with a modeless dye laser.
Vestin, Fredrik; Afzelius, Mikael; Bengtsson, Per-Erik
Single-shot thermometry with dual-broadband rotational coherent anti-Stokes Raman spectroscopy that employs amplified spontaneous emission from a broadband modeless dye laser has been examined. Evaluation of single-shot spectra of air, N2, and O2 showed an improved temperature precision at room temperature compared with the precision obtained with a conventional dye laser. A comparison was also made between the use of single-mode and multimode Nd:YAG lasers as sources for narrowband radiation, and in all cases the single-mode Nd:YAG laser resulted in higher precision. The experimental results are compared with theoretical predictions. PMID:16485686
Investigating Surface Mineralogy, Alteration Processes, and Biomarkers on Mars Using Laser Raman Spectroscopy
NASA Technical Reports Server (NTRS)
Wang, Alian; Jolliff, B. L.; Haskin, L. A.
Despite a wealth of information from past and ongoing missions to Mars, the capability to determine the mineralogy of surface materials and to connect mineralogy with lithologic characteristics that are diagnostic of the environment in which those materials formed remains inadequate. The 2003 Mars Exploration Rovers (MER) will carry a Mini-TES and a Mossbauer spectrometer, which will provide some detailed mineralogy information. For general characterization of minerals and/or biogenic phases (reduced carbon, PAHs, etc) on the surface of Mars, we have been developing a miniaturized laser Raman spectrometer for in situ analyses -- the Mars Microbeam Raman Spectrometer, MMRS. We are also developing strategies to use Raman spectroscopy as a stand-alone technique and to be used synergistically with other in situ analysis methods in future planetary missions. Through studies of Martian meteorites and terrestrial analogs, we are gaining experience of what compositional and structural information can be obtained on key mineral groups using in-situ Raman measurements. We are developing methods for determining mineral proportions in rocks or soils and identifying rock types from sets of closely spaced, rapidly acquired spectra. We are studying how weathering and alteration affect the Raman and luminescence features of minerals and rocks, and we are investigating the Raman characteristics of biogenic organisms and their remains. These studies form the scientific basis for in-situ planetary Raman spectroscopy, and they are being done in parallel with instrument development towards a flight version of the MMRS.
Characterisation of diamond coatings with different morphologies by Raman spectroscopy using various laser wavelengths.
Rudigier, Moritz; Haubner, Roland
Since the beginning of low-pressure diamond synthesis, Raman spectroscopy has been widely used to identify and characterise the quality of diamonds. The diamond crystal is characterised by a Raman peak at about 1,332Ācm(-1). Other peaks are associated with miscellaneous carbon structures, e.g. graphite and amorphous phases. In recent years, both well-faceted crystalline diamonds and nanocrystalline and ultrananocrystalline diamonds have been investigated. For these fine-grained materials, the diamond peak at 1,332Ācm(-1) disappears and the intensities of peaks at other wavelengths increase. To study the influence of the Raman laser wavelength, three lasers were used (472.681Ānm, blue; 532.1Ānm, green; 632.81Ānm, red). For well-faceted diamonds, the Raman spectra with blue and green laser light were similar. A shift of the peak maxima and different intensities were observed. With use of the red laser, a strong luminescence peak and low peak intensities for the various carbon-related peaks occurred. When the diamond morphology changes from well-faceted to fine-grained ballas diamond, the spectra are similar for all three lasers. PMID:22362277
Planetary geochemical investigations using Raman and laser-induced breakdown spectroscopy.
Clegg, Samuel M; Wiens, Roger; Misra, Anupam K; Sharma, Shiv K; Lambert, James; Bender, Steven; Newell, Raymond; Nowak-Lovato, Kristy; Smrekar, Sue; Dyar, M Darby; Maurice, Sylvestre
An integrated Raman spectroscopy and laser-induced breakdown spectroscopy (LIBS) instrument is a valuable geoanalytical tool for future planetary missions to Mars, Venus, and elsewhere. The ChemCam instrument operating on the Mars Curiosity rover includes a remote LIBS instrument. An integrated Raman-LIBS spectrometer (RLS) based on the ChemCam architecture could be used as a reconnaissance tool for other contact instruments as well as a primary science instrument capable of quantitative mineralogical and geochemical analyses. Replacing one of the ChemCam spectrometers with a miniature transmission spectrometer enables a Raman spectroscopy mineralogical analysis to be performed, complementing the LIBS chemical analysis while retaining an overall architecture resembling ChemCam. A prototype transmission spectrometer was used to record Raman spectra under both Martian and Venus conditions. Two different high-pressure and high-temperature cells were used to collect the Raman and LIBS spectra to simulate surface conditions on Venus. The resulting LIBS spectra were used to generate a limited partial least squares Venus calibration model for the major elements. These experiments demonstrate the utility and feasibility of a combined RLS instrument. PMID:25226246
Three Powerful Research Tools from Single Cells into Single Molecules: AFM, Laser Tweezers, and Raman Spectroscopy
Yongkuan Wu; Kun Liu; Kedong Song; Shi Pan
By using three physical techniques (atomic force microscopy (AFM), laser tweezers, and Raman spectroscopy), many excellent\\u000a works in single-cell\\/molecule research have been accomplished. In this review, we present a brief introduction to the principles\\u000a of these three techniques, and their capabilities toward single-cell\\/molecule research are highlighted. Afterward, the advances\\u000a in single-cell\\/molecule research that have been facilitated by these three techniques
Sensitivity map of laser tweezers Raman spectroscopy for single-cell analysis of colorectal cancer.
Zheng, Feng; Qin, Yejun; Chen, Kun
Raman spectroscopy on single, living epithelial cells captured in a laser trap is shown to have diagnostic power over colorectal cancer. This new single-cell technology comprises three major components: primary culture processing of human tissue samples to produce single-cell suspensions, Raman detection on singly trapped cells, and diagnoses of the cells by artificial neural network classifications. It is compared with DNA flow cytometry for similarities and differences. Its advantages over tissue Raman spectroscopy are also discussed. In the actual construction of a diagnostic model for colorectal cancer, real patient data were taken to generate a training set of 320 Raman spectra and a test set of 80. By incorporating outlier corrections to a conventional binary neural classifier, our network accomplished significantly better predictions than logistic regressions, with sensitivity improved from 77.5% to 86.3% and specificity improved from 81.3% to 86.3% for the training set and moderate improvements for the test set. Most important, the network approach enables a sensitivity map analysis to quantitate the relevance of each Raman band to the normal-to-cancer transform at the cell level. Our technique has direct clinic applications for diagnosing cancers and basic science potential in the study of cell dynamics of carcinogenesis. PMID:17614710
Remote pulsed laser Raman spectroscopy system for detecting water, ice, and hydrous minerals
NASA Astrophysics Data System (ADS)
Garcia, Christopher S.; Abedin, M. Nurul; Sharma, Shiv K.; Misra, Anupam K.; Ismail, Syed; Singh, Upendra N.; Refaat, Tamer F.; Elsayed-Ali, Hani E.; Sandford, Steve P.
For exploration of planetary surfaces, detection of water and ice is of great interest in supporting existence of life on other planets. Therefore, a remote Raman spectroscopy system was demonstrated at NASA Langley Research Center in collaboration with the University of Hawaii for detecting ice-water and hydrous minerals on planetary surfaces. In this study, a 532 nm pulsed laser is utilized as an excitation source to allow detection in high background radiation conditions. The Raman scattered signal is collected by a 4-inch telescope positioned in front of a spectrograph. The Raman spectrum is analyzed using a spectrograph equipped with a holographic super notch filter to eliminate Rayleigh scattering, and a holographic transmission grating that simultaneously disperses two spectral tracks onto the detector for higher spectral range. To view the spectrum, the spectrograph is coupled to an intensified charge-coupled device (ICCD), which allows detection of very weak Stokes line. The ICCD is operated in gated mode to further suppress effects from background radiation and long-lived fluorescence. The sample is placed at 5.6 m from the telescope, and the laser is mounted on the telescope in a coaxial geometry to achieve maximum performance. The system was calibrated using the spectral lines of a Neon lamp source. To evaluate the system, Raman standard samples such as calcite, naphthalene, acetone, and isopropyl alcohol were analyzed. The Raman evaluation technique was used to analyze water, ice and other hydrous minerals and results from these species are presented.
Remote Pulsed Laser Raman Spectroscopy System for Detecting Qater, Ice, and Hydrous Minerals
NASA Technical Reports Server (NTRS)
Garcia, Christopher S.; Abedin, M. Nuraul; Sharma, Shiv K.; Misra, Anupam K.; Ismail, Syed; Singh, Upendra; Refaat, Tamer F.; Elsayed-Ali, Hani; Sandford, Steve
For exploration of planetary surfaces, detection of water and ice is of great interest in supporting existence of life on other planets. Therefore, a remote Raman spectroscopy system was demonstrated at NASA Langley Research Center in collaboration with University of Hawaii for detecting ice-water and hydrous minerals on planetary surfaces. In this study, a 532 nm pulsed laser is utilized as an excitation source to allow detection in high background radiation conditions. The Raman scattered signal is collected by a 4-inch telescope positioned in front of a spectrograph. The Raman spectrum is analyzed using a spectrograph equipped with a holographic super notch filter to eliminate Rayleigh scattering, and a holographic transmission grating that simultaneously disperses two spectral tracks onto the detector for higher spectral range. To view the spectrum, the spectrograph is coupled to an intensified charge-coupled device (ICCD), which allows detection of very weak Stokes line. The ICCD is operated in gated mode to further suppress effects from background radiation and long-lived fluorescence. The sample is placed at 5.6 m from the telescope, and the laser is mounted on the telescope in a coaxial geometry to achieve maximum performance. The system was calibrated using the spectral lines of a Neon lamp source. To evaluate the system, Raman standard samples such as calcite, naphthalene, acetone, and isopropyl alcohol were analyzed. The Raman evaluation technique was used to analyze water, ice and other hydrous minerals and results from these species are presented.
Application of laser Raman spectroscopy in concentration measurements of multiple analytes in human body fluids
NASA Astrophysics Data System (ADS)
Qu, Jianan Y.; Suria, David; Wilson, Brian C.
The primary goal of these studies was to demonstrate that NIR Raman spectroscopy is feasible as a rapid and reagentless analytic method for clinical diagnostics. Raman spectra were collected on human serum and urine samples using a 785 nm excitation laser and a single-stage holographic spectrometer. A partial east squares method was used to predict the analyte concentrations of interest. The actual concentrations were determined by a standard clinical chemistry. The prediction accuracy of total protein, albumin, triglyceride and glucose in human sera ranged from 1.5 percent to 5 percent which is greatly acceptable for clinical diagnostics. The concentration measurements of acetaminophen, ethanol and codeine inhuman urine have demonstrated the potential of NIR Raman technology in screening of therapeutic drugs and substances of abuse.
Time evolution studies of laser induced chemical changes in InAs nanowire using Raman spectroscopy
Pal, Suparna; Aggarwal, R.; Kumari Gupta, Vandna; Ingale, Alka [Laser Physics Application Section, Raja Ramanna Centre for Advanced Technology, Indore 452013, MP (India)
We report the study of time evolution of chemical changes on the surface of an InAs nanowire (NW) on laser irradiation in different power density regime, using Raman spectroscopy for a time span of 8¢16 min. Mixture of metastable oxides like InAsO{sub 4,} As{sub 2}O{sub 3} are formed upon oxidation, which are reflected as sharp Raman peaks at ?240¢254 and 180¢200?cm{sup ?1}. Evidence of removal of arsenic layer by layer is also observed at higher power density. Position controlled laser induced chemical modification on a nanometer scale, without changing the core of the NW, can be useful for NW based device fabrication.
Raman spectroscopy study of laser-shocked TATB-based explosives
NASA Astrophysics Data System (ADS)
Hebert, Philippe; Bouyer, Viviane; Rideau, Joel; Doucet, Michel; Terzulli, Louis-Pierre
We have developed a single-pulse Raman spectroscopy experiment dedicated to the study of laser-shocked explosives. The shocks were generated using the laser-driven flyer technique. The nanosecond pulse of a Nd:YAG laser (? = 1064 nm) was focused on a BK7 substrate coated with an ablation and an aluminium (Al) layer. The Al layer was used as the flyer. Our set-up can provide flyer velocities in the range 1500 to 3000 m/s with 15 ?m thick Al foils which yields to maximum peak pressure of about 20 GPa on TATB samples. Single-shot Raman spectroscopy of shocked samples was performed using the second harmonic of a nanosecond Nd:YAG laser (? = 532 nm) focused on the back side of the samples through a glass window. In order to estimate the pressure of the probed sample, measurements of the particle velocity at the explosive-window interface were performed at the same time using the Photon Doppler Velocimetry system developed at CEA. Hydrodynamic simulations were also carried out. The first results obtained with this set-up on pressed samples of TATB based explosives are presented in this paper.
Imaging with Raman Spectroscopy
Zhang, Yin; Hong, Hao; Cai, Weibo
Raman spectroscopy, based on the inelastic scattering of a photon, has been widely used as an analytical tool in many research fields. Recently, Raman spectroscopy has also been explored for biomedical applications (e.g. cancer diagnosis) because it can provide detailed information on the chemical composition of cells and tissues. For imaging applications, several variations of Raman spectroscopy have been developed to enhance its sensitivity. This review article will provide a brief summary of Raman spectroscopy-based imaging, which includes the use of coherent anti-Stokes Raman spectroscopy (CARS, primarily used for imaging the C-H bond in lipids), surface-enhanced Raman spectroscopy (SERS, for which a variety of nanoparticles can be used as contrast agents), and single-walled carbon nanotubes (SWNTs, with its intrinsic Raman signal). The superb multiplexing capability of SERS-based Raman imaging can be extremely powerful in future research where different agents can be attached to different Raman tags to enable the interrogation of multiple biological events simultaneously in living subjects. The primary limitations of Raman imaging in humans are those also faced by other optical techniques, in particular limited tissue penetration. Over the last several years, Raman spectroscopy imaging has advanced significantly and many critical proof-of-principle experiments have been successfully carried out. It is expected that imaging with Raman Spectroscopy will continue to be a dynamic research field over the next decade. PMID:20497112
Raman laser spectroscopy of Wannier Stark states G. Tackmann, B. Pelle, A. Hilico, Q. Beaufils, F. Pereira dos Santos
Paris-Sud XI, Universitķ de
Raman laser spectroscopy of Wannier Stark states G. Tackmann, B. Pelle, A. Hilico, Q. Beaufils, F transitions in the bottom band of the lattice between Wannier Stark states corresponding to neighboring wells are observed. Couplings between such states are measured as a function of the lattice laser intensity
Raman laser spectroscopy of Wannier Stark states G. Tackmann, B. Pelle, A. Hilico, Q. Beaufils, F. Pereira dos Santos
Paris-Sud XI, Universitķ de
Raman laser spectroscopy of Wannier Stark states G. Tackmann, B. Pelle, A. Hilico, Q. Beaufils, F in the bottom band of the lattice between Wannier Stark states corresponding to neighboring wells are observed. Couplings between such states are measured as a function of the lattice laser intensity and compared
On-line tritium process gas analysis by laser Raman spectroscopy at TSTA
O'hira, S.; Nakamura, H.; Konishi, S.; Hayashi, T.; Okuno, K.; Naruse, Y. (Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tritium Engineering Lab.); Sherman, R.H.; Taylor, D.J.; King, M.A.; Bartlit, J.R.; Anderson, J.L. (Los Alamos National Lab., NM (United States). Materials Science and Technology Div.)
Laser Raman spectroscopy has been applied to the on-line analysis of the operation of the cryogenic Isotope Separation System (ISS) at the Tritium Systems Test Assembly (TSTA). A flow-through cell was employed to permit near real-time observation of the dynamic response of the 3-column ISS. Accurate analysis of hydrogen isotopic mixtures may be made in less than 2 minutes. Full response to a change in the sampling point is achieved in approximately one minute. In this paper, response measurements are shown as well as static column profiles and dynamic response to induced parameter changes. Cross check of analysis was performed with radio-gas chromatography.
Raman spectroscopy measurements of CO2 dissolved in water and CO2 bubbles for laser remote sensing in water
NASA Astrophysics Data System (ADS)
Somekawa, Toshihiro; Takeuchi, Tomoki; Yamanaka, Chihiro; Fujita, Masayuki
We examined the applicability of Raman spectroscopy as a laser remote sensing tool for monitoring the gases dissolved in water and gas bubbles. A frequency doubled Q-switched Nd:YAG laser (532 nm) is irradiated to CO2 gas bubbles generated by an air pump. The Raman signals at 1383 cm-1 from CO2 and 1645 cm-1 from water were detected. It has been shown that the CO2/H2O Raman signal ratio is dependent on the CO2 bubble rate.
Raman spectroscopy of organic dyes adsorbed on pulsed laser deposited silver thin films
NASA Astrophysics Data System (ADS)
Fazio, E.; Neri, F.; Valenti, A.; Ossi, P. M.; Trusso, S.; Ponterio, R. C.
The results of a surface-enhanced Raman scattering (SERS) study performed on representative organic and inorganic dyes adsorbed on silver nanostructured thin films are presented and discussed. Silver thin films were deposited on glass slides by focusing the beam from a KrF excimer laser (wavelength 248 nm, pulse duration 25 ns) on a silver target and performing the deposition in a controlled Ar atmosphere. Clear Raman spectra were acquired for dyes such as carmine lake, garanza lake and brazilwood overcoming their fluorescence and weak Raman scattering drawbacks. UV-visible absorption spectroscopy measurements were not able to discriminate among the different chromophores usually referred as carmine lake (carminic, kermesic and laccaic acid), as brazilwood (brazilin and brazilein) and as garanza lake (alizarin and purpurin). SERS measurements showed that the analyzed samples are composed of a mixture of different chromophores: brazilin and brazilein in brazilwood, kermesic and carminic acid in carmine lake, alizarin and purpurin in garanza lake. Detection at concentration level as low as 10-7 M in aqueous solutions was achieved. Higher Raman intensities were observed using the excitation line of 632.8 nm wavelength with respect to the 785 nm, probably due to a pre-resonant effect with the molecular electronic transitions of the dyes.
Technique of laser confocal and Raman spectroscopy for living cell analysis
NASA Astrophysics Data System (ADS)
Meng, Xiaochen; Zhu, Lianqing
Because of the shortcomings of the main methods used to analysis single cell, the need of single living cell analysis with no damage, unmarked and in situ dynamic multi-parameter measurement is urgent in the life sciences and biomedical advanced research field. And the method of for living cells analysis is proposed. The spectral pretreatment technology of living cell is the key work of laser confocal Raman spectroscopy. To study the spectrum processing methods for Raman spectrum on single living cell and develop the pre-process techniques to enhance the signal-to-noise ratio, sensitivity, and decrease the influence of fluorescence, elimination the cosmic rays was used to improve the spectrum. The classification, average and filtration of spectrum were applied to enhance signal-to-noise ratio. The fluorescence was depressed for quantity analysis or utilized for analysis by comparing the background and the spectrum. The results show that the proposed technique for laser confocal Raman spectrum of single cell can perform the sensitive and weak intensity peaks and reflect the information of molecules structures very well.
Scanning cavity-enhanced droplet spectroscopy: Tuning of the excitation laser for obtaining a continuous Raman spectrum
NASA Astrophysics Data System (ADS)
Hoshino-Nagasaka, Mariko; Isoda, Toshihiro; Takeshima, Tooru; Kohno, Jun-ya
Scanning cavity-enhanced droplet spectroscopy (S-CEDS) has been developed to obtain Raman spectra of liquid media with high sensitivity. Cavity-enhanced Raman spectra of a water droplet are measured by irradiation of a laser with nine different wavelengths. Each of the spectra consists of a series of intense and narrow peaks resulting from the cavity-enhancement conditions, and the envelope of their peak apexes displays a stimulated Raman spectrum of liquid water. A series of continuous Raman spectra of liquid water is obtained by scanning the laser wavelength, which dissolves the discreteness of each spectrum. S-CEDS provides a novel method to obtain stimulated Raman spectra of liquid media keeping their continuous spectral shapes.
Planetary Surface Analysis Using Fast Laser Spectroscopic Techniques: Combined Microscopic Raman, LIBS, and Fluorescence Spectroscopy
NASA Astrophysics Data System (ADS)
Blacksberg, J.; Rossman, G. R.; Maruyama, Y.; Charbon, E.
In situ exploration of planetary surfaces has to date required multiple techniques that, when used together, yield important information about their formation histories and evolution. We present a time-resolved laser spectroscopic technique that could potentially collect complementary sets of data providing information on mineral structure, composition, and hydration state. Using a picosecond-scale pulsed laser and a fast time-resolved detector we can simultaneously collect spectra from Raman, Laser Induced Breakdown Spectroscopy (LIBS), and fluorescence emissions that are separated in time due to the unique decay times of each process. The use of a laser with high rep rate (40 KHz) and low pulse energy (1 ?J/pulse) allows us to rapidly collect high signal to noise Raman spectra while minimizing sample damage. Increasing the pulse energy by about an order of magnitude creates a microscopic plasma near the surface and enables the collection of LIBS spectra at an unusually high rep rate and low pulse energy. Simultaneously, broader fluorescence peaks can be detected with lifetimes varying from nanosecond to microsecond. We will present Raman, LIBS, and fluorescence spectra obtained on natural mineral samples such as sulfates, clays, pyroxenes and carbonates that are of interest for Mars mineralogy. We demonstrate this technique using a photocathode-based streak camera detector as well as a newly-developed solid state Single Photon Avalanche Diode (SPAD) sensor array based on Complementary Metal-Oxide Semiconductor (CMOS) technology. We will discuss the impact of system design and detector choice on science return of a potential planetary surface mission, with a specific focus on size, weight, power, and complexity. The research described here was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (NASA).
Fast single-photon avalanche diode arrays for laser Raman spectroscopy.
Blacksberg, Jordana; Maruyama, Yuki; Charbon, Edoardo; Rossman, George R
We incorporate newly developed solid-state detector technology into time-resolved laser Raman spectroscopy, demonstrating the ability to distinguish spectra from Raman and fluorescence processes. As a proof of concept, we show fluorescence rejection on highly fluorescent mineral samples willemite and spodumene using a 128ū128 single-photon avalanche diode (SPAD) array with a measured photon detection efficiency of 5%. The sensitivity achieved in this new instrument architecture is comparable to the sensitivity of a technically more complicated system using a traditional photocathode-based imager. By increasing the SPAD active area and improving coupling efficiency, we expect further improvements in sensitivity by over an order of magnitude. We discuss the relevance of these results to in situ planetary instruments, where size, weight, power, and radiation hardness are of prime concern. The potential large-scale manufacturability of silicon SPAD arrays makes them prime candidates for future portable and in situ Raman instruments spanning numerous applications where fluorescence interference is problematic. PMID:21931428
In situ high P-T Raman spectroscopy and laser heating of carbon dioxide Mario Santoro,a)
Lin, Jung-Fu "Afu"
In situ high P-T Raman spectroscopy and laser heating of carbon dioxide Mario Santoro,a) Jung interpretation of the high P-T phase diagram of carbon dioxide. Furthermore, our approach opens a new way. The transformation temperature threshold and the transformation dynamics from the molecular phases III and II
Evaluation of thermal residual stresses in laser drilled alumina ceramics using Micro-Raman spectroscopy and COMSOL Multiphysics
NASA Astrophysics Data System (ADS)
Bharatish, A.; Narasimha Murthy, H. N.; Aditya, G.; Anand, B.; Satyanarayana, B. S.; Krishna, M.
This paper presents evaluation of thermal residual stresses in the heat affected zone of laser drilled alumina ceramic by using Micro-Raman spectroscopy. The residual stresses were evaluated for the holes corresponding to the optimal parameters of laser power, scanning speed, frequency and hole diameter. Three such cases were considered for the study. Residual stresses were obtained as a function of the Raman shifts. The nature and magnitude of the residual stresses were indicative of the extent of damage caused in the heat affected zone. In cases where the initial tensile residual stresses exceeded the tensile strength of alumina, cracks were initiated. Laser drilling with higher laser power and lower scanning speed induced initially high compressive and cyclic thermal stresses, causing greater damage to the hole. Transient thermal analysis was performed using COMSOL Multiphysics to predict residual thermal stresses and to validate the micro-Raman results. Scanning Electron Microscopy was used to confirm the damage caused in the heat affected zone.
Monitoring Dynamic Protein Expression in Single Living E. Coli. Bacterial Cells by Laser Tweezers Raman Spectroscopy
Chan, J W; Winhold, H; Corzett, M H; Ulloa, J M; Cosman, M; Balhorn, R; Huser, T
Laser tweezers Raman spectroscopy (LTRS) is a novel, nondestructive, and label-free method that can be used to quantitatively measure changes in cellular activity in single living cells. Here, we demonstrate its use to monitor changes in a population of E. coli cells that occur during overexpression of a protein, the extracellular domain of myelin oligodendrocyte glycoprotein (MOG(1-120)) Raman spectra were acquired of individual E. coli cells suspended in solution and trapped by a single tightly focused laser beam. Overexpression of MOG(1-120) in transformed E. coli Rosetta-Gami (DE3)pLysS cells was induced by addition of isopropyl thiogalactoside (IPTG). Changes in the peak intensities of the Raman spectra from a population of cells were monitored and analyzed over a total duration of three hours. Data was also collected for concentrated purified MOG(1-120) protein in solution, and the spectra compared with that obtained for the MOG(1-120) expressing cells. Raman spectra of individual, living E. coli cells exhibit signatures due to DNA and protein molecular vibrations. Characteristic Raman markers associated with protein vibrations, such as 1257 cm{sup -1}, 1340 cm{sup -1}, 1453 cm{sup -1} and 1660 cm{sup -1}, are shown to increase as a function of time following the addition of IPTG. Comparison of these spectra and the spectra of purified MOG protein indicates that the changes are predominantly due to the induction of MOG protein expression. Protein expression was found to occur mostly within the second hour, with a 470% increase relative to the protein expressed in the first hour. A 230% relative increase between the second and third hour indicates that protein expression begins to level off within the third hour. It is demonstrated that LTRS has sufficient sensitivity for real-time, nondestructive, and quantitative monitoring of biological processes, such as protein expression, in single living cells. Such capabilities, which are not currently available in flow cytometry, open up new possibilities for analyzing cellular processes occurring in single microbial and eukaryotic cells.
Evidence of laser induced decomposition of triaminotrinitrobenzene from surface enhanced Raman spectroscopy
F. J. Owens
It is observed that the focused 632 nm laser of the confocal micro-Raman spectrometer decomposes triaminotrinitrobenzene (TATB). The temperature generated in the laser spot determined by measuring the ratio of the intensities of the anti-Stokes to Stokes spectra is too low to cause thermal decomposition. The observed decomposition is suggested to be a result of laser induced electronic excitation. The
Dual-wavelength Y-branch distributed Bragg reflector diode laser at 785 nanometers for shifted excitation Raman difference spectroscopy.
Maiwald, Martin; Eppich, Bernd; Fricke, J÷rg; Ginolas, Arnim; Bugge, Frank; Sumpf, Bernd; Erbert, G÷tz; Trõnkle, G³nther
A dual-wavelength Y-branch distributed Bragg reflector (DBR) diode laser at 785 nm is presented as an excitation light source for shifted excitation Raman difference spectroscopy (SERDS). The monolithic device was realized with deeply etched surface DBR gratings using one-step epitaxy. An optical output power of 140 mW was obtained in continuous-wave (CW) operation for each laser cavity, with emission wavelengths of the device at 784.50 and 785.12 nm. A spectral width of the laser emission of 30 pm (0.5 cm(-1)), including 95% of optical power, was measured. The mean spectral distance of both excitation lines is 0.63 nm (10.2 cm(-1)) over the whole operating range. Raman experiments using polystyrene as the test sample and ambient light as the interference source were carried out and demonstrate the suitability of the dual-wavelength diode laser for SERDS. PMID:25061785
Assessment of argon ion laser dispersive Raman spectroscopy for hot cell applications
Crawford, B.A.
Characterization of high-level waste tank materials at Hanford is conducted to support safety assessments and waste treatment activities. Raman spectroscopy is expected to give chemical species information which may assist in defining layering in tank waste. This report describes the dispersive Raman system used in this year`s investigation and the methology used to collect and evaluate data taken on tank waste samples. The current argon-ion Raman system was found not to be suitable for screening of tank cores, owing to silica interference, fluorescence interferences, and the extensive time required to collect and treat the data. Recommendations are given for further development.
Evaluation of Residual Strain and Oxygen Vacancy in Multilayer Ceramic Capacitor Using Laser Raman Spectroscopy
NASA Astrophysics Data System (ADS)
Nishida, Ken; Kishi, Hiroshi; Funakubo, Hiroshi; Takeuchi, Hironari; Katoda, Takashi; Yamamoto, Takashi
Micro-Raman spectroscopy was employed to investigate the residual strain and oxygen vacancies of BaTiO3-based multilayer ceramic capacitors (MLCCs) with a Ni internal electrode. Strain was found to accumulate around the internal Ni electrodes layers than at other parts of the MLCCs. In addition, the number of oxygen vacancies near the internal Ni electrode was larger than that at any other parts of the MLCCs. These observations clearly show that Raman spectroscopy is extremely useful for evaluating the residual strain and oxygen vacancies in MLCC devices.
[Laser tweezers Raman spectroscopy analysis of cold-adapted aromatic hydrocarbons-degradating strains isolated from Antarctic Sea].
Wang, Yi-Bin; Miao, Jin-Lai; He, Bi-Juan; Liang, Qiang; Liu, Fang-Ming; Zheng, Zhou
Laser tweezers Raman spectroscopy can help with observing and studying individual cells or organelles in a natural state for a relatively long period. In the present experiment, Laser tweezers Raman spectroscopy (LTRS) was used as a tool to report physiological metabolism such as cells growth and nucleic acid, proteins, lipid and glucose of a single active cold-adapted Aromatic hydrocarbons-degradating strains isolated from Antarctic Sea. After the Raman spectrum was collected and analyzed, the findings are as follows: Raman spectrum identified the components of a single cold-adapted Aromatic hydrocarbons-degradating strain and there were more proteins and carbohydrate produced during the Planococcus sp. NJ41 and Shewanella sp. NJ49 growth and degradation; but there was more lipid than the proteins produced during the Pseudoalteromonas sp. NJ289 growth and degradation; the amount of proteins produced by the strains corresponds with the production of degradation rate-limiting enzyme, and was also related to the capacity of low-temperature degradation of aromatic hydrocarbons. PMID:21510394
In vivo molecular evaluation of guinea pig skin incisions healing after surgical suture and laser tissue welding using Raman spectroscopy.
Alimova, A; Chakraverty, R; Muthukattil, R; Elder, S; Katz, A; Sriramoju, V; Lipper, Stanley; Alfano, R R
The healing process in guinea pig skin following surgical incisions was evaluated at the molecular level, in vivo, by the use of Raman spectroscopy. After the incisions were closed either by suturing or by laser tissue welding (LTW), differences in the respective Raman spectra were identified. The study determined that the ratio of the Raman peaks of the amide III (1247 cm(-1)) band to a peak at 1326 cm(-1) (the superposition of elastin and keratin bands) can be used to evaluate the progression of wound healing. Conformational changes in the amide I band (1633-1682 cm(-1)) and spectrum changes in the range of 1450-1520 cm(-1) were observed in LTW and sutured skin. The stages of the healing process of the guinea pig skin following LTW and suturing were evaluated by Raman spectroscopy, using histopathology as the gold standard. LTW skin demonstrated better healing than sutured skin, exhibiting minimal hyperkeratosis, minimal collagen deposition, near-normal surface contour, and minimal loss of dermal appendages. A wavelet decomposition-reconstruction baseline correction algorithm was employed to remove the fluorescence wing from the Raman spectra. PMID:19581109
ExoMars Raman laser spectrometer overview
F. Rull; A. Sansano; E. DĒaz; C. P. Canora; A. G. Moral; C. Tato; M. Colombo; T. Belenguer; M. Fernßndez; J. A. R. Manfredi; R. Canchal; B. Dßvila; A. Jimķnez; P. Gallego; S. Ibarmia; J. A. R. Prieto; A. Santiago; J. Pla; G. Ramos; C. Gonzßlez
The Raman Laser Spectrometer (RLS) is one of the Pasteur Payload instruments, within the ESA's Aurora Exploration Programme, ExoMars mission. The RLS Instrument will perform Raman spectroscopy on crushed powered samples deposited on a small container after crushing the cores obtained by the Rover's drill system. This is the first time that a Raman spectrometer will be launched in an
Wavelength Selection For Laser Raman Spectroscopy of Putative Martian Habitats and Biomolecules
D. D. Wynn-Williams; E. M. G. Newton; H. G. M. Edwards
Pigments are key potential biomarkers for any former life on Mars because of the selective pressure of solar radiation on any biological system that could have evolved at its surface. We have found that the near -Infrared laser Raman spectrometer available to use was eminently suitable for diagnostic analysis of pigments because of their minimal autofluorescence at its 1064 nm
Raman spectroscopy of doped and compensated laser crystallized polycrystalline silicon thin films
R. Saleh; N. H. Nickel
The influence of dopant and the microstructure on hydrogen bonding in doped and compensated laser crystallized polycrystalline silicon (poly-Si) films were investigated using Raman backscattering spectrometry. With increasing boron and phosphorous concentration, the LO-TO phonon line in doped as well as in compensated films shifts to smaller wave numbers and broadens asymmetrically. The results are discussed in terms of resonant
Surface Enhanced Raman Spectroscopy Surface Enhanced Raman Spectroscopy Surface Enhanced Raman Spectroscopy Surface Enhanced Raman Spectroscopy
Scott Parker
Recently, Surface enhanced Raman Spectroscopy (SERS) has been rediscovered as a powerful experimental technique. In this report, I will discuss the development and theory of SERS. I will discuss its discovery and early theoretical models and present a simplified conceptual model which illustrates the key features of SERS. A general experimental method will be presented in the context of modern
Applications of a modulated laser for FT Raman spectroscopy. Part 2. Signal-to-noise enhancement and removal of thermal backgrounds
NASA Astrophysics Data System (ADS)
Bennett, R.
This paper describes the benefits of using a synchronously gain switched Nd:YAG laser as an excitation source for FT Raman spectroscopy. Results show that improvements in signal-to-noise ratios of better than a factor of four are obtained when using the same average d.c. laser power compared with the normal CW experiment. This technique is simple to apply to modern FT Raman spectrometers requiring little modification to the analogue electronics.
Laser irradiation effects on the CdTe/ZnTe quantum dot structure studied by Raman and AFM spectroscopy
Zielony, E.; Placzek-Popko, E.; Henrykowski, A.; Gumienny, Z.; Kamyczek, P.; Jacak, J. [Institute of Physics, Wroclaw University of Technology, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw (Poland); Nowakowski, P.; Karczewski, G. [Institute of Physics, Polish Academy of Sciences, al. Lotnikow 32/46, 02-668 Warsaw (Poland)
Micro-Raman spectroscopy has been applied to investigate the impact of laser irradiation on semiconducting CdTe/ZnTe quantum dots (QDs) structures. A reference sample (without dots) was also studied for comparison. Both samples were grown by molecular beam epitaxy technique on the p-type GaAs substrate. The Raman spectra have been recorded for different time of a laser exposure and for various laser powers. The spectra for both samples exhibit peak related to the localized longitudinal (LO) ZnTe phonon of a wavenumber equal to 210 cm{sup -1}. For the QD sample, a broad band corresponding to the LO CdTe phonon related to the QD-layer appears at a wavenumber of 160 cm{sup -1}. With increasing time of a laser beam exposure and laser power, the spectra get dominated by tellurium-related peaks appearing at wavenumbers around 120 cm{sup -1} and 140 cm{sup -1}. Simultaneously, the ZnTe surface undergoes rising damage, with the formation of Te aggregates at the pinhole edge as reveal atomic force microscopy observations. Local temperature of irradiated region has been estimated from the anti-Stokes/Stokes ratio of the Te modes intensity and it was found to be close or exceeding ZnTe melting point. Thus, the laser damage can be explained by the ablation process.
New applications of laser-induced breakdown and stand-off Raman spectroscopy
Marion Lawrence Snyder
Two novel spectroscopic applications, with the common theme of remote spectroscopy are described. In one application, laser-induced breakdown spectroscopy (LIBS) is investigated for deep ocean measurements of hydrothermal vent chemistry. This technique is demonstrated for the first time for solution measurements at pressures corresponding to those found at hydrothermal vent sites, at ocean depths of one to three kilometers. In
Wavelength Selection For Laser Raman Spectroscopy of Putative Martian Habitats and Biomolecules
NASA Astrophysics Data System (ADS)
Wynn-Williams, D. D.; Newton, E. M. G.; Edwards, H. G. M.
Pigments are key potential biomarkers for any former life on Mars because of the selective pressure of solar radiation on any biological system that could have evolved at its surface. We have found that the near -Infrared laser Raman spectrometer available to use was eminently suitable for diagnostic analysis of pigments because of their minimal autofluorescence at its 1064 nm excitation wav elength. However, we have now evaluated a diverse range of excitation wavelengths to confirm this choice, to ensure that we have the best technique to seek for pigments and their derivatives from any former surface life on Mars. The Raman is weak relative to fluorescence, which results in elevated baseline and concurrent swamping of Raman bands. We confirm the molecular information available from near-IR FT Raman spectra for two highly pigmented UV-tolerant epilithic Antarctic lichens (Acarospora chlorop hana and Caloplaca saxicola) from Victoria Land, a whole endolithic microbial community and endolithic cyanobacterium Chroococcidiopsis from within translucent sandstone of the Trans -Antarctic Mountains, and the free- living cyanobacterium Nostoc commune from Alexander Island, Antarctic Peninsula region. We also show that much of the information we require on biomolecules is not evident from lasers of shorter wavelengths. A miniature 1064 nm Raman spectrometer with an In-Ga-As detector sensitive to IR is being developed by Montana State University (now existing as a prototype) as the prime instrument for a proposed UK-led Mars rover mission (Vanguard). Preliminary spectra from this system confirm the suitability of the near-IR laser.
Stimulated Raman Scattering in Analytical Spectroscopy
Hassan S. Ghaziaskar; Edward P. C. Lai
Stimulated Raman scattering (SRS) was first observed by Woodbury and Ng [l] using a nitrobenzene Kerr shutter as the Q-switch of a ruby laser, and then identified by Eckhardt et al. [2]. If threshold requirements for the pump intensity and the interaction length were fulfilled for a given gain medium, SRS could be performed in a simple laser spectroscopy experiment
NASA Astrophysics Data System (ADS)
Katori, H.; Yoneda, H.; Nakagawa, K.; Shimizu, F.
Anderson localization of matter-waves in a controlled disorder: a quantum simulator? / A. Aspect ... [et al.] -- Squeezing and entanglement in a Bose-Einstein condensate / C. Gross ... [et al.] -- New physics in dipolar Bose-Einstein condensates / Y. Kawaguchi, H. Saito, and M. Ueda -- Observation of vacuum fluctuations in a spinor Bose-Einstein condensate / C. Klempt ... [et al.] -- Negative-index media for matter waves / F. Perales ... [et al.] -- Entanglement of two individual atoms using the Rydberg blockade / A. Browaeys ... [et al.] -- Array of mesoscopic ensembles on a magnetic atom chip / A. F. Tauschinsky ... [et al.] -- Stability of the proton-to-electron mass ratio tested with molecules using an optical link to primary clock / A. Amy-Klein ... [et al.] -- Metastable helium: lifetime measurements using cold atoms as a test of QED / K. G. H. Baldwin ... [et al.] -- Optical lattice clocks with single occupancy bosons and spin-polarized fermions toward 10[symbol] accuracy / M. Takamoto ... [et al.] -- Frequency measurements of Al[symbol] and Hg[symbol] optical standards / W. M. Itano ... [et al.] -- Switching of light with light using cold atoms inside a hollow optical fiber / M. Bajcsy ... [et al.] -- Room-temperature atomic ensembles for quantum memory and magnetometry / K. Jensen ... [et al.] -- Components for multi-photon non-classical state preparation and measurement / G. Puentes ... [et al.] -- Quantum field state measurement and reconstruction in a cavity by quantum nondemolition photon counting / M. Brune ... [et al.] -- XUV frequency comb spectroscopy / C. Gohle ... [et al.] -- Ultrahigh-repetition-rate pulse train with absolute-phase control produced by an adiabatic raman process / M. Katsuragawa ... [et al.] -- Strongly correlated bosons and fermions in optical lattices / S. Will ... [et al.] -- Bragg spectroscopy of ultracold bose gases in optical lattices / L. Fallani ... [et al.] -- Synthetic quantum many-body systems / C. Guerlin ... [et al.] -- Ultracold Ytterbium atoms in optical lattices / S. Sugawa ... [et al.] -- Ultracold polar molecules in the rovibrational ground state / J. Deiglmayr ... [et al.] -- Polar molecules near quantum degeneracy / J. Ye and D. S. Jin -- Production of a quantum gas of rovibronic ground-state molecules in an optical lattice / J. G. Danzl ... [et al.] -- Recent progress in x-ray nonlinear optics / K. Tamasaku, K. Sawada, and T. Ishikawa -- Gas in scattering media absorption spectroscopy - laser spectroscopy in unconventional environments / S. Svanberg -- Laser spectroscopy on relativistic ion beams / S. Reinhardt ... [et al.] -- Single frequency microcavity lasers and applications / L. Xu ... [et al.].
Structural Comparison of Lunar, Terrestrial, and Synthetic Whitlockite Using Laser Raman Microprobe Spectroscopy
NASA Astrophysics Data System (ADS)
Jolliff, B. L.; Freeman, J. J.; Wopenka, B.
Raman spectra are sensitive to the structural and chemical characteristics of the phosphate mineral whitlockite. The number and specific frequency of the Raman bands in the 970 Delta cm^-1 spectral region caused by the nu(sub)1 symmetric stretching mode within the (PO4)^3- tetrahedra differ for REE-rich whitlockite (single, asymmetric band), REE-poor Ca- or Na-whitlockite (doublet), and terrestrial H-containing whitlockite (doublet). The presence of (HPO4)^2- groups in the latter produces a third nu(sub)1 band at 923 Delta cm^-1. Based on the Raman spectra of lunar, meteoritic, synthetic, and terrestrial whitlockite, we conclude that the incorporation of REE in REE-rich whitlockite (for which there is currently no X-ray structural refinement) causes a significant change to the structure compared to both meteoritic and terrestrial whitlockite. In addition, we can distinguish between high and low REE concentrations in whitlockite grains. All of this information can be obtained non-destructively, in-situ in grains as small as 3 micrometers (in loose rock fragments or in prepared sections) with a laser Raman microprobe.
Integrated amplification and passivation nanolayers for ultra-high-sensitivity photodetector arrays: application for laser-induced breakdown spectroscopy (LIBS) and Raman spectroscopy
NASA Astrophysics Data System (ADS)
Gardner, Patrick; Yao, Jie; Wang, Sean; Zhou, Jack; Li, Ken; Mokina, Irina; Lange, Michael; Yang, Weiguo; Peltz, Leora; Frampton, Robert; Hunt, Jeffrey H.; Becker, Jill
Miniaturized field-deployable spectrometers used for the rapid analysis of chemical and biological substances require high-sensitivity photo detectors. For example, in a Raman spectroscopy system, the receiver must be capable of high-gain, low-noise detection performance due to the intrinsically weak signals produced by the Raman effects of most substances. We are developing a novel, high-gain hetero-junction phototransistor (HPT) detector which employs two nano-structures simultaneously to achieve 100 times higher sensitivity than InGaAs avalanche photodiodes, the most sensitive commercially available photo-detector in the near infrared (NIR) wavelength range, under their normal operation conditions. Integrated into a detector array, this technology has application for Laser- Induced Breakdown Spectroscopy (LIBS), pollution monitoring, pharmaceutical manufacturing by reaction monitoring, chemical & biological transportation safety, and bio-chemical analysis in planetary exploration.
Investigation of secondary structures and macromolecular interactions in bacteriophage P22 by laser Raman spectroscopy
Fish, S.R. (Univ. of Rhode Island, Kingston); Fuller, M.T.; King, J.; Thomas, G.J. Jr
Laser Raman spectra of the DNA bacteriophage P22 and of its precursor particles and related structures have been obtained using 514.5-nm excitation. The spectra show that P22 DNA exists in the B form both inside of the phage head and after extraction from the phage. The major coat protein (gp5) contains a secondary structure composed of 18% ..cap alpha..-helix, 20% BETA-sheet and 62% irregular conformations. The scaffolding protein (gp8) in the phage prohead is substantially richer than gp5 in ..cap alpha..-helical content. Among the amino acid residues which give prominent Raman lines, the spectra show that tryptophans are exposed to solvent and most tyrosines are hydrogen bonded to positive donor groups. The above features of phage DNA and protein structures are nearly invariant to changes in temperature up to 80/sup 0/C, indicating a remarkable thermal stability of the phage head and its encapsulated DNA.
Unveiling the identity of distant targets through advanced Raman-laser-induced breakdown spectroscopy data fusion strategies.
Moros, Javier; Laserna, J Javier
Data fusion is the process of combining data gathered from two or more sensors to produce a more specific, comprehensive and unified dataset of the inspected target. On this basis, much has been said about the possible benefits resulting from the use of molecular and atomic information for the detection of explosives. The orthogonal nature of the spectral and compositional information provided by Raman spectroscopy and laser-induced breakdown spectroscopy (LIBS) makes them suitable candidates for an optimal combination of their data, thus achieving inferences that are not feasible using a single sensor. The present manuscript evaluates several architectures for the combination of spectral outputs from these two sensors in order to compare the benefits and drawbacks of data fusion for improving the overall identification performance. From the simple assembling (concatenation or addition) of Raman and LIBS spectra to signals' processing on the basis of linear algebra (either the outer product or the outer sum), different identification patterns of several compounds (explosives, potential confusants and supports) have been built. The efficiency on target differentiation by using each of the architectures has been evaluated by comparing the identification yield obtained for all the inspected targets from correlation and similarity measurements. Additionally, a specific code integrated by several of these patterns to identify each compound has also been evaluated. This approach permits to obtain a better knowledge about the identity of an interrogated target, mainly in those decisive cases in which LIBS or Raman cannot be effective separately to reach a decision. PMID:25618716
Micro-mirror arrays for Raman spectroscopy
NASA Astrophysics Data System (ADS)
Duncan, W. M.
In this research we study Raman and fluorescence spectroscopies as non-destructive and noninvasive methods for probing biological material and "living systems." Particularly for a living material any probe need be non-destructive and non-invasive, as well as provide real time measurement information and be cost effective to be generally useful. Over the past few years the components needed to measure weak and complex processes such as Raman scattering have evolved substantially with the ready availability of lasers, dichroic filters, low noise and sensitive detectors, digitizers and signal processors. A Raman spectrum consists of a wavelength or frequency spectrum that corresponds to the inelastic (Raman) photon signal that results from irradiating a "Raman active" material. Raman irradiation of a material usually and generally uses a single frequency laser. The Raman fingerprint spectrum that results from a Raman interaction can be determined from the frequencies scattered and received by an appropriate detector. Spectra are usually "digitized" and numerically matched to a reference sample or reference material spectra in performing an analysis. Fortunately today with the many "commercial off-the-shelf" components that are available, weak intensity effects such as Raman and fluorescence spectroscopy can be used for a number of analysis applications. One of the experimental limitations in Raman measurement is the spectrometer itself. The spectrometer is the section of the system that either by interference plus detection or by dispersion plus detection that "signal" amplitude versus energy/frequency signals are measured. Particularly in Raman spectroscopy, optical signals carrying desired "information" about the analyte are extraordinarily weak and require special considerations when measuring. We will discuss here the use of compact spectrometers and a micro-mirror array system (used is the digital micro-mirror device (DMD) supplied by the DLP« Products group of Texas Instruments Incorporated) for analyzing dispersed light as needed in Raman and fluorescent applications.
A new compact instrument for Raman, laser-induced breakdown, and laser-induced fluorescence spectroscopy of works of art and their constituent materials
NASA Astrophysics Data System (ADS)
Osticioli, I.; Mendes, N. F. C.; Nevin, A.; Zoppi, A.; Lofrumento, C.; Becucci, M.; Castellucci, E. M.
A small, potentially transportable prototype instrument capable of carrying out Raman, laser-induced breakdown (LIB), and laser-induced fluorescence (LIF) spectroscopy using a single pulsed laser source was developed for the analysis of cultural heritage objects. The purpose of this instrumentation is to perform fast and reliable analysis of surfaces with minimum damage to an object. For this purpose, a compact (51ū203ū76 mm) nanosecond Q-switched neodymium doped yttrium aluminum garnet laser (8 ns, 20 Hz, 0.01-115 mJ/pulse) was used as an irradiation source. The use of a nanosecond-gated detector sensitive between 180 and 900 nm allows the acquisition of elemental emissions in LIB spectroscopy and can also be employed for both LIF and time-resolved Raman spectroscopy. In this work, attention is focused on the description of the instrument and its optical components, and two examples of applications for the analysis of pigments and binding media used in works of art are presented.
Polarized micro Raman spectroscopy of bilayer graphene
NASA Astrophysics Data System (ADS)
Moon, Hyerim; Yoon, Duhee; Son, Young-Woo; Cheong, Hyeonsik
The frequency of Raman 2D band of the graphite depends on the excitation laser energy. This phenomenon is explained with double resonance Raman process. In polarized micro-Raman spectroscopy of single layer graphene, Raman G band (ś1586 cm-1) is isotropic, and 2D band (ś2686 cm-1) strongly depends on relative polarizations of the incident and scattered photons. This strong polarization dependence originates from inhomogeneous optical absorption and emission mediated by resonant electron-phonon interaction. In bi-layer graphene, Raman 2D band can be decomposed into four Lorenztian peaks which can be interpreted in terms of the four transition paths in the double resonance Raman process. We investigated the polarization dependence of each Lorenztian peak in the Raman 2D band of bi-layer graphene for different excitation laser energies. Strong polarization dependence of the Raman 2D band, similar to the case of single layer graphene, is observed. The excitation energy dependence of the polarized Raman scattering is analyzed in terms of the band structure of bi-layer graphene.
The generation of quasi-continuous, tunable 200 nm excitation using the MHz amplified synchronously pumped dye laser: Application to UV resonance raman spectroscopy
Terry L. Gustafson
We demonstrate the generation of quasi-continuous, tunable excitation in the 200 nm region by sum frequency mixing the fundamental and second harmonic from the MHz amplified synchronously pumped dye laser in beta-BaB2O4. We use the output as the excitation source for ultraviolet resonance Raman spectroscopy.
Total internal reflection Raman spectroscopy.
Woods, David A; Bain, Colin D
Total internal reflection (TIR) Raman spectroscopy is an experimentally straightforward, surface-sensitive technique for obtaining chemically specific spectroscopic information from a region within approximately 100-200 nm of a surface. While TIR Raman spectroscopy has long been overshadowed by surface-enhanced Raman scattering, with modern instrumentation TIR Raman spectra can be acquired from sub-nm thick films in only a few seconds. In this review, we describe the physical basis of TIR Raman spectroscopy and illustrate the performance of the technique in the diverse fields of surfactant adsorption, liquid crystals, lubrication, polymer films and biological interfaces, including both macroscopic structures such as the surfaces of leaves, and microscopic structures such as lipid bilayers. Progress, and challenges, in using TIR Raman to obtain depth profiles with sub-diffraction resolution are described. PMID:22003492
Fluorescence and Raman spectroscopy.
Wong Kee Song, Louis-Michel; Marcon, Norman E
Table 2 provides a summary of selected in vivo fluorescence and Raman studies performed in BE. Although the findings from these studies appear promising, these techniques are still under development, and it is anticipated that technological refinements will further enhance their diagnostic accuracy. Ultimately, however, large-scale prospective clinical trials are required to determine their true diagnostic potential in BE and other sites. Ideally, the instrumentation of choice would be a real-time endoscopic system that combines excellent diagnostic accuracy with wide-area sampling. In this regard, fluorescence imaging is most appealing, although a variety of issues remain to be resolved, including the choice between autofluorescence versus drug-induced fluorescence and the problematic distinction between dysplastic (true positive) and confounding background metaplastic fluorescence (false positive), among others. It is also not clear whether exogenous fluorophores are necessary to achieve clinically useful sensitivity and specificity for lesion detection in BE. Point spectroscopic techniques, either fluorescence or Raman scattering, are inherently limited by the small volume of tissue (biopsy specimen size) they sample, but more detailed information can be extracted from the spectra, which may increase diagnostic accuracy. Moreover, it may be that the optimal system will be a combination of multiple optical spectroscopic or imaging techniques (multimodality approach), as suggested by Georgakoudi et al. For instance, a lesion could be detected by fluorescence imaging and its dysplastic nature characterized (graded) by Raman spectroscopy. In this era of cost containment, however, the critical challenge is to demonstrate whether an increase in diagnostic accuracy merits investment in costly technology, regardless of the technique used. PMID:12916660
Online fluorescence suppression in modulated Raman spectroscopy.
De Luca, Anna Chiara; Mazilu, Michael; Riches, Andrew; Herrington, C Simon; Dholakia, Kishan
Label-free chemical characterization of single cells is an important aim for biomedical research. Standard Raman spectroscopy provides intrinsic biochemical markers for noninvasive analysis of biological samples but is often hindered by the presence of fluorescence background. In this paper, we present an innovative modulated Raman spectroscopy technique to filter out the Raman spectra from the fluorescence background. The method is based on the principle that the fluorescence background does not change whereas the Raman scattering is shifted by the periodical modulation of the laser wavelength. Exploiting this physical property and importantly the multichannel lock-in detection of the Raman signal, the modulation technique fulfills the requirements of an effective fluorescence subtraction method. Indeed, once the synchronization and calibration procedure is performed, minimal user intervention is required, making the method online and less time-consuming than the other fluorescent suppression methods. We analyze the modulated Raman signal and shifted excitation Raman difference spectroscopy (SERDS) signal of 2 mum-sized polystyrene beads suspended in a solution of fluorescent dye as a function of modulation rate. We show that the signal-to-noise ratio of the modulated Raman spectra at the highest modulation rate is 3 times higher than the SERDS one. To finally evaluate the real benefits of the modulated Raman spectroscopy, we apply our technique to Chinese hamster ovary cells (CHO). Specifically, by analyzing separate spectra from the membrane, cytoplasm, and nucleus of CHO cells, we demonstrate the ability of this method to obtain localized sensitive chemical information from cells, away from the interfering fluorescence background. In particular, statistical analysis of the Raman data and classification using PCA (principal component analysis) indicate that our method allows us to distinguish between different cell locations with higher sensitivity and specificity, avoiding potential misinterpretation of the data obtained using standard background procedures. PMID:20017474
Applications of a modulated laser for FT Raman spectroscopy. Part 2. Signal-to-noise enhancement and removal of thermal backgrounds
R. Bennett
This paper describes the benefits of using a synchronously gain switched Nd:YAG laser as an excitation source for FT Raman spectroscopy. Results show that improvements in signal-to-noise ratios of better than a factor of four are obtained when using the same average d.c. laser power compared with the normal CW experiment. This technique is simple to apply to modern FT
[Determination of hydration number of methane hydrates using micro-laser Raman spectroscopy].
Liu, Chang-Ling; Ye, Yu-Guang; Meng, Qing-Guo
Methane hydrates are clathrate compounds that are formed by methane molecules and water molecules under low temperature and high pressure conditions. It was found that methane hydrates exist widely in sea-shelf floor and permafrost, and are considered as a potential energy resource. In the crystal lattice of clathrate hydrate, the water molecules form both large cages (5(12)6(2)) and small cages (5(12)) under the interaction of the hydrogen-hydrogen bond. In this paper, the authors designed a set of experimental apparatus for methane hydrates formation. Based on this equipment, the authors synthesized a series of methane hydrates in various systems in laboratory, including SDS solution (3% Wt) and methane, powdered ice and methane, and powdered ice and methane and natural sand with various sizes (i. e. 250-350, 180-250, 125-180 and 63-90 microm), under different temperature and pressure. The authors also designed a small device which was proved to be convenient for Raman determination of the methane hydrates. Raman spectroscopy was used to analyze the methane hydrates and to measure the structural parameters such as hydration numbers and cage occupancies. The results show that the methane hydrate samples are all in structure I type, and hydration numbers and cage occupancies are almost independent of the sediment sizes. In the three systems, the large cages of methane hydrate samples are nearly full occupied, with the occupancy ratios larger than 97%, whereas the small cages between 80% and 86%. The hydration numbers of these methane hydrate samples are between 6.05 and 6.15. PMID:20545140
Evaluating internal maturity of tomatoes using spatially offset Raman spectroscopy
Technology Transfer Automated Retrieval System (TEKTRAN)
Spatially offset Raman spectroscopy technique was investigated for evaluating internal maturity of intact tomatoes. A Raman spectroscopy system was assembled to acquire spatially offset spectra in the wavenumber range of 200¢2500 cm¢1. A 785-nm laser was used as the excitation source and the measure...
Raman spectroscopy: the gateway into tomorrow's virology
Phelps J Lambert; Audy G Whitman; Ossie F Dyson; Shaw M Akula
In the molecular world, researchers act as detectives working hard to unravel the mysteries surrounding cells. One of the researchers' greatest tools in this endeavor has been Raman spectroscopy. Raman spectroscopy is a spectroscopic technique that measures the unique Raman spectra for every type of biological molecule. As such, Raman spectroscopy has the potential to provide scientists with a library
Characterization of Kevlar Using Raman Spectroscopy
NASA Technical Reports Server (NTRS)
Washer, Glenn; Brooks, Thomas; Saulsberry, Regor
This paper explores the characterization of Kevlar composite materials using Raman spectroscopy. The goal of the research is to develop and understand the Raman spectrum of Kevlar materials to provide a foundation for the development of nondestructive evaluation (NDE) technologies based on the interaction of laser light with the polymer Kevlar. The paper discusses the fundamental aspects of experimental characterization of the spectrum of Kevlar, including the effects of incident wavelength, polarization and laser power. The effects of environmental exposure of Kevlar materials on certain characteristics of its Raman spectrum are explored, as well as the effects of applied stress. This data may provide a foundation for the development of NDE technologies intended to detect the in-situ deterioration of Kevlar materials used for engineering applications that can later be extended to other materials such as carbon fiber composites.
Molecular aggregation of ionic surfactants in formamide studied by laser Raman spectroscopy
NASA Astrophysics Data System (ADS)
Amorim da Costa, A. M.
Changes with concentration in Raman spectra of cetyltrimethylammonium bromide and sodium dodecyl sulfate/formamide solutions, above the respective Krafft temperatures, are interpreted in terms of structural changes analogous to the hydrophobic interactions responsible for micelle formation in aqueous solutions.
In situ high pressure-temperature Raman spectroscopy technique with laser-heated diamond anvil cells
Lin, Jung-Fu "Afu"
Geophysical Laboratory, Carnegie Institution of Washington, Washington, DC 20015 (Received 16 April 2004 furnace) in a diamond cell. The YLF laser is used to effectively laser-heat one side of a metal foil 5
Initial state resolved electronic spectroscopy of HNCO: Stimulated Raman preparation of initial states and laser induced fluorescence detection of photofragments
NASA Astrophysics Data System (ADS)
Brown, Steven S.; Berghout, H. Laine; Crim, F. Fleming
Stimulated Raman excitation (SRE) efficiently prepares excited vibrational levels in the ground electronic state of isocyanic acid, HNCO. Photofragment yield spectroscopy measures the electronic absorption spectrum out of initially selected states by monitoring laser induced fluorescence (LIF) of either NCO (X 2?) or NH (a 1?) photofragments. Near threshold, the N-H bond fission is predissociative, and there is well-resolved rotational and vibrational structure in the NCO yield spectra that allows assignment of Ka rotational quantum numbers to previously unidentified vibrational and rotational levels in the ?1 N-H stretch and ?3 N-C-O symmetric stretch fundamentals in the ground electronic state of HNCO. The widths of NCO yield resonances depend on the initial vibrational state, illustrating one way in which initial vibrational state selection influences dissociation dynamics. Initial excitation of unperturbed ?1 (N-H stretch) states leads to diffuse NCO yield spectra compared to excitation of mixed vibrational levels. The higher energy dissociation channel that produces NH (a 1?) has coarser structure near its threshold, consistent with a more rapid dissociation, but the resonance widths still depend on the initially selected vibrational state.
In-situ laser Raman scattering and far infrared spectroscopy studies of corrosion-passivation phenomena in metals.
Melendres, C. A.
Vibrational spectroscopic and electrochemical techniques are among the most useful tools for the elucidation of corrosion-passivation phenomena in metals. The former can provide information on the structure and composition of corrosion films ''in situ'' in aqueous solution environments, while thermodynamic and kinetic information may be obtained using electrochemical techniques. In this paper, we demonstrate the application of Laser Raman Scattering (LRS) and Synchrotrons Far Infrared Reflectance Spectroscopy (SFIRS), coupled with electrochemical methods, for the determination of the structure and composition of surface films on nickel and copper in aqueous solution environment. The corrosion film on nickel has been found to consist of NiO and Ni(OH){sub 2} in the passive region of potential and NiOOH in the transpassive region. The film on copper consists of Cu{sub 2}O, CUO and Cu(OH){sub 2}. We also show for the first time that SFIRS can be used to obtain information on the adsorption of ions on a metal surface with sub-monolayer sensitivity. Adsorption of Cl{sup {minus}}, Br{sup {minus}}, SO{sup {minus}2}, and PO{sub 4}{sup {minus}3} was found to occur at gold electrodes in perchloric acid solution. We also observed that when two different ions are present in solution, the more strongly adsorbed ion determined the corrosion behavior of the metal.
Nanosecond time-resolved Raman spectroscopy of laser-heated silicon
NASA Astrophysics Data System (ADS)
Wartmann, G.; Kemmler, M.; von der Linde, D.
We observe distinct shifts and broadenings of the optical-phonon Raman line, which are consistent with the lattice temperature rise predicted by a simple thermal heating model. The detailed temperature evolution obtained from measurements of the Stokes-to-anti-Stokes ratio demonstrates that the melting temperature is indeed reached precisely at the same time that the optical reflectivity jumps from the value of the solid to that of the liquid.
Remote adjustable focus Raman spectroscopy probe
Schmucker, John E. (Hurt, VA); Blasi, Raymond J. (Harrison City, PA); Archer, William B. (Bethel Park, PA)
A remote adjustable focus Raman spectroscopy probe allows for analyzing Raman scattered light from a point of interest external probe. An environmental barrier including at least one window separates the probe from the point of interest. An optical tube is disposed adjacent to the environmental barrier and includes a long working length compound lens objective next to the window. A beam splitter and a mirror are at the other end. A mechanical means is used to translated the prove body in the X, Y, and Z directions resulting in a variable focus optical apparatus. Laser light is reflected by the beam splitter and directed toward the compound lens objective, then through the window and focused on the point of interest. Raman scattered light is then collected by the compound lens objective and directed through the beam splitter to a mirror. A device for analyzing the light, such as a monochrometer, is coupled to the mirror.
Remote Adjustable focus Raman Spectroscopy Probe
Schmucker, John E.; Blasi, Raymond J.; Archer, William B.
A remote adjustable focus Raman spectroscopy probe allows for analyzing Raman scattered light from a point of interest external to the probe. An environmental barrier including at least one window separates the probe from the point of interest. An optical tube is disposed adjacent to the environmental barrier and includes along working length compound lens objective next to the window. A beam splitter and a mirror are at the other end. A mechanical means is used to translate the probe body in the X, Y, and Z directions resulting in a variable focus optical apparatus. Laser light is reflected by the beam splitter and directed toward the compound lens objective, then through the window and focused on the point of interest. Raman scattered light is then collected by the compound lens objective and directed through the beam splitter to a mirror. A device for analyzing the light, such as a monochrometer, is coupled to the mirror.
Raman Spectroscopy for Chemical Analysis
Richard L. McCreery
Many scientists have a passing familiarity with Raman spectroscopy and those of us who have tried using it, say 15 years ago, to identify chemical groups were probably disappointed. At the time, a long recording time and poor signal\\/noise ratios did not inspire strong recommendations for chemical analysis. This was disappointing because there was always a deep-seated feeling that here
Heterodyne laser spectroscopy system
Wyeth, R.W.; Paisner, J.A.; Story, T.
A heterodyne laser spectroscopy system utilizes laser heterodyne techniques for purposes of laser isotope separation spectroscopy, vapor diagnostics, processing of precise laser frequency offsets from a reference frequency and the like, and provides spectral analysis of a laser beam.
Semiconductors investigated by time resolved Raman absorption and photoluminescence spectroscopy using femtosecond and picosecond laser techniques
R. R. Alfano; A. G. Doukas
We report on the research performed during the period 1982-1983 under the auspices of AFOSR. The research effort follows two directions: (1) laser development: subpicosecond laser, application of anti-resonant cavity to Nd:glass, study of the emerald laser, and study of a new mode-locking dye for shorter pulses. (2) Time-resolved fluorescence and absorption studies of CdCr2Se4, GaAs and Ga(0,5)In(0.5)P with the
Raman scattering spectroscopy for explosives identification
NASA Astrophysics Data System (ADS)
Nagli, L.; Gaft, M.
Real time detection and identification of explosives at a standoff distance is a major issue in efforts to develop defense against so-called Improvised Explosive Devices (IED). It is recognized that the only technique, which is potentially capable to standoff detection of minimal amounts of explosives is laser-based spectroscopy. LDS technique belongs to trace detection, namely to its micro-particles variety. We applied gated Raman and time-resolved luminescence spectroscopy for detection of main explosive materials, both factory and homemade. Raman system was developed and tested by LDS for field remote detection and identification of minimal amounts of explosives on relevant surfaces at a distance of up to 30 meters.
Raman spectroscopy of thin films
NASA Astrophysics Data System (ADS)
Burgess, James Shaw
Raman spectroscopy was used in conjunction with x-ray diffraction and x-ray photoelectron spectroscopy to elucidate structural and compositional information on a variety of samples. Raman was used on the unique La 2NiMnO6 mixed double perovskite which is a member of the LaMnO3 family of perovskites and has multiferroic properties. Raman was also used on nanodiamond films as well as some boron-doped carbon compounds. Finally, Raman was used to identify metal-dendrimer bonds that have previously been overlooked. Vibrational modes for La2NiMnO6 were ascribed by comparing spectra with that for LaMnO3 bulk and thin film spectra. The two most prominent modes were labeled as an asymmetric stretch (A g) centered around 535 cm-1 and a symmetric stretch (B g) centered around 678 cm. The heteroepitaxial quality of La2NiMnO 6 films on SrTiO3 (100) and LaAlO3 (100) substrates were examined using the Raman microscope by way of depth profile experiments and by varying the thickness of the films. It was found that thin films (10 nm) had much greater strain on the LaAlO3 substrate than on the SrTiO3 substrate by examining the shifts of the Ag and the Bg modes from their bulk positions. Changes in the unit cell owing to the presence of oxygen defects were also monitored using Raman spectroscopy. It was found that the Ag and Bg modes shifted between samples formed with different oxygen partial pressures. These shifts could be correlated to changes in the symmetry of the manganese centers due to oxygen defects. Raman spectroscopy was used to examine the structural and compositional characteristics of carbon materials. Nanocrystalline diamond coated cutting tools were examined using the Raman Microscope. Impact, abrasion, and depth profile experiments indicated that delamination was the primary cause of film failure in these systems. Boron doped material of interest as catalyst supports were also examined. Monitoring of the G-mode and intensities of the D- and G-modes indicated that boron was successfully introduced into both a bulk powder fabricated in a quartz furnace using a BCl3/C6H 6 precursor and for a thin film (30 nm) deposited in a vacuum chamber using d.c. magnetron cosputtering. In addition to Raman, x-ray diffraction and x-ray photoelectron spectroscopy were used to verify boron-doping of the materials. Generation 4 Poly(amidoamine) dendrimers were used to form platinum and cobalt nanoparticles to form dendrimer-encapsulated nanoparticles (DENs). It was seen using both Raman and infrared spectroscopy that these metals bonded with the dendrimers after reduction. These studies highlight the efficacy of Raman in the study of a wide variety of materials to obtain both compositional and structural information.
Semiconductors investigated by time resolved Raman absorption and photoluminescence spectroscopy using femtosecond and picosecond laser techniques
NASA Astrophysics Data System (ADS)
Alfano, R. R.; Doukas, A. G.
We report on the research performed during the period 1982-1983 under the auspices of AFOSR. The research effort follows two directions: (1) laser development: subpicosecond laser, application of anti-resonant cavity to Nd:glass, study of the emerald laser, and study of a new mode-locking dye for shorter pulses. (2) Time-resolved fluorescence and absorption studies of CdCr2Se4, GaAs and Ga(0,5)In(0.5)P with the goal to understand the interaction and kinetics of photogenerated carriers and basic assignments of the valence-conduction band transitions (CdCr2Se4). We have also investigated the dynamics of semi-insulating CdSe. Finally we have continued the research on radiation damage (neutrons and protons) in CdSe and GaAs.
The application of surface-enhanced Raman spectroscopy for the detection of excitatory amino acidsĀ
O'Neal, Dennis Patrick Doucet
enhanced Raman spectroscopy (SERS) on aqueous silver colloids. This study examines methods to monitor the colloidal reactions for the calibration of the enhancement observed. Thirty second Raman spectral scans were taken utilizing a 50 mW argon laser...
Raman spectroscopy of bone metastasis
NASA Astrophysics Data System (ADS)
Esmonde-White, Karen A.; Sottnik, Joseph; Morris, Michael; Keller, Evan
Raman spectroscopy of bone has been used to characterize chemical changes occurring in diseases such as osteoporosis, osteoarthritis and osteomyelitis. Metastasis of cancer into bone causes changes to bone quality that are similar to those observed in osteoporosis, such as decreased bone strength, but with an accelerated timeframe. In particular, osteolytic (bone degrading) lesions in bone metastasis have a marked effect on patient quality of life because of increased risk of fractures, pain, and hypercalcemia. We use Raman spectroscopy to examine bone from two different mouse models of osteolytic bone metastasis. Raman spectroscopy measures physicochemical information which cannot be obtained through standard biochemical and histological measurements. This study was reviewed and approved by the University of Michigan University Committee on the Care and Use of Animals. Two mouse models of prostate cancer bone metastasis, RM1 (n=3) and PC3-luc (n=4) were examined. Tibiae were injected with RM1 or PC3-luc cancer cells, while the contralateral tibiae received a placebo injection for use as controls. After 2 weeks of incubation, the mice were sacrificed and the tibiae were examined by Raman microspectroscopy (?=785 nm). Spectroscopic markers corresponding to mineral stoichiometry, bone mineralization, and mineral crystallinity were compared in spectra from the cancerous and control tibiae. X-ray imaging of the tibia confirmed extensive osteolysis in the RM1 mice, with tumor invasion into adjoining soft tissue and moderate osteolysis in the PC3-luc mice. Raman spectroscopic markers indicate that osteolytic lesions are less mineralized than normal bone tissue, with an altered mineral stoichiometry and crystallinity.
Wavelength dependent resonance Raman band intensity of broadband stimulated Raman spectroscopy of malachite green in ethanol.
Cen, Qiongyan; He, Yuhan; Xu, Mei; Wang, Jingjing; Wang, Zhaohui
Resonance broadband stimulated Raman spectroscopy of malachite green in ethanol has been performed. With a tuning picosecond visible laser source and a broadband Raman probe, the Raman gain and loss spectra have been measured simultaneously. By scanning the Raman pump across the first absorption band of the molecule, we found that the resonant Raman bands could be only seen when the pump laser tuned in the range of the red edge of the S1?S0 transition. Dispersive lineshapes of resonant Raman bands have been observed in the Raman loss spectra, while the line shape is normal (same as spontaneous Raman) in the Raman gain spectra. Although, the resonant bands in the loss spectrum are usually stronger than that in the gain spectrum, the band intensities of both loss and gain linearly increase with the pump energy. The relative magnitude of each corresponding resonant band in the Raman loss and gain varies with the pump wavelength. Mode specified Raman excitation profiles have been obtained through broadband stimulated Raman measurement. PMID:25796242
Development and deployment of a precision underwater positioning system for in situ laser Raman spectroscopy in the deep ocean
NASA Astrophysics Data System (ADS)
White, Sheri N.; Kirkwood, William; Sherman, Alana; Brown, Mark; Henthorn, Richard; Salamy, Karen; Walz, Peter; Peltzer, Edward T.; Brewer, Peter G.
The field of ocean geochemistry has recently been expanded to include in situ laser Raman spectroscopic measurements in the deep ocean. While this technique has proved to be successful for transparent targets, such as fluids and gases, difficulty exists in using deep submergence vehicle manipulators to position and control the very small laser spot with respect to opaque samples of interest, such as many rocks, minerals, bacterial mats, and seafloor gas hydrates. We have developed, tested, and successfully deployed by remotely operated vehicle (ROV) a precision underwater positioner (PUP) which provides the stability and precision movement required to perform spectroscopic measurements using the Deep Ocean Raman In situ Spectrometer (DORISS) instrument on opaque targets in the deep ocean for geochemical research. The positioner is also adaptable to other sensors, such as electrodes, which require precise control and positioning on the seafloor. PUP is capable of translating the DORISS optical head with a precision of 0.1 mm in three dimensions over a range of at least 15 cm, at depths up to 4000 m, and under the normal range of oceanic conditions (T, P, current velocity). The positioner is controlled, and spectra are obtained, in real time via Ethernet by scientists aboard the surface vessel. This capability has allowed us to acquire high quality Raman spectra of targets such as rocks, shells, and gas hydrates on the seafloor, including the ability to scan the laser spot across a rock surface in sub-millimeter increments to identify the constituent mineral grains. These developments have greatly enhanced the ability to obtain in situ Raman spectra on the seafloor from an enormous range of specimens.
Transcutaneous Raman Spectroscopy of Bone
NASA Astrophysics Data System (ADS)
Maher, Jason R.
Clinical diagnoses of bone health and fracture risk typically rely upon measurements of bone density or structure, but the strength of a bone is also dependent upon its chemical composition. One technology that has been used extensively in ex vivo, exposed-bone studies to measure the chemical composition of bone is Raman spectroscopy. This spectroscopic technique provides chemical information about a sample by probing its molecular vibrations. In the case of bone tissue, Raman spectra provide chemical information about both the inorganic mineral and organic matrix components, which each contribute to bone strength. To explore the relationship between bone strength and chemical composition, our laboratory has contributed to ex vivo, exposed-bone animal studies of rheumatoid arthritis, glucocorticoid-induced osteoporosis, and prolonged lead exposure. All of these studies suggest that Raman-based predictions of biomechanical strength may be more accurate than those produced by the clinically-used parameter of bone mineral density. The utility of Raman spectroscopy in ex vivo, exposed-bone studies has inspired attempts to perform bone spectroscopy transcutaneously. Although the results are promising, further advancements are necessary to make non-invasive, in vivo measurements of bone that are of sufficient quality to generate accurate predictions of fracture risk. In order to separate the signals from bone and soft tissue that contribute to a transcutaneous measurement, we developed an overconstrained extraction algorithm that is based upon fitting with spectral libraries derived from separately-acquired measurements of the underlying tissue components. This approach allows for accurate spectral unmixing despite the fact that similar chemical components (e.g., type I collagen) are present in both soft tissue and bone and was applied to experimental data in order to transcutaneously detect, to our knowledge for the first time, age- and disease-related spectral differences in murine bone.
Power scaling of Raman fiber lasers
NASA Astrophysics Data System (ADS)
Feng, Yan; Zhang, Lei; Jiang, Huawei
Raman fiber laser is an efficient way to expand the spectral coverage of fiber lasers. In recent years, output power of Raman fiber laser has been scaled quickly. There is a great potential in further power scaling, technical innovations, and scientific applications. An integrated ytterbium-Raman fiber amplifier architecture was proposed, which allows power scaling of Raman fiber laser to over kilowatt and more. Hundred watt level single frequency Raman fiber amplifier was achieved, which allows the generation of high power sodium guide star laser. New scheme of cladding pumped Raman fiber laser is studied in order to improve the brightness enhancement. Furthermore, possible application in spectral beam combing is discussed.
Raman spectroscopy for diagnosis of glioblastoma multiforme
NASA Astrophysics Data System (ADS)
Clary, Candace Elise
Glioblastoma multiforme (GBM), the most common and most fatal malignant brain tumor, is highly infiltrative and incurable. Although improved prognosis has been demonstrated by surgically resecting the bulk tumor, a lack of clear borders at the tumor margins complicates the selection decision during surgery. This dissertation investigates the potential of Raman spectroscopy for distinguishing between normal and malignant brain tissue and sets the groundwork for a surgical diagnostic guide for resection of gross malignant gliomas. These studies revealed that Raman spectroscopy was capable of discriminating between normal scid mouse brain tissue and human xenograft tumors induced in those mice. The spectra of normal and malignant tissue were normalized by dividing by the respective magnitudes of the peaks near 1440 cm -1. Spectral differences include the shape of the broad peaks near 1440 cm-1 and 1660 cm-1 and the relative magnitudes of the peaks at 1264 cm-1, 1287 cm-1, 1297 cm-1, 1556 cm -1, 1586 cm-1, 1614 cm-1, and 1683 cm-1. From these studies emerged questions regarding how to objectively normalize and compare spectra for future automation. Some differences in the Raman spectra were shown to be inherent in the disease states of the cells themselves via differences in the Raman spectra of normal human astrocytes in culture and cultured cells derived from GBM tumors. The spectra of astrocytes and glioma cells were normalized by dividing by the respective magnitudes of the peaks near 1450 cm-1. The differences between the Raman spectra of normal and transformed cells include the ratio of the 1450 cm-1/1650 cm-1 peaks and the relative magnitudes of the peaks at 1181 cm-1, 1191 cm-1, 1225 cm-1, 1263 cm -1, 1300 cm-1, 1336 cm-1, 1477 cm-1, 1494 cm-1, and 1695 cm -1. Previous Raman spectroscopic studies of biological cells have shown that the magnitude of the Raman signal decreases over time, indicating sample damage. Cells exposed to laser excitation at similar power densities were evaluated in terms of mitochondrial oxidative/reductive activity as well as protein, RNA, and DNA syntheses. Although cell death was not significant, the cells' abilities to synthesize DNA, RNA, and protein were profoundly affected by the laser irradiation.
Raman accumulator as a fusion laser driver
George, E. Victor (Livermore, CA); Swingle, James C. (Livermore, CA)
Apparatus for simultaneous laser pulse amplification and compression, using multiple pass Raman scattering in one Raman cell and pulse switchout from the optical cavity through use of a dichroic device associated with the Raman cell.
ExoMars Raman laser spectrometer breadboard overview
E. DĒaz; A. G. Moral; C. P. Canora; G. Ramos; O. Barcos; J. A. R. Prieto; I. B. Hutchinson; R. Ingley; M. Colombo; R. Canchal; B. Dßvila; J. A. R. Manfredi; A. Jimķnez; P. Gallego; J. Pla; R. Margoillķs; F. Rull; A. Sansano; G. L¾pez; A. Catalß; C. Tato
The Raman Laser Spectrometer (RLS) is one of the Pasteur Payload instruments, within the ESA's Aurora Exploration Programme, ExoMars mission. The RLS Instrument will perform Raman spectroscopy on crushed powdered samples deposited on a small container after crushing the cores obtained by the Rover's drill system. In response to ESA requirements for delta-PDR to be held in mid 2012, an
Improved accuracy of quantification of analytes in human body fluids by near-IR laser Raman spectroscopy with new algorithms
NASA Astrophysics Data System (ADS)
Qu, Jianan Y.; Yau, On L.; Yau, SzeFong M.
Near infrared Raman spectroscopy has been successfully used to analyze ethanol and acetaminophen in human urine samples quantitatively. The new algorithms incorporating the intrinsic spectrum of the analyte of interest into the multivariate calibration were examined to improve the accuracy of the predicted concentrations. Comparing with commonly used partial least squares calibration, it was found that the methods using the intrinsic spectrum of the analyte of interest always achieved much higher accuracy, particularly when the interference from other undesired chemicals in the samples are severe.
In Vivo Analysis of Laser Preconditioning in Incisional Wound Healing of Wild-Type and HSP70 Knockout Mice With Raman Spectroscopy
Makowski, Alexander J.; Davidson, Jeffrey M.; Mahadevan-Jansen, Anita; Jansen, E. Duco
Background and Objective Laser preconditioning augments incisional wound healing by reducing scar tissue and increasing maximum tensile load of the healed wound [.Wilmink et al. (2009) J Invest Dermatol 129(1): 205¢216]. Recent studies have optimized treatments or confirmed results using HSP70 as a biomarker. Under the hypothesis that HSP70 plays a role in reported results and to better understand the downstream effects of laser preconditioning, this study utilized a probe-based Raman spectroscopy (RS) system to achieve an in vivo, spatiotemporal biochemical profile of murine skin incisional wounds as a function of laser preconditioning and the presence of HSP70. Study Design/Materials and Methods A total of 19 wild-type (WT) and HSP70 knockout (HSP70?/?) C57BL/ 6 mice underwent normal and laser preconditioned incisional wounds. Laser thermal preconditioning was conducted via previously established protocol (? = 1.85 Ąm, H0 =7.64 mJ/cm2 per pulse, spot diameter = 5 mm, Rep. rate = 50 Hz, ?p = 2 milliseconds, exposure time = 10 minutes) with an Aculight Renoir diode laser, with tissue temperature confirmed by real-time infrared camera measurements. Wound-healing progression was quantified by daily collection of a spatial distribution of Raman spectra. The results of RS findings were then qualified using standard histology and polarization microscopy. Results Raman spectra yielded significant differences (t-test; ? =0.05) in several known biochemical peaks between WT and HSP70 (?/?) mice on wounds and in adjacent tissue early in the wound-healing process. Analysis of peak ratios implied (i) an increase in protein configuration in and surrounding the wound in WT mice, and (ii) an increased cellular trend in WT mice that was prolonged due to laser treatment. Polarization microscopy confirmed that laser treated WT mice showed increased heterogeneity in collagen orientation. Conclusions The data herein supports the theory that HSP70 is involved in normal skin protein configuration and the cellularity of early wound healing. Laser preconditioning extends cellular trends in the presence of HSP70. Despite study limitations, RS provided a non-invasive method for quantifying temporal trends in altered wound healing, narrowing candidates and design for future studies with clinically applicable instrumentation. PMID:22275297
Proximal and point detection of contaminated surfaces using Raman spectroscopy
NASA Astrophysics Data System (ADS)
Guicheteau, Jason A.; Christesen, Steven D.; Tripathi, Ashish; Emmons, Erik D.; Wilcox, Phillip G.; Emge, Darren K.; Pardoe, Ian J.; Fountain, Augustus W., III
We are actively investigating the use of Raman spectroscopy for proximal standoff detection of chemicals and explosive materials on surfaces. These studies include Raman Chemical Imaging of contaminated fingerprints for forensic attribution and the assessments of commercial handheld or portable Raman instruments operating with near-infrared (IR) as well as ultraviolet (UV) laser excitation specifically developed for on-the-move reconnaissance of chemical contamination. As part of these efforts, we have measured the Raman cross sections of chemical agents, toxic industrial chemicals, and explosives from the UV to NIR. We have also measured and modeled the effect interrogation angle has on the Raman return from droplets on man-made surfaces. Realistic droplet distributions have been modeled and tested against variations in surface scan patterns and laser spot size for determining the optimum scan characteristics for detection of relevant surface contamination.
Raman Spectroscopy and Related Techniques in Biomedicine
Downes, Andrew; Elfick, Alistair
In this review we describe label-free optical spectroscopy techniques which are able to non-invasively measure the (bio)chemistry in biological systems. Raman spectroscopy uses visible or near-infrared light to measure a spectrum of vibrational bonds in seconds. Coherent anti-Stokes Raman (CARS) microscopy and stimulated Raman loss (SRL) microscopy are orders of magnitude more efficient than Raman spectroscopy, and are able to acquire high quality chemically-specific images in seconds. We discuss the benefits and limitations of all techniques, with particular emphasis on applications in biomedicineŚboth in vivo (using fiber endoscopes) and in vitro (in optical microscopes). PMID:21151763
A study on Raman Injection LaserĀ
Liu, Debin
The Raman Injection Laser is a new type of laser which is based on triply resonant stimulated Raman scattering between quantum confined states within the active region of a Quantum Cascade Laser that serves as an internal optical pump. The Raman...
Diagnostic potential of near-infrared Raman spectroscopy in the stomach: differentiating dysplasia from normal tissue
S K Teh; W Zheng; K Y Ho; M Teh; K G Yeoh; Z Huang
Raman spectroscopy is a molecular vibrational spectroscopic technique that is capable of optically probing the biomolecular changes associated with diseased transformation. The purpose of this study was to explore near-infrared (NIR) Raman spectroscopy for identifying dysplasia from normal gastric mucosa tissue. A rapid-acquisition dispersive-type NIR Raman system was utilised for tissue Raman spectroscopic measurements at 785 nm laser excitation. A
TOPICAL REVIEW: Prospects for in vivo Raman spectroscopy
NASA Astrophysics Data System (ADS)
Hanlon, E. B.; Manoharan, R.; Koo, T.-W.; Shafer, K. E.; Motz, J. T.; Fitzmaurice, M.; Kramer, J. R.; Itzkan, I.; Dasari, R. R.; Feld, M. S.
Raman spectroscopy is a potentially important clinical tool for real-time diagnosis of disease and in situ evaluation of living tissue. The purpose of this article is to review the biological and physical basis of Raman spectroscopy of tissue, to assess the current status of the field and to explore future directions. The principles of Raman spectroscopy and the molecular level information it provides are explained. An overview of the evolution of Raman spectroscopic techniques in biology and medicine, from early investigations using visible laser excitation to present-day technology based on near-infrared laser excitation and charge-coupled device array detection, is presented. State-of-the-art Raman spectrometer systems for research laboratory and clinical settings are described. Modern methods of multivariate spectral analysis for extracting diagnostic, chemical and morphological information are reviewed. Several in-depth applications are presented to illustrate the methods of collecting, processing and analysing data, as well as the range of medical applications under study. Finally, the issues to be addressed in implementing Raman spectroscopy in various clinical applications, as well as some long-term directions for future study, are discussed.
Laser Raman and fluorescence microprobing techniques
NASA Astrophysics Data System (ADS)
Wallart, F.; Dhamelincourt, P.
The increasing need for non-destructive analytical methods and the developments in instrumentation during the past decade have greatly stimulated interest in the use of spontaneous Raman scattering for molecular microanalysis, but only recently has this potential been realized. The purpose of this paper is to give a brief review of the fundamentals as well as the methodology of laser Raman micro-spectroscopy and to demonstrate the practical uses of the technique in several major application areas. Emphasis is also put on the advantages of employing modern multi-channel detection techniques that offer a significant improvement in performance. Lastly, more recently, these techniques have led to the development of a very sensitive laser microfluorometer which offers in biology great possibilities for investigations at the single living cell level.
Ultrafast surface-enhanced Raman spectroscopy.
Keller, Emily L; Brandt, Nathaniel C; Cassabaum, Alyssa A; Frontiera, Renee R
Ultrafast surface-enhanced Raman spectroscopy (SERS) with pico- and femtosecond time resolution has the ability to elucidate the mechanisms by which plasmons mediate chemical reactions. Here we review three important technological advances in these new methodologies, and discuss their prospects for applications in areas including plasmon-induced chemistry and sensing at very low limits of detection. Surface enhancement, arising from plasmonic materials, has been successfully incorporated with stimulated Raman techniques such as femtosecond stimulated Raman spectroscopy (FSRS) and coherent anti-Stokes Raman spectroscopy (CARS). These techniques are capable of time-resolved measurement on the femtosecond and picosecond time scale and can be used to follow the dynamics of molecules reacting near plasmonic surfaces. We discuss the potential application of ultrafast SERS techniques to probe plasmon-mediated processes, such as H2 dissociation and solar steam production. Additionally, we discuss the possibilities for high sensitivity SERS sensing using these stimulated Raman spectroscopies. PMID:26016991
Raman and SHG spectroscopy of ligand-stabilized Si nanocrystals
Shvets, Gennady
Raman and SHG spectroscopy of ligand-stabilized Si nanocrystals Op properties originate from a combination of quantum confinement and Si NC/SiO2 interfaces. Si nanocrystals nanocrystals embedded in SiO2 Pavesi et al., Nature 408, 440 (2000) Si lasers? Walters et al, Nature Mat. 4
Gated Raman Spectroscopy of Twisted Bilayer Graphene
NASA Astrophysics Data System (ADS)
Huang, Shengqiang; Chattrakun, Kanokporn; Yankowitz, Matthew; Sandhu, Arvinder; Leroy, Brian
The interaction of charge carriers with lattice vibrations in graphene exhibits many intriguing physical phenomena. Raman spectroscopy is a powerful non-destructive technique to probe these interactions. In twisted bilayer graphene, the electronic band structure and phonon dispersion depend on the rotation angle between the layers. Here we present a systematic Raman spectroscopy study of twisted bilayer graphene, using a 532 nm laser, with controllable charge densities up to 2 ū1013cm-2. The twist angle is first identified by the observation of a moire pattern in STM measurements. In the angle range between 5 and 8 degrees, the R' peak softens and weakens with increasing charge density. Near 12 degrees, the G peak is enhanced due to the increased density of states in twisted bilayer graphene. However, the G peak area quickly decreases with increasing charge density. Lastly, we observed several unusual effects for the G peak for all angles from 2 to 10 degrees as a function of increasing charge density. We found that the G peak broadened, split and oscillated in position. All these results demonstrate that twisted bilayer graphene has rich optoelectronic properties.
Technology Transfer Automated Retrieval System (TEKTRAN)
The classification of cereals using near-infrared Fourier transform Raman (NIR-FT/Raman) spectroscopy was accomplished. A total of 120 cereal based food samples were prepared and ground. Samples were scanned on a Nicolet Raman instrument with a 1064 nm (NIR) excitation laser using 500mW of power and...
Raman-induced Kerr-effect dual-comb spectroscopy
Ideguchi, Takuro; Guelachvili, Guy; Hõnsch, Theodor W; Picquķ, Nathalie
We report on the first demonstration of nonlinear dual-frequency-comb spectroscopy. In multi-heterodyne femtosecond Raman-induced Kerr-effect spectroscopy, the Raman gain resulting from the coherent excitation of molecular vibrations by a spectrally-narrow pump is imprinted onto the femtosecond laser frequency comb probe spectrum. The birefringence signal induced by the nonlinear interaction of these beams and the sample is heterodyned against a frequency comb local oscillator with a repetition frequency slightly different from that of the comb probe. Such time-domain interference provides multiplex access to the phase and amplitude Raman spectra over a broad spectral bandwidth within a short measurement time. Experimental demonstration, at a spectral resolution of 200 GHz, a measurement time of 293 {\\mu}s and a sensitivity of 10^-6, is given on liquid samples exhibiting a C-H stretch Raman shift.
Raman spectroscopy: the gateway into tomorrow's virology.
Lambert, Phelps J; Whitman, Audy G; Dyson, Ossie F; Akula, Shaw M
In the molecular world, researchers act as detectives working hard to unravel the mysteries surrounding cells. One of the researchers' greatest tools in this endeavor has been Raman spectroscopy. Raman spectroscopy is a spectroscopic technique that measures the unique Raman spectra for every type of biological molecule. As such, Raman spectroscopy has the potential to provide scientists with a library of spectra that can be used to unravel the makeup of an unknown molecule. However, this technique is limited in that it is not able to manipulate particular structures without disturbing their unique environment. Recently, a novel technology that combines Raman spectroscopy with optical tweezers, termed Raman tweezers, evades this problem due to its ability to manipulate a sample without physical contact. As such, Raman tweezers has the potential to become an incredibly effective diagnostic tool for differentially distinguishing tissue, and therefore holds great promise in the field of virology for distinguishing between various virally infected cells. This review provides an introduction for a virologist into the world of spectroscopy and explores many of the potential applications of Raman tweezers in virology. PMID:16805914
Investigation of the chemical stability of the laser-induced fluorescence tracers acetone, diethylketone, and toluene under IC engine conditions using Raman spectroscopy.
Trost, Johannes; Zigan, Lars; Eichmann, Simone C; Seeger, Thomas; Leipertz, Alfred
This paper reports on an investigation of the chemical stability of the common laser-induced fluorescence (LIF) tracers acetone, diethylketone, and toluene. Stability is analyzed using linear Raman spectroscopy inside a heated pressure cell with optical access, which is used for the LIF calibration of these tracers. The measurements examine the influence of temperature, pressure, and residence time on tracer oxidation, which occurs without a rise in temperature or pressure inside the cell, highlighting the need for optical detection. A comparison between the three different tracers shows large differences, with diethylketone having the lowest and toluene by far the highest stability. An analysis of the sensitivity of the measurement shows that the detection limit of the oxidized tracer is well below 3% molar fraction, which is typical for LIF applications in combustion devices such as internal combustion (IC) engines. Furthermore, the effect on the LIF signal intensity is examined in an isothermal turbulent mixing study. PMID:24085091
Laser Raman Spectrum of Triglycine Sulfate
Armen Galustian
The laser Raman spectrum of ferroelectric triglycine sulfate has been determined by the use of an argon ion gas laser. The observed Raman lines are compared with reported assignments in the literature by Taurel and Krishnan, Determination of depolarization ratio of the sulfate line at 980 cm shows that the Raman band is highly polarizable and the molecular vibration is
Probing the Ni(111)-graphene interface using Raman spectroscopy
NASA Astrophysics Data System (ADS)
Cheng, Guangjun; Calizo, Irene; Hight Walker, Angela
Theoretical simulations have shown that due to the hybridization of Ni d-electrons with the ?-orbitals of graphene, graphene phonon dispersion is significantly altered (Nano Lett, 2010, 10, 4335-4340). There is no Raman signal from graphene on Ni(111) due to the suppression of the Kohn anomaly. In our work, we deposit a Ni thin film by thermal evaporation onto mechanically exfoliated graphene, few-layer graphene (FLG), and graphite, and probe the Ni-graphene interface using Raman spectroscopy. When the sample is annealed in forming gas, a Ni(111) thin film is produced on graphene, FLG, and graphite. We observe the disappearance of Raman signals from graphene underneath Ni(111) when using low laser power and the re-appearance of the Raman signals from the graphene with a higher power excitation laser. This work provides direct experimental evidence for the strong interaction between Ni(111) and graphene.
Ultimate sensing resolution of water temperature by remote Raman spectroscopy.
Oh, Myoung-Kyu; Kang, Hoonsoo; Yu, Nan Ei; Kim, Bok Hyeon; Kim, JoonHeon; Lee, JoonSeok; Hyung, Gi Woo
The limit of sensing resolution of water temperature by remote Raman spectroscopy was investigated experimentally. A remote Raman spectrometer, which employed a telescope of 20Ācm in pupil size and the second harmonic generation (SHG) of a Q-switched Nd:YAG laser, was used for the measurement. By analyzing the broad O-H stretching Raman band located near 3500??cm-1, a parameter which is in second-order polynomial relation with water temperature from 13░C to 50░C could be obtained. The resolution of our remote Raman temperature sensor was better than ▒0.2░C with measurement time shorter than 10Ās. The influence of the Raman signal's signal-to-noise ratio on the resolution and salinity effect on the accuracy of temperature sensing were also investigated. PMID:25967170
Commercial anesthetic-respiratory gas monitor utilizing Raman spectroscopy
NASA Astrophysics Data System (ADS)
Gregonis, Donald E.; Van Wagenen, Richard A.; Coleman, D.; Mitchell, John R.
A commercial gas monitor which utilizes Raman Spectroscopy has been developed to monitor anesthetic and respiratory gases in the hospital operating room. The instrument measures all molecular gases administered by the anesthesiologist in real time with fast response of breath waveform. These gases include carbon dioxide, nitrous oxide, oxygen, nitrogen and various volatile halogenated organic anesthetics, e.g. halothane, isoflurane, enflurane, sevoflurane and desflurane. The key feature of this instrument which allows it to produce adequate Raman signals with a low cost argon ion laser is measuring these gases inside the laser resonant cavity.
Epi-detected hybrid coherent Raman micro-spectroscopy
Jiahui Peng; Alexei V. Sokolov
We demonstrate efficient epi-detected coherent Raman micro-spectroscopy using a simple laser system based on a femtosecond mode-locked oscillator. In our experiment, the non-resonant background is eliminated by using a hybrid technique, which combines laser pulse shaping and timing with frequency-resolved detection, and is based on the different temporal behavior of parametric and nonparametric processes. We perform careful analysis to make
Raman spectroscopy using a spatial heterodyne spectrometer: proof of concept.
Gomer, Nathaniel R; Gordon, Christopher M; Lucey, Paul; Sharma, Shiv K; Carter, J Chance; Angel, S Michael
The use of a spatial heterodyne interferometer-based spectrometer (SHS) for Raman spectroscopy is described. The motivation for this work is to develop a small, rugged, high-resolution ultraviolet (UV) Raman spectrometer that is compatible with pulsed laser sources and that is suitable for planetary space missions. UV Raman is a particular technical challenge for space applications because dispersive (grating) approaches require large spectrographs and very narrow slits to achieve the spectral resolution required to maximize the potential of Raman spectroscopy. The heterodyne approach of the SHS has only a weak coupling of resolution and throughput, so a high-resolution UV SHS can both be small and employ a wide slit to maximize throughput. The SHS measures all optical path differences in its interferogram simultaneously with a detector array, so the technique is compatible with gated detection using pulsed lasers, important to reject ambient background and mitigate fluorescence (already low in the UV) that might be encountered on a planetary surface where samples are uncontrolled. The SHS has no moving parts, and as the spectrum is heterodyned around the laser wavelength, it is particularly suitable for Raman measurements. In this preliminary report we demonstrate the ability to measure visible wavelength Raman spectra of liquid and solid materials using an SHS Raman spectrometer and a visible laser. Spectral resolution and bandpass are also discussed. Separation of anti-Stokes and Stokes Raman bands is demonstrated using two different approaches. Finally spectral bandpass doubling is demonstrated by forming an interference pattern in both directions on the ICCD detector followed by analysis using a two-dimensional Fourier transform. PMID:21819774
Molecular velocimetry using stimulated Raman spectroscopy
NASA Technical Reports Server (NTRS)
Exton, R. J.; Hillard, M. E.
Molecular flow velocity of N2 was measured in a supersonic wind tunnel using inverse Raman spectroscopy. This technique employs the large Doppler shift exhibited by the molecules when the pump and probe laser beams are counter-propagating (backward scattering). A retrometer system is employed to yield a vibration-free optical configuration which has the additional advantage of obtaining both the forward and backward scattered spectra simultaneously. The linebreadths and their relative Doppler shift can be used to determine the static pressure, translational temperature, and molecular flow velocity. A demonstration of the concept was performed in a supersonic wind tunnel and included: (1) measurements over the Mach number range 2.50 to 4.63; (2) static pressure measurements (at Mach 2.50) corresponding to a Reynolds number per foot range of 1 to 5 x 10 to the 6th power; and (3) measurements behind the shock wave of a flat plate model.
Foundations of Laser Spectroscopy
Stig Stenholm; John E. Thomas
Presents the theoretical foundations of steady state laser spectroscopy at an elementary level. General foundations and specific features of nonlinear effects are summarized, laser operation and laser spectroscopy are presented, and laser field fluctuations and the effects of field quantization are dealt with. It gives detailed derivations so the reader can work out all results. References are collected in separate
Sequentially shifted excitation Raman spectroscopy: novel algorithm and instrumentation for fluorescence-free Raman spectroscopy in spectral space.
Cooper, John B; Abdelkader, Mohamed; Wise, Kent L
A novel Raman spectrometer is presented in a handheld format. The spectrometer utilizes a temperature-controlled, distributed Bragg reflector diode laser, which allows the instrument to operate in a sequentially shifted excitation mode to eliminate fluorescence backgrounds, fixed pattern noise, and room lights, while keeping the Raman data in true spectral space. The cost-efficient design of the instrument allows rapid acquisition of shifted excitation data with a shift time penalty of less than 2 s. The Raman data are extracted from the shifted excitation spectra using a novel algorithm that is typically three orders of magnitude faster than conventional shifted-excitation algorithms operating in spectral space. The superiority of the instrument and algorithm in terms of background removal and signal-to-noise ratio is demonstrated by comparison to FT-Raman, standard deviation spectra, shifted excitation Raman difference spectroscopy (SERDS), and conventional multiple-shift excitation methods. PMID:23876736
Nondestructive evaluation of internal maturity of tomatoes using spatially offset Raman spectroscopy
Technology Transfer Automated Retrieval System (TEKTRAN)
This research explored the use of spatially offset Raman spectroscopy (SORS) for nondestructive evaluation of internal maturity of tomatoes. A Raman spectroscopy system using a 785 nm laser was developed to collect spatially-offset spectra in the wavenumber range of 200 ¢ 2500. The SORS measuremen...
Scanning angle Raman spectroscopy: Investigation of Raman scatter enhancement techniques for chemical analysis
Meyer, Matthew W. [Ames Laboratory
This thesis outlines advancements in Raman scatter enhancement techniques by applying evanescent fields, standing-waves (waveguides) and surface enhancements to increase the generated mean square electric field, which is directly related to the intensity of Raman scattering. These techniques are accomplished by employing scanning angle Raman spectroscopy and surface enhanced Raman spectroscopy. A 1064 nm multichannel Raman spectrometer is discussed for chemical analysis of lignin. Extending dispersive multichannel Raman spectroscopy to 1064 nm reduces the fluorescence interference that can mask the weaker Raman scattering. Overall, these techniques help address the major obstacles in Raman spectroscopy for chemical analysis, which include the inherently weak Raman cross section and susceptibility to fluorescence interference.
Noninvasive glucose sensing by transcutaneous Raman spectroscopy
Shih, Wei-Chuan
We present the development of a transcutaneous Raman spectroscopy system and analysis algorithm for noninvasive glucose sensing. The instrument and algorithm were tested in a preclinical study in which a dog model was used. ...
Raman spectroscopy for noninvasive glucose measurements
Enejder, Annika M. K.
We report the first successful study of the use of Raman spectroscopy for quantitative, noninvasive (ōtranscutaneousö) measurement of blood analytes, using glucose as an example. As an initial evaluation of the ability of ...
Raman beam cleanup of excimer laser radiation
Lou Qihong; Huo Yunsheng; Dong Jinxing; Ding Zean; Wei Yunrong (Shanghai Institute of Optics and Fine Mechanics, Academia Sinica (CN))
Stimulated Raman scattering is one of the methods to shift the UV excimer laser radiation into the specific wavelengths in the near UV and visible regions. Diffraction-limited first Stokes output can be obtained by means of Raman beam cleanup. The effects of the beam quality of the injected emission on the Raman beam cleanup was investigated in this paper. The Raman gain coefficients and the saturated parameters of a Raman amplifier were deduced for different H{sub 2} gas pressures.
Standoff detection of explosive molecules using nanosecond gated Raman spectroscopy
NASA Astrophysics Data System (ADS)
Chung, Jin Hyuk; Cho, Soo Gyeong
Recently, improvised explosive device (IED) has been a serious threat for many countries. One of the approaches to alleviate this threat is standoff detection of explosive molecules used in IEDs. Raman spectroscopy is a prospective method among many technologies under research to achieve this goal. It provides unique information of the target materials, through which the ingredients used in IEDs can be analyzed and identified. The main problem of standoff Raman spectroscopic detection is the large background noise hindering weak Raman signals from the target samples. Typical background noise comes from both ambient fluorescent lights indoor and sunlight outdoor whose intensities are usually much larger than that of Raman scattering from the sample. Under the proper condition using pulse laser and ICCD camera with nanosecond pulse width and gating technology, we succeed to separate and remove these background noises from Raman signals. For this experiment, we build an optical system for standoff detection of explosive molecules. We use 532 nm, 10 Hz, Q-switching Nd:YAG laser as light source, and ICCD camera triggered by laser Qswitching time with proper gate delay regarding the flight time of Raman from target materials. Our detection system is successfully applied to detect and identify more than 20 ingredients of IEDs including TNT, RDX, and HMX which are located 10 to 54 meters away from the system.
Debris of potassium-magnesium silicate glass generated by femtosecond laser-induced ablation in air: An analysis by near edge X-ray absorption spectroscopy, micro Raman and energy dispersive X-ray spectroscopy
NASA Astrophysics Data System (ADS)
Grehn, M.; Seuthe, T.; Reinhardt, F.; H÷fner, M.; Griga, N.; Eberstein, M.; Bonse, J.
The redeposited material (debris) resulting from ablation of a potassium-magnesium silicate glass upon scanning femtosecond laser pulse irradiation (130 fs, 800 nm) in air environment is investigated by means of three complementary surface analytical methods. Changes in the electronic band structure of the glass constituent Magnesium (Mg) were identified by X-ray Absorption Near Edge Structure spectroscopy (XANES) using synchrotron radiation. An up-shift of ?0.8 eV of a specific Magnesium K-edge absorption peak in the spectrum of the redeposited material along with a significant change in its leading edge position was detected. In contrast, the surface left after laser ablation exhibits a downshift of the peak position by ?0.9 eV. Both observations may be related to a change of the Mg coordinative state of the laser modified/redeposited glass material. The presence of carbon in the debris is revealed by micro Raman spectroscopy (?-RS) and was confirmed by energy dispersive X-ray spectroscopy (EDX). These observations are attributed to structural changes and chemical reactions taking place during the ablation process.
Continuous-wave stimulated Raman gain spectroscopy with cavity ringdown detection
Florian V. Englich; Yabai He; Brian J. Orr
Cavity ringdown (CRD) spectroscopy is extended for the first time from its conventional optical-absorption mode of operation\\u000a into the regime of coherent Raman spectroscopy. Continuous-wave (cw) stimulated Raman gain (SRG) spectra of the 2916.5-cm-1 ?1 rovibrational fundamental Raman band of methane (CH4) gas are measured, using tunable cw laser light at ?1544Ānm to probe ringdown decay from a rapidly swept
Imaging EGFR distribution using surface-enhanced Raman spectroscopy
NASA Astrophysics Data System (ADS)
Lucas, L.; Chen, X. K.; Smith, A.; Korbelik, M.; Zeng, H.; Lee, P. W. K.; Hewitt, K. C.
The purpose of this study is to explore the feasibility of using Surface Enhanced Raman Spectroscopy (SERS) to image the distribution of Epidermal Growth Factor Receptor (EGFR) in cells. To accomplish this task, 30 nm gold nanoparticles (AuNPs) tagged with antibodies to EGFR (1012 per ml) are incubated with cells (106 per ml) of the A431 human epidermoid carcinoma cell line and normal human bronchial epithelial (NHBE) cells. Using the 632.8 nm excitation line of a He-Ne laser, Raman spectroscopy measurements are performed using a point mapping scheme. SERS signals are observed with an overall enhancement of 4-7 orders of magnitude. Raman intensity maps of the 1480 and 1583 cm-1 peaks correlate well with the expected distribution of AuNPs and EGFR. Normal cells show little to no enhancement. The results therefore present a simple yet effective means to image EGFR over-expression.
In situ quantitative analysis of individual H 2O¢CO 2 fluid inclusions by laser Raman spectroscopy
Tristan Azbej; Matthew J. Severs; Brian G. Rusk; Robert J. Bodnar
Raman spectral parameters for the Raman ?1 (1285Ācm?1) and 2?2 (1388Ācm?1) bands for CO2 and for the O¢H stretching vibration band of H2O (3600Ācm?1) were determined in H2O¢CO2 fluid inclusions. Synthetic fluid inclusions containing 2.5 to 50Āmol% CO2 were analyzed at temperatures equal to or greater than the homogenization temperature. The results were used to develop an empirical relationship between
High Fidelity Nano-Hole Enhanced Raman Spectroscopy.
Bahns, John T; Guo, Qiti; Montgomery, Jason M; Gray, Stephen K; Jaeger, Heinrich M; Chen, Liaohai
Surface Enhanced Raman Spectroscopy (SERS) is a sensitive technique that can even detect single molecules. However, in many SERS applications, the strongly inhomogeneous distribution of intense local fields makes it very difficult for a quantitive assessment of the fidelity, or reproducibility of the signal, which limits the application of SERS. Herein we report the development of exceptionally high fidelity Hole-Enhanced Raman Spectroscopy (HERS) from ordered, two-dimensional hexagonal nanohole arrays. We take the fidelity f to be a measure of the percent deviation of the Raman peaks from measurement to measurement. Overall, area averaged fidelities for 12 gold array samples ranged from f ~ 2% - 15% for HERS using aqueous R6G molecules. Furthermore, intensity modulations of the enhanced Raman spectra were measured for the first time as a function of polarization angle. The best of these measurements, which focus on static laser spots on the sample, could be consistent with even higher fidelities than the area-averaged results. Nanohole arrays in silver provided supporting polarization measurements and a more complete enhanced Raman fingerprint for phenylalanine molecules. We also carried out finite-difference time-domain calculations to assist in the interpretation of the experiments, identifying the polarization dependence as possibly arising from hole-hole interactions. Our results represent a step towards making quantitative and reproducible enhanced Raman measurements possible and also open new avenues for a large scale source of highly uniform hot spots. PMID:20161411
Airborne chemistry coupled to Raman spectroscopy.
Santesson, Sabina; Johansson, Jonas; Taylor, Lynne S; Levander, Ia; Fox, Shannon; Sepaniak, Michael; Nilsson, Staffan
In this paper, the use of airborne chemistry (acoustically levitated drops) in combination with Raman spectroscopy is explored. We report herein the first Raman studies of crystallization processes in levitated drops and the first demonstration of surface-enhanced Raman scattering (SERS) detection in this medium. Crystallization studies on the model compounds benzamide and indomethacin resulted in the formation of two crystal modifications for each compound, suggesting that this methodology may be useful for investigation of polymorphs. SERS detection resulted in a signal enhancement of 27 000 for benzoic acid and 11 000 for rhodamine 6-G. The preliminary results presented here clearly indicate that several important applications of the combination between Raman spectroscopy and acoustic drop levitation can be expected in the future. PMID:12720359
Temporal and spatial resolution in transmission Raman spectroscopy.
Everall, Neil; Matousek, Pavel; MacLeod, Neil; Ronayne, Kate L; Clark, Ian P
Picosecond time-resolved transmission Raman data were acquired for 1 mm thick powder samples of trans-stilbene, and a Monte Carlo model was developed that can successfully model the laser and Raman pulse profiles. Photon migration broadened the incident (approximately 1 ps) probe pulse by two orders of magnitude. As expected from previous studies of Raman photon migration in backscattering mode, the transmitted Raman pulse was broader than the transmitted laser pulse and took longer to propagate through the sample. The late-arriving photons followed tortuous flight paths in excess of 50 mm on traversing the 1 mm sample. The Monte Carlo code was also used to study the spatial resolution (lateral and depth) of steady-state transmission Raman spectroscopy in the diffusion regime by examining the distribution of Raman generation positions as a function of incident beam size, sample thickness, and transport length. It was predicted that the lateral resolution should worsen linearly with sample thickness (typically the resolution was about 50% of the sample thickness), and this is an inevitable consequence of operating in the diffusion regime. The lateral resolution was better at the sample surface (essentially determined by the probe beam diameter or the collection aperture) than for buried objects, but transmission sampling was shown to be biased towards the mid-point of thick samples. Time-resolved transmission experiments should improve the lateral resolution by preferentially detecting snake photons, subject to constraints of signal-to-noise ratio. PMID:20132598
Raman Spectroscopy Using a Tilted 2D MOT
NASA Astrophysics Data System (ADS)
Kwolek, Jonathan M.; Knutson, Erin; Narducci, Frank A.
We demonstrate Raman spectroscopy using a cold and continuous beam of Rubidium atoms from a vapor-loaded, tilted two-dimensional magneto optical trap (2D MOT). The atoms emerge through a pinhole into an ultra-high vacuum chamber, and form a cold and slow moving beam of atoms with flux 109 atoms/sec with a most probable velocity of 10 m/s. The atoms travel across a set of laser beams which include an on-resonant state preparation beam, a beam tuned to drive a stimulated Raman transition, and another on-resonant readout beam. We observed Raman spectra which can include as many as 11 peaks. The width of the clock transition is consistent with the transit time of the atoms through the Raman fields. The width of the magnetic transitions is determined by laboratory magnetic noise. We have measured Rabi cycling on the clock transition using Raman beams in a co-propagating geometry by varying the laser power rather than pulse duration. Further developments will be made by introducing a momentum kick by using Raman beams in a counter-propagating geometry. Office of Naval Research.
Demonstration of directly modulated silicon Raman laser
Jalali. Bahram
Demonstration of directly modulated silicon Raman laser Ozdal Boyraz and Bahram Jalali Lett. 38, 1352-1354 (2002). 2. Ozdal Boyraz and Bahram Jalali, "Demonstration of a silicon Raman laser- 618 (2004). 10. Ozdal Boyraz, Dimitri Dimitropoulos and Bahram Jalali, "Observation of simultaneous
MicroRaman study of laser ablated GaAs
Garcia, C.; Jimenez, J.; Prieto, A.C.; Ramos, J.; Sanz, L.F.
Morphologic and structural changes induced by UV pulsed laser beams on GaAs are studied by means of surface inspection (optical interferometry) and MicroRaman spectroscopy. Crystal order and chemical composition (dopant distribution) are shown to be changed by the ablation.
Resonance Raman and Raman spectroscopy for breast cancer detection.
Liu, C-H; Zhou, Y; Sun, Y; Li, J Y; Zhou, L X; Boydston-White, S; Masilamani, V; Zhu, K; Pu, Y; Alfano, R R
Raman spectroscopy is a sensitive method to detect early changes of molecular _composition and structure that occur in lesions during carcinogenesis. The Raman spectra of normal, benign and cancerous breast tissues were investigated in vitro using a near-infrared (NIR) Raman system of 785?nm excitation and confocal micro resonance Raman system of 532?nm excitation. A total number of 491 Raman spectra were acquired from normal, benign and cancerous breast tissues taken from 15 patients. When the 785?nm excitation was used, the dominant peaks in the spectra were characteristic of the vibrations of proteins and lipids. The differences between the normal and cancerous breast tissues were observed in both the peak positions and the intensity ratios of the characteristic Raman peaks in the spectral region of 700-1800?cm(21). With 532?nm excitation, the resonance Raman (RR) spectra exhibited a robust pattern of peaks within the region of 500-4000?cm(21). The intensities of four distinct peaks at 1156, 1521, 2854 and 3013?cm(21) detected in the spectra collected from normal breast tissue were found to be stronger in comparison with those collected from cancerous breast tissue. The twelve dramatically enhanced characteristic peaks, including the enhanced amide II peak at 1548?cm(21) in the spectra collected from cancerous breast tissue, distinguished the cancerous tissue from the normal tissue. Principal component analysis (PCA) combined with support vector machine (SVM) analysis of the Raman and RR spectral data yielded a high performance in the classification of cancerous and benign lesions from normal breast tissue. PMID:23448574
Kilowatt Ytterbium-Raman fiber laser.
Zhang, Lei; Liu, Chi; Jiang, Huawei; Qi, Yunfeng; He, Bing; Zhou, Jun; Gu, Xijia; Feng, Yan
A kilowatt-level Raman fiber laser is demonstrated with an integrated Ytterbium-Raman fiber amplifier architecture. A high power Ytterbium-doped fiber master oscillator power amplifier at 1080 nm is seeded with a 1120 nm fiber laser at the same time. By this way, a kilowatt-level Raman pump laser at 1080 nm and signal laser at 1120 nm is combined in the fiber core. The subsequent power conversion from 1080 nm to 1120 nm is accomplished in a 70 m long passive fiber. A 1.28 kW all-fiber Raman amplifier at 1120 nm with an optical efficiency of 70% is demonstrated, limited only by the available pump power. To the best of our knowledge, this is the first report of Raman fiber laser with over one kilowatt output. PMID:25089467
Fourier-Transform Raman Spectroscopy Of Biological Assemblies
NASA Astrophysics Data System (ADS)
Levin, Ira W.; Lewis, E. Neil
Although the successful coupling of Raman scattered near-infrared radiation to a Michelson interferometer has recently created an outburst of intense interest in Fourier-transform (FT) Raman spectrometry," extended applications of the technique to macromolecular assemblies of biochemical and biophysical relevance have not progressed as rapidly as studies directed primarily at more conventional chemical characterizations. Since biological materials sampled with visible laser excitation sources typically emit a dominant fluorescence signal originating either from the intrinsic fluorescence of the molecular scatterer or from unrelenting contaminants, the use of near-infrared Nd:YAG laser excitation offers a convenient approach for avoiding this frequently overwhelming effect. In addition, the FT-Raman instrumentation provides a means of eliminating the deleterious resonance and decomposition effects often observed with the more accessible green and blue laser emissions. However, in choosing the incident near-infrared wavelength at, for example, 1064nm, the Raman scattered intensity decreases by factors of eighteen to forty from the Raman emissions induced by the shorter, visible excitations. Depending upon the experiment, this disadvantage is offset by the throughput and multiplex advantages afforded by the interferometric design. Thus, for most chemical systems, near-infrared FT-Raman spectroscopy, clearly provides a means for obtaining vibrational Raman spectra from samples intractable to the use of visible laser sources. In particular, for neat liquids, dilute solutions or polycrystalline materials, the ability to achieve high quality, reproducible spectra is, with moderate experience and perhaps relatively high laser powers, as straightforward as the conventional methods used to obtain Raman spectra with visible excitation and dispersive monochromators. In using near-infrared FT techniques to determine the Raman spectra of biological samples, one encounters new sets of experimental problems that may entail an initial, relatively steep learning curve. These difficulties originate particularly from the fragility of the weakly scattering aggregate paired with the dilute nature of the biochemical or cellular dispersion. Often, the Raman scattered intensity from these samples can be increased by carefully peileting the biological suspension using ultracentrifugation techniques. Since the overtone region of water, the usual medium for biological samples, absorbs radiation from both the Rayleigh signal at the exciting wavelength of the Nd:YAG laser and the longer wavelength Raman scattering from the sample, reproducible temperature measurements and temperature control become significant concerns. In these cases one appeals to internal temperature calibrations, use of deuterium oxide (D20) as a solvent (since absorptions of the laser exciting wavelength and Raman scattered photons are minimized), manipulation of incident laser spot size and the use of fiber optic bundles to carry the exciting and scattered radiation. In the present discussion we briefly cite some of the experimental approaches we have developed and experiences we have encountered in adapting near-infrared FT-Raman spectroscopy to the more challenging biophysical and biochemical systems amenable to vibrational analysis. We emphasize here the determination of the spectra of membrane assemblies and membrane related materials; in particular, we elucidate the interaction of several polyene antibiotics, including amphotericin A, amphotericin B and nystatin, with a model membrane system composed of dipalmitoylphosphatidylcholine bilayers.
Measuring Rocket Engine Temperatures with Hydrogen Raman Spectroscopy
NASA Technical Reports Server (NTRS)
Wehrmeyer, Joseph A.; Osborne, Robin J.; Trinh, Huu P.; Turner, James (Technical Monitor)
Optically accessible, high pressure, hot fire test articles are available at NASA Marshall for use in development of advanced rocket engine propellant injectors. Single laser-pulse ultraviolet (UV) Raman spectroscopy has been used in the past in these devices for analysis of high pressure H2- and CH4-fueled combustion, but relies on an independent pressure measurement in order to provide temperature information. A variation of UV Raman (High Resolution Hydrogen Raman Spectroscopy) is under development and will allow temperature measurement without the need for an independent pressure measurement, useful for flows where local pressure may not be accurately known. The technique involves the use of a spectrometer with good spectral resolution, requiring a small entrance slit for the spectrometer. The H2 Raman spectrum, when created by a narrow linewidth laser source and obtained from a good spectral resolution spectrograph, has a spectral shape related to temperature. By best-fit matching an experimental spectrum to theoretical spectra at various temperatures, a temperature measurement is obtained. The spectral model accounts for collisional narrowing, collisional broadening, Doppler broadening, and collisional line shifting of each Raman line making up the H2 Stokes vibrational Q-branch spectrum. At pressures from atmospheric up to those associated with advanced preburner components (5500 psia), collisional broadening though present does not cause significant overlap of the Raman lines, allowing high resolution H2 Raman to be used for temperature measurements in plumes and in high pressure test articles. Experimental demonstrations of the technique are performed for rich H2-air flames at atmospheric pressure and for high pressure, 300 K H2-He mixtures. Spectrometer imaging quality is identified as being critical for successful implementation of technique.
Coherent Raman spectroscopy for supersonic flow measurments
NASA Technical Reports Server (NTRS)
She, C. Y.
In collaboration with NASA/Langley Research Center, a truly nonintrusive and nonseeding method for measuring supersonic molecular flow parameters was proposed and developed at Colorado State University. The feasibility of this Raman Doppler Velocimetry (RDV), currently operated in a scanning mode, was demonstrated not only in a laboratory environment at Colorado State University, but also in a major wind tunnel at NASA/Langley Research Center. The research progress of the RDV development is summarized. In addition, methods of coherent Rayleigh-Brillouin spectroscopy and single-pulse coherent Raman spectroscopy are investigated, respectively, for measurements of high-pressure and turbulent flows.
Raman Characterisation of Diamond Coatings Using Different Laser Wavelengths
NASA Astrophysics Data System (ADS)
Haubner, Roland; Rudigier, Moritz
Diamond layers can show different morphologies, i.e. well-facetted, fine-grained and ballas diamond. Additionally, the types NCD (nanocrystalline diamond), UNCD (ultra nanocrystalline diamond) and various types of amorphous carbon (a- C, a-CH ģ) are known. To characterise the various carbon deposits Raman spectroscopy is most common, because this technique is simple to handle. With a modern Raman spectrometer, provided with three different laser units (wavelengths 472,681 nm/ blue, 532,1 nm/ green, 632,81 nm/ red), the same spot of a sample can be measured several times. A set of diamond coatings, representing the different morphologies, and moreover, boron doped levels were selected for Raman characterisation. Varying the laser wavelength, highly different Raman spectra were obtained and their interpretation is quite difficult.
Analytical procedure for characterization of medieval wall-paintings by X-ray fluorescence spectrometry, laser ablation inductively coupled plasma mass spectrometry and Raman spectroscopy
NASA Astrophysics Data System (ADS)
Syta, Olga; Rozum, Karol; Choi?ska, Marta; Zieli?ska, Dobrochna; ?ukowska, Gra?yna Zofia; Kijowska, Agnieszka; Wagner, Barbara
Analytical procedure for the comprehensive chemical characterization of samples from medieval Nubian wall-paintings by means of portable X-ray fluorescence (pXRF), laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) and Raman spectroscopy (RS) was proposed in this work. The procedure was used for elemental and molecular investigations of samples from archeological excavations in Nubia (modern southern Egypt and northern Sudan). Numerous remains of churches with painted decorations dated back to the 7th-14th century were excavated in the region of medieval kingdoms of Nubia but many aspects of this art and its technology are still unknown. Samples from the selected archeological sites (Faras, Old Dongola and Banganarti) were analyzed in the form of transfers (n = 26), small fragments collected during the excavations (n = 35) and cross sections (n = 15). XRF was used to collect data about elemental composition, LA-ICPMS allowed mapping of selected elements, while RS was used to get the molecular information about the samples. The preliminary results indicated the usefulness of the proposed analytical procedure for distinguishing the substances, from both the surface and sub-surface domains of the wall-paintings. The possibility to identify raw materials from the wall-paintings will be used in the further systematic, archeometric studies devoted to the detailed comparison of various historic Nubian centers.
NIR and VIS-raman spectroscopy of CVD diamond films
M. Griesser; M. Grasserbauer; R. Kellner; S. Bohr; R. Haubner; B. Lux
Raman spectroscopy is a widely used method for the analysis of CVD diamond layers, because it enables to distinguish between different carbon phases, such as diamond, graphite, amorphous carbon and nanocrystalline carbon, which are all commonly present in CVD diamond films. A comparison of visible Raman spectroscopy and near-infrared Raman spectroscopy applied to CVD diamond layers on various substrates (Si,
TOPICAL REVIEW: Prospects for in vivo Raman spectroscopy
E. B. Hanlon; R. Manoharan; T.-W. Koo; K. E. Shafer; J. T. Motz; M. Fitzmaurice; J. R. Kramer; I. Itzkan; R. R. Dasari; M. S. Feld
Raman spectroscopy is a potentially important clinical tool for real-time diagnosis of disease and in situ evaluation of living tissue. The purpose of this article is to review the biological and physical basis of Raman spectroscopy of tissue, to assess the current status of the field and to explore future directions. The principles of Raman spectroscopy and the molecular level
Raman spectroscopy in investigation of rheometric processes
NASA Astrophysics Data System (ADS)
Gnyba, Marcin; Bogdanowicz, Robert; Kozanecki, Marcin
Studies of application of Raman spectroscopy in measurement of important parameters of rheometric process, including profile of oil film thickness and composition of oil/paste system, were carried out. The films of silicone oil AK106 (Wacker) extracted from ceramic paste AlOOH were subjects of investigations presented in this paper. Boundary between oil film and extruded paste is not regular and ambiguous during the extrusion process of ceramic paste in capillary rheometer. Moreover, the pastes are scattering materials, what makes determination of the film thickness by conventional optical methods difficult. Preliminary Raman measurements were made separately for oil and paste samples in range extending from 50 to 3500 cm-1. Determination of main Raman bands assigned to oil, ceramics and glass showed that Raman spectroscopy enables discernment of these materials. During the next step, studies were conducted for a model sample of the oil spread on the paste, using Raman microscope. This device was equipped with long-working-distance objective which should enable remote measurements through a borosilicate, view-port-window in the wall of capillary rheometry die. Two methods of Raman determination of the thickness were compared. Results of analysis and experimental works suggest that one of them can be applied for in-situ monitoring of the extrusion process.
Theory of femtosecond stimulated Raman spectroscopy
Lee, Soo-Y.; Zhang, Donghui; McCamant, David W.; Kukura, Philipp; Mathies, Richard A.
Femtosecond broadband stimulated Raman spectroscopy (FSRS) is a new technique that produces high-resolution (time-resolved) vibrational spectra from either the ground or excited electronic states of molecules, free from background fluorescence. FSRS uses simultaneously a narrow bandwidth ?1 ¢ 3 ps Raman pump pulse with a continuum ?30¢ 50 fs Stokes probe pulse to produce sharp Raman gains, at positions corresponding to vibrational transitions in the sample, riding on top of the continuum Stokes probe spectrum. When FSRS is preceded by a femtosecond actinic pump pulse that initiates the photochemistry of interest, time-resolved Raman spectroscopy can be carried out. We present two theoretical approaches to FSRS: one is based on a coupling of Raman pump and probe light waves with the vibrations in the medium, and another is a quantum-mechanical description. The latter approach is used to discuss the conditions of applicability and limitations of the coupled-wave description. Extension of the quantum-mechanical description to the case where the Raman pump beam is on resonance with an excited electronic state, as well as when FSRS is used to probe a nonstationary vibrational wave packet prepared by an actinic pump pulse, is also discussed. PMID:15303930
Development of a drug assay using surface-enhanced Raman spectroscopy
NASA Astrophysics Data System (ADS)
Angel, S. M.; Roe, Jeffrey N.; Andresen, Brian D.; Myrick, Michael L.; Milanovich, Fred P.
Surface-enhanced Raman spectroscopy has been used to detect low levels of several chemical compounds, including the drugs of abuse -cocaine hydrochloride and methamphetamme hydrochloride. Raman spectra of these substances have also been taken over optical fibers using red-wavelength excitation. These measurements demonstrate the feasibility of the remote determination of various target chemicals using diode laser excitation and diode array detection.
Raman Spectroscopy of Graphene Edges
C. Casiraghi; A. Hartschuh; H. Qian; S. Piscanec; C. Georgi; A. Fasoli; K. S. Novoselov; D. M. Basko; A. C. Ferrari
Graphene edges are of particular interest, since their chirality determines the electronic properties. Here we present a detailed Raman investigation of graphene flakes with well defined edges oriented at different crystallographic directions. The position, width and intensity of G and D peaks at the edges are studied as a function of the incident light polarization. The D-band is strongest for
Raman spectroscopy of newberyite, hannayite and struvite
NASA Astrophysics Data System (ADS)
Frost, Ray L.; Weier, Matt L.; Martens, Wayde N.; Henry, Dermot A.; Mills, Stuart J.
The phosphate minerals hannayite, newberyite and struvite have been studied by Raman spectroscopy using a thermal stage. Hannayite and newberyite are characterised by an intense band at around 980 cm -1 assigned to the v symmetric stretching vibration of the HPO 4 units. In contrast the symmetric stretching mode is observed at 942 cm -1 for struvite. The Raman spectra are characterised by multiple v anti-symmetric stretching bands and v and v bending modes indicating strong distortion of the HPO 4 and PO 4 units. Hannayite and newberyite are defined by bands at 3382 and 3350 cm -1 attributed to HOPO 3 vibrations and hannayite and struvite by bands at 2990, 2973 and 2874 assigned to NH 4+ bands. Raman spectroscopy has proven most useful for the analysis of these 'cave' minerals where complex paragenetic relationships exist between the minerals.
Detection of counterfeit Viagra with Raman spectroscopy.
de Veij, Marleen; Deneckere, Annelien; Vandenabeele, Peter; de Kaste, Dries; Moens, Luc
During the last few years, counterfeiters have become increasingly sophisticated by falsifying drugs and making them look identical to genuine tablets. In this paper, Raman spectroscopy is proposed as a fast and reliable method for the detection of counterfeit Viagra tablets. This technique can easily differentiate genuine from counterfeit tablets without the need of sample preparation. In total 18 tablets were analysed which all contained the active ingredient sildenafil, but different excipients were used, as could be observed in the Raman spectra between 1150 and 700 cm(-1). So, the spectra could be divided into genuine or counterfeit. Additionally, principal component analysis (PCA), combined with hierarchical cluster analysis (HCA), was used to establish an automated approach for the discrimination of counterfeit from genuine Viagra tablets. Raman spectroscopy, combined with principal components analysis, could be used in the future by customs or in the field to identify counterfeit tablets on the spot without involvement of trained chemists. PMID:18054194
Optical coherence tomography and Raman spectroscopy of the retina
NASA Astrophysics Data System (ADS)
Evans, Julia W.; Zawadzki, Robert J.; Liu, Rui; Chan, James W.; Lane, Stephen M.; Werner, John S.
Imaging the structure and correlating it with the biochemical content of the retina holds promise for fundamental research and for clinical applications. Optical coherence tomography (OCT) is commonly used to image the 3D structure of the retina and while the added functionality of biochemical analysis afforded by Raman scattering could provide critical molecular signatures for clinicians and researchers, there are many technical challenges to combining these imaging modalities. We present an ex vivo OCT microscope combined with Raman spectroscopy capable of collecting morphological and molecular information about a sample simultaneously. The combined instrument will be used to investigate remaining technical challenges to combine these imaging modalities, such as the laser power levels needed to achieve a Raman signal above the noise level without damaging the sample.
Optical Coherence Tomography and Raman Spectroscopy of the retina
Evans, J W; Zawadzki, R J; Liu, R; Chan, J; Lane, S; Werner, J S
Imaging the structure and correlating it with the biochemical content of the retina holds promise for fundamental research and for clinical applications. Optical coherence tomography (OCT) is commonly used to image the 3D structure of the retina and while the added functionality of biochemical analysis afforded by Raman scattering could provide critical molecular signatures for clinicians and researchers, there are many technical challenges to combining these imaging modalities. We present an ex vivo OCT microscope combined with Raman spectroscopy capable of collecting morphological and molecular information about a sample simultaneously. The combined instrument will be used to investigate remaining technical challenges to combine these imaging modalities, such as the laser power levels needed to achieve a Raman signal above the noise level without damaging the sample.
Micro-Raman spectroscopy in the undergraduate research laboratory
NASA Astrophysics Data System (ADS)
Voor, R.; Chow, L.; Schulte, A.
Modern materials science requires processing and characterization techniques for microscopic structures. Molecular probes such as Raman spectroscopy are some of the most viable tools, particularly if they are supplemented by imaging to obtain spatially resolved compositional information of inhomogeneous or low volume samples. In order to introduce these techniques and materials science experiments into the advanced undergraduate laboratory, we have constructed an inexpensive micro-Raman attachment, which consists of an off-the-shelf microscope and the coupling optics to an existing Raman spectrometer. The modification of the microscope, the optical coupling, and a low cost viewing system for positioning the laser excitation on the sample are described in detail. The students study molecular spectra of new materials such as diamond films, Fullerenes, and biological compounds with spatial resolution of several microns.
Detection of counterfeit Viagra « with Raman spectroscopy
Marleen de Veij; Annelien Deneckere; Peter Vandenabeele; Dries de Kaste; Luc Moens
During the last few years, counterfeiters have become increasingly sophisticated by falsifying drugs and making them look identical to genuine tablets. In this paper, Raman spectroscopy is proposed as a fast and reliable method for the detection of counterfeit Viagra« tablets. This technique can easily differentiate genuine from counterfeit tablets without the need of sample preparation. In total 18 tablets
Estimating Atomic Sizes with Raman Spectroscopy
Du, Shengwang
and technology, such as designing, fabricating, and diagnosing nano materials and structures in the level of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China, 2 Wuhan Institute of Physics into the nano-scale channels of a zeolite single crystal. We found their polarized Raman spectroscopy, which
Raman spectroscopy of saliva as a perspective method for periodontitis diagnostics Raman spectroscopy of saliva
NASA Astrophysics Data System (ADS)
Gonchukov, S.; Sukhinina, A.; Bakhmutov, D.; Minaeva, S.
In view of its potential for biological tissues analyses at a molecular level, Raman spectroscopy in optical range has been the object of biomedical research for the last years. The main aim of this work is the development of Raman spectroscopy for organic content identifying and determination of biomarkers of saliva at a molecular level for periodontitis diagnostics. Four spectral regions were determined: 1155 and 1525 cm-1, 1033 and 1611 cm-1, which can be used as biomarkers of this widespread disease.
FT-Raman spectroscopy study of human breast tissue
NASA Astrophysics Data System (ADS)
Bitar Carter, Renata A.; Martin, Airton A.; Netto, Mario M.; Soares, Fernando A.
Optical spectroscopy has been extensively studied as a potential in vivo diagnostic tool to provide information about the chemical and morphologic structure of tissue. Raman Spectroscpy is an inelastic scattering process that can provide a wealth of spectral features that can be related to the specific molecular structure of the sample. This article reports results of an in vitro study of the FT-Raman human breast tissue spectra. An Nd:YAG laser at 1064nm was used as the excitation source in the FT-Raman Spectrometer. The neoplastic human breast samples, both Fibroadenoma and ICD, were obtained during therapeutical routine medical procedures required by the primary disease, and the non-diseased human tissue was obtained in plastic surgery. No sample preparation was needed for the FT-Raman spectra collection. The FT-Raman spectra were recorded from normal, benign (Fibroadenomas) and malignant (IDC-Intraductal Carcinoma) samples, adding up 51 different areas. The main spectral differences of a typical FT-Raman spectra of a Normal (Non-diseased), Fibroadenoma, and Infiltrating Ductal Carcinoma (IDC) breast tissue at the interval of 600 to 1800cm-1, which may differentiate diagnostically the sample, were found in the bands of 1230 to 1295cm-1, 1440 to 1460 cm-1 and 1650 to 1680 cm-1, assigned to the vibrational bands of the carbohydrate-amide III, proteins and lipids, and carbohydrate-amide I, respectively.
Micro-Raman spectroscopy on oral tissues
NASA Astrophysics Data System (ADS)
Zenone, F.; Lepore, M.; Perna, G.; Carmone, P.; Riccio, R.; Gaeta, G. M.; Capozzi, V.
Micro-Raman Spectroscopy (?-RS) provides a unique tool in medicine for a not invasive and real time analysis of biological tissue for biopsy and "in vivo" investigation. Based on the evaluation of molecular vibration frequencies, the ?-RS is able to detect the main molecular bonds of protein constituents, as the C-H and C-C ones. Changes in frequency or in the relative intensity of the vibration modes revealed by ?-RS can be related to changes of chemical bond and of protein structure induced by pathology. The ?-RS has been performed on samples of oral tissue from informed patients, affected by pemphigus vulgaris (an oral pathology) in an advanced regression state. The biopsies were thin slices (about 1mm thick) with 6mm diameter. The sample was measured through a 170 ?m thick cover-glass. The experimental set-up was mainly composed by a He-Ne laser and a monochromator equipped with a Peltier cell and with a grating of 1800 grooves/mm. The laser light was focused on the sample surface by means of a long focal length 50X optical objective. The main protein bonds are clearly detectable in the considered samples and this give important information on the integrity and on the state of tissue components (lipids and proteins), and consequently on the occurrence of pathology. The potential application of this method for in vivo analysis is an invaluable alternative to biopsy and pathological examinations for many medical application as screening diagnostic, therapy progress examination, and surgical support.
Intrinsic Raman spectroscopy for quantitative biological spectroscopy Part II
Bechtel, Kate L.; Shih, Wei-Chuan; Feld, Michael S.
We demonstrate the effectiveness of intrinsic Raman spectroscopy (IRS) at reducing errors caused by absorption and scattering. Physical tissue models, solutions of varying absorption and scattering coefficients with known concentrations of Raman scatterers, are studied. We show significant improvement in prediction error by implementing IRS to predict concentrations of Raman scatterers using both ordinary least squares regression (OLS) and partial least squares regression (PLS). In particular, we show that IRS provides a robust calibration model that does not increase in error when applied to samples with optical properties outside the range of calibration. PMID:18711512
A novel method for the identification of inorganic and organic gunshot residue particles of lead-free ammunitions from the hands of shooters using scanning laser ablation-ICPMS and Raman micro-spectroscopy.
Abrego, Zuri±e; Grijalba, Nagore; Unceta, Nora; Maguregui, Maite; Sanchez, Alicia; Fernßndez-Isla, Alberto; Goicolea, M Aranzazu; Barrio, Ram¾n J
A method based on scanning laser ablation and inductively coupled plasma-mass spectrometry (SLA-ICPMS) and Raman micro-spectroscopy for the detection and identification of compounds consistent with gunshot residue particles (GSR) has been developed. The method has been applied to the characterization of particles resulting from the discharge of firearms using lead-free ammunition. Modified tape lifts were used to collect the inorganic and organic residues from skin surfaces in a single sample. Using SLA-ICPMS, aggregates related to the composition of the ammunition, such as Cu-Zn-Sn, Zr-Sr, Cu-Zn, Al-Ti, or Al-Sr-Zr were detected, but this composition is only consistent with GSR from lead-free ammunitions. Additional evidence was provided by micro-Raman spectroscopy, which identified the characteristic organic groups of the particles as centralite, diphenylamine or their nitrated derivatives, which are indicative of GSR. PMID:25303642
The effect of aqueous solution in Raman spectroscopy
NASA Astrophysics Data System (ADS)
Kang, Jian; Yuan, Xiaojuan; Dong, Xiao; Gu, Huaimin
In Raman detection, the most popular solution for the samples is tri-distilled water. But the effect of aqueous solution is barely studied in Raman spectroscopy. In fact Raman spectroscopy of solid-state and liquid-state are obvious different. In addition, FWHM of Raman spectral peaks also change evidently. In this paper, several samples were selected for the experiment; including sodium nitrate, sodium nitrite, glucose and caffeine. By comparing the Raman spectroscopy of samples at different concentrations, it is found that the concentration of the sample can affect the strength of Raman spectroscopy, but it can hardly impact FWHM of Raman spectral peaks. By comparing the Raman spectroscopy of liquid-state with the Raman spectroscopy of solid-state, it is observed that the FWHM of some Raman spectral peaks varied obviously; that may be because when the sample was dissolved into the water, the crystal lattice structure was broken, and for some samples atom form became ion form in aqueous solution. Those structural variations caused the variation of the FWHM. The Raman spectroscopy of caffeine aqueous solution at very low concentration was also detected and analyzed. Compared with the Raman spectra of solid-state samples, it is found that some Raman spectral peaks disappeared when the sample was dissolved in water. It is possible that the low concentration of the sample result in the weakening of Raman signals and the disappearing of some weak Raman spectral peaks. Then Ag nanoparticles were added into the caffeine aqueous solution, the results suggest that surface enhanced Raman spectroscopy (SERS) not only can enhance the Raman spectral signal, but also can reduce the effect of aqueous solution. It is concluded that the concentration of sample only affects the strength of Raman spectroscopy; the aqueous solution can affect the FWHM of Raman spectral peaks; and SERS can reduce the effect of aqueous solution.
Raman imaging and spectroscopy of single functional erythrocytes: a feasibility study
NASA Astrophysics Data System (ADS)
Ramser, Kerstin; Bjerneld, Erik J.; Fant, Camilla; Kall, Mikael
Hemoglobin (Hb) within single erythrocytes (red blood cells), adsorbed on poly-lysine coated glass surfaces, was studied using resonance Raman spectroscopy and global Raman imaging. The erythrocytes were found to be sensitive to both surface adsorption and to the laser light. Topological changes of the cell membrane were observed immediately after cell adsorption in Raman images. We observed a photo-induced increase of the fluorescence background occurring simultaneously with a decrease in the Hb Raman signal. Concurrent changes in Raman spectra revealed a conversion of oxy-Hb to the met-Hb state. However, at a low accumulated photon dose, the preparation method enabled the recording of Raman spectra during the oxygenation cycle of a single red blood cell in buffer, which shows that Hb was in an in-vivo environment. Thus, Raman spectroscopy of functional Hb in isolated red blood cells is feasible.
UV gated Raman spectroscopy for standoff detection of explosives
NASA Astrophysics Data System (ADS)
Gaft, M.; Nagli, L.
Real-time detection and identification of explosives at a standoff distance is a major issue in efforts to develop defense against so-called improvised explosive devices (IED). It is recognized that the only method, which is potentially capable to standoff detection of minimal amounts of explosives is laser-based spectroscopy. LDS technique belongs to trace detection, namely to its micro-particles variety. It is based on commonly held belief that surface contamination was very difficult to avoid and could be exploited for standoff detection. We have applied gated Raman spectroscopy for detection of main explosive materials, both factory and homemade. We developed and tested a Raman system for the field remote detection and identification of minimal amounts of explosives on relevant surfaces at a distance of up to 30 m.
Monitoring of tritium purity during long-term circulation in the KATRIN test experiment LOOPINO using laser Raman spectroscopy
Fischer, Sebastian; Schl÷sser, Magnus; Bornschein, Beate; Drexlin, Guido; Priester, Florian; Lewis, Richard J; Telle, Helmut H
The gas circulation loop LOOPINO has been set up and commissioned at Tritium Laboratory Karlsruhe (TLK) to perform Raman measurements of circulating tritium mixtures under conditions similar to the inner loop system of the neutrino-mass experiment KATRIN, which is currently under construction. A custom-made interface is used to connect the tritium containing measurement cell, located inside a glove box, with the Raman setup standing on the outside. A tritium sample (purity > 95%, 20 kPa total pressure) was circulated in LOOPINO for more than three weeks with a total throughput of 770 g of tritium. Compositional changes in the sample and the formation of tritiated and deuterated methanes CT_(4-n)X_n (X=H,D; n=0,1) were observed. Both effects are caused by hydrogen isotope exchange reactions and gas-wall interactions, due to tritium {\\beta} decay. A precision of 0.1% was achieved for the monitoring of the T_2 Q_1-branch, which fulfills the requirements for the KATRIN experiment and demonstrates the feasibility ...
George, E. Victor (Livermore, CA)
Method and apparatus for use of a Raman or Brillouin switch together with a conventional laser and a saturable absorber that is rapidly bleached at a predetermined frequency .nu.=.nu..sub.0, to ultimately produce a Raman or Brillouin pulse at frequency .nu.=.nu..sub.0 .+-..nu..sub.Stokes.
Candida parapsilosis biofilm identification by Raman spectroscopy.
Samek, Ota; Mlynarikovß, Katarina; Bernatovß, Silvie; Je×ek, Jan; Krzy×ßnek, Vladislav; Ŗiler, Martin; Zemßnek, Pavel; R?×i?ka, Filip; Holß, Veronika; Mahelovß, Martina
Colonies of Candida parapsilosis on culture plates were probed directly in situ using Raman spectroscopy for rapid identification of specific strains separated by a given time intervals (up to months apart). To classify the Raman spectra, data analysis was performed using the approach of principal component analysis (PCA). The analysis of the data sets generated during the scans of individual colonies reveals that despite the inhomogeneity of the biological samples unambiguous associations to individual strains (two biofilm-positive and two biofilm-negative) could be made. PMID:25535081
Bright emission from a random Raman laser
Hokr, Brett H.; Bixler, Joel N.; Cone, Michael T.; Mason, John D.; Beier, Hope T.; Noojin, Gary D.; Petrov, Georgi I.; Golovan, Leonid A.; Thomas, Robert J.; Rockwell, Benjamin A.; Yakovlev, Vladislav V.
Random lasers are a developing class of light sources that utilize a highly disordered gain medium as opposed to a conventional optical cavity. Although traditional random lasers often have a relatively broad emission spectrum, a random laser that utilizes vibration transitions via Raman scattering allows for an extremely narrow bandwidth, on the order of 10?cm?1. Here we demonstrate the first experimental evidence of lasing via a Raman interaction in a bulk three-dimensional random medium, with conversion efficiencies on the order of a few percent. Furthermore, Monte Carlo simulations are used to study the complex spatial and temporal dynamics of nonlinear processes in turbid media. In addition to providing a large signal, characteristic of the Raman medium, the random Raman laser offers us an entirely new tool for studying the dynamics of gain in a turbid medium. PMID:25014073
J. Raman Spectroscopy 38 [6] (2007) 598-603 Special Issue Raman spectroscopy of Nanomaterials, Ph. Colomban & G. Gouadec, Guest Editors
Paris-Sud XI, Universitķ de
J. Raman Spectroscopy 38 [6] (2007) 598-603 Special Issue Raman spectroscopy of Nanomaterials, Ph signature. Keywords Nanomaterials, nanostructure, nanoparticles, nanotubes, TERS, phonon confinement, modeling Raman spectroscopy status as a nanomaterials investigation technique is presented at the light
Metallized Capillaries as Probes for Raman Spectroscopy
NASA Technical Reports Server (NTRS)
Pelletier, Michael
A class of miniature probes has been proposed to supplant the fiber-optic probes used heretofore in some Raman and fluorescence spectroscopic systems. A probe according to the proposal would include a capillary tube coated with metal on its inside to make it reflective. A microlens would be hermetically sealed onto one end of the tube. A spectroscopic probe head would contain a single such probe, which would both deliver laser light to a sample and collect Raman or fluorescent light emitted by the sample.
Amplifier/compressor fiber Raman lasers
Islam, M.N.; Mollenauer, L.F.; Stolen, R.H.; Simpson, J.R.; Shang, H.T.
We show that the chirp from cross-phase modulation (XPM) dominates the operation of fiber Raman lasers (FRL's). Thus a FRL in the anomalous group-velocity regime is best described as a XPM-chirped Raman amplifier followed by a linear fiber compressor. While the output of such a laser is generally a narrow pulse with a broad pedestal, we show both experimentally and by computer simulation that negligible background is achievable.
[Laser Raman spectrum analysis of carbendazim pesticide].
Wang, Xiao-bin; Wu, Rui-mei; Liu, Mu-hua; Zhang, Lu-ling; Lin, Lei; Yan, Lin-yuan
Raman signal of solid and liquid carbendazim pesticide was collected by laser Raman spectrometer. The acquired Raman spectrum signal of solid carbendazim was preprocessed by wavelet analysis method, and the optimal combination of wavelet denoising parameter was selected through mixed orthogonal test. The results showed that the best effect was got with signal to noise ratio (SNR) being 62.483 when db2 wavelet function was used, decomposition level was 2, the threshold option scheme was 'rigisure' and reset mode was 'sln'. According to the vibration mode of different functional groups, the de-noised Raman bands could be divided into 3 areas: 1 400-2 000, 700-1 400 and 200-700 cm(-1). And the de-noised Raman bands were assigned with and analyzed. The characteristic vibrational modes were gained in different ranges of wavenumbers. Strong Raman signals were observed in the Raman spectrum at 619, 725, 964, 1 022, 1 265, 1 274 and 1 478 cm(-1), respectively. These characteristic vibrational modes are characteristic Raman peaks of solid carbendazim pesticide. Find characteristic Raman peaks at 629, 727, 1 001, 1 219, 1 258 and 1 365 cm(-1) in Raman spectrum signal of liquid carbendazim. These characteristic peaks were basically tallies with the solid carbendazim. The results can provide basis for the rapid screening of pesticide residue in food and agricultural products based on Raman spectrum. PMID:25358165
Shell-isolated nanoparticle-enhanced Raman spectroscopy
La Rosa, Andres H.
the substrate acts as the Raman signal amplifier. The drawback is that the total Raman scattering signal from from a Au tip that acts as the Raman signal amplifier (Fig. 1aŁc). The largely enhanced electromagneticLETTERS Shell-isolated nanoparticle-enhanced Raman spectroscopy Jian Feng Li1 , Yi Fan Huang1
Development of a rapid macro-Raman spectroscopy system for nasopharyngeal cancer detection based on surface-enhanced Raman spectroscopy
NASA Astrophysics Data System (ADS)
Lin, Duo; Chen, Guannan; Feng, Shangyuan; Pan, Jianji; Lin, Juqiang; Huang, Zufang; Chen, Rong
This study aims to evaluate the utility of a home-made surface-enhanced Raman spectroscopy (SERS) system for detection of nasopharyngeal cancer (NPC). A Raman spectral system with a special probe and a millimeter order excitation laser spot size was developed to acquire SERS signals of blood plasma. High quality SERS spectra can be recorded from blood plasma samples belonging to 60 healthy volunteers and 96 NPC patients, and the diagnostic sensitivity and specificity of 95.8% and 91.7%, respectively, can be achieved for classification between normal and cancer blood groups by principal component analysis combined with linear discriminant analysis (PCA-LDA). This exploratory study demonstrates that SERS based on a larger laser spot together with PCA-LDA has the potential for detection of nasopharyngeal cancer, and even for further in vivo cancer detection in the future.
The Impact of Array Detectors on Raman Spectroscopy
ERIC Educational Resources Information Center
Denson, Stephen C.; Pommier, Carolyn J. S.; Denton, M. Bonner
The impact of array detectors in the field of Raman spectroscopy and all low-light-level spectroscopic techniques is examined. The high sensitivity of array detectors has allowed Raman spectroscopy to be used to detect compounds at part per million concentrations and to perform Raman analyses at advantageous wavelengths.
In situ quantitative analysis of individual H2O-CO2 fluid inclusions by laser Raman spectroscopy
Azbej, T.; Severs, M.J.; Rusk, B.G.; Bodnar, R.J.
Raman spectral parameters for the Raman ??1 (1285??cm- 1) and 2??2 (1388??cm- 1) bands for CO2 and for the O-H stretching vibration band of H2O (3600??cm- 1) were determined in H2O-CO2 fluid inclusions. Synthetic fluid inclusions containing 2.5 to 50??mol% CO2 were analyzed at temperatures equal to or greater than the homogenization temperature. The results were used to develop an empirical relationship between composition and Raman spectral parameters. The linear peak intensity ratio (IR = ICO2/(ICO2 + IH2O)) is related to the CO2 concentration in the inclusion according to the relation:Mole % C O2 = e- 3.959 IR2 + 8.0734 IRwhere ICO2 is the intensity of the 1388 cm- 1 peak and IH2O is the intensity of the 3600 cm- 1 peak. The relationship between linear peak intensity and composition was established at 350????C for compositions ranging from 2.5 to 50??mol% CO2. The CO2-H2O linear peak intensity ratio (IR) varies with temperature and the relationship between composition and IR is strictly valid only if the inclusions are analyzed at 350????C. The peak area ratio is defined as AR = ACO2/(ACO2 + AH2O), where ACO2 is the integrated area under the 1388??cm- 1 peak and AH2O is the integrated area under the 3600??cm- 1 peak. The relationship between peak area ratio (AR) and the CO2 concentration in the inclusions is given as:Mole % C O2 = 312.5 AR. The equation relating peak area ratio and composition is valid up to 25??mol% CO2 and from 300 to 450????C. The relationship between linear peak intensity ratio and composition should be used for inclusions containing ??? 50??mol% CO2 and which can be analyzed at 350????C. The relationship between composition and peak area ratios should be used when analyzing inclusions at temperatures less than or greater than 350????C (300-450) but can only be used for compositions ??? 25??mol% CO2. Note that this latter relationship has a somewhat larger standard deviation compared to the intensity ratio relationship. Calibration relationships employing peak areas for both members of the Fermi diad (??1 at 1285??cm- 1 and 2??2 at 1388??cm- 1) were slightly poorer than those using only the 2??2 (1388??cm- 1) member owing to interference from quartz peak at approximately 1160??cm- 1. The technique has been applied to natural low-salinity H2O-CO2 inclusions from the Butte, Montana, porphyry copper-molybdenum deposit. Carbon dioxide concentrations obtained range from below detection to 4.2??mol% CO2, and are in good agreement with concentrations determined previously based on microthermometric and petrographic observations. ?? 2007 Elsevier B.V. All rights reserved.
In Vivo Blood Glucose Quantification Using Raman Spectroscopy
Shao, Jingwei; Lin, Manman; Li, Yongqing; Li, Xue; Liu, Junxian; Liang, Jianpin; Yao, Huilu
We here propose a novel Raman spectroscopy method that permits the noninvasive measurement of blood glucose concentration. To reduce the effects of the strong background signals produced by surrounding tissue and to obtain the fingerprint Raman lines formed by blood analytes, a laser was focused on the blood in vessels in the skin. The Raman spectra were collected transcutaneously. Characteristic peaks of glucose (1125 cm-1) and hemoglobin (1549 cm-1) were observed. Hemoglobin concentration served as an internal standard, and the ratio of the peaks that appeared at 1125 cm-1 and 1549 cm-1 peaks was used to calculate the concentration of blood glucose. We studied three mouse subjects whose blood glucose levels became elevated over a period of 2 hours using a glucose test assay. During the test, 25 Raman spectra were collected transcutaneously and glucose reference values were provided by a blood glucose meter. Results clearly showed the relationship between Raman intensity and concentration. The release curves were approximately linear with a correlation coefficient of 0.91. This noninvasive methodology may be useful for the study of blood glucose in vivo. PMID:23133555
NIR Raman spectroscopy in medicine and biology: results and aspects
NASA Astrophysics Data System (ADS)
Schrader, B.; Dippel, B.; Erb, I.; Keller, S.; L÷chte, T.; Schulz, H.; Tatsch, E.; Wessel, S.
Analyses of biomaterial by 'classical' Raman spectroscopy with excitation in the visible range has not been possible since the fluorescence of many essential constituents of all animal and plant cells and tissues overlays the Raman spectra completely. Fluorescence, however, is virtually avoided, when Raman spectra are excited with the Nd : YAG laser line at 1064 nm. Within seven dissertations we explored different fields of potential applications to medical diagnostics. Identification and qualification of tissues and cells is possible. Tumors show small but significant differences to normal tissues; in order to develop a reliable tool for tumor diagnostics more research is necessary, especially a collection of reference spectra in a data bank is needed. Raman spectra of biomineralization structures in teeth and bones show pathological tissues as well as the development of new mineralized structures. NIR Raman spectra of flowers, leaves, and fruit show, without special preparation, their constituents: alkaloids, the essential oils, natural dyes, flavors, spices and drugs. They allow application to taxonomy, optimizing plant breeding and control of food.
Summary report of FY 1995 Raman spectroscopy technology development
Douglas, J.G.
US DOE is sponsoring development of remote, fiber-optic Raman spectroscopy for rapid chemical characterization of Hanford high-level radioactive tank waste. Deployment targets for this technology are analytical hot cells and, via the Light-Duty Utility Arm and cone penetrometer, the waste tanks themselves. Perceived benefits of fiber-optic Raman spectroscopy are (1) rapid generation of tank-waste safety-related data, (2) reduced personnel exposure to highly radioactive waste, (3) reduced tank-waste sampling and analysis costs, and (4) reduced radioactive analytical waste. This document presents the results from the investigation of two dispersive, transmission-grating Raman systems and four fiber-optic Raman probe designs with non-radioactive tank waste simulants. One Raman system used a 532-nm, 400 mW, solid-state laser; the other used a 785-nm, 500 mW, solid-state diode laser. We found (1) the transmission-grating systems had better wavelength stability than previously tried Czerny-Turner-Based systems and (2) the 785-nm system`s specie detection limits in the spectral fingerprint regiion were at least as good as those for the 532-nm system. Based on these results, and the fact that some tank wastes luminesce with 514.5nm excitation, we selected the 785-nm system for hot-cell use. Of the four probes tested, three had a ``six-around-on`` fiber probe design; the fourth probe was a one-fiber-in-one-fiber-out, diffuse-relectance design. Comparison of the four probes` signal-to-noise rations, rations, transmission/collection efficiencies, and probe-silica Raman backgrounds showed that the best probe for use with Hanford-Site tank waste should (1) be filtered as close to the probe tip as possible to reduce the probe-silica Raman background and (2) have multiple collection fibers. The responses of all the probes tested showed a strong dependence on probe-sample distance, and the presence of a probe window appeared to increase the probe`s silica Raman background.
Single bacteria identification by Raman spectroscopy.
Strola, Samy Andrea; Baritaux, Jean-Charles; Schultz, Emmanuelle; Simon, Anne Catherine; Allier, Cķdric; Espagnon, Isabelle; Jary, Dorothķe; Dinten, Jean-Marc
We report on rapid identification of single bacteria using a low-cost, compact, Raman spectroscope. We demonstrate that a 60-s procedure is sufficient to acquire a comprehensive Raman spectrum in the range of 600 to 3300 cm?╣. This time includes localization of small bacteria aggregates, alignment on a single individual, and spontaneous Raman scattering signal collection. Fast localization of small bacteria aggregates, typically composed of less than a dozen individuals, is achieved by lensfree imaging over a large field of view of 24 mm▓. The lensfree image also allows precise alignment of a single bacteria with the probing beam without the need for a standard microscope. Raman scattered light from a 34-mW continuous laser at 532 nm was fed to a customized spectrometer (prototype Tornado Spectral Systems). Owing to the high light throughput of this spectrometer, integration times as low as 10 s were found acceptable. We have recorded a total of 1200 spectra over seven bacterial species. Using this database and an optimized preprocessing, classification rates of ~90% were obtained. The speed and sensitivity of our Raman spectrometer pave the way for high-throughput and nondestructive real-time bacteria identification assays. This compact and low-cost technology can benefit biomedical, clinical diagnostic, and environmental applications. PMID:25028774
Single bacteria identification by Raman spectroscopy
NASA Astrophysics Data System (ADS)
Strola, Samy Andrea; Baritaux, Jean-Charles; Schultz, Emmanuelle; Simon, Anne Catherine; Allier, Cķdric; Espagnon, Isabelle; Jary, Dorothķe; Dinten, Jean-Marc
We report on rapid identification of single bacteria using a low-cost, compact, Raman spectroscope. We demonstrate that a 60-s procedure is sufficient to acquire a comprehensive Raman spectrum in the range of 600 to 3300. This time includes localization of small bacteria aggregates, alignment on a single individual, and spontaneous Raman scattering signal collection. Fast localization of small bacteria aggregates, typically composed of less than a dozen individuals, is achieved by lensfree imaging over a large field of view of 24. The lensfree image also allows precise alignment of a single bacteria with the probing beam without the need for a standard microscope. Raman scattered light from a 34-mW continuous laser at 532 nm was fed to a customized spectrometer (prototype Tornado Spectral Systems). Owing to the high light throughput of this spectrometer, integration times as low as 10 s were found acceptable. We have recorded a total of 1200 spectra over seven bacterial species. Using this database and an optimized preprocessing, classification rates of ś90% were obtained. The speed and sensitivity of our Raman spectrometer pave the way for high-throughput and nondestructive real-time bacteria identification assays. This compact and low-cost technology can benefit biomedical, clinical diagnostic, and environmental applications.
Applications of Raman Spectroscopy to Virology and Microbial Analysis
NASA Astrophysics Data System (ADS)
Harz, Michaela; St÷ckel, Stephan; Ciobot?, Valerian; Cialla, Dana; R÷sch, Petra; Popp, J³rgen
This chapter reports from the utilization of Raman spectroscopic techniques like Raman microscopy, Raman optical activity (ROA), UV-resonance Raman (UVRR)-spectroscopy, surface enhanced Raman spectroscopy (SERS), and tip-enhanced Raman spectroscopy (TERS) for the investigation of viruses and microorganisms, especially bacteria and yeasts for medical and pharmaceutical applications. The application of these Raman techniques allows for the analysis of chemical components of cells and subcellular regions, as well as the monitoring of chemical differences occurring as a result of the growth of microorganisms. In addition, the interaction of microorganisms with active pharmaceutical agents can be investigated. In combination with chemometric methods Raman spectroscopy can also be applied to identify microorganisms both in micro colonies and even on single cells.
Dispersive Raman spectroscopy allows the identification and quantification of melanin types
Galvßn, Ismael; Jorge, Alberto
Melanins are the most prevalent pigments in animals and are involved in visual communication by producing colored traits that often evolve as intraspecific signals of quality. Identifying and quantifying melanins are therefore essential to understand the function and evolution of melanin-based signals. However, the analysis of melanins is difficult due to their insolubility and the lack of simple methods that allow the identification of their chemical forms. We recently proposed the use of Raman spectroscopy as a simple, noninvasive technique that can be used to identify and quantify melanins in feathers and hairs. Contrarily, other authors later stated that melanins are characterized by a lack of defined Raman signals. Here, we use confocal Raman microscopy to confirm previous analyses showing that the two main chemical forms of melanins (eumelanin and pheomelanin) exhibit distinct Raman signal and compare different excitation wavelengths to analyze synthetic pheomelanin and natural melanins in feathers of different species of birds. Our analyses indicate that only laser excitation wavelengths below 1064Ānm are useful for the analysis of melanins by Raman spectroscopy, and only 780-nm laser in the case of melanins in feathers. These findings show that the capacity of Raman spectroscopy to distinguish different chemical forms of melanins depends on laser power and integration time. As a consequence, Raman spectroscopy should be applied after preliminar analyses using a range of these parameters, especially in fragile biological tissues such as feathers. PMID:25897382
Dispersive Raman spectroscopy allows the identification and quantification of melanin types.
Galvßn, Ismael; Jorge, Alberto
Melanins are the most prevalent pigments in animals and are involved in visual communication by producing colored traits that often evolve as intraspecific signals of quality. Identifying and quantifying melanins are therefore essential to understand the function and evolution of melanin-based signals. However, the analysis of melanins is difficult due to their insolubility and the lack of simple methods that allow the identification of their chemical forms. We recently proposed the use of Raman spectroscopy as a simple, noninvasive technique that can be used to identify and quantify melanins in feathers and hairs. Contrarily, other authors later stated that melanins are characterized by a lack of defined Raman signals. Here, we use confocal Raman microscopy to confirm previous analyses showing that the two main chemical forms of melanins (eumelanin and pheomelanin) exhibit distinct Raman signal and compare different excitation wavelengths to analyze synthetic pheomelanin and natural melanins in feathers of different species of birds. Our analyses indicate that only laser excitation wavelengths below 1064Ānm are useful for the analysis of melanins by Raman spectroscopy, and only 780-nm laser in the case of melanins in feathers. These findings show that the capacity of Raman spectroscopy to distinguish different chemical forms of melanins depends on laser power and integration time. As a consequence, Raman spectroscopy should be applied after preliminar analyses using a range of these parameters, especially in fragile biological tissues such as feathers. PMID:25897382
Raman spectroscopy and magnetoelectric properties of laser ablated La and Cr doped BiFeO3 thin films
R. Palai; R. M. Valdes; S. P. Pavunny; R. S. Katiyar
Epitaxial thin films of multiferroics Bi1-xLaxO3 (x = 0.0, 0.05, 0.10, 0.15 and 0.20)and BiFe1-xCrxO3.....(x = 0.05, 0.10, 0.15 and 0.20) were grown on SrTiO3(100) and (110) substrates by pulsed laser deposition (PLD). X-ray diffraction (XRD)?? was used to study the structure, orientation, and crystallinity of the film. The growth mechanism and microstructure of the films were studied using atomic
Raman spectroscopy explores molecular structural signatures of hidden materials in depth: Universal Multiple Angle Raman Spectroscopy.
Sil, Sanchita; Umapathy, Siva
Non-invasive 3D imaging in materials and medical research involves methodologies such as X-ray imaging, MRI, fluorescence and optical coherence tomography, NIR absorption imaging, etc., providing global morphological/density/absorption changes of the hidden components. However, molecular information of such buried materials has been elusive. In this article we demonstrate observation of molecular structural information of materials hidden/buried in depth using Raman scattering. Typically, Raman spectroscopic observations are made at fixed collection angles, such as, 90░, 135░, and 180░, except in spatially offset Raman scattering (SORS) (only back scattering based collection of photons) and transmission techniques. Such specific collection angles restrict the observations of Raman signals either from or near the surface of the materials. Universal Multiple Angle Raman Spectroscopy (UMARS) presented here employs the principle of (a) penetration depth of photons and then diffuse propagation through non-absorbing media by multiple scattering and (b) detection of signals from all the observable angles. PMID:24930768
Surface enhanced Raman spectroscopy in breast cancer cells
Gonzßlez-SolĒs, JL; Luķvano-Colmenero, GH; Vargas-Mancilla, J
Background and aims: Raman spectroscopy is a vibrational technique which provides information about the chemical structure. Nevertheless, since many chemicals are present in a cell at very low concentration, the Raman signal observed from a single cell is extremely weak. In surface enhanced Raman scattering (SERS), Raman signals can be enhanced by many orders of magnitude when nanoparticles are incorporated into the cell. Materials (subjects) and methods: The tumor biopsies were obtained from 5 patients who were clinically diagnosed with breast cancer. Breast cancer cells isolated from the biopsy were washed, centrifuged and seeded out. Cultivation took place in DMEM at 37░C in a humidified of 5% CO2 in air with addition of colloidal silver nanoparticles of 40 nm into the cell by sonication. Immediately, the washed cells were analyzed in phosphate buffered saline (PBS) at pH 7. Raman analysis was carried out on the Jobin-Yvon LabRAM HR800 microscope system, with a NIR 830 nm laser excitation source. Results: The strongly enhanced Raman signals allow Raman measurements of a single cell in the 200¢1800 cm?1 range in relatively short collection times (5 second) using 17 mW near-infrared excitation. Observed spectral features differed across the cell, but chemical constituents in the cell nucleus and cytoplasm, such as DNA, RNA, and amino acids tyrosine and phenylalanine can be identified. Conclusions: Particularly strong field enhancement can be observed when nanoparticles form colloidal clusters. The results suggest that SERS could be a new technique for the identification of breast cancer cell. PMID:24155548
Raman and photothermal spectroscopies for explosive detection
NASA Astrophysics Data System (ADS)
Finot, Eric; Brulķ, Thibault; Rai, Padmnabh; Griffart, Aurķlien; Bouhķlier, Alexandre; Thundat, Thomas
Detection of explosive residues using portable devices for locating landmine and terrorist weapons must sat- isfy the application criteria of high reproducibility, specificity, sensitivity and fast response time. Vibrational spectroscopies such as Raman and infrared spectroscopies have demonstrated their potential to distinguish the members of the chemical family of more than 30 explosive materials. The characteristic chemical fingerprints in the spectra of these explosives stem from the unique bond structure of each compound. However, these spectroscopies, developed in the early sixties, suffer from a poor sensitivity. On the contrary, MEMS-based chemical sensors have shown to have very high sensitivity lowering the detection limit down to less than 1 picogram, (namely 10 part per trillion) using sensor platforms based on microcantilevers, plasmonics, or surface acoustic waves. The minimum amount of molecules that can be detected depends actually on the transducer size. The selectivity in MEMS sensors is usually realized using chemical modification of the active surface. However, the lack of sufficiently selective receptors that can be immobilized on MEMS sensors remains one of the most critical issues. Microcantilever based sensors offer an excellent opportunity to combine both the infrared photothermal spectroscopy in their static mode and the unique mass sensitivity in their dynamic mode. Optical sensors based on localized plasmon resonance can also take up the challenge of addressing the selectivity by monitoring the Surface Enhanced Raman spectrum down to few molecules. The operating conditions of these promising localized spectroscopies will be discussed in terms of reliability, compactness, data analysis and potential for mass deployment.
Infrared diode laser spectroscopy
S. Civis; J. Cihelka; I. Matulkovß
Three types of lasers (double-heterostructure 66 K InAsSb\\/InAsSbP laser diode, room temperature, multi quantum wells with\\u000a distributed feedback (MQW with DFB) (GaInAsSb\\/AlGaAsSb based) diode laser and vertical cavity surface emitting lasers (VCSELs)\\u000a (GaSb based) have been characterized using Fourier transform emission spectroscopy and compared. The photoacoustic technique\\u000a was employed to determine the detection limit of formaldehyde (less than 1 ppmV)
Raman spectroscopy of C-irradiated graphite
Hembree, D.M. Jr.; Pedraza, D.F.; Romanoski, G.R.; Withrow, S.P.; Annis, B.K.
Highly oriented pyrolytic graphite samples were irradiated with C{sup +} ions at 35 keV in a direction normal to the basal plane and subsequently annealed up to 1373 K. Substantial surface topography changes were observed at fluences of 5 {times} 10{sup 18} ions/m{sup 2} and higher using scanning electron and atomic force microscopies. Intricate networks of surface cracks and ridges developed after high dose implantation. A systematic study of the irradiation effects was conducted using Raman spectroscopy. Microstructural changes in irradiated regions were first detected at a dose of 1 {times} 10{sup 17} ions/m{sup 2} through the appearance of the Raman D-line at {approx}1360 cm{sup {minus}1}. The intensity of this line increases while that of the Raman G-line at 1580 cm{sup {minus}1} decreases as the irradiation dose is increased or the irradiation temperature is decreased. After irradiation at 280K to a fluence of 5 {times} 10{sup 19} ions/m{sup 2} or higher the first order spectrum exhibits one single line at a wavelength intermediate between the D- and G-lines. Damage recovery upon thermal annealing depends not only on the initial damage state but also on the annealing temperature sequence. Samples irradiated to a damage level where two distinct Raman peaks are no longer resolvable exhibited upon direct annealing at a high temperature two distinct Raman lines. By contrast, pre-annealing these highly irradiated specimens at lower temperatures produced less pronounced changes in the Raman spectra. Pre-annealing appears to stabilize damage structures that are more resistant to high-temperature annealing than those induced by irradiation.
Searching for minicharged particles via birefringence, dichroism and Raman spectroscopy of the vacuum polarized by a high-intensity laser wave
Villalba-Chßvez, S., E-mail: firstname.lastname@example.com; M³ller, C., E-mail: firstname.lastname@example.com
Absorption and dispersion of probe photons in the field of a high-intensity circularly polarized laser wave are investigated. The optical theorem is applied for determining the absorption coefficients in terms of the imaginary part of the vacuum polarization tensor. Compact expressions for the vacuum refraction indices and the photon absorption coefficients are obtained in various asymptotic regimes of interest. The outcomes of this analysis reveal that, far from the region relatively close to the threshold of the two-photon reaction, the birefringence and dichroism of the vacuum are small and, in some cases, strongly suppressed. On the contrary, in a vicinity of the region in which the photo-production of a pair occurs, these optical properties are manifest with lasers of moderate intensities. We take advantage of such a property in the search of minicharged particles by considering high-precision polarimetric experiments. In addition, Raman-like electromagnetic waves resulting from the inelastic part of the vacuum polarization tensor are suggested as an alternative form for finding exclusion limits on these hypothetical charge carriers. The envisaged parameters of upcoming high-intensity laser facilities are used for establishing upper bounds on the minicharged particles. -- Highlights: ĢVia dichroism and birefringence of the vacuum by a strong laser wave, minicharged particles can be probed. ĢThe discovery potential is the highest in a vicinity of the first pair production threshold. ĢAs alternative observable, Raman scattered waves are put forward.
Differential femtosecond coherent Stokes and anti-Stokes Raman spectroscopy
Ideguchi, Takuro; Yan, Ming; Guelachvili, Guy; Hõnsch, Theodor W; Picquķ, Nathalie
We demonstrate a novel technique of coherent Raman spectroscopy with a femtosecond laser. We apply to a molecular sample a sequence of pairs of ultrashort excitation and probe pulses, with a linearly increasing time delay between the two pulses from one pair to the next. We measure, as a function of the delay, the intensity modulation in the signal resulting from the differential detection of the Stokes and anti-Stokes radiations generated at the sample. The Fourier transform of such time-domain signal reveals the spectrum of the excited vibrational Raman transitions. The experimental proof-of-principle demonstrates high resolution, broad spectral span and suppression of the non-resonant background, as well as sensitivity enhancement due to the differential detection.
Confocal Raman spectroscopy of whole hairs.
Pudney, Paul D A; Bonnist, Eleanor Y M; Mutch, Kevin J; Nicholls, Rachel; Rieley, Hugh; Stanfield, Samuel
This paper describes the application of Raman spectroscopy to whole hair fibers. Previously this has proved difficult because the hairs are relatively opaque, and spatial resolution diminishes with depth because of the change in refractive index. A solution is to couple confocal Raman with multivariate curve resolution (MCR) data analysis, which separates spectral differences with depth despite this reduction in resolution. Initially, it is shown that the cuticle can be separated from the cortex, showing the differences in the proteins, which can then be plotted as a function of depth, with the cuticle factor being seen only at the surface as expected. Hairs that had been treated in different ways, e.g., by bleaching, treatment with the active molecule resorcinol followed by rinsing and treatment with a full hair care product, were also examined. In all cases, changes to the hair are identified and are associated with specific parts of the fiber. Since the hair fiber is kept intact, it can be repeatedly treated and measured, hence multistep treatment processes can be followed. This method expands the potential use of Raman spectroscopy in hair research. PMID:24359655
Noninvasive glucose sensing by transcutaneous Raman spectroscopy.
Shih, Wei-Chuan; Bechtel, Kate L; Rebec, Mihailo V
We present the development of a transcutaneous Raman spectroscopy system and analysis algorithm for noninvasive glucose sensing. The instrument and algorithm were tested in a preclinical study in which a dog model was used. To achieve a robust glucose test system, the blood levels were clamped for periods of up to 45 min. Glucose clamping and rise/fall patterns have been achieved by injecting glucose and insulin into the ear veins of the dog. Venous blood samples were drawn every 5 min and a plasma glucose concentration was obtained and used to maintain the clamps, to build the calibration model, and to evaluate the performance of the system. We evaluated the utility of the simultaneously acquired Raman spectra to be used to determine the plasma glucose values during the 8-h experiment. We obtained prediction errors in the range of ~1.5-2??mM. These were in-line with a best-case theoretical estimate considering the limitations of the signal-to-noise ratio estimates. As expected, the transition regions of the clamp study produced larger predictive errors than the stable regions. This is related to the divergence of the interstitial fluid (ISF) and plasma glucose values during those periods. Two key contributors to error beside the ISF/plasma difference were photobleaching and detector drift. The study demonstrated the potential of Raman spectroscopy in noninvasive applications and provides areas where the technology can be improved in future studies. PMID:25688542
Stand-off Raman spectroscopy of explosives
NASA Astrophysics Data System (ADS)
Zachhuber, Bernhard; Ramer, Georg; Hobro, Alison J.; Lendl, Bernhard
We present our work on stand-off Raman detection of explosives and related compounds. Our system employs 532 or 355 nm laser excitation wavelengths, operating at 10 Hz with a 4.4 ns pulse length and variable pulse energy (maximum 180 mJ/pulse at 532 nm and 120 mJ/pulse at 355 nm). The Raman scattered light is collected by a co-axially aligned 6" telescope and then transferred via a fiber optic cable and spectrograph to a fast gating iCCD camera capable of gating at 500 ps. We present results including the effect of different excitation wavelengths, showing that 355 nm excitation gives rise to significantly stronger stand-off Raman signals compared to that of 532 nm. We also show the effect of appropriate detector gating widths for discrimination of ambient light and the reduction of high background signals in the obtained Raman spectra. Our system can be used to identify explosives and their precursors in both bulk and trace forms such as RDX and PETN in the low mg range and TNT in the 700 ?g range at a distance of 20 m, as well as detection of a 1% or greater H2O2 solution at a distance of 6.3 m.
Chemical analysis of acoustically levitated drops by Raman spectroscopy.
Tuckermann, Rudolf; Puskar, Ljiljana; Zavabeti, Mahta; Sekine, Ryo; McNaughton, Don
An experimental apparatus combining Raman spectroscopy with acoustic levitation, Raman acoustic levitation spectroscopy (RALS), is investigated in the field of physical and chemical analytics. Whereas acoustic levitation enables the contactless handling of microsized samples, Raman spectroscopy offers the advantage of a noninvasive method without complex sample preparation. After carrying out some systematic tests to probe the sensitivity of the technique to drop size, shape, and position, RALS has been successfully applied in monitoring sample dilution and preconcentration, evaporation, crystallization, an acid-base reaction, and analytes in a surface-enhanced Raman spectroscopy colloidal suspension. PMID:19418043
Resonance Raman spectroscopy of optically trapped functional erythrocytes
Resonance Raman spectroscopy of optically trapped functional erythrocytes Kerstin Ramser Chalmers by measurements of trapped single func- tional erythrocytes using different excitation lines (488.0, 514
Helena Jelinkova; Jan Sulc; Maxim E. Doroschenko; Vadim V. Skornyakov; Sergey B. Kravtsov; Tasoltan T. Basiev; Peter G. Zverev
Properties of the laser operation and simultaneously stimulated Raman scattering in the new SRS-active neodymium doped SrWO4 crystal coherently end-pumped by alexandrite 752 nm laser radiation were investigated. The maximum generated energy 90 mJ from the free-running Nd3+:SrWO4 laser at 1057 nm wavelength was obtained with the output coupler reflectivity 52%. The slope efficiency reached s = 0.52, the beam
Raman gain suppression with multimode lasers
Heinrichs, R.M.; Winkler, I.C.
We have found the gain of a Raman amplifier to be almost completely suppressed when the amplifier is pumped by a multilongitudinal mode laser and seeded with an initially uncorrelated Stokes beam that is nearly as intense as the pump. This effect is predicted by a plane-wave model of Raman amplification that accounts for multimode pump and Stokes fields. Our experiments have also demonstrated that the beam quality of the pump is maintained to the extent that the amplification is suppressed.
High average power diamond Raman laser.
Feve, Jean-Philippe M; Shortoff, Kevin E; Bohn, Matthew J; Brasseur, Jason K
We report a pulsed Raman laser at 1193 nm based on synthetic diamond crystals with a record output power of 24.5 W and a slope efficiency of 57%. We compared the performance of an anti-reflection coated crystal at normal incidence with a Brewster cut sample. Raman oscillation was achieved at both room temperature and under cryogenic operation at 77 K. Modeling of these experiments allowed us to confirm the value of Raman gain coefficient of diamond, which was found to be 13.5 ▒ 2.0 cm/GW for a pump wavelength of 1030 nm. PMID:21263631
Raman spectroscopy of twisted bilayer graphene
NASA Astrophysics Data System (ADS)
Jorio, Ado; Canńado, Luiz Gustavo
Twisted bilayer graphene (tBLG) is a two-graphene layers system with a mismatch angle ? between the two hexagonal structures. The interference between the two rotated layers generates a superlattice with a ?-dependent wavevector that gives rise to van Hove singularities in the electronic density of states and activates phonons in the interior of the graphene Brillouin zone. Here we review the use of Raman spectroscopy to study tBLG, exploring the ?-dependent effects, corroborated by independent microscopy analysis. The phonon frequencies give a Raman signature of the specific tBLG, while their linewidths provide a straightforward test for tBLG structural homogeneity. Rich resonance effects, including single and multiple-resonances, intra- and inter-valley scattering events make it possible to accurately measure the energy of superlattice-induced van Hove singularities in the electronic joint density of states, as well as the phonon dispersion relation in tBLG, including the layer breathing vibrational modes.
New detector technologies and their impact on Raman spectroscopy
NASA Astrophysics Data System (ADS)
Denton, M. Bonner; Gilmore, D. A.
The latest generation of solid state detectors including Charged-Coupled Devices (CCD) and Charge-Injection Devices will be reviewed. Over the last several years, these detectors have contributed to major advances in Raman spectroscopy. Compact Raman systems using diode laser excitation, fiber-optic probes, and new generations of imaging spectrometers have been developed. New approaches for implementing very high throughput monochromators will be discussed, and their impact on the overall Raman system considered. Detection sensitivities obtained using these new optical geometries and array detector technologies are truly astounding. Even at an analyte concentration of a few ppm, a spectrum with several identifiable peaks can be obtained in a mater of seconds. This high sensitivity coupled with the ability of fiber optics to provide remote as well as in-situ sampling now make Raman a technique appropriate for many medical, environmental, and industrial applications. An overview of combining proper optical systems with currently available and soon to be introduced detectors will be presented. A variety of operating parameters for today's and tomorrow's arrays including readout noise, quantum efficiency, dark current, cosmic ray noise, and readout modes will be considered.
In vivo lipidomics using single-cell Raman spectroscopy
Wu, Huawen; Volponi, Joanne V.; Oliver, Ann E.; Parikh, Atul N.; Simmons, Blake A.; Singh, Seema
We describe a method for direct, quantitative, in vivo lipid profiling of oil-producing microalgae using single-cell laser-trapping Raman spectroscopy. This approach is demonstrated in the quantitative determination of the degree of unsaturation and transition temperatures of constituent lipids within microalgae. These properties are important markers for determining engine compatibility and performance metrics of algal biodiesel. We show that these factors can be directly measured from a single living microalgal cell held in place with an optical trap while simultaneously collecting Raman data. Cellular response to different growth conditions is monitored in real time. Our approach circumvents the need for lipid extraction and analysis that is both slow and invasive. Furthermore, this technique yields real-time chemical information in a label-free manner, thus eliminating the limitations of impermeability, toxicity, and specificity of the fluorescent probes common in currently used protocols. Although the single-cell Raman spectroscopy demonstrated here is focused on the study of the microalgal lipids with biofuel applications, the analytical capability and quantitation algorithms demonstrated are applicable to many different organisms and should prove useful for a diverse range of applications in lipidomics. PMID:21310969
Test report for remote vs. contact Raman spectroscopy
Kyle, K.R.
This report details the evaluation of two methods of spatially characterizing the chemical composition of tank core samples using Raman spectroscopy. One method involves a spatially-scanned fiber optic probe. The fiber optic probe must be in contact with a sample to interrogate its chemical composition. The second method utilizes a line-of-sight technique involving a remote imaging spectrometer that can perform characterization over an entire surface. Measurements using the imaging technique are done remotely, requiring no contact with the sample surface. The scope of this document studies the effects of laser power, distance from each type of probe to the sample surface, and interferences unique to the two methods. This report also documents the results of comparative studies of sensitivity to ferrocyanide, a key contaminant of concern in the underground storage tanks at DOE`s Hanford site. The effect of other factors on signal intensity such as moisture content is explored. The results from the two methods are compared, and a recommendation for a Raman hot cell core scanning system is presented based on the test results. This work is part of a joint effort involving several DOE laboratories for the design and development of Raman spectroscopy systems for tank waste characterization at Westinghouse Hanford Company under the auspices of the U.S. Department of Energy`s Underground Storage Tank Integrated Demonstration.
Raman Spectroscopy and instrumentation for monitoring soil carbon systems.
Stokes, D.L.
This work describes developments in the application of Raman scattering and surface-enhanced Raman scattering (SERS) towards the assessment/characterization of carbon in soil. In the past, the nonspecific total carbon mass content of soil samples has generally been determined through mass loss techniques and elemental analysis. However, because of the concern over CO{sub 2} buildup in the atmosphere and its possible role in the ''Greenhouse Effect,'' there is a need for better-defined models of global cycling of carbon. As a means towards this end, there is a need to know more about the structure and functionality of organic materials in soil. Raman spectroscopy may therefore prove to be an exceptional tool in soil carbon analysis. Based on vibrational transitions of irradiated molecules, it provides structural information that is often suitable for sample identification. Furthermore, Raman scattering yields very fine spectral features which offer the potential for multicomponent sample analysis with minimal or no sample pretreatment. Although the intensity of Raman scattering is generally extremely low, the surface-enhanced Raman scattering (SERS) effect can greatly enhance Raman signals (10{sup 6}-10{sup 8} range) through the adsorption of compounds on specially roughened metal surfaces. In our laboratory, we have investigated copper, gold and silver as possible substrate metals in the fabrication of SERS substrates. These substrates have included metal-coated microparticles, metal island films, and redox-roughened metal foils. We have evaluated several laser excitation sources spanning the 515-785 nm range for both Raman and SERS analysis. For this particular study, we have selected fulvic and humic acids as models for establishing the feasibility of using Raman and SERS in soil carbon analysis. Our studies thus far have demonstrated that copper substrates perform best in the SERS detection of humic and fulvic acids, particularly when coupled to electrochemical processes that enhance adsorption of specific compounds. This effect not only yields a stronger signal, but can also impart selectivity in the analysis of complex samples such as soil.
Coherent Raman spectro-imaging with laser frequency combs
Ideguchi, Takuro; Bernhardt, Birgitta; Guelachvili, Guy; Picquķ, Nathalie; Hõnsch, Theodor W
Optical spectroscopy and imaging of microscopic samples have opened up a wide range of applications throughout the physical, chemical, and biological sciences. High chemical specificity may be achieved by directly interrogating the fundamental or low-lying vibrational energy levels of the compound molecules. Amongst the available prevailing label-free techniques, coherent Raman scattering has the distinguishing features of high spatial resolution down to 200 nm and three-dimensional sectioning. However, combining fast imaging speed and identification of multiple - and possibly unexpected- compounds remains challenging: existing high spectral resolution schemes require long measurement times to achieve broad spectral spans. Here we overcome this difficulty and introduce a novel concept of coherent anti-Stokes Raman scattering (CARS) spectro-imaging with two laser frequency combs. We illustrate the power of our technique with high resolution (4 cm-1) Raman spectra spanning more than 1200 cm-1 recorded within le...
Cascaded Raman fiber laser in Fourier domain mode lock operation
Barry Vuong; Mark K. Harduar; Kyle H. Y. Cheng; Xijia Gu; Lawrence R. Chen; Beau A. Standish; Victor X. D. Yang
In this study, a cascaded Raman fiber laser in Fourier domain mode lock operation (FDML) is presented. This laser utilizes a Ytterbium doped twin core pump laser source at 1109 nm. The pump light is directed to a cascaded Raman cavity, which consists of multiple cascaded fiber Bragg grating pairs and 3.86 km of dispersion compensation fiber, which provides Raman
Characterization and identification of contraband using UV resonant Raman spectroscopy
NASA Astrophysics Data System (ADS)
Lacey, Richard J.; Hayward, Ian P.; Sands, H. S.; Batchelder, David N.
A range of explosives and narcotics have been examined using Raman spectroscopy with 244 nm excitation. This wavelength of excitation eliminates the fluorescence problems associated with excitation at visible wavelengths. Comparison with spectra obtained using visible excitation reveals that resonance Raman scattering is occurring. This results in simplified spectra, and enhanced Raman scattering efficiencies.
Applications of Microprobe Raman Spectroscopy in Food Science
A. Celed¾n; J. M. Aguilera
The Raman microprobe combines the analytical properties of Raman spectroscopy and the visualization capabilities of a high quality microscope, allowing localization and identification of species and phases in time intervals of seconds to a few minutes with a spatial resolution down to 1 Ąm. This article describes the basic principles of operation of the Raman microprobe and some applications that
Teaching Raman Spectroscopy in Both the Undergraduate Classroom and the Laboratory with a Portable Raman Instrument
Evan D. Hudspeth; Danielle Cleveland; Kathleen L. Batchler; Phuong A. Nguyen; Tracey L. Feaser; Lauren E. Quattrochi; Jesse Morenz; Shrimati A. Balram; Robert G. Michel; Jack Zhou; Daniel Lombardi
We have evaluated a small portable Raman instrument on loan from B&W Tek, Inc., and have determined that it can successfully be used in the classroom both as a visual aid for teaching the fundamentals of Raman spectroscopy and for a variety of undergraduate experiments as a normal component of an instrumental analysis class. Having portable Raman instrumentation would allow
Coherent anti-Stokes Raman spectroscopy temperature measurements in an internal combustion engine
Don Ball; H. Steve T. Driver; Richard J. Hutcheon; Russel J. Lockett; Gerald N. Robertson
Part of a project to investigate the physics and chemistry of alternative fuels in internal combustion engines is reported. Coherent anti-Stokes Raman spectroscopy (CARS) is used to probe the fuel-air mixture in the cylinder of a Richardo E6 variable compression ratio research engine. The laser system comprises a passively Q- switched single-longitudinal-mode frequency-doubled Nd:YAG laser and a broadband dye laser,
Teague, L.; Duff, M.
High quality CdZnTe (or CZT) crystals have the potential for use in room temperature gamma-ray and X-ray spectrometers. Over the last decade, the methods for growing high quality CZT have improved the quality of the produced crystals however there are material features that can influence the performance of these materials as radiation detectors. The presence of structural heterogeneities within the crystals, such as twinning, pipes, grain boundaries (polycrystallinity), and secondary phases (SPs) can have an impact on the detector performance. There is considerable need for reliable and reproducible characterization methods for the measurement of crystal quality. With improvements in material characterization and synthesis, these crystals may become suitable for widespread use in gamma radiation detection. Characterization techniques currently utilized to test for quality and/or to predict performance of the crystal as a gamma-ray detector include infrared (IR) transmission imaging, synchrotron X-ray topography, photoluminescence spectroscopy, transmission electron microscopy (TEM), atomic force microscopy (AFM) and Raman spectroscopy. In some cases, damage caused by characterization methods can have deleterious effects on the crystal performance. The availability of non-destructive analysis techniques is essential to validate a crystal's quality and its ability to be used for either qualitative or quantitative gamma-ray or X-ray detection. The work presented herein discusses the damage that occurs during characterization of the CZT surface by a laser during Raman spectroscopy, even at minimal laser powers. Previous Raman studies have shown that the localized annealing from tightly focused, low powered lasers results in areas of higher Te concentration on the CZT surface. This type of laser damage on the surface resulted in decreased detector performance which was most likely due to increased leakage current caused by areas of higher Te concentration. In this study, AFM was used to characterize the extent of damage to the CZT crystal surface following exposure to a Raman laser. AFM data reveal localized surface damage and increased conductivity in the areas exposed to the Raman laser beam.
Raman laser with controllable suppression of parasitics
George, E. Victor (Livermore, CA)
Method and apparatus for switching energy out of a Raman laser optical cavity. Coherent radiation at both the pump and first Stokes wave frequencies are introduced into the optical cavity from the same direction, and a second Stokes wave is utilized to switch the energy out of the cavity.
Characterization and calibration of a combined laser Raman, fluorescence and coherent Raman spectrometer
NASA Astrophysics Data System (ADS)
Lawhead, Carlos; Cooper, Nathan; Anderson, Josiah; Shiver, Tegan; Ujj, Laszlo
Electronic and vibrational spectroscopy is extremely important tools used in material characterization; therefore a table-top laser spectrometer system was built in the spectroscopy lab at the UWF physics department. The system is based upon an injection seeded nanosecond Nd:YAG Laser. The second and the third harmonics of the fundamental 1064 nm radiation are used to generate Raman and fluorescence spectra measured with MS260i imaging spectrograph occupied with a CCD detector and cooled to -85 ░C, in order to minimize the dark background noise. The wavelength calibration was performed with the emission spectra of standard gas-discharge lamps. Spectral sensitivity calibration is needed before any spectra are recorded, because of the table-top nature of the instrument. A variety of intensity standards were investigated to find standards suitable for our table top setup that do not change the geometry of the system. High quality measurement of Raman standards where analyzed to test spectral corrections. Background fluorescence removal methods were used to improve Raman signal intensity reading on highly fluorescent molecules. This instrument will be used to measure vibrational and electronic spectra of biological molecules.
[Rapid identification of potato cultivars using NIR-excited fluorescence and Raman spectroscopy].
Dai, Fen; Bergholt, Mads Sylvest; Benjamin, Arnold Julian Vinoj; Hong, Tian-Sheng; Zhiwei, Huang
Potato is one of the most important food in the world. Rapid and noninvasive identification of potato cultivars plays a important role in the better use of varieties. In this study, The identification ability of optical spectroscopy techniques, including near-infrared (NIR) Raman spectroscopy and NIR fluorescence spectroscopy, for invasive detection of potato cultivars was evaluated. A rapid NIR Raman spectroscopy system was applied to measure the composite Raman and NIR fluorescence spectroscopy of 3 different species of potatoes (98 samples in total) under 785 nm laser light excitation. Then pure Raman and NIR fluorescence spectroscopy were abstracted from the composite spectroscopy, respectively. At last, the partial least squares-discriminant analysis (PLS-DA) was utilized to analyze and classify Raman spectra of 3 different types of potatoes. All the samples were divided into two sets at random: the calibration set (74samples) and prediction set (24 samples), the model was validated using a leave-one-out, cross-validation method. The results showed that both the NIR-excited fluorescence spectra and pure Raman spectra could be used to identify three cultivars of potatoes. The fluorescence spectrum could distinguish the Favorita variety well (sensitivity: 1, specificity: 0.86 and accuracy: 0.92), but the result for Diamant (sensitivity: 0.75, specificity: 0.75 and accuracy: 0. 75) and Granola (sensitivity: 0.16, specificity: 0.89 and accuracy: 0.71) cultivars identification were a bit poorer. We demonstrated that Raman spectroscopy uncovered the main biochemical compositions contained in potato species, and provided a better classification sensitivity, specificity and accuracy (sensitivity: 1, specificity: 1 and accuracy: 1 for all 3 potato cultivars identification) among the three types of potatoes as compared to fluorescence spectroscopy. PMID:25208390
DNA-drug interaction. The effects of vitamin C on the solution structure of Calf-thymus DNA studied by FTIR and laser Raman difference spectroscopy.
Neault, J F; Naoui, M; Tajmir-Riahi, H A
The interaction of calf-thymus DNA with L-ascorbic acid was investigated in aqueous solution at pH=7.6 with drug/DNA(P)(P=phosphate) molar ratios (r) of 1/40, 1/20, 1/10, 1/5, 1/2, 1 and 2. Fourier Transform infrared (FTIR) and laser Raman difference spectroscopic techniques were used to establish correlations between spectral modifications and drug binding mode, sequence specificity, DNA melting and conformational changes, as well as structural variations of drug-DNA complexes in aqueous solution. Infrared and Raman spectroscopic results showed that at low drug concentration (r = 1/40), a B to A-type conformational conversion occurs with minor drug-DNA interaction through A-T bases. At r=1/20, drug-PO2 binding was also observed with reduced intensity of DNA inplane vibrational frequencies, due to the increased base-stacking interaction and duplex stability. At r> 1/20, major perturbations of DNA bases were observed for both A-T and G-C base pairs in the major and minor grooves of the duplex. Evidence for this comes form the shift of the infrared and Raman vibrations of the A-T and G-C bases on drug interaction. At r>1/5, a minor helix destabilization occurred with participation of several DNA donor sites in drug complexation. The ascorbate anion interaction occurred mainly through H-bonding of the acid OH and C-O groups with DNA phosphate, bases and doxyribose donor atoms. PMID:8579795
Searching for minicharged particles via birefringence, dichroism and Raman spectroscopy of the vacuum polarized by a high-intensity laser wave
S. Villalba-Chßvez; C. M³ller
Absorption and dispersion of probe photons in the field of a high-intensity circularly polarized laser wave are investigated. The optical theorem is applied for determining the absorption coefficients in terms of the imaginary part of the vacuum polarization tensor. Compact expressions for the vacuum refraction indices and the photon absorption coefficients are obtained in various asymptotic regimes of interest. The outcomes of this analysis reveal that, far from the region relatively close to the threshold of the two-photon reaction, the birefringence and dichroism of the vacuum are small and, in some cases, strongly suppressed. On the contrary, in a vicinity of the region in which the photo-production of a pair occurs, these optical properties are manifest with lasers of moderate intensities. We take advantage of such a property in the search of minicharged particles by considering high-precision polarimetric experiments. In addition, Raman-like electromagnetic waves resulting from the inelastic part of the vacuum polarization tensor are suggested as an alternative form for finding exclusion limits on these hypothetical charge carriers. The envisaged parameters of upcoming high-intensity laser facilities are used for establishing upper bounds on the minicharged particles.
Raman spectroscopy of human saliva for acute myocardial infarction detection
NASA Astrophysics Data System (ADS)
Chen, Maowen; Chen, Yuanxiang; Wu, Shanshan; Huang, Wei; Lin, Jinyong; Weng, Guo-Xing; Chen, Rong
Raman spectroscopy is a rapidly non-invasive technique with great potential for biomedical research. The aim of this study was to evaluate the feasibility of using Raman spectroscopy of human saliva for acute myocardial infarction (AMI) detection. Raman spectroscopy measurements were performed on two groups of saliva samples: one group from patients (n=30) with confirmed AMI and the other group from healthy controls (n=31). The diagnostic performance for differentiating AMI saliva from normal saliva was evaluated by multivariate statistical analysis. The combination of principal component analysis (PCA) and linear discriminate analysis (LDA) of the measured Raman spectra separated the spectral features of the two groups into two distinct clusters with little overlaps, rendering the sensitivity of 80.0% and specificity of 80.6%. The results from this exploratory study demonstrated that Raman spectroscopy of human saliva can serve as a potentially clinical tool for rapid AMI detection and screening.
Optical diagnosis of dengue virus infection in human blood serum using Raman spectroscopy
NASA Astrophysics Data System (ADS)
Saleem, M.; Bilal, M.; Anwar, S.; Rehman, A.; Ahmed, M.
We present the optical diagnosis of dengue virus infection in human blood serum using Raman spectroscopy. Raman spectra were acquired from 18 blood serum samples using a laser at 532 nm as the excitation source. A multivariate regression model based on partial least-squares regression is developed that uses Raman spectra to predict dengue infection with leave-one-sample-out cross validation. The prediction of dengue infection by our model yields correlation coefficient r2 values of 0.9998 between the predicted and reference clinical results. The model was tested for six unknown human blood sera and found to be 100% accurate in accordance with the clinical results.
Combined In Vivo Confocal Raman Spectroscopy and Confocal Microscopy of Human Skin
P. J. Caspers; G. W. Lucassen; G. J. Puppels
In vivo confocal Raman spectroscopy is a noninvasive optical method to obtain detailed information about the molecular composition of the skin with high spatial resolution. In vivo confocal scanning laser microscopy is an imaging modality that provides optical sections of the skin without physically dissecting the tissue. A combination of both techniques in a single instrument is described. This combination
Raman spectroscopy for optical diagnosis of laryngeal cancer
NASA Astrophysics Data System (ADS)
Teh, Seng Khoon; Zheng, Wei; Lau, David P.; Huang, Zhiwei
In this report, the diagnostic ability of near-infrared (NIR) Raman spectroscopy for identifying the malignant tumors from normal tissues in the larynx was studied. A rapid NIR Raman system was utilized. Multivariate statistical techniques were employed to develop effective diagnostic algorithms. Raman spectra in the range of 800-1,800 cm-1 differed significantly between normal and malignant tumor tissues. The diagnostic algorithms can yielded a diagnostic sensitivity of 92.9% and specificity 83.3% for separating malignant tumors from normal laryngeal tissues. NIR Raman spectroscopy with multivariate statistical techniques has a potential for the non-invasive detection of malignant tumors in the larynx.
Solid-core photonic crystal fiber as a Raman spectroscopy platform with a silica core as an internal reference
Denis Pristinski; Henry Du
We show that solid-core photonic crystal fiber (PCF) is a promising platform for evanescent-field Raman spectroscopy of low-volume analytes. The Raman peak ratio of a silica core as a background to acetonitrile solution as analyte contained in the air holes maintains a constant value despite varying laser power and fiber length in a set of measurements. The Raman signal from
Hydration of lysozyme studied by Raman spectroscopy.
Kocherbitov, Vitaly; Latynis, Jekaterina; Misiunas, Audrius; Barauskas, Justas; Niaura, Gediminas
Hydration plays a fundamental role in maintaining the three-dimensional structure and function of proteins. In this study, Raman spectroscopy was used to probe the hydration induced structural changes at various sites of lysozyme under isothermal conditions in the range of water contents from 0 to 44 wt %. Raman hydration curves were constructed from detailed analysis of marker bands. Transition inflection points (w(m)) and onsets determined from the hydration curves have shown that structural changes start at 7-10 and end at about 35 wt % water. The onset of structural changes coincides with the onset of the broad glass transition earlier observed in this system. The increase of ?-helix content starts at very low concentrations of water with w(m) = 12 wt %. Monitoring the development of importance for enzymatic action hydrophobic clusters has revealed wm = 15 wt % and completion of the process at 25 wt %. The parameters of 621 cm(-1) (Phe) and 1448 cm(-1) (CH2 bending) modes were found to be sensitive to hydration, suggesting changes in organization of water molecules near the protein surface. The native structure of lysozyme was achieved at 35 wt % water where its content is high enough for filling the space between lysozyme molecules. PMID:23557185
Measurement of clathrate hydrates via Raman spectroscopy
Sum, A.K.; Burruss, R.C.; Sloan, E.D., Jr.
Raman spectra of clathrate hydrate guest molecules are presented for three known structures (I (sI), II (sII), and H (sH)) in the following systems: CH4 (sI), CO2 (sI), C3H8 (sII), CH4 + CO2 (sI), CD4 + C3H8 (sII), CH4 + N2 (sI), CH4 + THF-d8 (sII), and CH4 + C7D14 (sH). Relative occupancy of CH4 in the large and small cavities of sI were determined by deconvoluting the ??1 symmetric bands, resulting in hydration numbers of 6.04 ?? 0.03. The frequency of the ??1 bands for CH4 in structures I, II, and H differ statistically, so that Raman spectroscopy is a potential tool to identify hydrate crystal structure. Hydrate guest compositions were also measured for two vapor compositions of the CH4 + CO2 system, and they compared favorably with predictions. The large cavities were measured to be almost fully occupied by CH4 and CO2, whereas only a small fraction of the small cavities are occupied by CH4. No CO2 was found in the small cavities. Hydration numbers from 7.27 to 7.45 were calculated for the mixed hydrate.
Raman spectroscopy of ion irradiated amorphous carbons
NASA Astrophysics Data System (ADS)
Baratta, G. A.; Arena, M. M.; Strazzulla, G.; Colangeli, L.; Mennella, V.; Bussoletti, E.
We have studied, by "in situ" Raman spectroscopy, the modifications induced by 3 keV He + ions on thin amorphous carbon grain deposits. Previous results obtained with our experimental apparatus show that in the case of carbon-containing frozen targets (such as benzene and butane) for doses greater than about 100 eV/mol, ion irradiation induces the formation of an hydrogenated amorphous carbon. In this paper, the bombarded material is already an amorphous carbon with a relatively high order degree. In this case ion irradiation progressively decreases the order degree in the amorphous carbon. This result is in agreement with analogous ion irradiation experiments carried out on highly ordered pyrolitic graphite crystals. These studies are important to understand physical characteristics and evolution of refractory carbon grains in astrophysical environments.
Urinalysis by surface-enhanced Raman spectroscopy
NASA Astrophysics Data System (ADS)
Farquharson, Stuart; Lee, Yuan-Hsiang; Kwon, Hyeog; Shahriari, Mahmoud; Rainey, Petrie
The overall objective of this Small Business Technology Transfer Research program is the development of a fiber optic sensor suitable for surface-enhanced Raman spectroscopy that provides reversible, reproducible, quantitative measurements of trace chemicals. The sensor is intended to benefit NASA and the International Space Station in several areas. For example, the sensor could provide real-time measurements for space-based research in the areas of chemistry and biotechnology, it could provide continuous water quality monitoring in the life support systems, or it could provide astronaut health monitoring through urine and blood chemical analysis. This paper describes the development of the SERS based sensor and its application to astronaut health monitoring through urinalysis. .
Raman spectroscopy of hypersonic shock waves
Ramos; Mate; Tejeda; Fernandez; Montero
Raman spectroscopy is shown to be an efficient diagnostic methodology for the study of hypersonic shock waves. As a test, absolute density and rotational population profiles have been measured across five representative normal shock waves of N2 generated in a free jet, spanning the Mach number range 7.7
Electronic Resonance Enhancement in Raman and CARS Spectroscopy: Surface Enhanced Scattering of Highly Fluorescent Molecules
NASA Astrophysics Data System (ADS)
Lawhead, Carlos; Ujj, Laszlo
Surface enhanced Raman spectroscopy (SERS) is an extremely useful tool in increasing sensitivity of Raman spectroscopy; this technique significantly increases the signal from vibrational resonances which can overcome background fluoresces. Silver nanoparticles coated substrates and the silver nanoparticles in solution were used on a variety of fluorescent molecules in order to overcome sample complexities and measure the vibrational spectra. The possible enhancement of SERS using a coherent Raman (CARS) method was investigated, but enhancement factors due to Surface Enhanced CARS have yet to be verified. The instrument used was developed in the University of West Florida Physics Department utilized the second harmonic of a Nd:YAG laser to provide the excitation wavelength at 532 nm and is capable of both transmission and reflection Raman measurements. Special thanks to the UWF Office of Undergraduate Research.
Periodontitis diagnostics using resonance Raman spectroscopy on saliva
NASA Astrophysics Data System (ADS)
Gonchukov, S.; Sukhinina, A.; Bakhmutov, D.; Biryukova, T.; Tsvetkov, M.; Bagratashvily, V.
In view of its wealth of molecular information, Raman spectroscopy has been the subject of active biomedical research. The aim of this work is Raman spectroscopy (RS) application for the determination of molecular biomarkers in saliva with the objective of early periodontitis detection. As was shown in our previous study, carotenoids contained in saliva can be molecular fingerprint information for the periodontitis level. It is shown here that the carotenoid RS lines at wavenumbers of 1156 and 1524 cm?1 can be easily detected and serve as reliable biomarkers of periodontitis using resonance Raman spectroscopy of dry saliva.
Forensic and homeland security applications of modern portable Raman spectroscopy.
Izake, Emad L
Modern detection and identification of chemical and biological hazards within the forensic and homeland security contexts may well require conducting the analysis in field while adapting a non-contact approach to the hazard. Technological achievements on both surface and resonance enhancement Raman scattering re-developed Raman spectroscopy to become the most adaptable spectroscopy technique for stand-off and non-contact analysis of hazards. On the other hand, spatially offset Raman spectroscopy proved to be very valuable for non-invasive chemical analysis of hazards concealed within non-transparent containers and packaging. PMID:20395087
Femtosecond stimulated Raman spectroscopy by six-wave mixing
NASA Astrophysics Data System (ADS)
Molesky, Brian P.; Guo, Zhenkun; Moran, Andrew M.
Femtosecond Stimulated Raman Spectroscopy (FSRS) is motivated by the knowledge of the molecular geometry changes that accompany sub-picosecond chemical reactions. The detection of vibrational resonances throughout the entire fingerprint region of the spectrum with sub-100-fs delay precision is fairly straightforward to accomplish with the FSRS technique. Despite its utility, FSRS must contend with substantial technical challenges that stem from a large background of residual laser light and lower-order nonlinearities when all laser pulses are electronically resonant with the equilibrium system. In this work, a geometry based on five incident laser beams is used to eliminate much of this undesired background in experiments conducted on metmyoglobin. Compared to a three-beam FSRS geometry with all electronically resonant laser pulses, the five-beam approach described here offers major improvements in the data acquisition rate, sensitivity, and background suppression. The susceptibility of the five-beam geometry to experimental artifacts is investigated using control experiments and model calculations. Of particular concern are undesired cascades of third-order nonlinearities, which are known to challenge FSRS measurements carried out on electronically off-resonant systems. It is generally understood that "forbidden" steps in the desired nonlinear optical processes are the origin of the problems encountered under off-resonant conditions. In contrast, the present experiments are carried out under electronically resonant conditions, where such unfortunate selection rules do not apply. Nonetheless, control experiments based on spectroscopic line shapes, signal phases, and sample concentrations are conducted to rule out significant contributions from cascades of third-order processes. Theoretical calculations are further used to estimate the relative intensities of the direct and cascaded responses. Overall, the control experiments and model calculations presented in this work suggest promise for multidimensional resonance Raman investigations of heme proteins.
Femtosecond stimulated Raman spectroscopy by six-wave mixing.
Molesky, Brian P; Guo, Zhenkun; Moran, Andrew M
Femtosecond Stimulated Raman Spectroscopy (FSRS) is motivated by the knowledge of the molecular geometry changes that accompany sub-picosecond chemical reactions. The detection of vibrational resonances throughout the entire fingerprint region of the spectrum with sub-100-fs delay precision is fairly straightforward to accomplish with the FSRS technique. Despite its utility, FSRS must contend with substantial technical challenges that stem from a large background of residual laser light and lower-order nonlinearities when all laser pulses are electronically resonant with the equilibrium system. In this work, a geometry based on five incident laser beams is used to eliminate much of this undesired background in experiments conducted on metmyoglobin. Compared to a three-beam FSRS geometry with all electronically resonant laser pulses, the five-beam approach described here offers major improvements in the data acquisition rate, sensitivity, and background suppression. The susceptibility of the five-beam geometry to experimental artifacts is investigated using control experiments and model calculations. Of particular concern are undesired cascades of third-order nonlinearities, which are known to challenge FSRS measurements carried out on electronically off-resonant systems. It is generally understood that "forbidden" steps in the desired nonlinear optical processes are the origin of the problems encountered under off-resonant conditions. In contrast, the present experiments are carried out under electronically resonant conditions, where such unfortunate selection rules do not apply. Nonetheless, control experiments based on spectroscopic line shapes, signal phases, and sample concentrations are conducted to rule out significant contributions from cascades of third-order processes. Theoretical calculations are further used to estimate the relative intensities of the direct and cascaded responses. Overall, the control experiments and model calculations presented in this work suggest promise for multidimensional resonance Raman investigations of heme proteins. PMID:26049425
Femtosecond Coherent Anti-Stokes Raman Spectroscopy (CARS) As Next Generation Nonlinear LIDAR Spectroscopy and Microscopy
Ooi, C. H. Raymond [School of Engineering, Monash University, Jalan Lagoon Selatan, Bandar Sunway, 46150 Selangor DarulEhsan, Malaysia and Department of Physics, Korea University, Anam-dong, Seongbuk-gu, Seoul, 136-713 (Korea, Republic of)
Nonlinear spectroscopy using coherent anti-Stokes Raman scattering and femtosecond laser pulses has been successfully developed as powerful tools for chemical analysis and biological imaging. Recent developments show promising possibilities of incorporating CARS into LIDAR system for remote detection of molecular species in airborne particles. The corresponding theory is being developed to describe nonlinear scattering of a mesoscopic particle composed of complex molecules by laser pulses with arbitrary shape and spectral content. Microscopic many-body transform theory is used to compute the third order susceptibility for CARS in molecules with known absorption spectrum and vibrational modes. The theory is combined with an integral scattering formula and Mie-Lorentz formulae, giving a rigorous formalism which provides powerful numerical experimentation of CARS spectra, particularly on the variations with the laser parameters and the direction of detection.
Chromosomal analysis and identification based on optical tweezers and Raman spectroscopy
NASA Astrophysics Data System (ADS)
Ojeda, Jenifer F.; Xie, Changan; Li, Yong-Qing; Bertrand, Fred E.; Wiley, John; McConnell, Thomas J.
The ability to identify specific chromosomes with certainty has been established by the development of several cytogenetic techniques based on staining. Here, we report the use of a new optical technique, laser tweezers and Raman spectroscopy (LTRS), to capture and manipulate chromosomes in order to obtain their spectral patterns for molecular analysis without the need for staining. The purpose of this study was to obtain Raman spectroscopy patterns for chromosomes number 1, 2, and 3 and to test if the Raman spectroscopy pattern could be used to distinguish these three chromosomes. In our experiment, optical tweezers were used to capture the individual chromosomes and the Raman spectral patterns were collected for the trapped chromosomes. Then, the captured chromosome was manipulated with the optical tweezers and moved to another chamber through a micro - channel, in which the chromosomes were G banded for positive identification as chromosome number 1, 2, or 3. Generalized discriminate analysis (GDA) was used to compare the Raman signatures. This analysis revealed that chromosomes 1, 2, and 3 could be distinguished and identified based on their Raman spectra. Development of this approach will lead to more rapid automatic methods for chromosome analysis and identification without the use of prior staining. Moreover, the Raman spectral patterns may lend themselves to more detailed analysis of chromosomal structure than is currently available with standard staining protocols. Such analysis may some day be useful for rapid, automated screening and diagnosis for certain cancers.
Optical diagnostic of hepatitis B (HBV) and C (HCV) from human blood serum using Raman spectroscopy
NASA Astrophysics Data System (ADS)
Anwar, Shahzad; Firdous, Shamaraz
Hepatitis is the second most common disease worldwide with half of the cases arising in the developing world. The mortality associated with hepatitis B and C can be reduced if the disease is detected at the early stages of development. The aim of this study was to investigate the potential of Raman spectroscopy as a diagnostic tool to detect biochemical changes accompanying hepatitis progression. Raman spectra were acquired from 20 individuals with six hepatitis B infected patients, six hepatitis C infected patients and eight healthy patients in order to gain an insight into the determination of biochemical changes for early diagnostic. The human blood serum was examined at a 532?nm excitation laser source. Raman characteristic peaks were observed in normal sera at 1006, 1157 and 1513?cm?1, while in the case of hepatitis B and C these peaks were found to be blue shifted with decreased intensity. New Raman peaks appeared in HBV and HCV infected sera at 1194, 1302, 844, 905, 1065 and 1303?cm?1 respectively. A Mat lab subroutine and frequency domain filter program is developed and applied to signal processing of Raman scattering data. The algorithms have been successfully applied to remove the signal noise found in experimental scattering signals. The results show that Raman spectroscopy displays a high sensitivity to biochemical changes in blood sera during disease progression resulting in exceptional prediction accuracy when discriminating between normal and malignant. Raman spectroscopy shows enormous clinical potential as a rapid non-invasive diagnostic tool for hepatitis and other infectious diseases.
A continuous-wave Raman silicon laser.
Rong, Haisheng; Jones, Richard; Liu, Ansheng; Cohen, Oded; Hak, Dani; Fang, Alexander; Paniccia, Mario
Achieving optical gain and/or lasing in silicon has been one of the most challenging goals in silicon-based photonics because bulk silicon is an indirect bandgap semiconductor and therefore has a very low light emission efficiency. Recently, stimulated Raman scattering has been used to demonstrate light amplification and lasing in silicon. However, because of the nonlinear optical loss associated with two-photon absorption (TPA)-induced free carrier absorption (FCA), until now lasing has been limited to pulsed operation. Here we demonstrate a continuous-wave silicon Raman laser. Specifically, we show that TPA-induced FCA in silicon can be significantly reduced by introducing a reverse-biased p-i-n diode embedded in a silicon waveguide. The laser cavity is formed by coating the facets of the silicon waveguide with multilayer dielectric films. We have demonstrated stable single mode laser output with side-mode suppression of over 55 dB and linewidth of less than 80 MHz. The lasing threshold depends on the p-i-n reverse bias voltage and the laser wavelength can be tuned by adjusting the wavelength of the pump laser. The demonstration of a continuous-wave silicon laser represents a significant milestone for silicon-based optoelectronic devices. PMID:15716948
Multivariate classification of pigments and inks using combined Raman spectroscopy and LIBS
Marek Hoehse; Andrea Paul; Igor Gornushkin; Ulrich Panne
The authenticity of objects and artifacts is often the focus of forensic analytic chemistry. In document fraud cases, the\\u000a most important objective is to determine the origin of a particular ink. Here, we introduce a new approach which utilizes\\u000a the combination of two analytical methods, namely Raman spectroscopy and laser-induced breakdown spectroscopy (LIBS). The\\u000a methods provide complementary information on both
Real-time in vivo cancer diagnosis using raman spectroscopy.
Wang, Wenbo; Zhao, Jianhua; Short, Michael; Zeng, Haishan
Raman spectroscopy has becoming a practical tool for rapid in vivo tissue diagnosis. This paper provides an overview on the latest development of real-time in vivo Raman systems for cancer detection. Instrumentation, data handling, as well as oncology applications of Raman techniques were covered. Optic fiber probes designs for Raman spectroscopy were discussed. Spectral data pre-processing, feature extraction, and classification between normal/benign and malignant tissues were surveyed. Applications of Raman techniques for clinical diagnosis for different types of cancers, including skin cancer, lung cancer, stomach cancer, oesophageal cancer, colorectal cancer, cervical cancer, and breast cancer, were summarized. Schematic of a real-time Raman spectrometer for skin cancer detection. Without correction, the image captured on CCD camera for a straight entrance slit has a curvature. By arranging the optic fiber array in reverse orientation, the curvature could be effectively corrected. PMID:25220508
Sensitivity of Raman spectroscopy to normal patient variability
NASA Astrophysics Data System (ADS)
Vargis, Elizabeth; Byrd, Teresa; Logan, Quinisha; Khabele, Dineo; Mahadevan-Jansen, Anita
Many groups have used Raman spectroscopy for diagnosing cervical dysplasia; however, there have been few studies looking at the effect of normal physiological variations on Raman spectra. We assess four patient variables that may affect normal Raman spectra: Race/ethnicity, body mass index (BMI), parity, and socioeconomic status. Raman spectra were acquired from a diverse population of 75 patients undergoing routine screening for cervical dysplasia. Classification of Raman spectra from patients with a normal cervix is performed using sparse multinomial logistic regression (SMLR) to determine if any of these variables has a significant effect. Results suggest that BMI and parity have the greatest impact, whereas race/ethnicity and socioeconomic status have a limited effect. Incorporating BMI and obstetric history into classification algorithms may increase sensitivity and specificity rates of disease classification using Raman spectroscopy. Studies are underway to assess the effect of these variables on disease.
Ultrafast Laser-Based Spectroscopy and Sensing: Applications in LIBS, CARS, and THz Spectroscopy
Leahy-Hoppa, Megan R.; Miragliotta, Joseph; Osiander, Robert; Burnett, Jennifer; Dikmelik, Yamac; McEnnis, Caroline; Spicer, James B.
Ultrafast pulsed lasers find application in a range of spectroscopy and sensing techniques including laser induced breakdown spectroscopy (LIBS), coherent Raman spectroscopy, and terahertz (THz) spectroscopy. Whether based on absorption or emission processes, the characteristics of these techniques are heavily influenced by the use of ultrafast pulses in the signal generation process. Depending on the energy of the pulses used, the essential laser interaction process can primarily involve lattice vibrations, molecular rotations, or a combination of excited states produced by laser heating. While some of these techniques are currently confined to sensing at close ranges, others can be implemented for remote spectroscopic sensing owing principally to the laser pulse duration. We present a review of ultrafast laser-based spectroscopy techniques and discuss the use of these techniques to current and potential chemical and environmental sensing applications. PMID:22399883
Structural analysis of unfolded peptides by Raman spectroscopy.
Schweitzer-Stenner, Reinhard; Soffer, Jonathan B; Toal, Siobhan; Verbaro, Daniel
Raman spectroscopy has positioned itself as an invaluable tool in the study of complex biological systems, consistently being used to obtain information illustrating a vast array of fundamental properties. Of primary interest, with respect to the focus of this chapter, are conformational changes of peptide backbones. For short peptides to larger biological systems this understanding can be extended to local hydrogen bonding interactions and the probing of other structural or organizational properties. With regard to unfolded peptides Raman spectroscopy can be used as a technique complementary to infrared (IR) and vibrational circular dichroism (VCD) spectroscopy. This chapter describes how high quality polarized Raman spectra of peptide can be recorded with a Raman microspectrometer and how the structure sensitive amide I band profiles of isotropic and anisotropic Raman scattering can be analyzed in conjunction with the respective IR and VCD profiles to obtain conformational distributions of short unfolded peptides. PMID:22760326
High-pressure Raman spectroscopy of phase change materials
Hsieh, Wen-Pin, E-mail: email@example.com; Mao, Wendy L. [SLAC National Accelerator Laboratory, Stanford Institute for Materials and Energy Sciences, Menlo Park, California 94025 (United States) [SLAC National Accelerator Laboratory, Stanford Institute for Materials and Energy Sciences, Menlo Park, California 94025 (United States); Department of Geological and Environmental Sciences, Stanford University, Stanford, California 94305 (United States); Zalden, Peter [SLAC National Accelerator Laboratory, Stanford Institute for Materials and Energy Sciences, Menlo Park, California 94025 (United States)] [SLAC National Accelerator Laboratory, Stanford Institute for Materials and Energy Sciences, Menlo Park, California 94025 (United States); Wuttig, Matthias [I. Physikalisches Institut (IA), RWTH Aachen University, 52056 Aachen (Germany) [I. Physikalisches Institut (IA), RWTH Aachen University, 52056 Aachen (Germany); JARA ¢ Fundamentals of Future Information Technology, RWTH Aachen University, 52056 Aachen (Germany); Lindenberg, Aaron M. [SLAC National Accelerator Laboratory, Stanford Institute for Materials and Energy Sciences, Menlo Park, California 94025 (United States) [SLAC National Accelerator Laboratory, Stanford Institute for Materials and Energy Sciences, Menlo Park, California 94025 (United States); Department of Materials Science and Engineering, Stanford University, Stanford, California 94305 (United States); SLAC National Accelerator Laboratory, PULSE Institute, Menlo Park, California 94025 (United States)
We used high-pressure Raman spectroscopy to study the evolution of vibrational frequencies of the phase change materials (PCMs) Ge{sub 2}Sb{sub 2}Te{sub 5}, GeSb{sub 2}Te{sub 4}, and SnSb{sub 2}Te{sub 4}. We found that the critical pressure for triggering amorphization in the PCMs decreases with increasing vacancy concentration, demonstrating that the presence of vacancies, rather than differences in the atomic covalent radii, is crucial for pressure-induced amorphization in PCMs. Compared to the as-deposited amorphous phase, the pressure-induced amorphous phase has a similar vibrational spectrum but requires much lower laser power to transform into the crystalline phase, suggesting different kinetics of crystallization, which may have implications for applications of PCMs in non-volatile data storage.
Multivariate reference technique for quantitative analysis of fiber-optic tissue Raman spectroscopy.
Bergholt, Mads Sylvest; Duraipandian, Shiyamala; Zheng, Wei; Huang, Zhiwei
We report a novel method making use of multivariate reference signals of fused silica and sapphire Raman signals generated from a ball-lens fiber-optic Raman probe for quantitative analysis of in vivo tissue Raman measurements in real time. Partial least-squares (PLS) regression modeling is applied to extract the characteristic internal reference Raman signals (e.g., shoulder of the prominent fused silica boson peak (~130 cm(-1)); distinct sapphire ball-lens peaks (380, 417, 646, and 751 cm(-1))) from the ball-lens fiber-optic Raman probe for quantitative analysis of fiber-optic Raman spectroscopy. To evaluate the analytical value of this novel multivariate reference technique, a rapid Raman spectroscopy system coupled with a ball-lens fiber-optic Raman probe is used for in vivo oral tissue Raman measurements (n = 25 subjects) under 785 nm laser excitation powers ranging from 5 to 65 mW. An accurate linear relationship (R(2) = 0.981) with a root-mean-square error of cross validation (RMSECV) of 2.5 mW can be obtained for predicting the laser excitation power changes based on a leave-one-subject-out cross-validation, which is superior to the normal univariate reference method (RMSE = 6.2 mW). A root-mean-square error of prediction (RMSEP) of 2.4 mW (R(2) = 0.985) can also be achieved for laser power prediction in real time when we applied the multivariate method independently on the five new subjects (n = 166 spectra). We further apply the multivariate reference technique for quantitative analysis of gelatin tissue phantoms that gives rise to an RMSEP of ~2.0% (R(2) = 0.998) independent of laser excitation power variations. This work demonstrates that multivariate reference technique can be advantageously used to monitor and correct the variations of laser excitation power and fiber coupling efficiency in situ for standardizing the tissue Raman intensity to realize quantitative analysis of tissue Raman measurements in vivo, which is particularly appealing in challenging Raman endoscopic applications. PMID:24160634
Turbidity corrected Raman spectroscopy for blood analyte detection
Barman, Ishan; Singh, Gajendra P.; Dasari, Ramachandra R.; Feld, Michael S.
A major challenge in quantitative biological Raman spectroscopy, particularly as applied to transcutaneous Raman spectroscopy measurements, is overcoming the deleterious effects of scattering and absorption (turbidity). The Raman spectral information is distorted by multiple scattering and absorption events in the surrounding medium, thereby diminishing the prediction capability of the calibration model. To account for these distortions, we present a novel analytical method, that we call turbidity corrected Raman spectroscopy (TCRS), which is based on the photon migration approach and employs alternate acquisition of diffuse reflectance and Raman spectra. We demonstrate that on application of TCRS, the widely varying Raman spectra observed from a set of tissue phantoms having the same concentration of Raman scatterers but different turbidities tend to collapse onto a single spectral profile. Furthermore, in a prospective study employing physical tissue models with varying turbidities and randomized concentrations of Raman scatterers and interferents, a 20% reduction in prediction error is obtained by applying the turbidity correction procedure to the observed Raman spectra. PMID:19413337
Hyperspectral Imaging with Stimulated Raman Scattering by Chirped Femtosecond Lasers
Xie, Xiaoliang Sunney
Hyperspectral Imaging with Stimulated Raman Scattering by Chirped Femtosecond Lasers Dan Fu, Gary imaging system using chirped femtosecond lasers to achieve rapid Raman spectra acquisition while retaining laser beams with an energy difference tuned to the vibrational frequency of the molecule of interest
Multimodal, multiplex, Raman spectroscopy of alcohol in diffuse, fluorescent media
Scott T. McCain; Michael E. Gehm; Yanqia Wang
Optical diagnostics in biological materials are hindered by fluorescence and scattering. We have developed a multimodal, multiplex, coded-aperture Raman spectrometer to detect alcohol in a lipid tissue phantom solution. Raman spectroscopy is a powerful diagnostic tool due to its high specificity and possibility for in vivo applications. At the same time, its very weak signal strength and incoherent scattering properties
In-vivo tissue characterization by Raman spectroscopy
NASA Astrophysics Data System (ADS)
Puppels, Gerwin J.; van Aken, Matthijs; Wolthuis, Rolf; Caspers, Peter J.; Bakker Schut, Tom C.; Bruining, Hajo A.; Roemer, Tjeerd J.; Buschman, Hendrik P. J.; Wach, Michael L.; Robinson, J. S., Jr.
Vibrational spectroscopies hold great promise for applications in medical diagnosis, especially if they can be applied in vivo. Recent advances in flexible fiber probe design, enable good quality Raman spectra of tissue to be obtained in vivo. Here we illustrate this with Raman spectra of rat tissues, obtained ex vivo and in vivo.
Applications of Ultraviolet Resonance Raman Spectroscopy: Residual Olefins in Polypropylene
Asher, Sanford A.
Applications of Ultraviolet Resonance Raman Spectroscopy: Residual Olefins in Polypropylene P. M of polymer, which probably end{cares photo-oxidative degra- dation. IndexHeadings: Ultraviolet resonance 1p~mAn~Polypropylene nm in resonance with olefin groups. We demonstrate that UV res- onance Raman spectra of polypropylene
Microfabricated out-of-plane scanning microlens for Raman Spectroscopy
Chin-Pang-Billy Siu; Haishan Zeng; Mu Chiao
We present a microfabricated out-of-plane scanning microlens for miniaturized Raman Spectroscopy. The out-of-plane actuation is electrostatic driven and achieves 90 mum scan range at 1 k Hz. A Raman spectrum analysis on drug, Tylenol, is reported.
Micro-Raman Spectroscopy of NWA 4047 Meteorite
NASA Astrophysics Data System (ADS)
Szurgot, M.; Kisiel, K.; Kisiel, R.
NWA 4047 ordinary chondrite was investigated by micro-Raman spectroscopy to reveal, identify and characterize minerals. Olivines, orthopyroxenes, clinopyroxene, plagioclase, whitlockite, coesite, tephroite, graphite and diamond have been identified.
Raman Spectroscopy of Organic Matter in Antarctic Micrometeorites
NASA Astrophysics Data System (ADS)
Haenecour, P.; Floss, C.; Wang, A.; Yada, T.
We report on the coordinated analysis (NanoSIMS 50, Auger Nanoprobe, Raman spectroscopy) of 15N-rich organic matter associated with iron oxide-hydroxide grains in three fine-grained Antarctic micrometeorites.
Investigation of biomineralization by Raman spectroscopy
NASA Astrophysics Data System (ADS)
Fatscher, Robert William
Biomineralization is a process in which living organism grow composite materials consisting of inorganic and organic materials. This produces a composite material consisting of both inorganic and organic components, with superior mechanical properties. In the human body bone and dentin are both examples of biominerals. In this research Raman spectroscopy was used to characterize dentin from mice and human teeth, to determine composition. In the mouse tooth samples areas of irregular dentin were found, along the inside of the tooth, to be in the process of mineralization. By analyzing the samples along these areas we were able to determine the composition of dentin and track how it changed in these area. By analysis of the mineral to matrix ratio the areas of irregular dentin were determined to have less mineral present. Observations of other organic components and collagen in increased concentrations in this area suggested these area were in the process of biomineralization. The understanding of the structure of dentin and its biomineralization process is of crucial importance when trying reproduce dentin. Scientists and engineers are able to produce dentin minerals in vitro by culturing various dental stem cells. The ability to create dentin mineral from cells could lead to methods of repairing dentin in patients, or even lead to the creation of a completely engineered tooth. While dentin-like materials can be produced in a laboratory environment, analysis and comparison of the composition of these materials must be performed to ensure the mineral produced is consistent with dentin. Mineralized nodules from six different dental stem cell lines were cultured to produce a mineralized deposit. Utilizing Raman spectroscopy, we were able to determine cell source dependent differences in a variety of dental stem cells, and compare the mineral produced to native dentin. Orthopedic implants are implants used to replace damaged bone, examples include knee, hip and dental implants. These implants are designed to osteointegrate with the native healthy tissues in order to create a functionally stable and structural interface. Biomaterials such as hydroxyapatite and titania are known to increase the rate of bone regeneration in vivo.1 By accelerating the early response of bone forming cells to these implants, better fixation is achieved between the implant and the bone, shortening recovery times and increasing the viability of these implants. In the last part of this research an investigation of osteoblasts cultured at 14 days on five different heat-treated titania substrates was investigated by Raman spectroscopy, in order to observe the initial cellular response to the titania substrates. The heat-treatment of titania changes the amount of oxygen on it's surface which in turn effects the surface energy. A change in the surface energy of a material will affect the cellular response, by culturing cells on various heat-treated titania substrates a relationship between the surface energy and cellular response can be investigated. A faster cellular response would lead to an increased rate of bone regeneration shortening healing times and allowing for better fixation of the implant.
Raman spectroscopy of phonons in optically confined semiconductor nanostructures
A. Fainstein; B. Jusserand
We describe two alternative schemes for optical resonant Raman enhancement using semiconductor planar microcavities. These geometries, which rely either on the angular tuning of laser and scattered photons, or alternatively on double mode structures, allow for inelastic light scattering amplifications of up to 105. We overview results of a series of investigations of phonon Raman scattering in semiconductor nanostructures which
Forensic and homeland security applications of modern portable Raman spectroscopy
Emad L. Izake
Modern detection and identification of chemical and biological hazards within the forensic and homeland security contexts may well require conducting the analysis in field while adapting a non-contact approach to the hazard. Technological achievements on both surface and resonance enhancement Raman scattering re-developed Raman spectroscopy to become the most adaptable spectroscopy technique for stand-off and non-contact analysis of hazards. On
In vivo infrared and Raman spectroscopy of human stratum corneum
Gerald W. Lucassen; Peter J. Caspers; Gerwin J. Puppels
ATR-FTIR spectroscopy and Raman spectroscopy were employed to obtain information about the molecular composition and hydration of skin in vivo. Both techniques enable the in vivo acquisition of high quality spectra within 10-30s at a spectral resolution of 8cm-1. The penetration depth of ATR-FTIR is about 1.5 (Mu) m. Raman spectra could be obtained with a resolution of about 5
Raman spectroscopy in biomedicine ¢ non-invasive in vitro analysis of cells and extracellular matrix components in tissues
Brauchle, Eva; Schenke-Layland, Katja
Raman spectroscopy is an established laser-based technology for the quality assurance of pharmaceutical products. Over the past few years, Raman spectroscopy has become a powerful diagnostic tool in the life sciences. Raman spectra allow assessment of the overall molecular constitution of biological samples, based on specific signals from proteins, nucleic acids, lipids, carbohydrates, and inorganic crystals. Measurements are non-invasive and do not require sample processing, making Raman spectroscopy a reliable and robust method with numerous applications in biomedicine. Moreover, Raman spectroscopy allows the highly sensitive discrimination of bacteria. Rama spectra retain information on continuous metabolic processes and kinetics such as lipid storage and recombinant protein production. Raman spectra are specific for each cell type and provide additional information on cell viability, differentiation status, and tumorigenicity. In tissues, Raman spectroscopy can detect major extracellular matrix components and their secondary structures. Furthermore, the non-invasive characterization of healthy and pathological tissues as well as quality control and process monitoring of in vitro-engineered matrix is possible. This review provides comprehensive insight to the current progress in expanding the applicability of Raman spectroscopy for the characterization of living cells and tissues, and serves as a good reference point for those starting in the field. PMID:23161832
Gated Raman spectroscopy (GRAS): A new experimental approach for the measurement of Raman signals of particles in suspension
NASA Astrophysics Data System (ADS)
de Grooth, B. G.; de Mul, F. F. M.; Greve, J.
A new technique for the measurement of Raman spectra of small particles in suspension, such as biological cells, is described. The particles flow through a rectangular glass capillary mounted at the sample position of a laser Raman microspectrometer. The measuring volume inside the glass capillary is comparable to the volume of the particles. The elastic forward light scattering of the laser beam by the particles is used to monitor the presence of a particle in the measuring volume. Photon pulses from the Raman detector are counted only when a particle is inside the measuring volume. In this way the background signal caused by the suspending medium is suppressed, thus allowing measurement at very low particle concentrations. The technique, which is called gated Raman spectroscopy (GRAS) combines features such as: efficient light collection, suppression of background, and the possibility to use high laser powers. A great advantage is that this technique can be used for the study of (living) biological cells under physiological conditions. The GRAS technique is demonstrated with polystyrene particles and with unicellular algae chlorella vulgaris.
Surface spectroscopic study of tungsten-alumina catalysts using x-ray photoelectron, ion scattering, and Raman spectroscopies
Lawrence Salvati; Leo E. Makovsky; J. M. Stencel; F. R. Brown; David M. Hercules
X-ray photoelectron spectroscopy (XPS) (= electron spectroscopy for chemical analysis (ESCA)), ion scattering spectroscopy (ISS), and laser Raman spectroscopy (LRS) have been used to characterize a series of WOŌ\\/AlŌOŌ (TA) catalysts. The results of this investigation show that WOŌ\\/AlŌOŌ catalysts are structurally similar to MoOŌ\\/AlŌOŌ catalysts. Three distinctly different tungsten species were identified by using LRS. At low WOŌ loadings
Structure and Composition of Air-Plane Soots and Surrogates Analyzed by Raman Spectroscopy and Laser/Ions Desorption Mass Spectrometry
NASA Astrophysics Data System (ADS)
Ortega, Ismael; Chazallon, Bertrand; Carpentier, Yvain; Irimiea, Cornelia; Focsa, Cristian; Ouf, Franńois-Xavier; Salm, Franńois; Delhaye, David; Gaffiķ, Daniel; Yon, Jķr¶me
Aviation alters the composition of the atmosphere globally and can thus drive climate change and ozone depletion [1]. An aircraft exhaust plume contains species emitted by the engines, species formed in the plume from the emitted species and atmospheric species that become entrained into the plume. The majority of emitted species (gases and soot particles) are produced by the combustion of kerosene with ambient air in the combustion chamber of the engine. Emissions of soot particles by air-planes produce persistent contrails in the upper troposphere in ice-supersaturated air masses that contribute to cloudiness and impact the radiative properties of the atmosphere. These aerosol-cloud interactions represent one of the largest sources of uncertainty in global climate models [2]. Though the formation of atmospheric ice particles has been studied since many years [3], there are still numerous opened questions on nucleation properties of soot particles [4], as the ice nucleation experiments showed a large spread in results depending on the nucleation mode chosen and origin of the soot produced. Most likely one of the reasons behind these discrepancies resides in the different physico-chemical properties (composition, structure) of soot particles produced in different conditions, e.g. with respect to fuel or combustion techniques. In this work, we use Raman microscopy (266, 514 and 785 nm excitation) and ablation techniques (SIMS, Secondary Ions Mass Spectrometry, and Laser Desorption Mass Spectrometry) to characterize soot particles produced from air-plane at different engine regimes simulating a landing and taking-off (LTO) cycle. First, the spectral parameters of the first-order Raman band of various soot samples, collected from three different sources in the frame of the MERMOSE project (http://mermose.onera.fr/): PowerJet SaM-146 turbofan (four engine regimes), CAST generator (propane fuel, four different global equivalence ratios), and Kerosene laboratory flame are provided. The spectra are analyzed by performing a de-convolution using the approach described by Sadezky et al. (2005). The soot obtained at different engine regimes presents very similar spectra, with the only exception of the soot obtained at 30% engine regime. In this case, the contribution of D2 band is similar to the contribution of D3 band, while for the samples obtained at 70%, 85% and 100% engine regimes D3 contribution is larger. The results point to a very little impact of engine regime on the generated soot structure. In contrast, surrogate soots show a dependence on the initial combustion parameters and collection conditions. Second, the surface chemical composition of the soot particles with special focus on PAHs are analyzed by two-Step (Desorption/Ionization) Laser Mass Spectrometry (L2MS) and Time of Fight Secondary Ion Mass Spectrometry (ToF-SIMS) techniques. In L2MS, the adsorbed phase is probed by nanosecond laser desorption (?d=532nm), then the ejected molecules are ionized with a second ns laser (?i=266nm) and further mass-separated by ToF-MS. In both techniques the spectra are obtained using positive polarity, which is better suited for detection of PAHs. A good agreement was obtained between the two techniques for the total PAH content of the analyzed samples. Moreover, the total PAH content followed the same trend as the OC/EC ratio measured with a thermo-optic analyzer (Improve protocol): the 30% engine regime soot presents a high concentration of PAHs and a high OC content, while the three other regimes give a relatively low content of PAHs and OC. References [1] Lee et al., Atmos. Env. 44, 4678-4734, 2010 [2] IPCC 2014, Chap7: http://www.ipcc.ch [3] L. Dufour, Ciel et Terre, vol 82, p1-36, 1966 [4] C. Hoose & O. M÷hler, Atmos.Chem.Phys. 12, 9817-9854, 2012 [5] Sadezky, et al., Carbon, 43, 1731-1742, 2005
Characterization of the pigment xanthomonadin in the bacterial genus Xanthomonas using micro- and resonance Raman spectroscopy
NASA Astrophysics Data System (ADS)
Paret, Mathews L.; Sharma, Shiv K.; Misra, Anupam K.; Acosta, Tayro; deSilva, Asoka S.; Vowell, Tomie; Alvarez, Anne M.
We used micro- and resonance Raman spectroscopy with 785 nm and 514.5 nm laser excitation, respectively, to characterize a plant pathogenic bacteria, Xanthomonas axonopodis pv. dieffenbachiae D150. The bacterial genus Xathomonas is closely related to bacterial genus Stenotrophomonas that causes an infection in humans. This study has identified for the first time the unique Raman spectra of the carotenoid-like pigment xanthomonadin of the Xanthomonas strain. Xanthomonadin is a brominated aryl-polyene pigment molecule similar to carotenoids. Further studies were conducted using resonance Raman spectroscopy with 514.5 nm laser excitation on several strains of the bacterial genus Xanthomonas isolated from numerous plants from various geographical locations. The current study revealed that the Raman bands representing the vibrations (v1, v2, v3) of the polyene chain of xanthomonadin are 1003-1005 (v3), 1135-1138 (v2), and 1530 (v1). Overtone bands representing xanthomonadin were identified as 2264-2275 (2v2), and combinational bands at 2653-2662 (v1+ v2). The findings from this study validate our previous finding that the Raman fingerprints of xanthomonadin are unique for the genus Xanthomonas. This facilitates rapid identification (~5 minutes) of Xanthomonas spp. from bacterial culture plates. The xanthomonadin marker is different from Raman markers of many other bacterial genus including Agrobacterium, Bacillus, Clavibacter, Enterobacter, Erwinia, Microbacterium, Paenibacillus, and Ralstonia. This study also identified Xanthomonas spp. from bacterial strains isolated from a diseased wheat sample on a culture plate.
Spatially offset Raman spectroscopy and diffuse Raman tomography: subsurface spectroscopy and imaging in animal tissue and other scattering media
Michael D. Morris
It has been less than three years since the beginnings of systematic development of fiber optic Raman illumination\\/collection systems for operation in the presence of extensive photon diffusion. These fiber optic probes depend on spatial separation of illumination and collection regions to deep Raman spectroscopy and imaging in highly scattering media. Both backscattering and transmission systems have been described in
Wurtele, Jonathan
of the Raman backward amplifier. ial damage, which is a very strong restriction in increas- ing the outputULTRAINTENSE AND ULTRASHORT LASER PULSES FROM RAMAN AMPLIFICATION IN PLASMA FOR LASER trapping effect in the Raman pulse amplification in plasma. An ultraintense and ultrashort laser pulse
Dealing with a local heating effect when measuring catalytic solids in a reactor with Raman spectroscopy.
Tinnemans, Stan J; Kox, Marianne H F; Sletering, Marco W; Nijhuis, T A Xander; Visser, Tom; Weckhuysen, Bert M
In continuation of our previous work on the applicability of the G(R(infinity)) correction factor for the quantification of Raman spectra of coke during propane dehydrogenation experiments (Phys. Chem. Chem. Phys., 2005, 7, 211), research has been carried out on the potential of this correction factor for the quantification of supported metal oxides during reduction experiments. For this purpose, supported chromium oxide catalysts have been studied by combined in situ Raman and UV-Vis spectroscopy during temperature programmed reduction experiments with hydrogen as reducing agent. The goal was to quantify on-line the amount of Cr(6+) in a reactor based on the measured in situ Raman spectra. During these experiments, a significant temperature effect was observed, which has been investigated in more detail with a thermal imaging technique. The results revealed a temperature 'on the spot' that can exceed 100 degrees C. It implies that Raman spectroscopy can have a considerable effect on the local reaction conditions and explains observed inconsistencies between the in situ UV-Vis and Raman data. In order to minimize this heating effect, reduction of the laser power, mathematical matching of the spectroscopic data, a different cell design and a change in reaction conditions has been evaluated. It is demonstrated that increasing the reactor temperature is the most feasible method to solve the heating problem. Next, it allows the application of in situ Raman spectroscopy in a reliable quantitative way without the need of an internal standard. PMID:16710489
Method And System For Examining Biological Materials Using Low Power Cw Excitation Raman Spectroscopy.
Alfano, Robert R. (Bronx, NY); Wang, Wubao (Flushing, NY)
A method and system for examining biological materials using low-power cw excitation Raman spectroscopy. A low-power continuous wave (cw) pump laser beam and a low-power cw Stokes (or anti-Stokes) probe laser beam simultaneously illuminate a biological material and traverse the biological material in collinearity. The pump beam, whose frequency is varied, is used to induce Raman emission from the biological material. The intensity of the probe beam, whose frequency is kept constant, is monitored as it leaves the biological material. When the difference between the pump and probe excitation frequencies is equal to a Raman vibrational mode frequency of the biological material, the weak probe signal becomes amplified by one or more orders of magnitude (typically up to about 10.sup.4 -10.sup.6) due to the Raman emission from the pump beam. In this manner, by monitoring the intensity of the probe beam emitted from the biological material as the pump beam is varied in frequency, one can obtain an excitation Raman spectrum for the biological material tested. The present invention may be applied to in the in vivo and/or in vitro diagnosis of diabetes, heart disease, hepatitis, cancers and other diseases by measuring the characteristic excitation Raman lines of blood glucose, cholesterol, serum glutamic oxalacetic transaminase (SGOT)/serum glutamic pyruvic transaminase (SGPT), tissues and other corresponding Raman-active body constituents, respectively.
NASA Astrophysics Data System (ADS)
Jelinkova, Helena; Sulc, Jan; Doroschenko, Maxim E.; Skornyakov, Vadim V.; Kravtsov, Sergey B.; Basiev, Tasoltan T.; Zverev, Peter G.
Properties of the laser operation and simultaneously stimulated Raman scattering in the new SRS-active neodymium doped SrWO4 crystal coherently end-pumped by alexandrite 752 nm laser radiation were investigated. The maximum generated energy 90 mJ from the free-running Nd3+:SrWO4 laser at 1057 nm wavelength was obtained with the output coupler reflectivity 52%. The slope efficiency reached s = 0.52, the beam characteristic parameters M2 and divergence q were 2.5 +/- 0.1, and 1.5 +/- 0.1 mrad, respectively. Maximal output energy of 1.46 mJ for the fundamental wavelength was obtained for Q-switched Nd3+:SrWO4 oscillator with a double Fabry-Perrot as the output coupler (R = 48%), and with the 5% initial transmission of LiF:F2- saturable absorber. Up to 0.74 mJ energy was registered at the first Stokes frequency. The pulse duration was 5 ns and 2.4 ns for the fundamental and Stokes radiation, respectively. The energy of 1.25 mJ at 1170 nm was obtained for closed Raman resonator with special mirrors. For the case of mode-locking, two dye saturable absorbers (ML51 dye in dichlorethan and 3955 dye in ethanol) were used and SRS radiation in the form of pulse train was observed. The influence of the various Raman laser output couplers reflectivity as well as the initial transmissions of passive absorbers were investigated with the goal of the output energy maximization at the Stokes wavelength. In the output, the total measured energy was 1.8 mJ (for ML51 dye) and 2.4 mJ (for 3955 dye). The SRS output at 1170 nm was approximately 20% of total energy.
Raman spectroscopy for forensic analysis of inks in questioned documents.
Braz, Andrķ; L¾pez-L¾pez, Maria; GarcĒa-Ruiz, Carmen
The methods for perpetrating forgery and alteration of documents are becoming increasingly more sophisticated. Forensic examinations of questioned documents routinely involve physical and chemical analysis of inks. Raman spectroscopy is a very attractive technique for ink analysis because it combines chemical selectivity with ease and fast analysis and it does not require sample preparation nor leads to destruction of the evidence. However, some limitations of this technique include low sensitivity and the overwhelming phenomenon of fluorescence, which can be solved by resonance Raman spectroscopy and surface-enhanced Raman spectroscopy. This article aims to demonstrate the great potential of the Raman-based techniques by providing an overview of their application to forensic examinations of ink evidence from pens and printers. Moreover, it is also addressed the chemistry of ink-paper interactions and the problematic of intersecting lines. PMID:24053882
A handheld laser scanning confocal reflectance imagingconfocal Raman
Maxwell, Bruce D.
and spectra from normal skin to demonstrate the instrument's capabilities for clinical diagnostics. ® 2012 microscopy; (170.5660) Raman spectroscopy; (170.1610) Clinical applications; (170.1870) Dermatology; (170 reflectance microscopy and confocal Raman spectroscopy have shown potential for non-destructive analysis
A versatile femtosecond stimulated Raman spectroscopy setup with tunable pulses in the visible to near infrared
NASA Astrophysics Data System (ADS)
Zhu, Liangdong; Liu, Weimin; Fang, Chong
We demonstrate a versatile and efficient setup to perform femtosecond stimulated Raman spectroscopy (FSRS). Technical innovations are implemented to achieve the wavelength tunability for both the picosecond narrowband Raman pump pulse and femtosecond broadband Raman probe pulse. Using a simplified one-grating scheme in a home-built second harmonic bandwidth compressor followed by a two-stage noncollinear optical parametric amplifier, we tune the Raman pump pulse from ca. 480 to 750 nm. To generate the suitable Raman probe pulse in tandem, we rely on our recently demonstrated broadband up-converted multicolor array technique that readily provides tunable broadband laser sidebands across the visible to near-infrared range. This unique setup has unparalleled flexibility for conducting FSRS. We measure the ground-state Raman spectra of a cyclohexane standard using tunable pump-probe pairs at various wavelengths across the visible region. The best spectral resolution is ś12 cm-1. By tuning the pump wavelength closer to the electronic absorption band of a photoacid pyranine in water, we observe the pre-resonantly enhanced Raman signal. The stimulated Raman gain of the 1627 cm-1 mode is increased by over 15 times.
Chemical Sensing With Laser Spectroscopy
Sune Svanberg
SUMMARY Laser spectroscopic techniques constitute powerful tools for chemical sensing. Atoms and molecules can be identified and quantified by their specific spectral signatures and the strength of the signals. A wide variety of methods for establishing spectroscopic contact with the species exist: absorption, emission, fluorescence, Raman scattering, acousto-optic, and opto-galvanic phenomena can be employed. Extreme sensitivity and specificity characterise the
JOURNAL OF RAMAN SPECTROSCOPY J. Raman Spectrosc. 2007; 38: 802818
Lombardi, John R.
) and quercetin (3,5,7,3 ,4 pentahydroxyflavone) have been obtained. The normal Raman (NR) spectra were taken berries), which contains quercetin, is presented. Copyright 2007 John Wiley & Sons, Ltd. KEYWORDS in plants exist as sugar derivatives (glycosides).2 Owing to their active role in pho- tosensitization
JOURNAL OF RAMAN SPECTROSCOPY J. Raman Spectrosc. 2008; 39: 19071914
Lombardi, John R.
are a class of natural dyes characterized by bright colors ranging from yellow to orange. As they present scattering (SERS) has demonstrated its potential in the analysis of natural dyes.8Ł12 This technique combines article, we successfully used surface-enhanced Raman scattering (SERS) in the analysis of the alkaloid dye
Decoupling of epitaxial graphene via gold intercalation probed by dispersive Raman spectroscopy
NASA Astrophysics Data System (ADS)
Pillai, P. B.; DeSouza, M.; Narula, R.; Reich, S.; Wong, L. Y.; Batten, T.; Pokorny, J.
Signatures of a superlattice structure composed of a quasi periodic arrangement of atomic gold clusters below an epitaxied graphene (EG) layer are examined using dispersive Raman spectroscopy. The gold-graphene system exhibits a laser excitation energy dependant red shift of the 2D mode as compared to pristine epitaxial graphene. The phonon dispersions in both the systems are mapped using the experimentally observed Raman signatures and a third-nearest neighbour tight binding electronic band structure model. Our results reveal that the observed excitation dependent Raman red shift in gold EG primarily arise from the modifications of the phonon dispersion in gold-graphene and shows that the extent of decoupling of graphene from the underlying SiC substrate can be monitored from the dispersive nature of the Raman 2D modes. The intercalated gold atoms restore the phonon band structure of epitaxial graphene towards free standing graphene.
Raman Spectroscopy for the Undergraduate Teaching Laboratory: Quantification of Ethanol Concentration in Consumer Alcoholic Beverages and Qualitative Identification of Marine Diesels Using a Miniature Raman Spectrometer
Danielle Cleveland; Matthew Carlson; Evan D. Hudspeth; Lauren E. Quattrochi; Kathleen L. Batchler; Shrimati A. Balram; Seongun Hong; Robert G. Michel
Raman spectroscopy has steadily gained popularity as a powerful tool in both the analytical lab and the undergraduate classroom. The technique is attractive because it allows for rapid, nondestructive qualitative or quantitative analyses of many analytes with little or no sample preparation requirements. The introduction of less expensive, smaller, and more powerful diode laser excitation sources and the recent availability
Continuous-wave solid-state two-Stokes Raman laser
Grabchikov, A S; Lisinetskii, V A; Orlovich, V A [B.I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, Minsk (Belarus); Schmitt, M; Schluecker, S; Kuestner, B; Kiefer, W [Institut fuer Physikalische Chemie, Universitat Wuerzburg, Wuerzburg (Germany)
We report an experimental study of the first cw solid-state Raman laser operating simultaneously at the frequencies of the first and second Stokes components. Simultaneous generation is ensured by a cavity with an enhanced finesse at both Stokes frequencies. The threshold pump powers for the first (3.4 W) and second (3.67 W) Stokes components suggest that the second Stokes generation follows a cascade mechanism. We demonstrate for the first time Raman conversion with intensity stability exceeding the pump radiation stability and show that this approach may find application in Raman spectroscopy. (special issue devoted to the 80th birthday of S.A. Akhmanov)
Laser optogalvanic spectroscopy of molecules
NASA Technical Reports Server (NTRS)
Webster, C. R.; Rettner, C. T.
In laser optogalvanic (LOG) spectroscopy, a tunable laser is used to probe the spectral characteristics of atomic or molecular species within an electrical discharge in a low pressure gas. Optogalvanic signals arise when the impedance of the discharge changes in response to the absorption of laser radiation. The technique may, therefore, be referred to as impedance spectroscopy. This change in impedance may be monitored as a change in the voltage across the discharge tube. LOG spectra are recorded by scanning the wavelength of a chopped CW dye laser while monitoring the discharge voltage with a lock-in amplifier. LOG signals are obtained if the laser wavelength matches a transition in a species present in the discharge (or flame), and if the absorption of energy in the laser beam alters the impedance of the discharge. Infrared LOG spectroscopy of molecules has been demonstrated and may prove to be the most productive application in the field of optogalvanic techniques.
Studies of Minerals, Organic and Biogenic Materials through Time-Resolved Raman Spectroscopy
NASA Technical Reports Server (NTRS)
Garcia, Christopher S.; Abedin, M. Nurul; Ismail, Syed; Sharma, Shiv K.; Misra, Anupam K.; Nyugen, Trac; Elsayed-Ali, hani
A compact remote Raman spectroscopy system was developed at NASA Langley Research center and was previously demonstrated for its ability to identify chemical composition of various rocks and minerals. In this study, the Raman sensor was utilized to perform time-resolved Raman studies of various samples such as minerals and rocks, Azalea leaves and a few fossil samples. The Raman sensor utilizes a pulsed 532 nm Nd:YAG laser as excitation source, a 4-inch telescope to collect the Raman-scattered signal from a sample several meters away, a spectrograph equipped with a holographic grating, and a gated intensified CCD (ICCD) camera system. Time resolved Raman measurements were carried out by varying the gate delay with fixed short gate width of the ICCD camera, allowing measurement of both Raman signals and fluorescence signals. Rocks and mineral samples were characterized including marble, which contain CaCO3. Analysis of the results reveals the short (approx.10-13 s) lifetime of the Raman process, and shows that Raman spectra of some mineral samples contain fluorescence emission due to organic impurities. Also analyzed were a green (pristine) and a yellow (decayed) sample of Gardenia leaves. It was observed that the fluorescence signals from the green and yellow leaf samples showed stronger signals compared to the Raman lines. Moreover, it was also observed that the fluorescence of the green leaf was more intense and had a shorter lifetime than that of the yellow leaf. For the fossil samples, Raman shifted lines could not be observed due the presence of very strong short-lived fluorescence.
Remote Raman Spectroscopy of Minerals at Elevated Temperature Relevant to Venus Exploration
NASA Technical Reports Server (NTRS)
Sharma, Shiv K.; Misra, Anupam K.; Singh, Upendra N.
We have used a remote time-resolved telescopic Raman system equipped with 532 nm pulsed laser excitation and a gated intensified CCD (ICCD) detector for measuring Raman spectra of a number of minerals at high temperature to 970 K. Remote Raman measurements were made with samples at 9-meter in side a high-temperature furnace by gating the ICCD detector with 2 micro-sec gate to minimize interference from blackbody emission from mineral surfaces at high temperature as well as interference from ambient light. A comparison of Raman spectra of gypsum (CaSO4.2H2O), dolomite (CaMg(CO3)2), and olivine (Mg2Fe2-xSiO4), as a function of temperature shows that the Raman lines remains sharp and well defined even in the high-temperature spectra. In the case of gypsum, Raman spectral fingerprints of CaSO4.H2O at 518 K were observed due to dehydration of gypsum. In the case of dolomite, partial mineral dissociation was observed at 973 K at ambient pressure indicating that some of the dolomite might survive on Venus surface that is at approximately 750 K and 92 atmospheric pressure. Time-resolved Raman spectra of low clino-enstatite (MgSiO3) measured at 75 mm from the sample in side the high-temperature furnace also show that the Raman lines remains sharp and well defined in the high temperature spectra. These high-temperature remote Raman spectra of minerals show that time-resolved Raman spectroscopy can be used as a potential tool for exploring Venus surface mineralogy at shorter (75 mm) and long (9 m) distances from the samples both during daytime and nighttime. The remote Raman system could also be used for measuring profiles of molecular species in the dense Venus atmosphere during descent as well as on the surface.
Raman spectroscopy of individual monocytes reveals that single-beam optical trapping of mononuclear cells occurs by their nucleus
NASA Astrophysics Data System (ADS)
Fore, Samantha; Chan, James; Taylor, Douglas; Huser, Thomas
We show that laser tweezers Raman spectroscopy of eukaryotic cells with a significantly larger diameter than the tight focus of a single-beam laser trap leads to optical trapping of the cell by its optically densest part, i.e. typically the cell's nucleus. Raman spectra of individual optically trapped monocytes are compared with location-specific Raman spectra of monocytes adhered to a substrate. When the cell's nucleus is stained with a fluorescent live cell stain, the Raman spectrum of the DNA-specific stain is observed only in the nucleus of individual monocytes. Optically trapped monocytes display the same behavior. We also show that the Raman spectra of individual monocytes exhibit the characteristic Raman signature of cells that have not yet fully differentiated and that individual primary monocytes can be distinguished from transformed monocytes based on their Raman spectra. This work provides further evidence that laser tweezers Raman spectroscopy of individual cells provides meaningful biochemical information in an entirely non-destructive fashion that permits discerning differences between cell types and cellular activity.
Rapid detection of chlorpyrifos pesticide residue concentration in agro-product using Raman spectroscopy
NASA Astrophysics Data System (ADS)
Dhakal, Sagar; Peng, Yankun; Li, Yongyu; Chao, Kuanglin; Qin, Jianwei; Zhang, Leilei; Xu, Tianfeng
Different chemicals are sprayed in fruits and vegetables before and after harvest for better yield and longer shelf-life of crops. Cases of pesticide poisoning to human health are regularly reported due to excessive application of such chemicals for greater economic benefit. Different analytical technologies exist to detect trace amount of pesticides in fruits and vegetables, but are expensive, sample destructive, and require longer processing time. This study explores the application of Raman spectroscopy for rapid and non-destructive detection of pesticide residue in agricultural products. Raman spectroscopy with laser module of 785 nm was used to collect Raman spectral information from the surface of Gala apples contaminated with different concentrations of commercially available organophosphorous (48% chlorpyrifos) pesticide. Apples within 15 days of harvest from same orchard were used in this study. The Raman spectral signal was processed by Savitzky-Golay (SG) filter for noise removal, Multiplicative Scatter Correction (MSC) for drift removal and finally polynomial fitting was used to eliminate the fluorescence background. The Raman spectral peak at 677 cm-1 was recognized as Raman fingerprint of chlorpyrifos. Presence of Raman peak at 677 cm-1 after fluorescence background removal was used to develop classification model (presence and absence of pesticide). The peak intensity was correlated with actual pesticide concentration obtained using Gas Chromatography and MLR prediction model was developed with correlation coefficient of calibration and validation of 0.86 and 0.81 respectively. Result shows that Raman spectroscopy is a promising tool for rapid, real-time and non-destructive detection of pesticide residue in agro-products.
Raman Spectroscopy of UH3 from the Hydrogen Corrosion of Uranium
Smyrl, N. R.; Stowe, A. C.; Powell, G. L.
Hydrogen reacts with a uranium surface to form a fine, pyrophoric metal power (UH{sub 3}). Few spectroscopic studies have been conducted to study this reaction. Advances in Raman spectroscopy permit the application of the Raman method to formally difficult areas of chemistry such as the hydrogen corrosion of uranium: availability of multiple laser excitation wavelengths; fiber optics delivery and collection systems; upgraded instrumentation and detection techniques; and development of special enclosed in situ reactor cells. UH{sub 3} vibrations are expected to occur at low frequencies due to extended U-H-U structure.
Multidimensional resonance raman spectroscopy by six-wave mixing in the deep UV
NASA Astrophysics Data System (ADS)
Molesky, Brian P.; Giokas, Paul G.; Guo, Zhenkun; Moran, Andrew M.
Two-dimensional (2D) resonance Raman spectroscopies hold great potential for uncovering photoinduced relaxation processes in molecules but are not yet widely applied because of technical challenges. Here, we describe a newly developed 2D resonance Raman experiment operational at the third-harmonic of a Titanium-Sapphire laser. High-sensitivity and rapid data acquisition are achieved by combining spectral interferometry with a background-free (six-pulse) laser beam geometry. The third-harmonic laser pulses are generated in a filament produced by the fundamental and second-harmonic pulses in neon gas at pressures up to 35 atm. The capabilities of the setup are demonstrated by probing ground-state wavepacket motions in triiodide. The information provided by the experiment is explored with two different representations of the signal. In one representation, Fourier transforms are carried out with respect to the two experimentally controlled delay times to obtain a 2D Raman spectrum. Further insights are derived in a second representation by dispersing the signal pulse in a spectrometer. It is shown that, as in traditional pump-probe experiments, the six-wave mixing signal spectrum encodes the wavepacket's position by way of the (time-evolving) emission frequency. Anharmonicity additionally induces dynamics in the vibrational resonance frequency. In all cases, the experimental signals are compared to model calculations based on a cumulant expansion approach. This study suggests that multi-dimensional resonance Raman spectroscopies conducted on systems with Franck-Condon active modes are fairly immune to many of the technical issues that challenge off-resonant 2D Raman spectroscopies (e.g., third-order cascades) and photon-echo experiments in the deep UV (e.g., coherence spikes). The development of higher-order nonlinear spectroscopies operational in the deep UV is motivated by studies of biological systems and elementary organic photochemistries.
A MEMS based handheld confocal microscope with Raman spectroscopy for in-vivo skin cancer diagnosis
NASA Astrophysics Data System (ADS)
Arrasmith, Christopher L.; Patil, Chetan A.; Dickensheets, David L.; Mahadevan-Jansen, Anita
Both Confocal Microscopy and Raman Spectroscopy have shown potential for diagnosis and differentiation of cancerous and normal skin. Many current studies utilizing these techniques use large bench-top microscopes, and are not suited for in-vivo diagnosis in a clinical setting. We have developed a microscope which combines confocal reflectance imaging with Raman spectroscopy into a compact handheld probe, allowing images and Raman spectra to be taken in-vivo. The compact design of this handheld unit is largely due to the use of a MEMS mirror which scans the illumination laser light in two dimensions to produce the confocal reflectance image of the skin. An integrated CCD camera provides a large area view of the skin surface which helps to guide the location of the confocal reflectance image area. Using this probe, in-vivo confocal reflectance images and Raman spectra of normal skin have been obtained with axial resolutions of 4 ?m for the confocal channel and 10 ?m for the Raman channel. This paper presents the instrument design and optical characteristics, including representative in-vivo images and Raman data from normal skin tissue.
Raman Spectroscopy of Atomically Thin MX2 Materials
NASA Astrophysics Data System (ADS)
Drapcho, Steven; Kim, Jonghwan; Hong, Xiaoping; Jin, Chenhao; Shi, Sufei; Zhang, Yu; Tongay, Sefaattin; Yuk, Jongmin; Zettl, Alex; Wu, Junqiao; Zhang, Yanfeng; Wang, Feng
There has been growing interest in atomically thin layers of MX2 materials, such as MoS2, WS2, MoSe2, and WSe2. Monolayers of these materials exhibit many physical properties distinctly different from those of bulk crystals, such as a direct rather than an indirect band gap, strong photoluminescence, and large exciton binding energies. Raman spectroscopy provides a powerful tool to characterize atomically thin 2D materials, having been utilized to probe the electron-phonon coupling and identify the layer thickness of MX2 materials. To better understand Raman spectra, we perform systematic studies of Raman scattering in different MX2 materials as a function of the photon excitation energy, light polarization, and spatial position. I will discuss their implications for quantitative characterization of MX2 materials using Raman spectroscopy.
Examination of cellulose textile fibres in historical objects by micro-Raman spectroscopy.
Kavkler, Katja; DemÜar, Andrej
The investigation and characterisation of historical objects can be an exacting piece of work because of the small quantity of material that can be investigated and the degradation of the material and its value, which sometimes demands only non-destructive methods. In this study, as one such method, Raman spectroscopy was used to investigate the cellulose fibres of painting canvases and linings. Historical samples of fabrics were taken from different paintings and their linings from different locations in Slovenia. Raman spectra were recorded on the fibres of these historical samples. Additionally, a database of the Raman spectra of modern cellulose fibres was created and compared with the literature data. Differences in the Raman spectra of different cellulose fibres were observed, and on this basis fibres of different types were discriminated. The recorded Raman spectra of historical samples were compared with the database spectra of modern cellulose fibres. Strong luminescence effects because of the changes caused by ageing, degradation products and surface contamination caused difficulties in interpreting the Raman spectra of historical fibres. The luminescence effects were partly overcome by prolonged exposition times and previous "signal quenching" with the laser. The Raman spectra of historical cotton showed no luminescence effects, and only slight differences to the reference spectra of modern cotton fibres appeared, whereas the Raman spectra of historical flax fibres were overwhelmed with luminescence and showed changes in spectra through degradation. The research showed that by using Raman spectroscopy the identification and differentiation of different cellulose fibres and materials that accompany cellulose in the fibres are possible and that degraded and aged material can be differentiated. PMID:21190892
Rong, Haisheng; Liu, Ansheng; Jones, Richard; Cohen, Oded; Hak, Dani; Nicolaescu, Remus; Fang, Alexander; Paniccia, Mario
The possibility of light generation and/or amplification in silicon has attracted a great deal of attention for silicon-based optoelectronic applications owing to the potential for forming inexpensive, monolithic integrated optical components. Because of its indirect bandgap, bulk silicon shows very inefficient band-to-band radiative electron-hole recombination. Light emission in silicon has thus focused on the use of silicon engineered materials such as nanocrystals, Si/SiO2 superlattices, erbium-doped silicon-rich oxides, surface-textured bulk silicon and Si/SiGe quantum cascade structures. Stimulated Raman scattering (SRS) has recently been demonstrated as a mechanism to generate optical gain in planar silicon waveguide structures. In fact, net optical gain in the range 2-11 dB due to SRS has been reported in centimetre-sized silicon waveguides using pulsed pumping. Recently, a lasing experiment involving silicon as the gain medium by way of SRS was reported, where the ring laser cavity was formed by an 8-m-long optical fibre. Here we report the experimental demonstration of Raman lasing in a compact, all-silicon, waveguide cavity on a single silicon chip. This demonstration represents an important step towards producing practical continuous-wave optical amplifiers and lasers that could be integrated with other optoelectronic components onto CMOS-compatible silicon chips. PMID:15635371
Plasmon-assisted chemical reactions revealed by high-vacuum tip-enhanced Raman spectroscopy
NASA Astrophysics Data System (ADS)
Lu, Shuaicheng; Sheng, Shaoxiang; Zhang, Zhenglong; Xu, Hongxing; Zheng, Hairong
Tip-enhanced Raman spectroscopy (TERS) is the technique that combines the nanoscale spatial resolution of a scanning probe microscope and the highly sensitive Raman spectroscopy enhanced by the surface plasmons. It is suitable for chemical analysis at nanometer scale. Recently, TERS exhibited powerful potential in analyzing the chemical reactions at nanoscale. The high sensitivity and spatial resolution of TERS enable us to learn the reaction processes more clearly. More importantly, the chemical reaction in TERS is assisted by surface plasmons, which provides us an optical method to manipulate the chemical reactions at nanoscale. Here using our home-built high-vacuum tip-enhanced Raman spectroscopy (HV-TERS) setup, we successfully observed the plasmon-assisted molecule dimerization and dissociation reactions. In HV-TERS system, under laser illumination, 4-nitrobenzenethiol (4NBT) molecules can be dimerized to p,p'-dimercaptoazobenzene (DMAB), and dissociation reaction occurs for malachite green (MG) molecules. Using our HV-TERS setup, the dynamic processes of the reactions are clearly revealed. The chemical reactions can be manipulated by controlling the plasmon intensity through changing the power of the incident laser, the tunneling current and the bias voltage. We also investigated the role of plasmonic thermal effect in the reactions by measuring both the Stokes and anti- Stokes Raman peaks. Our findings extend the applications of TERS, which can help to study the chemical reactions and understand the dynamic processes at single molecular level, and even design molecules by the plasmon-assisted chemical reactions.
Raman Spectroscopy: A New Proposal for the Detection of Leukemia Using Blood Samples
Martinez-Espinosa, J. C.; Gonzalez-Solis, J. L.; Miranda-Beltran, M. L.; Soria-Fregoso, C.; Medina-Valtierra, J.; Sanchez-Gomez, R. [Centro Universitario de Lagos, Universidad de Guadalajara Enrique Diaz de Leon S/N, Paseo de la Montana, CP 47460, Lagos de Moreno, Jalisco (Mexico); Frausto-Reyes, C. [Centro de Investigaciones en Optica, A. C. Prolongacion Constitucion 607, Fracc. Reserva Lomas Bonita, CP 20200, Aguascalientes (Mexico)
The use of Raman spectroscopy to analyze blood biochemistry and hence distinguish between normal and abnormal blood was investigated. The blood samples were obtained from 6 patients who were clinically diagnosed with leukemia and 6 healthy volunteer. The imprint was put under the microscope and several points were chosen for Raman measurement. All spectra were collected at confocal Raman micro-spectroscopy (Renishaw) with NIR 830 nm laser. It is shown that the serum samples from patients with leukemia and from the control group can be discriminated when the multivariate statistical methods of principal component analysis (PCA) and linear discriminated analysis (LDA) is applied to their Raman spectra. The ratios of some band intensities were analyzed and some band ratios were significant and corresponded to proteins, phospholipids, and polysaccharides. In addition, currently the degree of damage to the bone marrow is estimated through biopsies and therefore it is a very procedure painful. The preliminary results suggest that Raman spectroscopy could be a new technique to study the bone marrow using just blood samples.
Micro-Raman spectroscopy of isolated single wall carbon nanotube
R. Saito; A. Jorio; A. G. Souza Filho; J. H. Hafner; C. M. Lieber; M. Hunter; T. McClure; M. A. Pimenta; A. M. Rao; G. Dresselhaus; M. S. Dresselhaus
Micro-Raman spectroscopy of an isolated single wall carbon nanotube is overviewed in connection with the recent observation of (1) the chirality-dependent G-band Raman intensity, (2) BWF line analysis and (3) D-band feature of an individual single wall carbon nanotube. The localized phonons appeared around a point defect of carbon nanotube might be relevant to D-band intensity. .
Shell-isolated nanoparticle-enhanced Raman spectroscopy.
Li, Jian Feng; Huang, Yi Fan; Ding, Yong; Yang, Zhi Lin; Li, Song Bo; Zhou, Xiao Shun; Fan, Feng Ru; Zhang, Wei; Zhou, Zhi You; Wu, De Yin; Ren, Bin; Wang, Zhong Lin; Tian, Zhong Qun
Surface-enhanced Raman scattering (SERS) is a powerful spectroscopy technique that can provide non-destructive and ultra-sensitive characterization down to single molecular level, comparable to single-molecule fluorescence spectroscopy. However, generally substrates based on metals such as Ag, Au and Cu, either with roughened surfaces or in the form of nanoparticles, are required to realise a substantial SERS effect, and this has severely limited the breadth of practical applications of SERS. A number of approaches have extended the technique to non-traditional substrates, most notably tip-enhanced Raman spectroscopy (TERS) where the probed substance (molecule or material surface) can be on a generic substrate and where a nanoscale gold tip above the substrate acts as the Raman signal amplifier. The drawback is that the total Raman scattering signal from the tip area is rather weak, thus limiting TERS studies to molecules with large Raman cross-sections. Here, we report an approach, which we name shell-isolated nanoparticle-enhanced Raman spectroscopy, in which the Raman signal amplification is provided by gold nanoparticles with an ultrathin silica or alumina shell. A monolayer of such nanoparticles is spread as 'smart dust' over the surface that is to be probed. The ultrathin coating keeps the nanoparticles from agglomerating, separates them from direct contact with the probed material and allows the nanoparticles to conform to different contours of substrates. High-quality Raman spectra were obtained on various molecules adsorbed at Pt and Au single-crystal surfaces and from Si surfaces with hydrogen monolayers. These measurements and our studies on yeast cells and citrus fruits with pesticide residues illustrate that our method significantly expands the flexibility of SERS for useful applications in the materials and life sciences, as well as for the inspection of food safety, drugs, explosives and environment pollutants. PMID:20237566
A nondestructive tool for nanomaterials: Raman and photoluminescence spectroscopy
NASA Astrophysics Data System (ADS)
Singha, A.; Dhar, P.; Roy, Anushree
Modern materials science requires efficient processing and characterization techniques for low dimensional systems. Raman and photoluminescence spectroscopy are important nondestructive tools which provide much information about such systems. Commercial Raman spectrometers are expensive. We discuss a less expensive apparatus with assembled collection optics. Studies of Ge nanoparticles, porous silicon (nanowire), carbon nanotubes, and two-dimensional InGaAs quantum layers demonstrate that this apparatus is useful for teaching and research on nanomaterials.
A nondestructive tool for nanomaterials: Raman and photoluminescence spectroscopy
A. Singha; P. Dhar; Anushree Roy
Modern materials science requires efficient processing and characterization techniques for low dimensional systems. Raman and photoluminescence spectroscopy are important nondestructive tools which provide much information about such systems. Commercial Raman spectrometers are expensive. We discuss a less expensive apparatus with assembled collection optics. Studies of Ge nanoparticles, porous silicon (nanowire), carbon nanotubes, and two-dimensional InGaAs quantum layers demonstrate that this
Micro-Raman spectroscopy: a powerful technique for materials research
S Jimenez-Sandoval
Since the development of the holographic notch filters during the last decade and novel detectors such as charge coupled devices, Raman spectroscopy instrumentation has evolved rapidly, so that modern spectrometers are orders of magnitude faster, present much lower signal-to-noise ratio and simplified optics than their predecessors. These advances have also had a significant effect in the construction of novel micro-Raman-dedicated
Applications of laser Raman and FT-IR techniques to leprology, neurology, bacteriology and traumatology
S. Mishra; Ravindra Kumar; S. K. Aryal; S. Kumar; Rajesh Kumar; M. M. Bajaj
The application of Fourier transform infrared spectroscopy and laser Raman spectroscopy for obtaining structural information\\u000a about the subtle changes occurring at the molecular level following leprosy, pulmonary tuberculosis, infected burns, epilepsy\\u000a and Duchenne muscular dystrophy (DMD) are reported in this paper. It is shown that IR spectra exhibit specific signals for\\u000a each disease. Results of the observed bands of hemoproteins
Surface spectroscopic study of COMO\\/AlŌOŌ catalysts using ESCA, ISS, XRD, and Raman spectroscopy. I
L. E. Makovsky; J. M. Stencel; F. R. Brown; R. E. Tischer; S. S. Pollack
Laser Raman spectroscopy, X-ray photoelectron spectroscopy, low-energy ion-scattering spectroscopy, and X-ray diffraction have been used to characterize a series of Co-Mo\\/AlŌOŌ catalysts containing 15 wt% MoOŌ and 0 to 8 wt% CoO in their oxide, reduced, and sulfided forms. These data show that the catalyst surface contains CoMoOŌ and irreducible Co\\/sup 2 +\\/ ions of tetrahedral symmetry when the CoO
Fiber-optic Raman Spectroscopy of Joint Tissues
Esmonde-White, Karen A.; Esmonde-White, Francis W.L.; Morris, Michael D.
In this study, we report adaptation of Raman spectroscopy for arthroscopy of joint tissues using a custom-built fiber optic probe. Differentiation of healthy and damaged tissue or examination of subsurface tissue, such as subchondral bone, is a challenge in arthroscopy because visual inspection may not provide sufficient contrast. Discrimination of healthy versus damaged tissue may be improved by incorporating point spectroscopy or hyperspectral imaging into arthroscopy where contrast is based on molecular structure or chemical composition. Articular joint surfaces of knee cadaveric human tissue and tissue phantoms were examined using a custom-designed Raman fiber optic probe. Fiber-optic Raman spectra were compared against reference spectra of cartilage, subchondral bone and cancellous bone collected using Raman microspectroscopy. In fiber-optic Raman spectra of the articular surface, there was an effect of cartilage thickness on recovery of signal from subchondral bone. At sites with intact cartilage, the bone mineralization ratio decreased but there was a minimal effect in the bone mineral chemistry ratios. Tissue phantoms were prepared as experimental models of the osteochondral interface. Raman spectra of tissue phantoms suggested that optical scattering of cartilage has a large effect on the relative cartilage and bone signal. Finite element analysis modeling of light fluence in the osteochondral interface confirmed experimental findings in human cadaveric tissue and tissue phantoms. These first studies demonstrate proof of principle for Raman arthroscopic measurement of joint tissues and provide a basis for future clinical or animal model studies. PMID:21359366
The potential of Raman spectroscopy in glass studies
NASA Astrophysics Data System (ADS)
Baert, Kitty; Meulebroeck, Wendy; Ceglia, Andrea; Wouters, Hilde; Cosyns, Peter; Nys, Karin; Thienpont, Hugo; Terryn, Herman
Raman spectroscopy is presented as a suitable and fast non-destructive technique to obtain qualitative information about glass samples of various origins (ancient and modern/industrial glass). A first application is the broad corpus of archaeological window glass that still needs to be investigated. For many sites, archaeologists have to deal with large collections of excavated glass samples and a selection of the most appropriate samples for chemical analysis is necessary. A fast classification can be made based on Raman spectra: different kind of glasses (Alkali-glass, High Lime-Low Alkali glass (HLLA)) have their own typical Raman signature. Even for glasses giving strong fluorescence, a classification is possible after a simple treatment of the Raman data. Raman spectroscopy has also been utilized to identify iron containing glasses. The effect of the iron content in glass samples is reflected on the topology of the Raman spectra: a strong link between the ratio of the Q2/Q3 vibration units of the silica tetrahedral structure is seen. Even (semi-) quantitative results can be determined from calibration lines if matrix effects are taken into account (similar glasses). In amber colored glasses, an extra peak ~415cm-1 in the Raman spectra indicates the presence of a Fe-S chromophore. Finally, in the fluorescent signals of some yellow and red glasses two peaks of Zn-Se-Cd-S nanocrystals have been identified.
Using micro-Raman spectroscopy for nasopharyngeal cancerous tissue detection
NASA Astrophysics Data System (ADS)
Wu, Shanshan; Sun, Liqing; Chen, Maowen; Lin, Jia; Cao, Gang; Huang, Wei; Chen, Rong
Micro-Raman spectroscopy is widely used for non-invasive tissue diagnosis and detection, as it provides detailed information about biomolecular composition, structure, and interaction of tissue. In this work, micro-Raman spectroscopy was used to investigate non-cancerous and cancerous nasopharyngeal tissues. The obtained nasopharyngeal tissue samples in vitro are divided into two groups: cancerous (n=12, undifferentiated non-keratinizing carcinomas) and non-cancerous (n=10, 7 chronic inflammations, 2 lymphomas and 1 lymphocytosis). Firstly, we analyzed the Raman spectra in the fingerprint (FP, 400-1800cm-1) region acquired. Preliminary results showed that there are some spectral differences in different pathological conditions. Furthermore, Raman spectra from cancerous and non-cancerous nasopharyngeal tissue in the high wavenumber region (HW, 2800-3100cm-1) were also reported for the first time. After detailed analysis, we achieved significant differences in Raman bands at 2854, 2874, 2934, and 3067cm-1 between cancerous and non-cancerous nasopharyngeal tissues. This study demonstrates that both fingerprint and high wavenumber regions of micro-Raman spectroscopy have the potential for the early detection of nasopharyngeal carcinomas.
Applications of modern micro-Raman spectroscopy for cell analyses.
Mariani, Melissa M; Day, Philip J R; Deckert, Volker
Raman spectroscopy assesses the chemical composition of a sample by exploiting the inherent and unique vibrational characteristics of chemical bonds. Initial applications of Raman were identified in the industrial and chemical sectors, providing a rapid non-invasive method to identify sample components or perform quality control assessments. Applications have since increased and sample sizes decreased, leading to the onset of micro-Raman spectroscopy. Coupling with microscopy enabled label-free sample analysis and the unveiling of total chemical composition. Latter adaptations of Raman have advanced into biomedical diagnostics and research. Alongside technical developments in filter systems and detectors, spectral peak intensities and improved signal-to-noise ratios have facilitated target molecule measurement within a variety of samples. Quantitative sample analysis applications of Raman have contributed to its increasing popularity. Through these exceptional capabilities, potential Raman spectroscopy utility in biomedical research applications has expanded, exemplifying why there is continued interest in this highly sensitive and often under-used technique. PMID:20473387
Development of a nanosecond-laser-pumped Raman amplifier for short laser pulses in plasma
Development of a nanosecond-laser-pumped Raman amplifier for short laser pulses in plasma Y. Ping,1 December 2009 Progress on developing a plasma amplifier/compressor based on stimulated Raman scattering limit of the pump intensity to avoid angular spray of the amplified seed has been determined. The Raman
Cell identification using Raman spectroscopy in combination with optical trapping and microfluidics
NASA Astrophysics Data System (ADS)
Krafft, Christoph; Dochow, Sebastian; Beleites, Claudia; Popp, J³rgen
Cell identification by Raman spectroscopy has evolved to be an attractive complement to established optical techniques. Raman activated cell sorting (RACS) offers prospects to complement the widely applied fluorescence activated cell sorting. RACS can be realized by combination with optical traps and microfluidic devices. The progress of RACS is reported for a cellular model system that can be found in peripheral blood of tumor patients. Lymphocytes and erythrocytes were extracted from blood samples. Breast carcinoma derived tumor cells (MCF-7, BT-20) and acute myeloid leukemia cells (OCI-AML3) were grown in cell cultures. First, Raman images were collected from dried cells on calcium fluoride slides. Support vector machines (SVM) classified 99.7% of the spectra to the correct cell type. Second, a 785 nm laser was used for optical trapping of single cells in aqueous buffer and for excitation of the Raman spectrum. SVM distinguished 1210 spectra of tumor and normal cells with a sensitivity of >99.7% and a specificity of >99.5%. Third, a microfluidic glass chip was designed to inject single cells, modify the flow speed, accommodate fibers of an optical trap and sort single cells after Raman based identification with 514 nm for excitation. Forth, the microfluidic chip was fabricated by quartz which improved cell identification results with 785 nm excitation. Here, partial least squares discriminant analysis gave classification rates of 98%. Finally, a Raman-on-chip approach was developed that integrates fibers for trapping, Raman excitation and signal detection in a single compact unit.
Combined Raman spectrometer/laser-induced breakdown spectrometer for the next ESA mission to Mars.
Bazalgette CourrĶges-Lacoste, Grķgory; Ahlers, Berit; Pķrez, Fernando Rull
Among the different instruments that have been pre-selected to be on-board the Pasteur payload on ExoMars is the Raman/laser induced breakdown spectroscopy (LIBS) instrument. Raman spectroscopy and LIBS will be integrated into a single instrument sharing many hardware commonalities. An international team under the lead of TNO has been gathered to produce a design concept for a combined Raman spectrometer/LIBS elegant bread-board (EBB). The instrument is based on a specially designed, extremely compact, spectrometer with high resolution over a large wavelength range, suitable for both Raman spectroscopy and LIBS measurements. Low mass, size and power consumption are the main drivers of the instrument's design concept. In this paper, science objectives for the combined instrument are detailed. Background information on Raman spectroscopy and LIBS are presented, focussing on the synergy of these two techniques. In the last section, the instrument concept resulting from the assessment of the feasibility of the combined Raman/LIBS EBB is presented. PMID:17466575
Subframe Burst Gating for Raman Spectroscopy in Combustion
NASA Technical Reports Server (NTRS)
Kojima, Jun; Fischer, David; Nguyen, Quang-Viet
We describe an architecture for spontaneous Raman scattering utilizing a frame-transfer CCD sensor operating in a subframe burst-gating mode to realize time-resolved combustion diagnostics. The technique permits all-electronic optical gating with microsecond shutter speeds 5 J.Ls) without compromising optical throughput or image fidelity. When used in conjunction with a pair of orthogonally polarized excitation lasers, the technique measures single-shot vibrational Raman scattering that is minimally contaminated by problematic optical background noise.
Subframe burst gating for Raman spectroscopy in combustion.
Kojima, Jun; Fischer, David; Nguyen, Quang-Viet
We describe an architecture for spontaneous Raman scattering utilizing a frame-transfer CCD sensor operating in a subframe burst-gating mode to realize time-resolved combustion diagnostics. The technique permits all-electronic optical gating with microsecond shutter speeds (<5 micros) without compromising optical throughput or image fidelity. When used in conjunction with a pair of orthogonally polarized excitation lasers, the technique measures single-shot vibrational Raman scattering that is minimally contaminated by problematic optical background noise. PMID:20436556
Two-dimensional Raman-terahertz spectroscopy of water
Savolainen, Janne; Ahmed, Saima; Hamm, Peter
Two-dimensional Raman-terahertz (THz) spectroscopy is presented as a multidimensional spectroscopy directly in the far-IR regime. The method is used to explore the dynamics of the collective intermolecular modes of liquid water at ambient temperatures that emerge from the hydrogen-bond networks water forming. Two-dimensional Raman-THz spectroscopy interrogates these modes twice and as such can elucidate couplings and inhomogeneities of the various degrees of freedoms. An echo in the 2D Raman-THz response is indeed identified, indicating that a heterogeneous distribution of hydrogen-bond networks exists, albeit only on a very short 100-fs timescale. This timescale appears to be too short to be compatible with more extended, persistent structures assumed within a two-state model of water. PMID:24297930
Modulated Fourier Transform Raman Fiber-Optic Spectroscopy
NASA Technical Reports Server (NTRS)
Jensen, Brian J. (Inventor); Cooper, John B. (Inventor); Wise, Kent L. (Inventor)
A modification to a commercial Fourier Transform (FT) Raman spectrometer is presented for the elimination of thermal backgrounds in the FT Raman spectra. The modification involves the use of a mechanical optical chopper to modulate the continuous wave laser, remote collection of the signal via fiber optics, and connection of a dual-phase digital-signal-processor (DSP) lock-in amplifier between the detector and the spectrometer's collection electronics to demodulate and filter the optical signals. The resulting Modulated Fourier Transform Raman Fiber-Optic Spectrometer is capable of completely eliminating thermal backgrounds at temperatures exceeding 300 C.
Operation of a Raman laser in bulk silicon.
Rhee, Hanjo; Lux, Oliver; Meister, Stefan; Woggon, Ulrike; Kaminskii, Alexander A; Eichler, Hans Joachim
A Raman laser based on a bulk silicon single crystal with 1.127 ?m emission wavelength is demonstrated. The Si crystal with 30 mm length was placed into an external cavity and pumped by a Q-switched Nd:YAG master oscillator power amplifier system. Strong defocusing of the pump and Raman laser beam by free carriers was compensated by an intracavity lens. Raman laser operation with a pulse duration of 2.5 ns was identified by a Raman laser threshold significantly lower than the single-pass stimulated Raman-scattering threshold. Linear absorption losses of the 1.06415 ?m pump radiation are strongly reduced by cooling the Si crystal to a temperature of 10 K. PMID:21540955
Feedback-controlled Raman dissipative solitons in a fiber laser.
Kharenko, Denis S; Bednyakova, Anastasia E; Podivilov, Evgeniy V; Fedoruk, Mikhail P; Apolonski, Alexander; Babin, Sergey A
Energy of chirped dissipative solitons (DS) generated in fiber lasers may exceed a threshold of stimulated Raman scattering (SRS) leading to formation of a noisy Raman pulse (RP). As we demonstrated recently, a feedback loop providing re-injection of the Raman pulse into the laser cavity can form a Raman dissipative soliton (RDS) with similar characteristics to those of the main dissipative soliton. Here, we present the results of feedback optimization of the generated RDS spectra. First experimental results of coherent combining of DS and RDS are also shown. PMID:25835939
Analysis of hydrocarbon fuel properties by means of Raman spectroscopy
NASA Astrophysics Data System (ADS)
Flatley, Martin W.
The project is focused on the determination of Raman spectra of hydrocarbon fuel samples using a spectrometer employing a silicon linear array detector which has a spectral range of 400 nm to 1.1 mum. The spectra are processed using chemometric techniques in order to determine the concentrations of the tracked blend components and analytical values that are used to ensure that desired specifications are achieved. The verification is based on the American Standard Testing Methods procedures for the determination of the motor, research, and road octane numbers, simulated distillation and Reid vapour pressure. Blending is one of the most important steps in the final production of hydrocarbon fuels; as many as ten complex components are mixed to achieve the desired properties of the final product. Traditionally, blending relies on well-established analytical methods such as gas chromatography for component and simulated distillation analysis, knock engines and near infrared spectroscopy for octane analysis. All of these methods are reliable and accurate, but their results are not available in real time but rather with a substantial delay, since it is in the nature of the methods that the sample must be transported from a test site to the site where the instrument is located. Additional time is required for performing the analytical procedure; e.g. the results of a gas chromatography analysis are only available from minutes to hours after the sample has been introduced into the instrument. Consequently, the results, although accurate, become only available after the process of blending has been completed. The thesis describes an implementation of a Raman spectroscopic method, which is novel in the given context, since it allows monitoring and control of the blending process online, in real time. A Raman spectrometer was designed, using a solid state laser for excitation (785 nm, 800 mW), a blazed grating for the diffraction (600 lines-per-millimeter, 750 nm blaze, 635 nm spectral range). The spectrometer was integrated with a silicon, linear array detector, cooled with a Peltier effect stack. In order to make the optical system of the spectrometer suitable for industrial use, the instrument comprised optical fiber conduits that have alleviated the alignment difficulties, eliminated the sample transport delay, and allowed the sample collection via an optical probe. The spectrometer has been tested in an industrial environment and the results obtained compared with the data yielded by the traditional analytical method of gas chromatography, and the contemporary near infrared spectroscopy. For benzene, which was used as a standard, the noise-limited detection limit of the spectrometer was 1600 ppmv for the Raman spectrometer, which compares to the detection limit of 5000 ppmv of the near infrared spectrometer, and the typical value of 10 ppm yielded by a gas chromatograph. The time interval between the sampling and availability of results was from 10 to 30 seconds for the near infrared the Raman instruments, which compared favourably with the approximately 5 to 120 minute interval required in gas chromatography.
Raman spectroscopy of perovskite and post-perovskite phases of MgGeO3 to 123 GPa
Duffy, Thomas S.
Raman spectroscopy of perovskite and post-perovskite phases of MgGeO3 to 123 GPa Sang-Heon Shim a 19 May 2007 Editor: G.D. Price Available online 26 May 2007 Abstract Raman spectra of the perovskite (Pv) and post-perovskite (PPv) phases of MgGeO3 were measured in the laser-heated diamond cell up
Raman micro spectroscopy for in vitro drug screening: subcellular localisation and interactions of doxorubicin.
Farhane, Z; Bonnier, F; Casey, A; Byrne, H J
Vibrational spectroscopy, including Raman micro spectroscopy, has been widely used over the last few years to explore potential biomedical applications. Indeed, Raman micro spectroscopy has been demonstrated to be a powerful non-invasive tool in cancer diagnosis and monitoring. In confocal microscopic mode, the technique is also a molecularly specific analytical tool with optical resolution which has potential applications in subcellular analysis of biochemical processes, and therefore as an in vitro screening tool of the efficacy and mode of action of, for example, chemotherapeutic agents. In order to demonstrate and explore the potential in this field, established, model chemotherapeutic agents can be valuable. In this study paper, Raman micro spectroscopy coupled with confocal microscopy were used for the localization and tracking of the commercially available drug, doxorubicin (DOX), in the intracellular environment of the lung cancer cell line, A549. Cytotoxicity assays were employed to establish clinically relevant drug doses for 24 h exposure, and Confocal Laser Scanning Fluorescence Microscopy was conducted in parallel with Raman micro spectroscopy profiling to confirm the drug internalisation and localisation. Multivariate statistical analysis, consisting of PCA (principal components analysis) was used to highlight doxorubicin interaction with cancer cells and spectral variations due to its effects before and after DOX spectral features subtraction from nuclear and nucleolar spectra, were compared to non-exposed control spectra. Results show that Raman micro spectroscopy is not only able to detect doxorubicin inside cells and profile its specific subcellular localisation, but, it is also capable of elucidating the local biomolecular changes elicited by the drug, differentiating the responses in different sub cellular regions. Further analysis clearly demonstrates the early apoptotic effect in the nuclear regions and the initial responses of cells to this death process, demonstrating the potential of the technique to monitor the mechanisms of action and response on a molecular level, with subcellular resolution. PMID:25919793
Single Molecule Raman Spectroscopy Under High Pressure
NASA Astrophysics Data System (ADS)
Fu, Yuanxi; Dlott, Dana
Pressure effects on surface-enhanced Raman scattering spectra of Rhdoamine 6G adsorbed on silver nanoparticle surfaces was studied using a confocal Raman microscope. Colloidal silver nanoparticles were treated with Rhodamine 6G (R6G) and its isotopically substituted partner, R6G-d4. Mixed isotopomers let us identify single-molecule spectra, since multiple-molecule spectra would show vibrational transitions from both species. The nanoparticles were embedded into a poly vinyl alcohol film, and loaded into a diamond anvil cell for the high-pressure Raman scattering measurement. Argon was the pressure medium. Ambient pressure Raman scattering spectra showed few single-molecule spectra. At moderately high pressure ( 1GPa), a surprising effect was observed. The number of sites with observable spectra decreased dramatically, and most of the spectra that could be observed were due to single molecules. The effects of high pressure suppressed the multiple-molecule Raman sites, leaving only the single-molecule sites to be observed.
A high efficiency architecture for cascaded Raman fiber lasers.
Supradeepa, V R; Nichsolson, Jeffrey W; Headley, Clifford E; Yan, Man F; Palsdottir, Bera; Jakobsen, Dan
We demonstrate a new high efficiency architecture for cascaded Raman fiber lasers based on a single pass cascaded amplifier configuration. Conversion is seeded at all intermediate Stokes wavelengths using a multi-wavelength seed source. A lower power Raman laser based on the conventional cascaded Raman resonator architecture provides a convenient seed source providing all the necessary wavelengths simultaneously. In this work we demonstrate a 1480nm laser pumped by an 1117nm Yb-doped fiber laser with maximum output power of 204W and conversion efficiency of 65% (quantum-limited efficiency is ~75%). We believe both the output power and conversion efficiency (relative to quantum-limited efficiency) are the highest reported for cascaded Raman fiber lasers. PMID:23546098
A High Efficiency Architecture for Cascaded Raman Fiber Lasers
Supradeepa, V R; Headley, Clifford E; Yan, Man F; Palsdottir, Bera; Jakobsen, Dan
We demonstrate a new high efficiency architecture for cascaded Raman fiber lasers based on a single pass cascaded amplifier configuration. Conversion is seeded at all intermediate Stokes wavelengths using a multi-wavelength seed source. A lower power Raman laser based on the conventional cascaded Raman resonator architecture provides a convenient seed source providing all the necessary wavelengths simultaneously. In this work we demonstrate a 1480nm laser pumped by an 1117nm Yb-doped fiber laser with maximum output power of 204W and conversion efficiency of 65% (quantum-limited efficiency is ~75%). We believe both the output power and conversion efficiency (relative to quantum-limited efficiency) are the highest reported for Raman fiber lasers.
On the potential of Raman-spectroscopy-based carbonate mass spectrometry
Downs, Robert T.
On the potential of Raman-spectroscopy-based carbonate mass spectrometry Nicholas P. Mc; oxygen; calcite Introduction Raman spectroscopy can potentially be used as a non-destructive, high in individual microbes.[2] Here, we investigate the potential of Raman spectroscopy as a method to directly
Dengue blood analysis by Raman spectroscopy
NASA Astrophysics Data System (ADS)
Rehman, A.; Anwar, S.; Firdous, S.; Ahmed, M.; Rasheed, R.; Nawaz, M.
In this work Raman spectra of normal and dengue infected serum and whole blood were analyzed. In normal whole blood and serum characteristic peaks were observed when excited at 442 and 532 nm. In dengue whole blood and serum all peaks found to be blue shifted with reduced Raman intensity. Dengue whole blood and serum shows two peaks at 1614 and 1750 cm-1 which are due to presence of Immunoglobulin antibodies IgG and IgM. Whole study provides a route of information for diagnosis of dengue viral infection.
Vibrational characterization of pheomelanin and trichochrome F by Raman spectroscopy
NASA Astrophysics Data System (ADS)
Galvßn, Ismael; Jorge, Alberto; Solano, Francisco; Wakamatsu, Kazumasa
We characterize for the first time the vibrational state of natural pheomelanin using Raman spectroscopy and model pigment synthesized from 5-S-cysteinyldopa. The shape of the Raman spectrum was very different from that of eumelanin. Four Raman bands were visible in the 500-2000 cm-1 wavenumber region about 500, 1150, 1490 and 2000 cm-1, which we assigned to the out-of-plane deformation and the stretching vibration of the phenyl rings, to the stretching vibration of C-N bonds or the stretching and wagging vibration of CH2, and to overtone or combination bands. Interestingly, we also show that the Raman spectrum of synthetic trichochrome F, a pigment that may be produced along with pheomelanin during pheomelanogenesis, is different from that of pheomelanin and similar to the spectrum of eumelanin. We could detect Raman signal of both eumelanin and pheomelanin in feathers and hairs where both pigments simultaneously occur without the need of isolating the pigment. This indicates that Raman spectroscopy represents a non-invasive method to detect pheomelanin and distinguish it from other pigments. This may be especially relevant to detect pheomelanin in animal skin including humans, where it has been associated with animal appearance and classification, human phototypes, prevention of skin diseases and cancer risk.
Nondestructive analysis of nanomaterials using optofluidic assisted Raman spectroscopy
NASA Astrophysics Data System (ADS)
Helmy, Amr S.; Mak, Jacky S. W.; Rutledge, S. A.; Ramanan, J.
This talk will review and compare the different optofluidic techniques for enhancing the retrieved Raman signal of nanomaterials in liquids and aerosols. Recent progress on this front utilizing optofluidics such as photonic crystal waveguides will be discussed. Techniques and applications to combine surface enhanced with optofluidic-assisted Raman spectroscopy will be also reviewed. Challenges and future opportunities to advance optofluidics-assisted Raman spectroscopy that are carried out using portable Raman spectrometers and controlled using handheld controllers such as mobile phones will be presented. As an example, a detailed, non-destructive characterization of CdTe nanoparticles using Raman spectroscopy using concentrations of 2 mg/mL, will be highlighted. Our platform allows clear vibrational modes corresponding to the structure and interactions of the QDs to be observed. These vibrational modes include those of the CdTe core, Te defects, CdSTe interface, thiol agent and carboxylate-metal complexes. These modes are correlated with the crystallinity of the QD core, interfacial structure formed upon stabilization, QD-thiol interaction mechanisms, water solubility of the QDs and their potential bio-conjugation abilities.
Shell-isolated nanoparticle-enhanced Raman spectroscopy
Jian Feng Li; Yi Fan Huang; Yong Ding; Zhi Lin Yang; Song Bo Li; Xiao Shun Zhou; Feng Ru Fan; Wei Zhang; Zhi You Zhou; De Yin Wu; Bin Ren; Zhong Lin Wang; Zhong Qun Tian
Surface-enhanced Raman scattering (SERS) is a powerful spectroscopy technique that can provide non-destructive and ultra-sensitive characterization down to single molecular level, comparable to single-molecule fluorescence spectroscopy. However, generally substrates based on metals such as Ag, Au and Cu, either with roughened surfaces or in the form of nanoparticles, are required to realise a substantial SERS effect, and this has severely
Analysis of milk by FT-Raman spectroscopy.
Mazurek, Sylwester; Szostak, Roman; Czaja, Tomasz; Zachwieja, Andrzej
Fat, protein, carbohydrates and dry matter were quantified in commercial bovine milk samples, with the relative standard errors of prediction (RSEP) in the 3.4-6.1% range, using the partial least squares (PLS) method based on Raman spectra of liquid milk samples. Results of a better quality were obtained from a PLS model derived from IR spectra registered using single reflection ATR diamond accessory, which yielded RSEP values of 2.4-4.4%. The data indicated IR single reflection ATR spectroscopy and Raman spectroscopy in combination with multivariate modelling using the PLS method, allowed for the reliable, simultaneous quantitative determination of macronutrients in milk. The low signal to noise ratio of Raman spectra affects the quality of fat quantification especially for strongly defatted milk samples. PMID:25863403
Monitoring lignocellulosic bioethanol production processes using Raman spectroscopy.
Iversen, Jens A; Ahring, Birgitte K
Process control automation in the emerging biorefinery industry may be achieved by applying effective methods for monitoring compound concentrations during the production processes. This study examines the application of Raman spectroscopy with an excitation wavelength of 785nm and an immersion probe for in situ monitoring the progression of pretreatment, hydrolysis and fermentation processes in the production of lignocellulosic ethanol. Raman signals were attenuated by light scattering cells and lignocellulosic particulates, which the quantification method to some degree could correct for by using an internal standard in the spectra. Allowing particulates to settle by using a slow stirring speed further improved results, suggesting that Raman spectroscopy should be used in combination with continuous separation when used to monitor process mixtures with large amounts of particulates. The root mean square error of prediction (RMSE) of ethanol and glucose measured in real-time was determined to be 0.98g/L and 1.91g/L respectively. PMID:25255187
Direct characterization of nanocrystal size distribution using Raman spectroscopy
NASA Astrophysics Data System (ADS)
Do?an, ?lker; van de Sanden, Mauritius C. M.
We report a rigorous analytical approach based on one-particle phonon confinement model to realize direct detection of nanocrystal size distribution and volume fraction by using Raman spectroscopy. For the analysis, we first project the analytical confinement model onto a generic distribution function, and then use this as a fitting function to extract the required parameters from the Raman spectra, i.e., mean size and skewness, to plot the nanocrystal size distribution. Size distributions for silicon nanocrystals are determined by using the analytical confinement model agree well with the one-particle phonon confinement model, and with the results obtained from electron microscopy and photoluminescence spectroscopy. The approach we propose is generally applicable to all nanocrystal systems, which exhibit size-dependent shifts in the Raman spectrum as a result of phonon confinement.
Assessment of thermal coagulation in ex-vivo tissues using Raman spectroscopy.
Rodrigues, Matthew; Weersink, Robert A; Whelan, William M
Raman spectroscopy is used to study the effects of heating on specific molecular bonds present in albumen-based coagulation phantoms and ex-vivo tissues. Thermal coagulation is induced by submerging albumen-based phantoms in a 75░C water bath to achieve target temperatures of 45, 55, 65, and 75░C. Laser photocoagulation is performed on ex-vivo bovine muscle samples, yielding induced temperatures between 46 and 90░C, as reported by implanted microthermocouples. All phantoms and tissue samples are cooled to room temperature, and Raman spectra are acquired at the microthermocouple locations. Shifts in major Raman bands are observed with laser heating in bovine muscle, specifically from the amide-1 ?-helix group (?1655 cm(-1)), the CH(2)/CH(3) group (?1446 cm(-1)), the C?-H stretch group (?1312 cm(-1)), and the CN stretch group (?1121cm(-1)). Raman bands at 1334 cm(-1) (tryptophan), 1317 cm(-1) [?(C?-H)], and 1655 cm(-1) (amide-1 ?-helix) also show a decrease in intensity following heating. The results suggest that Raman band locations and relative intensities are affected by thermal denaturation of proteins, and hence, may be a useful tool for monitoring the onset and progression of coagulation during thermal therapies. PMID:21198214
ARTICLES: Selective effect of laser radiation on cancer cells and laser spectroscopy of the cell (review)
NASA Astrophysics Data System (ADS)
Kamalov, Valey F.; Stepanova, N. V.; Chernyaeva, E. B.; Chikishev, A. Yu
A review is presented of the literature on the selective effect of optical radiation on cancer cells sensitized with porphyrin dyes. Particular attention is paid to an explanation of the fundamental principles of photodynamic cancer therapy and the physical mechanisms of the accompanying processes. The results are presented of the first applications of photodynamic therapy in the treatment of oncological diseases and the laser requirements are formulated. The use of fluorescence spectroscopy for cancer diagnostics is considered. Modern laser spectroscopic techniques used to study individual cells and cell cultures are discussed: laser picosecond fluorescence microscopy and Raman light scattering spectroscopy.
Next generation hazard detection via ultrafast coherent anti-Stokes Raman spectroscopy
NASA Astrophysics Data System (ADS)
Brady, John J.; Pellegrino, Paul M.
Multiplex coherent anti-Stokes Raman spectroscopy (MCARS) is used to detect an explosive precursor material and two chemical warfare simulants. The spectral bandwidth of the femtosecond laser pulse used in these studies is sufficient to coherently and simultaneously drive all the vibrational modes in the molecule of interest. The research performed here demonstrates that MCARS has the capability to detect an explosive precursor (e.g., acetone) and hazardous materials, such as dimethyl methylphosphonate and 2-chloroethyl methyl sulfide (a sarin and a mustard gas chemical warfare simulant, respectively), with high specificity. Evidence shows that MCARS is capable of overcoming common the sensitivity limitations of spontaneous Raman scattering, thus allowing for the detection of the target material in milliseconds with standard USB spectrometers as opposed to seconds with intensified spectrometers. The exponential increase in the number of scattered photons suggests that the MCARS technique may be capable of overcoming range detection challenges common to spontaneous Raman scattering.
Interference Effects in Resonance Raman Spectroscopy Dr. Lasse Jensen
Bj°rnstad, Ottar Nordal
Interference Effects in Resonance Raman Spectroscopy Dr. Lasse Jensen Assistant Professor a possibility that interference effects may occur. Interference can be constructive and result in an increased/TCNE complex two overlapping CT excitations causes interference effects that change relative peak intensities
Postdoc Position in Microfluidics and Single Cell Raman Spectroscopy
Horn, Matthias
Postdoc Position in Microfluidics and Single Cell Raman Spectroscopy Department of Microbial and Environmental Microfluidics Group (http://web.mit.edu/romanstocker) Department of Civil & Environmental (junior or senior) with strong expertise in microfluidics and an interest in applying it to microbial
Quantitative analysis of anatase in Georgia kaolins using Raman spectroscopy
Paul A. Schroeder; Nathan D. Melear; Robert J. Pruett
Raman spectroscopy of Georgia kaolins ubiquitously show a strong Eg frequency near 144 cm?1. Analysis of the band intensity shows that under specific source, sample, and optical conditions, peak area measurements are predictable and reproducible. Using standard additions, successful quantitative techniques have been developed that allow analysis of 25% solids water slurries, which achieve anatase detection limits down to 0.3%
Raman spectroscopy for monitoring protein structure in muscle food systems.
Herrero, Ana M
Raman spectroscopy offers structural information about complex solid systems such as muscle food proteins. This spectroscopic technique is a powerful and a non-invasive method for the study of protein changes in secondary structure, mainly quantified, analysing the amide I (1650-1680 cm(- 1)) and amide III (1200-1300 cm(- 1)) regions and C-C stretching band (940 cm(- 1)), as well as modifications in protein local environments (tryptophan residues, tyrosil doublet, aliphatic aminoacids bands) of muscle food systems. Raman spectroscopy has been used to determine structural changes in isolated myofibrillar and connective tissue proteins by the addition of different compounds and by the effect of the conservation process such as freezing and frozen storage. It has been also shown that Raman spectroscopy is particularly useful for monitoring in situ protein structural changes in muscle food during frozen storage. Besides, the possibilities of using protein structural changes of intact muscle to predict the protein functional properties and the sensory attributes of muscle foods have been also investigated. In addition, the application of Raman spectroscopy to study changes in the protein structure during the elaboration of muscle food products has been demonstrated. PMID:18568857
Stress Analysis of SiC MEMS Using Raman Spectroscopy
NASA Astrophysics Data System (ADS)
Ness, Stanley J.; Marciniak, M. A.; Lott, J. A.; Starman, L. A.; Busbee, J. D.; Melzak, J. M.
During the fabrication of Micro-Electro-Mechanical Systems (MEMS), residual stress is often induced in the thin films that are deposited to create these systems. These stresses can cause the device to fail due to buckling, curling, or fracture. Industry is looking for ways to characterize the stress during the deposition of thin films in order to reduce or eliminate device failure. Micro-Raman spectroscopy has been successfully used to characterize poly-Si MEMS devices made with the MUMPS« process. Raman spectroscopy was selected because it is nondestructive, fast and has the potential for in situ stress monitoring. This research attempts to use Raman spectroscopy to analyze the stress in SiC MEMS made with the MUSiC« process. Raman spectroscopy is performed on 1-2-micron-thick SiC thin films deposited on silicon, silicon nitride, and silicon oxide substrates. The most common poly-type of SiC found in thin film MEMS made with the MUSiC« process is 3C-SiC. Research also includes baseline spectra of 6H, 4H, and 15R poly-types of bulk SiC.
Raman spectroscopy of carbon nanotubes with electrostatically attached cytochrome c
Nabben, Reinhard
Raman spectroscopy of carbon nanotubes with electrostatically attached cytochrome c SWCNTs with cytochrome cMotivation Results Conclusion Jan Laudenbach1, Zois Syrgiannis2, Matthias M³ller1, Christian of Cc to the SWCNTs Cytochrome c Oxidized SWCNT+ +++ ++ + ++ - - - Si/SiO2 1Institut f³r
Micro-Raman spectroscopy in the undergraduate research laboratory
R. Voor; L. Chow; A. Schulte
Modern materials science requires processing and characterization techniques for microscopic structures. Molecular probes such as Raman spectroscopy are some of the most viable tools, particularly if they are supplemented by imaging to obtain spatially resolved compositional information of inhomogeneous or low volume samples. In order to introduce these techniques and materials science experiments into the advanced undergraduate laboratory, we have
Surface-enhanced Raman spectroscopy using linearly arranged gold nanoparticles embedded in nanochannels
NASA Astrophysics Data System (ADS)
Sugano, Koji; Suekuni, Keisuke; Takeshita, Toshimitsu; Aiba, Kiyohito; Isono, Yoshitada
A micro/nanofluidic device containing linearly arranged gold nanoparticles embedded in nanochannels was developed for highly sensitive and highly efficient surface-enhanced Raman spectroscopy (SERS). The Si nanochannel array was fabricated using a photolithography-based process. The nanochannel width was controlled from 100 to 400 nm. Synthesized particles of mean diameter 100 nm were arranged linearly in the nanochannels, using a nanotrench-guided self-assembly process. We developed a process for integrating linearly arranged nanoparticles and micro/nanofluidic components. The particle geometry provided significant Raman enhancement. Furthermore, efficient Raman analysis was possible by scanning a laser spot, because the particles were arranged in one direction. The fabricated structures were evaluated for SERS using 4,4?-bipyridine molecules at concentrations of 1 mM and 10 ĄM. The Raman peaks was obtained from a few hot spots. The Raman spectra showed that the molecule-specific Raman intensities were correlated with the number of hot spots in the nanochannel.
Measurement of diabetic sugar concentration in human blood using Raman spectroscopy
NASA Astrophysics Data System (ADS)
Firdous, S.; Nawaz, M.; Ahmed, M.; Anwar, S.; Rehman, A.; Rashid, R.; Mahmood, A.
This study demonstrates the use of Raman spectroscopy for the direct measurement of diabetic sugar in human blood using 532 nm laser system. Raman spectra were collected from whole blood drawn from 21 individuals. We have elicited a reliable glucose signature in diabetic patients, and measured glucose levels in blood serum of normal, healthy diabetic and diabetic patients with other malignancies like cancer and hepatitis. Quantitative predictions of glucose spectra illustrate the predictions based on molecular information carried by the Raman light in highly light-scattering and absorbing media. Raman spectrum peaks for diabetic blood serum are observed at 1168, 1531, 1463, 1021 cm-1 with intensity level 17000 to 18500 pixels attributed to carbohydrates, proteins, lipids, collagen, and skeletal C-C stretch of lipids acyl chains. Raman spectra for normal, diabetic patients having cancer and hepatitis were also recorded. This in vitro glucose monitoring methodology will lead in vivo noninvasive on-line monitoring having painless and at the same time the data will be displayed on-line and in real time. The measured Raman peaks provides detailed bio-chemical fingerprint of the sample and could confer diagnostic benefit in a clinical setting.
Raman spectroscopy of the ?1 N-H stretch fundamental in isocyanic acid (HNCO): State mixing probed by photoacoustic spectroscopy and by photodissociation of vibrationally excited states
NASA Astrophysics Data System (ADS)
Brown, Steven S.; Berghout, H. Laine; Crim, F. Fleming
We report the first gas-phase Raman spectrum of isocyanic acid. Using stimulated Raman excitation (SRE) to prepare vibrationally excited states, we detect transitions by both photoacoustic Raman spectroscopy (PARS) and action spectroscopy. In this paper we present results on the ?1 N-H stretch fundamental, leaving the spectra of the N-C-O symmetric and antisymmetric stretch modes for a separate publication. The Raman spectrum shows extensive state mixing in the ?1 fundamental, in agreement with previous infrared work. Measurement of the effective b-axis rotational constants for different mixed vibrational states in this near-prolate symmetric top limits the number of candidates for perturbing states and shows which vibrational modes participate. Double resonance photodissociation further probes the vibrational spectroscopy of isocyanic acid. The scheme is first to prepare a vibrationally excited state by SRE, then photodissociate only the molecules prepared in the first step, and finally probe the decomposition products by laser-induced fluorescence (LIF). An action spectrum, obtained by scanning the vibrational excitation laser (Stokes) wavelength with the photolysis laser wavelength fixed and the probe laser tuned to a LIF transition in one of the photofragments, is the key to unraveling the spectroscopy. The intensity differences between PARS and action spectrum transitions reveal the vibrational state mixing and provide the Franck-Condon factors for transitions to the excited electronic state.
Near-IR Fourier transform Raman spectroscopy in surgery and medicine: detection of renal stones and bladder cancer
NASA Astrophysics Data System (ADS)
Nie, Shuming; Redd, Douglas C. B.; Li, Yunzhi; Yu, Nai-Teng
Tissue diagnosis and characterization are critically important to the development and applications of laser-based therapeutic procedures in urology (viz., laser lithotripsy and bladder cancer treatment). Recently, we demonstrated for the first time that the new technique of near-infrared laser excited Fourier transform (FT)-Raman spectroscopy can readily differentiate various types of renal stones and bladder cancer from normal kidney/bladder tissues. It has thus become possible to develop an FT-Raman-based fiberoptic sensor for clinical use in laser lithotripsy and bladder cancer treatment. The future development of such a diagnostic modality will allow a surgeon/physician to take real-time Raman spectra of urinary calculi or cancerous tissue via a flexible fiberoptic probe.
Stimulated Raman scattering microscopy with a robust fibre laser source
NASA Astrophysics Data System (ADS)
Freudiger, Christian W.; Yang, Wenlong; Holtom, Gary R.; Peyghambarian, Nasser; Xie, X. Sunney; Kieu, Khanh Q.
Stimulated Raman scattering microscopy allows label-free chemical imaging and has enabled exciting applications in biology, material science and medicine. It provides a major advantage in imaging speed over spontaneous Raman scattering and has improved image contrast and spectral fidelity compared to coherent anti-Stokes Raman scattering. Wider adoption of the technique has, however, been hindered by the need for a costly and environmentally sensitive tunable ultrafast dual-wavelength source. We present the development of an optimized all-fibre laser system based on the optical synchronization of two picosecond power amplifiers. To circumvent the high-frequency laser noise intrinsic to amplified fibre lasers, we have further developed a high-speed noise cancellation system based on voltage-subtraction autobalanced detection. We demonstrate uncompromised imaging performance of our fibre-laser-based stimulated Raman scattering microscope with shot-noise-limited sensitivity and an imaging speed up to 1 frame s-1.
Laser intracavity absorption spectroscopy
V. M. Baev; T. Latz; P. E. Toschek
. ĀĀEmission spectra of multimode lasers are very sensitive to spectrally selective extinction in their cavity. This phenomenon\\u000a allows the quantitative measurement of absorption. The sensitivity of measurements of intracavity absorption grows with the\\u000a laser pulse duration. The ultimate sensitivity obtained with a cw laser is set by various perturbations of the light coherence,\\u000a such as quantum noise, Rayleigh scattering,
[Laser flash photolysis, EPR and Raman studies of liquids at elevated pressures
Eyring, E.M.
The proposed research will solve a number of analytical chemical problems in solutions with measurement techniques that benefit from the use of elevated hydrostatic pressures: stopped-flow spectrophotometry (Gd[sup 3+] + L(ligand), [RuL[sub 5]H[sub 2]O][sup 2+], laser flash photolysis of Mo(CO)[sub 6] + L, flash photolysis of binuclear metalloproteins), EPR spectroscopy (Gd[sup 3+] ion-exchanged into ETS-10 and ETAS-10 molecular sieves), laser flash photolysis kinetic studies of Mo(CO)[sub 6]-2,2'-bipyridine, and electrochemical studies of metalloporphyrins using resonance Raman spectroscopy.
Demonstration of a silicon Raman laser Ozdal Boyraz and Bahram Jalali
Jalali. Bahram
.K. Liang and H.K. Tsang, "Pulsed-pumped silicon-on-insulator waveguide Raman amplifier," ProceedingsDemonstration of a silicon Raman laser Ozdal Boyraz and Bahram Jalali Optoelectronic Circuits://www.ee.ucla.edu/~oecs/ Abstract: We report the demonstration of the first silicon Raman laser. Experimentally, pulsed Raman laser
Maturation grade of coals as revealed by Raman spectroscopy: progress and problems.
Quirico, Eric; Rouzaud, Jean-Noļl; Bonal, Lydie; Montagnac, Gilles
The present study questions the sensitivity and the accuracy of Raman spectroscopy as a tool for determining the maturity of natural organic matter (NOM). It focuses on the definition of optimized experimental parameters in order to maximize the quality of the Raman signal and control the accuracy and reproducibility of measurements. A series of 11 coals has been investigated, sampling a wide maturity range (2-7% vitrinite reflectance VR). The role of experimental parameters is first investigated. An excitation wavelength of 514.5 nm gives better results than 457.9 and 632.8 nm, minimizing the fluorescence background observed in the spectra of low-rank coals. Both Raman and fluorescence spectra were investigated with time-resolved experiments in air and argon. These data show that fluorescence and Raman spectra are sensitive to acquisition time and laser power parameters, and reveal a physicochemical instability of the samples under laser irradiation, mostly due to photo-oxidation processes. These data clearly show that the experiments, especially in air, should be performed with strictly constant acquisition parameters. In addition, the results of a whole series of coal measurements performed in air under constant experimental conditions show that Raman spectroscopy is definitely sensitive to the maturity of coal samples with VR> approximately 1%. The most sensitive spectral maturity tracers are the width of the D-band (FWHM-D), the ratio of the peak intensities of the D- and G-bands (I(D)/I(G)), the normalized ratio of the band integrated intensities A(D)/[A(D)+A(G)] for the maturity range VR=3-7% and the width of the G-band (FWHM-G) for VR=1-5%. However, the accuracy and reproducibility are definitely weaker in such measurements compared to the standard VR. Future work must solve the problem of sample stability under laser irradiation, and greatly increase the number of samples to improve the statistical significance of the results. PMID:16029859
Raman spectroscopy for the characterization of algal cells
NASA Astrophysics Data System (ADS)
Samek, Ota; JonßÜ, Alexandr; Pilßt, Zden?k; Zemßnek, Pavel; Nedbal, Ladislav; T?Ēska, Jan; Kotas, Petr; TrtĒlek, Martin
Raman spectroscopy can elucidate fundamental questions about intercellular variability and what governs it. Moreover, knowing the metabolic response on single cell level this can significantly contribute to the study and use of microalgae in systems biology and biofuel technology. Raman spectroscopy is capable to measure nutrient dynamics and metabolism in vivo, in real-time, label free making it possible to monitor/evaluate population variability. Also, degree of unsaturation of the algae oil (iodine value) can be measured using Raman spectra obtained from single microalgae. The iodine value is the determination of the amount of unsaturation contained in fatty acids (in the form of double bonds). Here we demonstrate the capacity of the spatially resolved Raman microspectroscopy to determine the effective iodine value in lipid storage bodies of individual living algal cells. We employed the characteristic peaks in the Raman scattering spectra at 1,656 cm-1 (cis C=C stretching mode) and 1,445 cm-1 (CH2 scissoring mode) as the markers defining the ratio of unsaturated-to-saturated carbon-carbon bonds of the fatty acids in the algal lipids.
Raman spectroscopy of Bacillus thuringiensis physiology and inactivation
NASA Astrophysics Data System (ADS)
Morrow, J. B.; Almeida, J.; Cole, K. D.; Reipa, V.
The ability to detect spore contamination and inactivation is relevant to developing and determining decontamination strategy success for food and water safety. This study was conducted to develop a systematic comparison of nondestructive vibrational spectroscopy techniques (Surface-Enhanced Raman Spectroscopy, SERS, and normal Raman) to determine indicators of Bacillus thuringiensis physiology (spore, vegetative, outgrown, germinated and inactivated spore forms). SERS was found to provide better resolution of commonly utilized signatures of spore physiology (dipicolinic acid at 1006 cm-1 and 1387 cm-1) compared to normal Raman and native fluorescence indigenous to vegetative and outgrown cell samples was quenched in SERS experiment. New features including carotenoid pigments (Raman features at 1142 cm-1, 1512 cm-1) were identified for spore cell forms. Pronounced changes in the low frequency region (300 cm-1 to 500 cm-1) in spore spectra occurred upon germination and inactivation (with both free chlorine and by autoclaving) which is relevant to guiding decontamination and detection strategies using Raman techniques.
Distinguishing Cancerous Liver Cells Using Surface-Enhanced Raman Spectroscopy.
Huang, Jing; Liu, Shupeng; Chen, Zhenyi; Chen, Na; Pang, Fufei; Wang, Tingyun
Raman spectroscopy has been widely used in biomedical research and clinical diagnostics. It possesses great potentials for the analysis of biochemical processes in cell studies. In this article, the surface-enhanced Raman spectroscopy (SERS) of normal and cancerous liver cells incubated with SERS active substrates (gold nanoparticle) was measured using confocal Raman microspectroscopy technology. The chemical components of the cells were analyzed through statistical methods for the SERS spectrum. Both the relative intensity ratio and principal component analysis (PCA) were used for distinguishing the normal liver cells (QSG-7701) from the hepatoma cells (SMMC-7721). The relative intensity ratio of the Raman spectra peaks such as I937/I1209, I1276/I1308, I1342/I1375, and I1402/I1435 was set as the judge boundary, and the sensitivity and the specificity using PCA method were calculated. The results indicated that the surface-enhanced Raman spectrum could provide the chemical information for distinguishing the normal cells from the cancerous liver cells and demonstrated that SERS technology possessed the possible applied potential for the diagnosis of liver cancer. PMID:25432931
A System For Semiconductor Characterization By Both Photoluminescence And Raman Spectroscopy
NASA Astrophysics Data System (ADS)
Purcell, F. J...; Kaminski, Raymond
Characterization of semiconductor materials has been rapidly enhanced by the application of photoluminescence and laser-Raman spectroscopy. Photoluminescence is uniquely suited for identifying impurities as well as mapping whole wafers to determine the distribution of dislocation densities or impurity clusters over the surface. Assessment of subsurface damage is also possible. Such data has been correlated with the threshold voltages of finished devices. Laser-Raman spectroscopy, on the other hand, will identify surface contaminants and determine lattice disorder, residual strain and free-carrier density. Separate, dedicated instruments are typically employed for each type of investigation, In this paper, the authors present an automated system that delivers both photoluminescence and Raman capabilities. Wafers up to 4 inches in diameter were characterized at room temperature and while cooled by liquid helium. Sample materials included Si, AlGaAs, GaAs, LiNbO and In?. Information from spectra, wafer maps and peak shifts is presented and discussed. The quality of semiconductor devices and their mass-production yields depend largely on how well the materials from which the devices are fabricated can be characterized. Equally important is the effect of processing upon these materials. Currently, optical spectroscopy is emerging as a primary source of such information for both fundamental research and quality control in manufacturing. The non-contact and non-destructive nature of optical spectroscopic analyses is one of the most attractive reasons for the popularity of these characterization techniques. Capable of being fully automated through microprocessor control, optical spectroscopy also generates a range of data unmatched by other methods. And among the spectroscopic techniques currently available, photoluminescence and Raman spectroscopy are especially effective for characterizing semiconductor materials like silicon, gallium arsenide or indium phosphide. In its most basic form, photoluminescence (P1) involves exciting a sample with photons for higher energy than the semiconductor's band gap and observing any emission that results. In addition of providing a measure of crystal quality, photoluminescence has been used extensively to study the role of dopants in the production of Si, semi--insulating GaAs and InP. In the evaluation of ion-implanted III-V semiconductor, photoluminescence has been employed to map the distribution of impurities, surface degradation from implantation and annealing, as well as lattice reconstruction during annealing. Raman spectroscopy complements photoluminescence characterization by providing a more comprehensive structural and molecular picture of semiconductor materials . The important parameters of a Raman semiconductor spectrum are the peak position and line shape of the longitudinal optic (LO) and transverse optic (TO).
Characterization of bundled and individual triple-walled carbon nanotubes by resonant Raman spectroscopy.
Hirschmann, Thomas Ch; Araujo, Paulo T; Muramatsu, Hiroyuki; Zhang, Xu; Nielsch, Kornelius; Kim, Yoong Ahm; Dresselhaus, Mildred S
The optical characterization of bundled and individual triple-walled carbon nanotubes was studied for the first time in detail by using resonant Raman spectroscopy. In our approach, the outer tube of a triple-walled carbon nanotube system protects the two inner tubes (or equivalently the inner double-walled carbon nanotube) from external environment interactions making them a partially isolated system. Following the spectral changes and line-widths of the radial breathing modes and G-band by performing laser energy dependent Raman spectroscopy, it is possible to extract important information as regards to the electronic and vibrational properties, tube diameters, wall-to-wall distances, radial breathing mode, and G-band resonance evolutions as well as high-curvature intertube interactions in isolated double- and triple-walled carbon nanotube systems. PMID:23311296
Ultrasensitive Laser Spectroscopy.
ERIC Educational Resources Information Center
Kliger, David S.
Examines techniques used to make ultrasensitive spectroscopic measurements. They include excitation, thermal lens, photo acoustic, and ionization spectroscopies. Guidelines and methods are provided for each technique; common uses and applications are explained. (DH)
Hamdi et al, Laser Spectroscopy with nanometric gas cells: ... Laser spectroscopy with nanometric gas cells
Paris-Sud XI, Universitķ de
Hamdi et al, Laser Spectroscopy with nanometric gas cells: ... Laser spectroscopy with nanometric The high sensitivity of Laser Spectroscopy has made possible the exploration of atomic resonances in newly of interatomic collisions processes under the effect of confinement. 1 #12;Hamdi et al, Laser Spectroscopy
Quality assessment for processed and sterilized bone using Raman spectroscopy.
Yamamoto, Takeaki; Uchida, Kentaro; Naruse, Kouji; Suto, Mitsutoshi; Urabe, Ken; Uchiyama, Katsufumi; Suto, Kaori; Moriya, Mitsutoshi; Itoman, Moritoshi; Takaso, Masashi
To eliminate the potential for infection, many tissue banks routinely process and terminally sterilize allografts prior to transplantation. A number of techniques, including the use of scanning electron microscopy, bone graft models, and mechanical property tests, are used to evaluate the properties of allograft bone. However, as these methods are time consuming and often destroy the bone sample, the quality assessment of allograft bones are not routinely performed after processing and sterilization procedures. Raman spectroscopy is a non-destructive, rapid analysis technique that requires only small sample volumes and has recently been used to evaluate the mineral content, mineral crystallinity, acid phosphate and carbonate contents, and collagen maturity in human and animal bones. Here, to establish a quality assessment method of allograft bones using Raman spectroscopy, the effect of several common sterilization and preservation procedures on rat femoral bones were investigated. We found that freeze-thawing had no detectable effects on the composition of bone minerals or matrix, although heat treatment and gamma irradiation resulted in altered Raman spectra. Our findings suggest Raman spectroscopy may facilitate the quality control of allograft bone after processing and sterilization procedures. PMID:21901322
Raman spectroscopy on simple molecular systems at very high density
Schiferl, D.; LeSar, R.S.; Moore, D.S.
We present an overview of how Raman spectroscopy is done on simple molecular substances at high pressures. Raman spectroscopy is one of the most powerful tools for studying these substances. It is often the quickest means to explore changes in crystal and molecular structures, changes in bond strength, and the formation of new chemical species. Raman measurements have been made at pressures up to 200 GPa (2 Mbar). Even more astonishing is the range of temperatures (4-5200/degree/K) achieved in various static and dynamic (shock-wave) pressure experiments. One point we particularly wish to emphasize is the need for a good theoretical understanding to properly interpret and use experimental results. This is particularly true at ultra-high pressures, where strong crystal field effects can be misinterpreted as incipient insulator-metal transitions. We have tried to point out apparatus, techniques, and results that we feel are particularly noteworthy. We have also included some of the /open quotes/oral tradition/close quotes/ of high pressure Raman spectroscopy -- useful little things that rarely or never appear in print. Because this field is rapidly expanding, we discuss a number of exciting new techniques that have been informally communicated to us, especially those that seem to open new possibilities. 58 refs., 18 figs.
Raman-shifted dye laser for water vapor DIAL measurements
NASA Technical Reports Server (NTRS)
Grossmann, B. E.; Singh, U. N.; Cotnoir, L. J.; Wilkerson, T. D.; Higdon, N. S.; Browell, E. V.
For improved DIAL measurements of water vapor in the upper troposphere or lower stratosphere, narrowband (about 0.03/cm) laser radiation at 720- and 940-nm wavelengths was generated by stimulated Raman scattering (SRS), using the narrow linewidth (about 0.02/cm) output of a Nd:YAG-pumped dye laser. For a hydrogen pressure of 350 psi, the first Stokes conversion efficiencies to 940 nm were 20 percent and 35 percent, when using a conventional and waveguide Raman cell, respectively. The linewidth of the first Stokes line at high cell pressures, and the inferred collisional broadening coefficients, agree well with those previously measured in spontaneous Raman scattering.
Solid-core photonic crystal fiber as a Raman spectroscopy platform with a silica core as an internal reference
NASA Astrophysics Data System (ADS)
Pristinski, Denis; Du, Henry
We show that solid-core photonic crystal fiber (PCF) is a promising platform for evanescent-field Raman spectroscopy of low-volume analytes. The Raman peak ratio of a silica core as a background to acetonitrile solution as analyte contained in the air holes maintains a constant value despite varying laser power and fiber length in a set of measurements. The Raman signal from the silica core can be used to eliminate the need to account for the coupling losses. These results demonstrate the feasibility of quantitative measurements using PCF as a Raman platform with silica as an internal reference. In addition, integrated Raman intensity increases with the length of the PCF due to long path length of light.
Solid-core photonic crystal fiber as a Raman spectroscopy platform with a silica core as an internal reference.
Pristinski, Denis; Du, Henry
We show that solid-core photonic crystal fiber (PCF) is a promising platform for evanescent-field Raman spectroscopy of low-volume analytes. The Raman peak ratio of a silica core as a background to acetonitrile solution as analyte contained in the air holes maintains a constant value despite varying laser power and fiber length in a set of measurements. The Raman signal from the silica core can be used to eliminate the need to account for the coupling losses. These results demonstrate the feasibility of quantitative measurements using PCF as a Raman platform with silica as an internal reference. In addition, integrated Raman intensity increases with the length of the PCF due to long path length of light. PMID:17072385
Verifying of endocrine disruptor chemical affect to the mouse testes: can raman spectroscopy support histology study?
NASA Astrophysics Data System (ADS)
Andriana, Bibin B.; Oshima, Yusuke; Takanezawa, Sota; Tay, Tat W.; Rosawati Soeratman, Catherine Linda; Alam, Mohammad S.; Mitsuoka, Hiroki; Zhu, Xiao B.; Suzuki, Toshiaki; Yamamoto, Yuko S.; Tsunekawa, Naoki; Kanai, Yoshiakira; Kurohmaru, Masamichi; Sato, Hidetoshi
One of suspect environmental endocrine disruptors that affect mouse male reproduction by altering the morphology of Sertoli cells and spermatogenic cells is phthalate. The effects of mono(2-ethylhexyl)phthalate (MEHP), one of metabolites of di(2-ethylhexyl)phthalate , on immature mouse testes in vivo were examined. We have recently shown that MEHP induced Sertoli cells necrosis and spermatogenic cells apoptosis in mice by TUNEL method, F-actin staining, and ultrastructural study, but there is no data for biochemical changing of testes due to those methods could not explore. To verify in detail of it, we conducted Raman spectroscopy study with 785 nm wavelength laser line, 50mW of laser power and 3 minutes of exposure time to analysis the MEHP-treated testicular tissue, which has been fixatived by 4% paraformaldehyde (PFA). Five weeks old (5 w.o) male mice were used in this experiment. As the results, the alterations were observed by Raman spectroscopy that there are significantly differences of DNA, actin filament, type IV collagen and amide I between control group (0 ?M MEHP) and treatment group (100 ?M MEHP). These results significantly support histology staining observation (such as the apoptotic spermatogenic cells which is associated with DNA fragmentation and F-actin disruption) and ultrastructural observation (such as mitochondria rupture and disintegration of nucleus membrane). Raman spectroscopy can be used for 4% PFA-fixatived tissue observation. However, we recommend that Raman spectroscopy may be able to be expanded as an armamentarium not just for the clarification of histology staining and ultrastructural study, but furthermore, it may be as a non-invasion assessment for screening animal tissue toxicity of chemical in future.
Raman spectroscopy of iodine molecules trapped in zeolite crystals
NASA Astrophysics Data System (ADS)
Guo, Wenhao; Wang, Dingdi; Hu, Juanmei; Tang, Z. K.; Du, Shengwang
We study the Raman spectroscopy of neutral iodine molecules confined in the channels of zeolite AlPO4-5 (AFI) and AlPO4-11 (AEL) crystals, which shows that the molecular vibration states are significantly modified by the confinements from the nanosize channels. An iodine molecule trapped in the AEL crystal has an effective internuclear potential close to an ideal harmonic oscillator, while that in the AFI crystal behaves similarly to that in free space. The results are further confirmed by measuring the temperature dependence of Raman spectral width.
Femtosecond coherent anti-Stokes Raman scattering spectroscopy using frequency-tunable radiation generated in microstructure fibres
Akimov, Denis A; Konorov, Stanislav O; Fedotov, Andrei B [Department of Physics, M.V. Lomonosov Moscow State University, Moscow (Russian Federation); Alfimov, Mikhail V; Ivanov, Anatoliy A; Petrov, A N [Photochemistry Center, Russian Academy of Sciences, Moscow (Russian Federation); Beloglazov, V I; Skibina, N B [Institute of Technology and Processing of Glass Structures, Russian Academy of Sciences, Saratov (Russian Federation); Sidorov-Biryukov, D A; Zheltikov, Aleksei M [International Laser Center, M. V. Lomonosov Moscow State University, Moscow (Russian Federation)
Microstructure fibres with a special dispersion profile are shown to allow the creation of highly efficient sources of frequency-tunable ultrashort pulses with a smooth envelope and a controlled chirp for high-resolution time-resolved coherent anti-Stokes Raman scattering spectroscopy. We present pulse-duration and group-delay measurements for anti-Stokes signals generated in microstructure fibres by femtosecond pulses of a Cr : forsterite laser. Frequency-tunable anti-Stokes pulses produced and shaped in microstructure fibres are employed for coherent anti-Stokes Raman scattering spectroscopy of toluene solution. (nonlinear optical phenomena)
Modern Raman Imaging: Vibrational Spectroscopy on the Micrometer and Nanometer Scales
NASA Astrophysics Data System (ADS)
Opilik, Lothar; Schmid, Thomas; Zenobi, Renato
Raman microscopes are currently used in various fields of research because they allow for label-free sample investigation. Moreover, the inherently low scattering cross section of Raman spectroscopy, as well as its diffraction-limited lateral resolution, has been overcome by new Raman microscopy techniques. Nonlinear methods such as coherent anti-Stokes Raman spectroscopy and stimulated Raman spectroscopy reduce measurement times and improve z resolution, allowing for three-dimensional spectroscopic imaging of biological samples. Moreover, tip-enhanced Raman spectroscopy, a near-field optical technique that combines scanning-probe microscopy with the enhancement offered by surface-enhanced Raman scattering, enables Raman spectroscopic imaging far below the optical diffraction limit. We cover the theoretical and technical aspects of Raman microscopy and related new imaging techniques and review some very recent applications in graphene research and cell biology.
Standoff laser-based spectroscopy for explosives detection
NASA Astrophysics Data System (ADS)
Gaft, M.; Nagli, L.
Real time detection and identification of explosives at a standoff distance is a major issue in efforts to develop defense against so-called Improvised Explosive Devices (IED). It is recognized that the only technique, which is potentially capable to standoff detection of minimal amounts of explosives is laser-based spectroscopy. LDS activity is based on a combination of laser-based spectroscopic methods with orthogonal capabilities. Our technique belongs to trace detection, namely to its micro-particles variety. It is based on commonly held belief that surface contamination was very difficult to avoid and could be exploited for standoff detection. We has applied optical techniques including gated Raman and time-resolved luminescence spectroscopy for detection of main explosive materials, both factory and homemade. We developed and tested a Raman system for the field remote detection and identification of minimal amounts of explosives on relevant surfaces at a distance of up to 30 meters.
Fe-Ti-Cr-Oxides in Martian Meteorite EETA79001 Studied by Point-counting Procedure Using Raman Spectroscopy
NASA Technical Reports Server (NTRS)
Wang, Alian; Kuebler, Karla E.; Jolliff, Bradley L.; Haskin, Larry A.
Fe-Ti-Cr-Oxide minerals contain much information about rock petrogenesis and alteration. Among the most important in the petrology of common intrusive and extrusive rocks are those of the FeO-TiO2-Cr2O3 compositional system chromite, ulv spinel-magnetite, and ilmenite-hematite. These minerals retain memories of oxygen fugacity. Their exsolution into companion mineral pairs give constraints on formation temperature and cooling rate. Laser Raman spectroscopy is anticipated to be a powerful technique for characterization of materials on the surface of Mars. A Mars Microbeam Raman Spectrometer (MMRS) is under development. It combines a micro sized laser beam and an automatic point-counting mechanism, and so can detect minor minerals or weak Raman-scattering phases such as Fe- Ti-Cr-oxides in mixtures (rocks & soils), and provide information on grain size and mineral mode. Most Fe-Ti-Cr-oxides produce weaker Raman signals than those from oxyanionic minerals, e.g. carbonates, sulfates, phosphates, and silicates, partly because most of them are intrinsically weaker Raman scatters, and partly because their dark colors limit the penetration depth of the excitation laser beam (visible wavelength) and of the Raman radiation produced. The purpose of this study is to show how well the Fe-Ti-Cr-oxides can be characterized by on-surface planetary exploration using Raman spectroscopy. We studied the basic Raman features of common examples of these minerals using well-characterized individual mineral grains. The knowledge gained was then used to study the Fe-Ti-Cr-oxides in Martian meteorite EETA79001, especially effects of compositional and structural variations on their Raman features.
Interference-free optical detection for Raman spectroscopy
NASA Technical Reports Server (NTRS)
Nguyen, Quang-Viet (Inventor); Fischer, David G (Inventor); Kojima, Jun (Inventor)
An architecture for spontaneous Raman scattering (SRS) that utilizes a frame-transfer charge-coupled device (CCD) sensor operating in a subframe burst gating mode to realize time-resolved combustion diagnostics is disclosed. The technique permits all-electronic optical gating with microsecond shutter speeds (<5 .mu.s), without compromising optical throughput or image fidelity. When used in conjunction with a pair of orthogonally-polarized excitation lasers, the technique measures time-resolved vibrational Raman scattering that is minimally contaminated by problematic optical background noise.
Modulated Raman Spectroscopy for Enhanced Cancer Diagnosis at the Cellular Level.
De Luca, Anna Chiara; Dholakia, Kishan; Mazilu, Michael
Raman spectroscopy is emerging as a promising and novel biophotonics tool for non-invasive, real-time diagnosis of tissue and cell abnormalities. However, the presence of a strong fluorescence background is a key issue that can detract from the use of Raman spectroscopy in routine clinical care. The review summarizes the state-of-the-art methods to remove the fluorescence background and explores recent achievements to address this issue obtained with modulated Raman spectroscopy. This innovative approach can be used to extract the Raman spectral component from the fluorescence background and improve the quality of the Raman signal. We describe the potential of modulated Raman spectroscopy as a rapid, inexpensive and accurate clinical tool to detect the presence of bladder cancer cells. Finally, in a broader context, we show how this approach can greatly enhance the sensitivity of integrated Raman spectroscopy and microfluidic systems, opening new prospects for portable higher throughput Raman cell sorting. PMID:26110401
Modulated Raman Spectroscopy for Enhanced Cancer Diagnosis at the Cellular Level
De Luca, Anna Chiara; Dholakia, Kishan; Mazilu, Michael
Raman spectroscopy is emerging as a promising and novel biophotonics tool for non-invasive, real-time diagnosis of tissue and cell abnormalities. However, the presence of a strong fluorescence background is a key issue that can detract from the use of Raman spectroscopy in routine clinical care. The review summarizes the state-of-the-art methods to remove the fluorescence background and explores recent achievements to address this issue obtained with modulated Raman spectroscopy. This innovative approach can be used to extract the Raman spectral component from the fluorescence background and improve the quality of the Raman signal. We describe the potential of modulated Raman spectroscopy as a rapid, inexpensive and accurate clinical tool to detect the presence of bladder cancer cells. Finally, in a broader context, we show how this approach can greatly enhance the sensitivity of integrated Raman spectroscopy and microfluidic systems, opening new prospects for portable higher throughput Raman cell sorting. PMID:26110401
Laser spectroscopy and quantum optics
T. W. Hõnsch; H. Walther
In this paper the authors discuss recent advances and trends in laser spectroscopy and quantum optics. It is obvious that both are fields that experienced a tremendous development in the last twenty years. Therefore the survey must be incomplete, and only a few highlights are touched on.
TOPICAL REVIEW: Surface-enhanced Raman scattering and biophysics
Katrin Kneipp; Harald Kneipp; Irving Itzkan; Ramachandra R. Dasari; Michael S. Feld
Surface-enhanced Raman scattering (SERS) is a spectroscopic technique which combines modern laser spectroscopy with the exciting optical properties of metallic nanostructures, resulting in strongly increased Raman signals when molecules are attached to nanometre-sized gold and silver structures. The effect provides the structural information content of Raman spectroscopy together with ultrasensitive detection limits, allowing Raman spectroscopy of single molecules. Since SERS
ccsd00003162, Raman spectroscopy of iodine-doped double-walled carbon
ccsdŁ00003162, version 1 Ł 26 Oct 2004 Raman spectroscopy of iodine-doped double-walled carbon) Abstract We present a Raman spectroscopy study of iodine-intercalated (p-type doped) double-walled car- bon the spectral moment method. The changes in the Raman spectrum upon iodine doping are analysed. Poly-iodine
Stimulated coherent anti-Stokes Raman spectroscopy (CARS) resonances originate from double-slit
Mukamel, Shaul
Stimulated coherent anti-Stokes Raman spectroscopy (CARS) resonances originate from double January 21, 2010 (received for review September 3, 2009) Coherent anti-Stokes Raman spectroscopy (CARS with re- spect to pulse parameters. CARS microscopy pulse shaping ultrafast spectroscpy Coherent Raman
Gate dependent Raman spectroscopy of graphene on hexagonal boron nitride.
Chattrakun, Kanokporn; Huang, Shengqiang; Watanabe, K; Taniguchi, T; Sandhu, A; LeRoy, B J
Raman spectroscopy, a fast and nondestructive imaging method, can be used to monitor the doping level in graphene devices. We fabricated chemical vapor deposition (CVD) grown graphene on atomically flat hexagonal boron nitride (hBN) flakes and SiO2 substrates. We compared their Raman response as a function of charge carrier density using an ion gel as a top gate. The G peak position, the 2D peak position, the 2D peak width and the ratio of the 2D peak area to the G peak area show a dependence on carrier density that differs for hBN compared to SiO2. Histograms of two-dimensional mapping are used to compare the fluctuations in the Raman peak properties between the two substrates. The hBN substrate has been found to produce fewer fluctuations at the same charge density owing to its atomically flat surface and reduced charged impurities. PMID:24275340
Investigations of coherent anti-Stokes Raman spectroscopy /CARS/ for combustion diagnostics
NASA Technical Reports Server (NTRS)
Eckbreth, A. C.; Hall, R. J.; Shirley, J. A.
Investigations of coherent anti-Stokes Raman spectroscopy (CARS) in a variety of flames are presented. Thermometry has received the primary emphasis in these studies, but species spectral and sensitivity studies will also be described. CARS is generated by mixing a 10 pps, frequency-doubled neodymium 'pump' laser with a spectrally broadband, laser-pumped, Stokes-shifted dye laser. This approach obviates the requirement to frequency scan the dye laser and generates the entire CARS spectrum with each pulse permitting, in principle, instantaneous measurements of medium properties. CARS spectra of N2, CO, O2, H2O, CO2 and CH4 in flames will be presented. In general these spectra exhibit very good agreement with computer synthesized spectra and permit measurements of temperature and species concentration. To illustrate the applicability of CARS to practical combustion diagnostics, CARS signatures from N2 have been employed to map the temperature field throughout a small, luminous, highly sooting propane diffusion flame
Raman Spectroscopy: A Suitable Tool For Planetary Investigations
NASA Astrophysics Data System (ADS)
Popp, J.; Tarcea, N.; Schmitt, M.; Kiefer, W.; Hochleitner, R.; Simon, G.; Hofer, S.; Schmidt, E.; Stuffler, T.; Hilchenbach, M.
For a fundamental understanding of the origin and evolution of planets information on the surface material is required. Raman spectroscopy represents one possible method for performing mineralogical studies. Raman imaging, delivers information about the identity and the spatial distribution of the various components of the sample. One way of performing this type of measurements is to bring a Raman device on the surface of the remote planet. MIRAS (Mineral Investigation by in situ Raman Spectroscopy) is a running project which deals with such an approach. A way of getting an idea about the mineralogical composition of Mars is to investigate some of the meteorites which are originating from this planet. Spatial distribution of different minerals on the sur- face of Mars meteorite slices have been measured by employing Raman spectroscopy. The method used for imaging the investigated surfaces was point by point scanning. Slices from Zagami and Dar al Gani 735 meteorites have been investigated. Surfaces of approximately 100x100 mum were imaged with a spatial sampling step size of roughly 2.5 mum. The Raman sampling surface was around 1 mum(2) . For the mineralogical assignment, Raman spectra of some well characterized standard mineral samples were recorded for comparison. For the Zagami meteorite, the major miner- als observed are in good agreement with what has been reported in literature. Apart from pyroxene, phosphates (apatite and whitlockite) or glassy materials, organic con- taminants (in this case originating from handling the meteorite slices on earth) were observed. The spatial distribution of these organic contaminants is of great interest as a test for further dealing with structural fossils or chemical traces of extinct or extant life. For Dar al Gani 735 meteorite, pyroxene, olivine, magnetite, calcite and whit- lockite have been identified on the scanned surface. This meteorite is considered to be paired with DaG 476 meteorite. DaG 735 was reported to be less weathered than DaG 476 and without terrestrial carbonate veins. However in our investigation, calcite was found in DaG 735. The spatial distribution on the scanned surface sustains the idea of veins, formed by contamination with water from the soil at the landing place. The first steps have been done for developing a Raman device which might be used as a remote automated mineralogist for in situ planetary investigations. Its name: MIRAS.
Nanoscale chemical imaging using tip-enhanced Raman spectroscopy: a critical review.
Schmid, Thomas; Opilik, Lothar; Blum, Carolin; Zenobi, Renato
Methods for chemical analysis at the nanometer scale are crucial for understanding and characterizing nanostructures of modern materials and biological systems. Tip-enhanced Raman spectroscopy (TERS) combines the chemical information provided by Raman spectroscopy with the signal enhancement known from surface-enhanced Raman scattering (SERS) and the high spatial resolution of atomic force microscopy (AFM) or scanning tunneling microscopy (STM). A metallic or metallized tip is illuminated by a focused laser beam and the resulting strongly enhanced electromagnetic field at the tip apex acts as a highly confined light source for Raman spectroscopic measurements. This Review focuses on the prerequisites for the efficient coupling of light to the tip as well as the shortcomings and pitfalls that have to be considered for TERS imaging, a fascinating but still challenging way to look at the nanoworld. Finally, examples from recent publications have been selected to demonstrate the potential of this technique for chemical imaging with a spatial resolution of approximately 10 nm and sensitivity down to the single-molecule level for applications ranging from materials sciences to life sciences. PMID:23610002
Comparative study of Raman spectroscopy in graphene and MoS2-type transition metal dichalcogenides.
Pimenta, Marcos A; Del Corro, Elena; Carvalho, Bruno R; Fantini, Cristiano; Malard, Leandro M
CONSPECTUS: Raman spectroscopy is one of the most powerful experimental tools to study graphene, since it provides much useful information for sample characterization. In this Account, we show that this technique is also convenient to study other bidimensional materials beyond graphene, and we will focus on the semiconducting transition metal dichalcogenides (MX2), specifically on MoS2 and WS2. We start by comparing the atomic structure of graphene and 2H-MX2 as a function of the number of layers in the sample. The first-order Raman active modes of each material can be predicted on the basis of their corresponding point-group symmetries. We show the analogies between graphene and 2H-MX2 in their Raman spectra. Using several excitation wavelengths in the visible range, we analyze the first- and second-order features presented by each material. These are the E2g and 2TO(K) bands in graphene (also known as the G and 2D bands, respectively) and the A1', E', and 2LA(M) bands in 2H MX2. The double-resonance processes that originate the second-order bands are different for both systems, and we will discuss them in terms of the different electronic structure and phonon dispersion curves presented by each compound. According to the electronic structure of graphene, which is a zero band gap semiconductor, the Raman spectrum is resonant for all the excitation wavelengths. Moreover, due to the linear behavior of the electronic dispersion near the K point, the double-resonance bands of graphene are dispersive, since their frequencies vary when we change the laser energy used for the sample excitation. In contrast, the semiconducting MX2 materials present an excitonic resonance at the direct gap, and consequently, the double-resonance Raman bands of MX2 are not dispersive, and only their intensities depend on the laser energy. In this sense, resonant Raman scattering experiments performed in transition metal dichalcogenides using a wide range of excitation energies can provide information about the electronic structure of these materials, which is complementary to other optical spectroscopies, such as absorption or photoluminescence. Raman spectroscopy can also be useful to address disorder in MX2 samples in a similar way as it is used in graphene. Both materials exhibit additional Raman features associated with phonons within the interior of the Brillouin zone that are activated by the presence of defects and that are not observed in pristine samples. Such is the case of the well-known D band of graphene. MX2 samples present analogous features that are clearly observed at specific excitation energies. The origins of these double-resonance Raman bands in MX2 are still subjects of current research. Finally, we discuss the suitability of Raman spectroscopy as a strain or doping sensor. Such applications of Raman spectroscopy are being extensively studied in the case of graphene, and considering its structural analogies with MX2 systems, we show how this technique can also be used to provide strain/doping information for transition metal dichalcogenides. PMID:25490518
Nano-star formation in Al-doped ZnO thin film deposited by dip-dry method and its characterization using atomic force microscopy, electron probe microscopy, photoluminescence and laser Raman spectroscopy
D. Behera; B. S. Acharya
Zinc oxide doped with Al (AZO) thin films were prepared on borosilicate glass substrates by dip and dry technique using sodium zincate bath. Effects of doping on the structural and optical properties of ZnO film were investigated by XRD, EPMA, AFM, optical transmittance, PL and Raman spectroscopy. The band gap for ZnO:Al (5.0at.wt.%) film was found to be 3.29eV compared
Resonance Raman Spectroscopy of Single-Wall Carbon Nanotubes Separated via Aqueous Two-Phase Extraction
NASA Astrophysics Data System (ADS)
Simpson, J. R.; Fagan, J. A.; Hight Walker, A. R.
We report Resonance Raman Spectroscopy (RRS) measurements of single-wall carbon nanotube (SWCNT) samples dispersed in aqueous solutions via surfactant wrapping and separated using aqueous two-phase extraction (ATPE) into chirality-enriched semiconducting and metallic SWCNT species. ATPE provides a rapid, robust, and remarkably tunable separation technique that allows isolation of high-purity, individual SWCNT chiralities via modification of the surfactant environment. We report RRS measurements of individual SWCNT species of various chiral index including, armchair and zigzag metals. Raman provides a powerful technique to quantify the metallic SWCNTs in ATPE fractions separated for metallicity. We measure Raman spectra over a wide range of excitation wavelengths from 457 nm to 850 nm using a series of discrete and continuously tunable laser sources coupled to a triple-grating spectrometer with a liquid-nitrogen-cooled detector. The spectra reveal Raman-active vibrational modes, including the low-frequency radial breathing mode (RBM) and higher-order modes. SWCNT chiral vectors are determined from the Raman spectra, specifically the RBM frequencies and corresponding energy excitation profiles, together with input from theoretical models.
Detection and characterization of stomach cancer and atrophic gastritis with fluorescence and Raman spectroscopy
NASA Astrophysics Data System (ADS)
Li, Xiaozhou; Lin, Junxiu; Jia, Chunde; Wang, Rong
In this paper, we attempt to find a valid method to distinguish gastric cancer and atrophic gastritis. Auto-fluorescence and Raman spectroscopy of laser induced (514.5 nm and 488.0 nm) was measured. The serum spectrum is different between normal and cancer. Average value of diagnosis parameter for normal serum, red shift is less than 12 nm and Raman relative intensity of peak C by 514.5 nm excited is stronger than that of 488.0 nm. To gastric cancer, its red shift of average is bigger than 12 nm and relative intensity of Raman peak C by 514.5 nm excited is weaker than that by 488.0 nm. To atrophic gastritis, the distribution state of Raman peaks is similar with normal serum and auto-fluorescence spectrum's shape is similar to that of gastric cancer. Its average Raman peak red shift is bigger than 12 nm and the relative intensity of peak C by 514.5 excited is stronger than that of by 488.0. We considered it as a criterion and got an accuracy of 85.6% for diagnosis of gastric cancer compared with the result of clinical diagnosis.
Single-Pulse Raman And Photoacoustic Spectroscopy Studies Of Triaminotrinitrobenzene (TATB) And Related Compounds
NASA Astrophysics Data System (ADS)
Trott, W. M.; Renlund, A. M.; Jungst, R. G.
Pulsed-laser-excited Raman scattering methods and photoacoustic spectroscopy have been applied to the study of porous, granular samples (i.e., pressed pellets) of 1,3,5-trinitrobenzene (TNB), 1-amino-2,4,6-trinitrobenzene (MATB), 1,3-diamino-2,4,6-trinitrobenzene (DATB) and 1,3,5-triamino-2,4,6-trinitrobenzene (TATB). Single-pulse spontaneous Raman spectra have been obtained for all four materials. Using 532-nm excitation, the intensity of the background emission observed with the Raman scattered light varies as TNB > MATB > DATB > TATB. This trend is compared to information on the long-wavelength absorption edge of MATB, DATB and TATB as determined by the photoacoustic spectra of these materials. Stimulated Raman scattering has been observed for three of the compounds with conversion efficiency as follows: DATB > TATB > MATB. In the case of TATB, this process may be limited by photo-induced chemical reactions. The relatively efficient formation of one or more stable photolysis products in TATB is evident on the basis of its photoacoustic spectrum. Preliminary single-pulse Raman scattering measurements on shocked TATB are also described.
Application of micro-Raman spectroscopy for fight against terrorism and smuggling
NASA Astrophysics Data System (ADS)
Almaviva, Salvatore; Botti, Sabina; Palucci, Antonio; Puiu, Adriana; Schn³rer, Frank; Schweikert, Wenka; Romolo, Francesco Saverio
We report the results of Raman measurements on some common military explosives and explosives precursors deposited on clothing fabrics, both synthetic and natural, in concentration comparable to those obtained from a single fingerprint or mixed with similar harmless substances to detect illegal compounds for smuggling activities. Raman spectra were obtained using an integrated portable Raman system equipped with an optical microscope and a 785-nm laser in an analysis of <1 min. The spectral features of each illicit substance have been identified and distinguished from those belonging to the substrate fabric or from the interfering compound. Our results show that the application of Raman spectroscopy (RS) with a microscope-based portable apparatus can provide interpretable Raman spectra for a fast, in-situ analysis, directly from explosive particles of some ?, despite the contribution of the substrate, leaving the sample completely unaltered for further, more specific, and propedeutic laboratory analysis. We also show how the RS is suitable for detecting illegal compounds mixed with harmless substances for smuggling purposes or for counterfeiting activities.
Quantitative detection of astaxanthin and cantaxanthin in Atlantic salmon by resonance Raman spectroscopy
NASA Astrophysics Data System (ADS)
Ermakov, Igor V.; Ermakova, Maia R.; Gellermann, Werner
Two major carotenoids species found in salmonids muscle tissues are astaxanthin and cantaxanthin. They are taken up from fish food and are responsible for the attractive red-orange color of salmon filet. Since carotenoids are powerful antioxidants and biomarkers of nutrient consumption, they are thought to indicate fish health and resistance to diseases in fish farm environments. Therefore, a rapid, accurate, quantitative optical technique for measuring carotenoid content in salmon tissues is of economic interest. We demonstrate the possibility of using fast, selective, quantitative detection of astaxanthin and cantaxanthin in salmon muscle tissues, employing resonance Raman spectroscopy. Analyzing strong Raman signals originating from the carbon-carbon double bond stretch vibrations of the carotenoid molecules under blue laser excitation, we are able to characterize quantitatively the concentrations of carotenoids in salmon muscle tissue. To validate the technique, we compared Raman data with absorption measurements of carotenoid extracts in acetone. A close correspondence was observed in absorption spectra for tissue extract in acetone and a pure astaxanthin solution. Raman results show a linear dependence between Raman and absorption data. The proposed technique holds promise as a method of rapid screening of carotenoid levels in fish muscle tissues and may be attractive for the fish farm industry to assess the dietary status of salmon, risk for infective diseases, and product quality control.
Picosecond timescale Raman processes and spectroscopy
Johnson, Carey K.; Dalickas, G. A.; Payne, S. A.; Hochstrasser, R. M.
with the 1218 Controller and the 1215 Console. Figure 5. Picosecond multiplexed CARS spectrum of 992 cm1 mode of liquid benzene resulting from 50 laser shots in 0.2 nm pathlength cell, superimposed with the R6G dye laser spectral output. Figure 6. Picosecond.... The curves display the expected squared dependence on benzene vapor pressure. Figure 5 shows a spectrum of liquid benzene taken in the region of the 992 cm mode using this arrangement. Figure 6 shows the CARS spectrum of gaseous benzene at three pres- sures...
Advances in Raman spectroscopy for explosive identification in aviation security
NASA Astrophysics Data System (ADS)
Santillßn, Javier D.; Brown, Christopher D.; Jalenak, Wayne
In the operational airport environment, the rapid identification of potentially hazardous materials such as improvised explosive devices, chemical warfare agents and flammable and explosive liquids is increasingly critical. Peroxide-based explosives pose a particularly insidious threat because they can be made from commonly available and relatively innocuous household chemicals, such as bleach and hydrogen peroxide. Raman spectroscopy has been validated as a valuable tool for rapid identification of chemicals, explosives, and narcotics and their precursors while allowing "line-of-sight" interrogation through bottles or other translucent containers. This enables safe identification of both precursor substances, such as acetone, and end-products, such as TATP, without direct sampling, contamination and exposure by security personnel. To date, Raman systems have been laboratory-based, requiring careful operation and maintenance by technology experts. The capital and ongoing expenses of these systems is also significant. Recent advances in Raman component technologies have dramatically reduced the footprint and cost, while improving the reliability and ease of use of Raman spectroscopy systems. Such technologies are not only bringing the lab to the field, but are also protecting civilians and security personnel in the process.
Raman Spectroscopy-Compatible Inactivation Method for Pathogenic Endospores?
St÷ckel, S.; Schumacher, W.; Meisel, S.; Elschner, M.; R÷sch, P.; Popp, J.
Micro-Raman spectroscopy is a fast and sensitive tool for the detection, classification, and identification of biological organisms. The vibrational spectrum inherently serves as a fingerprint of the biochemical composition of each bacterium and thus makes identification at the species level, or even the subspecies level, possible. Therefore, microorganisms in areas susceptible to bacterial contamination, e.g., clinical environments or food-processing technology, can be sensed. Within the scope of point-of-care-testing also, detection of intentionally released biosafety level 3 (BSL-3) agents, such as Bacillus anthracis endospores, or their products is attainable. However, no Raman spectroscopy-compatible inactivation method for the notoriously resistant Bacillus endospores has been elaborated so far. In this work we present an inactivation protocol for endospores that permits, on the one hand, sufficient microbial inactivation and, on the other hand, the recording of Raman spectroscopic signatures of single endospores, making species-specific identification by means of highly sophisticated chemometrical methods possible. Several physical and chemical inactivation methods were assessed, and eventually treatment with 20% formaldehyde proved to be superior to the other methods in terms of sporicidal capacity and information conservation in the Raman spectra. The latter fact has been verified by successfully using self-learning machines (such as support vector machines or artificial neural networks) to identify inactivated B. anthracis-related endospores with adequate accuracies within the range of the limited model database employed. PMID:20208030
Two-dimensional micro-near-IR/FT-Raman spectroscopy
NASA Astrophysics Data System (ADS)
Schrader, Bernhard D.; Hoffmann, Andreas; Podschadlowski, Rolf; Simon, Arno
Optical micro methods have an enormous potential of supplying analytical information: For every volume element complete spectra may be recorded. Since these techniques are non-destructive repeated analyses may be made even from precious samples. Micro techniques applying the methods of vibrational spectroscopy may supply detailed information concerning the composition of a sample, the identity and the structure of its components. The resolvable volume element is determined by the resolving power of the microscope and by the minimal amount of sample defined by the limit of detection. For Raman microscopes this is in the order of 1 cubic micrometer, for infrared microscopes in the order of 1000 cubic micrometers. Microscopes, however have an optical conductance) inferior to that of modern spectrometers. A compromise has to be found between the utilizable Raman light flux and spatial resolution. Both cannot be maximal under the same conditions. FT IR microscopes as well as Raman microscopes with dispersive spectrometers are supplied by several companies. The recently developed NIR FT Raman spectroscopy2 has the advantage of being essentially immune against fluorescence of impurities or products of decomposition.
Breast cancer diagnosis using FT-RAMAN spectroscopy
NASA Astrophysics Data System (ADS)
Bitar, Renata A.; Martin, Airton A.; Criollo, Carlos J. T.; Ramalho, Leandra N. Z.
In this study FT-RAMAN spectra of breast tissue from 35 patients were obtained and separated into nine groups for histopathologic analysis, which are as follows: normal breast tissue, fibrocystic condition, in situ ductal carcinoma, in situ ductal carcinoma with necrosis, infiltrate ductal carcinoma, infiltrate inflammatory ductal carcinoma, infiltrate medullar ductal carcinoma, infiltrate colloid ductal carcinoma, and infiltrate lobular carcinoma. Using spectrum averages taken from each group a qualitative analysis was performed to compare these molecular compositions to those known to be present in abnormal concentrations in pathological situations, e.g. the development of desmoplastic lesions with a stroma of dense collagen in tumoral breast tissues which substitute adipose stroma of non-diseased breast tissue. The band identified as amino acids, offered basis for observation in the existence of alterations in the proteins, thus proving Raman Spectroscopic capacity in identification of primary structures of proteins; secondary protein structure was also identified through the peptic links, Amide I and Amide III, which have also been identified by various authors. Alterations were also identified in the peaks and bandwidths of nucleic acids demonstrating the utilization of Raman Spectroscopy in the analysis of the cells nucleus manifestations. All studies involving Raman Spectroscopy and breast cancer have shown excellent result reliability and therefore a basis for the technical theory.
Tissue classification and diagnostics using a fiber probe for combined Raman and fluorescence spectroscopy
NASA Astrophysics Data System (ADS)
Cicchi, Riccardo; Anand, Suresh; Rossari, Susanna; Sturiale, Alessandro; Giordano, Flavio; De Giorgi, Vincenzo; Maio, Vincenza; Massi, Daniela; Nesi, Gabriella; Buccoliero, Anna Maria; Tonelli, Francesco; Guerrini, Renzo; Pimpinelli, Nicola; Pavone, Francesco S.
Two different optical fiber probes for combined Raman and fluorescence spectroscopic measurements were designed, developed and used for tissue diagnostics. Two visible laser diodes were used for fluorescence spectroscopy, whereas a laser diode emitting in the NIR was used for Raman spectroscopy. The two probes were based on fiber bundles with a central multimode optical fiber, used for delivering light to the tissue, and 24 surrounding optical fibers for signal collection. Both fluorescence and Raman spectra were acquired using the same detection unit, based on a cooled CCD camera, connected to a spectrograph. The two probes were successfully employed for diagnostic purposes on various tissues in a good agreement with common routine histology. This study included skin, brain and bladder tissues and in particular the classification of: malignant melanoma against melanocytic lesions and healthy skin; urothelial carcinoma against healthy bladder mucosa; brain tumor against dysplastic brain tissue. The diagnostic capabilities were determined using a cross-validation method with a leave-one-out approach, finding very high sensitivity and specificity for all the examined tissues. The obtained results demonstrated that the multimodal approach is crucial for improving diagnostic capabilities. The system presented here can improve diagnostic capabilities on a broad range of tissues and has the potential of being used for endoscopic inspections in the near future.
An Yb-Raman cascaded fiber laser with temporal stability
NASA Astrophysics Data System (ADS)
Wenliang, Wang; Jinyong, Leng; Yang, Gao; Shaofeng, Guo; Zongfu, Jiang
We report a new structure of fiber laser, which has the advantages of temporal stability and wavelength agility. An Yb-Raman cascaded fiber oscillator generating 168 mW 1137 nm stable CW signal with 18.2% slope efficiency is demonstrated. In this fiber oscillator, the gain from both Yb ion and SRS effect is utilized. By comparison, the characteristics of the 1137 nm Yb-doped fiber laser are studied. The results show that the serious self-pulsation effect in the Yb-doped fiber laser is suppressed in the Yb-Raman cascaded fiber oscillator.
Raman Spectroscopy of Bacillus megaterium Using an Optical Multi-channel Analyzer
NASA Astrophysics Data System (ADS)
Layne, Scott P.; Bigio, Irving J.
Using a spectrometer equipped with an optical multi-channel analyzer as the detector, we have observed the Stokes laser-Raman spectra of metabolically active B. megaterium from 930-1720 cm-1. No Raman lines attributable to the metabolic process nor the cells themselves were found. This result is consistent with our previous laser-Raman measurements of synchronous E. coli cultures.
Exploitation of resonance Raman spectroscopy as a remote chemical sensor
Sedlacek, A.J.; Chen, C.L.
We have discussed recent experimental results using a resonance-Raman-based LIDAR system as a remote chemical sensor. This spectroscopy has the fundamental advantage that it is based on optical fingerprints that are insensitive to environmental perturbations. By taking advantage of resonance enhancement, which 6 orders-of-magnitude, can be as large as 4 to an increased sensing range for a given chemical concentration or lower detection limit for a given stand-off distance can be realized. The success discussed above can in part be traced back to the use of new state-of-the-art technologies which, only recently, have allowed the phenomenon of resonance-enhanced Raman spectroscopy to be fully exploited as a remote chemical sensor platform. Since many chemicals have electronic transitions in the UV/IS, it is expected that many will have pronounced resonance enhancements.
Identification of active fluorescence stained bacteria by Raman spectroscopy
NASA Astrophysics Data System (ADS)
Krause, Mario; Beyer, Beatrice; Pietsch, Christian; Radt, Benno; Harz, Michaela; R÷sch, Petra; Popp, J³rgen
Microorganisms can be found everywhere e.g. in food both as useful ingredients or harmful contaminations causing food spoilage. Therefore, a fast and easy to handle analysis method is needed to detect bacteria in different kinds of samples like meat, juice or air to decide if the sample is contaminated by harmful microorganisms. Conventional identification methods in microbiology require always cultivation and therefore are time consuming. In this contribution we present an analysis approach to identify fluorescence stained bacteria on strain level by means of Raman spectroscopy. The stained bacteria are highlighted and can be localized easier against a complex sample environment e.g. in food. The use of Raman spectroscopy in combination with chemometrical methods allows the identification of single bacteria within minutes.
Ring solid-state Raman laser at 1538 nm
NASA Astrophysics Data System (ADS)
Dashkevich, V. I.; Orlovich, V. A.
A ring KG(WO4)2 (KGW) Raman laser converting the multimode radiation of a Q-switched Nd:KGW pump laser oscillating on the 4F3/2 ? 4I13/2 transition into the first Stokes at 1538 nm has been demonstrated for the first time as far as we know. With a 22-mm crystal in each section of a three-mirror ring cavity, the Raman laser generates eye-safe radiation of energy ~ 7 mJ and duration ~ 15 ns. The beam divergence does not exceed 4.7 mrad. The conversion efficiency reaches ~ 20%, and the slope efficiency is ~ 42%. Upon elimination of the parasitic Stokes radiation induced by the Fresnel reflection from the AR-coated crystal ends in the opposite direction along the path of the pump beam the Raman laser provides unidirectional oscillation without using auxiliary optical elements.
Single nanoparticle detection using split-mode microcavity Raman lasers.
Li, Bei-Bei; Clements, William R; Yu, Xiao-Chong; Shi, Kebin; Gong, Qihuang; Xiao, Yun-Feng
Ultrasensitive nanoparticle detection holds great potential for early-stage diagnosis of human diseases and for environmental monitoring. In this work, we report for the first time, to our knowledge, single nanoparticle detection by monitoring the beat frequency of split-mode Raman lasers in high-Q optical microcavities. We first demonstrate this method by controllably transferring single 50-nm-radius nanoparticles to and from the cavity surface using a fiber taper. We then realize real-time detection of single nanoparticles in an aqueous environment, with a record low detection limit of 20 nm in radius, without using additional techniques for laser noise suppression. Because Raman scattering occurs in most materials under practically any pump wavelength, this Raman laser-based sensing method not only removes the need for doping the microcavity with a gain medium but also loosens the requirement of specific wavelength bands for the pump lasers, thus representing a significant step toward practical microlaser sensors. PMID:25267618
Single molecule laser spectroscopy
NASA Astrophysics Data System (ADS)
Atta, Diaa; Okasha, Ali
In this article, we discussed some single molecule spectroscopy techniques and methods. We have chosen the simplicity in this survey based on our laboratory experience in this field. We concentrated on the imaging by both techniques the wide field and the scanning microscopes. Other imaging enhancements on the technique like extended resolution wide field, the total internal reflection imaging, and its derivatives are also reviewed. In addition to the imaging techniques, some diffusion techniques also are discussed like fluorescence correlation spectroscopy. The related methods like Forester resonance transfer, photo-induced electron transfer and anisotropy (steady state and time decay) are also discussed. In addition, we elucidated some simple details about the theory behind the FCS and its resulting curve fitting. This review is preceded by general introduction and ended with the conclusion.
High-temperature and pressure Raman spectroscopy of diamond
En-Ping Huang; Eugene Huang; Shu-Cheng Yu; Yen-Hua Chen; Jiann-Shing Lee; Jiann-Neng Fang
This study presents the results of the first use of the moissanite anvil cell (MAC) for the in-situ high-temperature and pressure Raman spectroscopy measurement of diamond. It is observed that the T2g vibrational mode of diamond shifts toward low frequency with increasing temperature; on the other hand, the vibration band shifts toward high frequency with increasing pressure. In the high-temperature
Raman Spectroscopy for Monitoring Protein Structure in Muscle Food Systems
Ana M. Herrero
Raman spectroscopy offers structural information about complex solid systems such as muscle food proteins. This spectroscopic technique is a powerful and a non-invasive method for the study of protein changes in secondary structure, mainly quantified, analysing the amide I (1650¢1680 cm) and amide III (1200¢1300 cm) regions and C-C stretching band (940 cm), as well as modifications in protein local
Assessment of Raman Spectroscopy as a Silicone Pad Production Diagnostic
Saab, A P; Balazs, G B; Maxwell, R S
Silicone pressure pads are currently deployed in the W80. The mechanical properties of these pads are largely based on the degree of crosslinking between the polymer components that comprise the raw gumstock from which they are formed. Therefore, it is desirable for purposes of both production and systematic study of these materials to have a rapid, reliable means of assaying the extent of crosslinking. The present report describes the evaluation of Raman spectroscopy in this capacity.
Label-Free Fingerprinting of Pathogens by Raman Spectroscopy Techniques
Ann E. Grow
Raman spectroscopy is a label-free technique for generating unique spectral fingerprints from intact microorganisms. Studies\\u000a conducted for more than a decade have shown that these ōwhole-organism fingerprintsö can be used to identify pathogens, including\\u000a bacteria, yeasts, and spores, at the strain level, even when the microorganisms are so closely related that they are difficult\\u000a to distinguish by conventional techniques. Emerging
Stable isotope laser spectroscopy
NASA Technical Reports Server (NTRS)
Becker, J. F.; Yaldaei, Ramil; Mckay, Christopher P.
Recent advances in semiconductor laser technology have produced a reliable lightweight device ideally suited for a spacecraft high resolution molecular spectrometer. Lead-salt tunable diode lasers (TDL) emit in several spectral modes, each with a very narrow linewidth of -0.0003/cm. This spectral resolution is much narrower than typical Doppler broadened molecular linewidths in the mid-IR range. Thus it is possible to detect individual rotational lines within the vibrational band and measure their intensity, which can be used to determine gas concentration. The narrow spectral lines of any impurity gas tend to lie between the narrow lines of the gas of interest. This represents a major advantage over the accepted gas chromatograph mass spectrometer (GCMS) technique for measuring gas concentrations and isotope ratios. The careful and extensive gas purification procedures required to remove impurities for reliable GCMS measurements will not be required for an IR laser gas analysis. The infrared laser gas analysis technique is being developed to measure stable isotopic ratios of gases such as CO2, CH4, N2O, and NH3. This will eventually lead to development of instruments capable of in situ istopic measurements on planets such as Mars. The carbon (C-12, C-13) isotope ratio is indicative of the type of carbon fixation mechanisms (e.g., photosynthesis, respiration) in operation on a planet, while the nitrogen (N-14, N-15) isotope ratio can probably be used to date nitrogen-bearing Martian samples. The absorbance ratio of two adjacent lines of CO2 in the 2300/cm (4.3 micron) region of the spectrum was measured. The precision of the measurement is presently better than 1 percent and significant improvement is anticipated as rapid sweep-integration techniques and computer controlled data acquistion capabilities are incorporated.
Detection of human serum proteins using Raman and SERS spectroscopy
NASA Astrophysics Data System (ADS)
Ruan, Qiuyong; Liao, Fadian; Lin, Juqiang; Liu, Nenrong; Lin, Jinyong; Zeng, Yongyi; Li, Ling; Huang, Zufang; Chen, Rong
The use of normal Raman (NR) spectroscopy and surface enhanced Raman scattering (SERS) spectroscopy to analyze the biochemical information of human serum proteins and hence distinguish between normal and primary hepatic carcinoma (PHC) serum samples was investigated. The serum samples were obtained from patients who were clinically diagnosed with PHC (n=20) and healthy volunteers (n=20). All spectra were collected in the spectral range of 400-1800 cm-1 and analyzed through the multivariate statistical methods of principal component analysis (PCA). The results showed that both NR and SERS combined with PCA had good performance in distinguishing the human serum proteins between PHC patients and healthy volunteers with high sensitivity and specificity of 100%. And we can get more detail information of component and conformation of human serum proteins by considering NR and SERS spectrum. Our results support the concept again that serum protein Raman and SERS spectroscopy combined with PCA analysis both can become noninvasive and rapid diagnostic tools to detect the primary hepatic carcinoma.
Stimulated Raman scattering imaging by continuous-wave laser excitation
Cheng, Ji-Xin
microscopy [8]. By cw laser excitation, SRS spectroscopy of liquid benzene was shown in 1977 [9]. Recently]. In this work, SRS imaging of biologi- cal tissue by using cw lasers as excitation sources is demonstrated
Polarized Raman investigations of oriented animal muscle fibers affected by storage time applying a 671 nm diode laser
NASA Astrophysics Data System (ADS)
Al Ebrahim, Halah; Sowoidnich, Kay; Schmidt, Heinar; Kronfeldt, Heinz-Detlef
Due to its analytical ability and sensitivity to molecular vibrations, Raman spectroscopy provides valuable information of the secondary structure of proteins. Moreover, polarized Raman spectroscopy is shown to be a useful instrument to investigate the structural changes resulting from the aging and spoilage process of meat. In this work, polarized Raman spectra were measured on oriented cuts of pork and turkey. Fresh meat slices were stored at 5 ░C and measured for a consecutive time period of 10 days. A 671 nm microsystem diode laser was used as excitation light source. The laser power at the sample was 50 mW and the integration time of each Raman spectrum was set to 5 seconds. Measurements were performed with a laser beam orientation perpendicular to the long axis of the muscle fibers. In that arrangement, the fibers were aligned either parallel or perpendicular to the polarization direction of the laser source. By using the statistical method of principal components analysis (PCA), a clear separation of the meat samples can be found for fresh meat according to the orientation (parallel or perpendicular) using the first two principal components. During the storage period, this separation subsequently vanishes due to the aging process and due to an increase of the microbial spoilage of the meat surface. For the latter effect, a time-dependent distinction of the Raman spectra is presented as well. Furthermore, specific changes of conformation-sensitive Raman bands were recognized, notably a decrease of the intensities of ?-helical protein conformation.
Endoscopic Raman Spectroscopy for Molecular Fingerprinting of Gastric Cancer: Principle to Implementation
Currently, positive endoscopic biopsy is the standard criterion for gastric cancer diagnosis but is invasive, often inconsistent, and delayed although early detection and early treatment is the most important policy. Raman spectroscopy is a spectroscopic technique based on inelastic scattering of monochromatic light. Raman spectrum represents molecular composition of the interrogated volume providing a direct molecular fingerprint. Several investigations revealed that Raman spectroscopy can differentiate normal, dysplastic, and adenocarcinoma gastric tissue with high sensitivity and specificity. Moreover, this technique can indentify malignant ulcer and showed the capability to analyze the carcinogenesis process. Automated on-line Raman spectral diagnostic system raised possibility to use Raman spectroscopy in clinical field. Raman spectroscopy can be applied in many fields such as guiding a target biopsy, optical biopsy in bleeding prone situation, and delineating the margin of the lesion. With wide field technology, Raman spectroscopy is expected to have specific role in our future clinical field.
Free-electron laser system with Raman amplifier outcoupling
Linford, G.J.
A free-electron laser system is described comprising: a free-electron laser pump beam generator producing a high-power optical output beam in a vacuum environement; a Raman amplifier cell located in the path of the output beam from the pump beam generator; means for generating and introducing a Stokes seed beam into the Raman amplifier cell, a pair of gaseous windows through which the output beam enters and leaves the Raman amplifier cell, each window having a stream of gas moving continuously in a direction generally perpendicular to the beam; and a mirror positioned in the path of the output beam from the Raman amplifier, the mirror functioning to reflect and further direct the output beam, but not the unwanted spectral components.
Controllable continuous-wave Nd:YVO? self-Raman lasers using intracavity adaptive optics.
Li, Ran; Griffith, Mike; Laycock, Leslie; Lubeigt, Walter
A controllable self-Raman laser using an adaptive optics (AO)-based control loop featuring an intracavity deformable mirror is reported. This method has the potential to alleviate thermal lensing within the Raman and laser gain media, and enable solid-state Raman lasers to reach new power levels. A proof-of-concept experiment using a Nd:YVO4 self-Raman laser and resulting in 18% enhancement of the first Stokes output power is reported. Moreover, wavelength selection between two Raman laser outputs (?=1109 and 1176 nm) emanating from the 379 and 893 cm(-1) Raman shifts of YVO4, respectively, was achieved using this AO technique. PMID:25121868
New Material for Surface-Enhanced Raman Spectroscopy
NASA Technical Reports Server (NTRS)
Farquharson, Stuart; Nelson, Chad; Lee, Yuan
A chemical method of synthesis and application of coating materials that are especially suitable for surface-enhanced Raman spectroscopy (SERS) has been developed. The purpose of this development is to facilitate the utilization of the inherently high sensitivity of SERS to detect chemicals of interest (analytes) in trace amounts, without need for lengthy sample preparation. Up to now, the use of SERS has not become routine because the methods available have not been able to reproduce sampling conditions and provide quantitative measurements. In contrast, the coating materials of the present method enable analysis with minimum preparation of samples, and SERS measurements made using these materials are reproducible and reversible. Moreover, unlike in methods investigated in prior efforts to implement SERS, sampling is not restricted to such specific environments as electrolytes or specific solvents. The coating materials of this method are porous glasses, formed in sol-gel processes, that contain small particles of gold or silver metal. Materials of this type can be applied to the sample-contact surfaces of a variety of sampling and sensing devices, including glass slides, glass vials, fiber-optic probes, and glass tubes. Glass vials with their insides coated according to this method are particularly convenient for SERS to detect trace chemicals in solutions: One simply puts a sample solution containing the analyte(s) into a vial, then puts the vial into a Raman spectrometer for analysis. The chemical ingredients and the physical conditions of the sol-gel process have been selected so that the porous glass formed incorporates particles of the desired metal with size(s) to match the wavelength(s) of the SERS excitation laser in order to optimize the generation of surface plasmons. The ingredients and processing conditions have further been chosen to tailor the porosity and polarity of the glass to optimize the sample flow and the interaction between the analyte(s) and the plasmon field that generates Raman photons. The porous silica network of a sol-gel glass creates a unique environment for stabilizing SERS-active metal particles. Relative to other material structures that could be considered for SERS, the porous silica network offers higher specific surface area and thus greater interaction between analyte molecules and metal particles. Efforts to perform SERS measurements with the help of sampling devices coated by this method have been successful. In tests, numerous organic and inorganic chemicals were analyzed in several solvents, including water. The results of the tests indicate that the SERS measurements were reproducible within 10 percent and linear over five orders of magnitude. One measure of the limits of detectability of chemicals in these tests was found to be a concentration of 300 parts per billion. Further development may eventually make it possible to realize the full potential sensitivity of SERS for detecting some analytes in quantities as small as a single molecule.
Pulsed-laser-excited Raman spectra of shock compressed triaminotrinitrobenzene
Wayne M. Trott; Anita M. Renlund
Pulsed-laser-excited Raman scattering methods were used to examine sustained shock compression of 1,3,5-triamino 2,4,6-trinitrobenzene (TATB) at an optical window interface. Records of vibrational frequency shifts and line shape changes were obtained under variable and well-controlled shock loading using a 63 mm-diameter compressed gas gun to provide a planar impact geometry. To facilitate interpretation of the shock data. Raman spectra of
The effect of laser wavelength on the Raman Spectra of phenanthrene, chrysene, and tetracene: Implications for extra-terrestrial detection of polyaromatic hydrocarbons
A. I. Alajtal; H. G. M. Edwards; M. A. Elbagerma; I. J. Scowen
Raman spectroscopy, with visible laser (514 and 633nm) and near infrared (785 and 1064nm) excitation, has been used to obtain high quality spectra of phenanthrene, chrysene, and tetracene. Samples with dimensions from a minimum size of 10?m have been analyzed utilizing a Raman microprobe fitted with a charge-coupled device (CCD) array detector and a FT-Raman instrument. Fluorescence is observed for
Polycrystalline LiNbO3 thin films characterized by infrared and Raman spectroscopy
NASA Astrophysics Data System (ADS)
Zezulovß, M.; JelĒnek, M.; Kocourek, T.; VorlĒ?ek, V.; Äelezn², V.
Thin films of lithium niobate (LiNbO3) were studied by Fourier transform infrared and micro-Raman spectroscopy. The films were prepared on SiO2/Si substrate at substrate temperatures of 650, 700 and 750 ░C from monocrystalline or sintered LiNbO3 targets, using KrF excimer laser ablation. The films were polycrystalline. The changes of film properties and E and A1 phonon spectra with deposition conditions were studied, and were compared with bulk data.
Thin magnetite films on an oxidized silicon surface: Raman spectroscopy study
NASA Astrophysics Data System (ADS)
Vikulov, V. A.; Balashev, V. V.; Pisarenko, T. A.; Dimitriev, A. A.; Korobtsov, V. V.
Polycrystalline films of magnetite (Fe3O4) formed by the reactive sputtering of iron in oxygen on Si(001) substrates covered by thin (1.4 nm) or thick (1200 nm) SiO2 layers have been studied by Raman spectroscopy. It is established that (i) the ?-Fe2O3 phase is formed due to the laser-induced heating in magnetite films synthesized on thick SiO2 layers and (ii) the formation of ?-Fe2O3 phase depends on the thickness of the buffer SiO2 layer.
Application of Raman spectroscopy to identification and sorting of post-consumer plastics for recycling
Sommer, Edward J. (Nashville, TN); Rich, John T. (Lebanon, TN)
A high accuracy rapid system for sorting a plurality of waste products by polymer type. The invention involves the application of Raman spectroscopy and complex identification techniques to identify and sort post-consumer plastics for recycling. The invention reads information unique to the molecular structure of the materials to be sorted to identify their chemical compositions and uses rapid high volume sorting techniques to sort them into product streams at commercially viable throughput rates. The system employs a laser diode (20) for irradiating the material sample (10), a spectrograph (50) is used to determine the Raman spectrum of the material sample (10) and a microprocessor based controller (70) is employed to identify the polymer type of the material sample (10).
Characterization of a Raman spectroscopy probe system for intraoperative brain tissue classification
Desroches, Joannie; Jermyn, Michael; Mok, Kelvin; Lemieux-Leduc, Cķdric; Mercier, Jeanne; St-Arnaud, Karl; Urmey, Kirk; Guiot, Marie-Christine; Marple, Eric; Petrecca, Kevin; Leblond, Frķdķric
A detailed characterization study is presented of a Raman spectroscopy system designed to maximize the volume of resected cancer tissue in glioma surgery based on in vivo molecular tissue characterization. It consists of a hand-held probe system measuring spectrally resolved inelastically scattered light interacting with tissue, designed and optimized for in vivo measurements. Factors such as linearity of the signal with integration time and laser power, and their impact on signal to noise ratio, are studied leading to optimal data acquisition parameters. The impact of ambient light sources in the operating room is assessed and recommendations made for optimal operating conditions. In vivo Raman spectra of normal brain, cancer and necrotic tissue were measured in 10 patients, demonstrating that real-time inelastic scattering measurements can distinguish necrosis from vital tissue (including tumor and normal brain tissue) with an accuracy of 87%, a sensitivity of 84% and a specificity of 89%.
Structural investigation of Bi doped InSe chalcogenide thin films using Raman spectroscopy
NASA Astrophysics Data System (ADS)
Sharma, Shaveta; Sharma, Rita; Kumar, Praveen; Chander, Ravi; Thangaraj, R.; Mian, M.
The infrared transparency of the chalcogenide glasses have been investigated presently for the CO/CO2 laser power in various medical diagnostic applications. The addition of Bi improves the chemical durability and broadens the IR transparency region of various chalcogenide glassy systems. In the present work, we have studied the effect of Bi addition on the structural properties of In-Se thin films by using the RAMAN spectroscopy. The melt quenched bulk ingot of BixIn25-xSe75 (1? x? 7) alloys were used for the vacuum thermal evaporation of films in a vacuum better than 10-5 mbar. RAMAN bands at 1575, 1354 and 525 cm-1 has been observed, while with the increase in the Bi concentration vibrational band disappear at 525 cm-1 in sample x=7.
Reductive unfolding of serum albumins uncovered by Raman spectroscopy.
David, Catalina; Foley, Sarah; Mavon, Christophe; Enescu, Mironel
The reductive unfolding of bovine serum albumin (BSA) and human serum albumin (HSA) induced by dithiothreitol (DTT) is investigated using Raman spectroscopy. The resolution of the S-S Raman band into both protein and oxidized DTT contributions provides a reliable basis for directly monitoring the S-S bridge exchange reaction. The related changes in the protein secondary structure are identified by analyzing the protein amide I Raman band. For the reduction of one S-S bridge of BSA, a mean Gibbs free energy of -7 kJ mol(-1) is derived by studying the reaction equilibrium. The corresponding value for the HSA S-S bridge reduction is -2 kJ mol(-1). The reaction kinetics observed via the S-S or amide I Raman bands are identical giving a reaction rate constant of (1.02 +/- 0.11) M(-1) s(-1) for BSA. The contribution of the conformational Gibbs free energy to the overall Gibbs free energy of reaction is further estimated by combining experimental data with ab initio calculations. PMID:18322931
Genomic DNA characterization of pork spleen by Raman spectroscopy
NASA Astrophysics Data System (ADS)
Guzmßn-Emb·s, D. A.; Orrego Cardozo, M.; Vargas-Hernßndez, C.
In this paper, the study of Raman signal enhancement due to interaction between ZnO rods and pork spleen DNA is reported. ZnO microstructures were synthesized by the Sol-Gel method and afterward combined with porcine spleen DNA extracted in the previous stages, following standardized cell lysis, deproteinization, and precipitation processes. Raman spectroscopy was used for the characterization of structures of ZnO and ZnO-DNA complex, and the results show the respective bands of ZnO wurtzite hexagonal phase for modes E2 (M), A1(TO), E2(High), E1(LO), and 2LO. Due to the SERS effect in the spectral range from 200 to 1800 cm,-1 Raman bands caused by vibrations of the deoxyribose C-O-C binding were also observed, producing deformation of the ring as shown in the 559 cm-1 peak. The broad band at 782 cm-1, together with the complex vibration of the string 5'-COPO-C3', is over a wide band of thymine (790 cm-1) or cytosine (780 cm-1). A prominent band near 1098 cm-1 assigned to symmetric stretching vibration phosphodioxy group (PO2-) DNA backbone is most favoured in intensity by the addition of ZnO particles originated by the SERS effect. This effect suggests a possible mechanism for enhancing the Raman signal due to the electromagnetic interaction between a DNA molecule and the flat surface of the ZnO rod.
Force and Raman spectroscopy of single red blood cell
NASA Astrophysics Data System (ADS)
Raj, Saurabh; Wojdyla, Michal; Marro Sanchez, Monica; Petrov, Dmitri
Viscoelastic and spectroscopic properties of single RBC are probed using dual beam optical tweezers and Raman techniques, respectively. Complex response function of cell was measured by means of one and two particles passive microrheology at different stretching states yielding local and overall mechanical properties of exactly the same human erythrocyte. The frequency dependent response function (measured up to 10 kHz) was corrected for the presence of the traps and spectral distribution of complex stiffness over controlled range of cell deformation is calculated and discussed. The presence of non-thermal sources of membrane motions is also explored based on comparison of passive and active microrheology experiments. In order to get insight into structural changes of RBC due to deformation, Raman spectra of single cell were recorded. Evolution of Raman bands with cell deformation was analyzed using sensitive 2D correlation method. The combination of force and Raman spectroscopy is promising and potentially very powerful method to establish essential linkages between structure, mechanical properties and functions of living cells.
Diode- and flashlamp-pumped solid state Raman lasers
NASA Astrophysics Data System (ADS)
Cerny, Pavel; Jelinkova, Helena; Jabczynski, Jan K.; Zendzian, Waldemar; Sulc, Jan
We report on the development of passively Q-switched Nd:YAG and Nd:YAP lasers with solid-state stimulated Raman scattering (SRS) frequency conversion to 1.2-?m. A new barium tungstate (BaWO4) crystal was investigated as nonlinear converter. Diode pumped Nd:YAG quasi-continuous-wave slab laser, operated at 14-Hz repetition rate, was passively Q-switched by a Cr4+:YAG crystal. A three-mirror linear laser cavity with BaWO4 crystal produced the maximal Raman-shifted output pulse energy of 2.3 mJ. The first Stokes output energy was 1.5 mJ corresponding to 0.4 MW peak power. The SRS conversion efficiency with respect to laser operation at the fundamental wavelength was estimated to 55%. Flashlamp-pumped Nd:YAP laser was passively Q-switched by a BDN II thin film and the repetition rate was 2 Hz. The maximal first Stokes output energy was 12 mJ and the pulse peak power was 1.7 MW. Solid state Raman laser technology can therefore be employed to reach new laser output wavelengths using simple, reliable, and compact arrangements with a use of well-developed Nd-doped host lasers.
Near-infrared-excited confocal Raman spectroscopy advances in vivo diagnosis of cervical precancer.
Duraipandian, Shiyamala; Zheng, Wei; Ng, Joseph; Low, Jeffrey J H; Ilancheran, Arunachalam; Huang, Zhiwei
Raman spectroscopy is a unique optical technique that can probe the changes of vibrational modes of biomolecules associated with tissue premalignant transformation. This study evaluates the clinical utility of confocal Raman spectroscopy over near-infrared (NIR) autofluorescence (AF) spectroscopy and composite NIR AF/Raman spectroscopy for improving early diagnosis of cervical precancer in vivo at colposcopy. A rapid NIR Raman system coupled with a ball-lens fiber-optic confocal Raman probe was utilized for in vivo NIR AF/Raman spectral measurements of the cervix. A total of 1240 in vivo Raman spectra [normal (n=993), dysplasia (n=247)] were acquired from 84 cervical patients. Principal components analysis (PCA) and linear discriminant analysis (LDA) together with a leave-one-patient-out, cross-validation method were used to extract the diagnostic information associated with distinctive spectroscopic modalities. The diagnostic ability of confocal Raman spectroscopy was evaluated using the PCA-LDA model developed from the significant principal components (PCs) [i.e., PC4, 0.0023%; PC5, 0.00095%; PC8, 0.00022%, (p<0.05)], representing the primary tissue Raman features (e.g., 854, 937, 1095, 1253, 1311, 1445, and 1654 cm(-1)). Confocal Raman spectroscopy coupled with PCA-LDA modeling yielded the diagnostic accuracy of 84.1% (a sensitivity of 81.0% and a specificity of 87.1%) for in vivo discrimination of dysplastic cervix. The receiver operating characteristic curves further confirmed that the best classification was achieved using confocal Raman spectroscopy compared to the composite NIR AF/Raman spectroscopy or NIR AF spectroscopy alone. This study illustrates that confocal Raman spectroscopy has great potential to improve early diagnosis of cervical precancer in vivo during clinical colposcopy. PMID:23797897
Near-infrared-excited confocal Raman spectroscopy advances in vivo diagnosis of cervical precancer
NASA Astrophysics Data System (ADS)
Duraipandian, Shiyamala; Zheng, Wei; Ng, Joseph; Low, Jeffrey J. H.; Ilancheran, Arunachalam; Huang, Zhiwei
Raman spectroscopy is a unique optical technique that can probe the changes of vibrational modes of biomolecules associated with tissue premalignant transformation. This study evaluates the clinical utility of confocal Raman spectroscopy over near-infrared (NIR) autofluorescence (AF) spectroscopy and composite NIR AF/Raman spectroscopy for improving early diagnosis of cervical precancer in vivo at colposcopy. A rapid NIR Raman system coupled with a ball-lens fiber-optic confocal Raman probe was utilized for in vivo NIR AF/Raman spectral measurements of the cervix. A total of 1240 in vivo Raman spectra [normal (n=993), dysplasia (n=247)] were acquired from 84 cervical patients. Principal components analysis (PCA) and linear discriminant analysis (LDA) together with a leave-one-patient-out, cross-validation method were used to extract the diagnostic information associated with distinctive spectroscopic modalities. The diagnostic ability of confocal Raman spectroscopy was evaluated using the PCA-LDA model developed from the significant principal components (PCs) [i.e., PC4, 0.0023% PC5, 0.00095% PC8, 0.00022%, (p<0.05)], representing the primary tissue Raman features (e.g., 854, 937, 1095, 1253, 1311, 1445, and 1654 cm-1). Confocal Raman spectroscopy coupled with PCA-LDA modeling yielded the diagnostic accuracy of 84.1% (a sensitivity of 81.0% and a specificity of 87.1%) for in vivo discrimination of dysplastic cervix. The receiver operating characteristic curves further confirmed that the best classification was achieved using confocal Raman spectroscopy compared to the composite NIR AF/Raman spectroscopy or NIR AF spectroscopy alone. This study illustrates that confocal Raman spectroscopy has great potential to improve early diagnosis of cervical precancer in vivo during clinical colposcopy.
Plasmonic lens focused longitudinal field excitation for tip-enhanced Raman spectroscopy
NASA Astrophysics Data System (ADS)
Zhang, Mingqian; Wang, Jia
A novel tip-enhanced Raman spectroscopy setup with longitudinal field excitation generated by a plasmonic lens is investigated. A symmetry-breaking structure plasmonic lens that is expected to realize a strong longitudinal electric field focus has been designed to generate suitable excitation for enhancement in a tip antenna. The focusing performance of the plasmonic lens is theoretically simulated by the finite-difference time-domain method and experimentally verified by the detection of optical near-field distribution. A plasmonic lens assisted tip-enhanced Raman spectroscopy setup has been constructed and used to investigate specimens of carbon nanotubes. Tip-enhanced Raman spectra with distinct excitation wavelengths show similar Raman shifts but different intensities. Experimental results presented in this paper demonstrate that the Raman signal is considerably enhanced. It indicates that the novel tip-enhanced Raman spectroscopy configuration is feasible and is a promising technique for tip-enhanced Raman spectroscopy measurements and characterizations.
Multiwavelength Raman fiber laser with a continuously-tunable spacing
NASA Astrophysics Data System (ADS)
Dong, Xinyong; Shum, P.; Ngo, N. Q.; Chan, C. C.
A spacing-tunable multiwavelength Raman fiber laser with an independently-adjustable channel number is proposed and demonstrated. It uses a novel free-spectral-range (FSR)-tunable comb filter based on a superimposed chirped-fiber Bragg grating (CFBG) and a linear cavity formed by a bandwidth-tunable CFBG reflector, a pumped highly-nonlinear fiber for Raman gain, and an optical circulator based loop mirror. Multiwavelength laser operations with spacing tuning from 0.3 to 0.6 nm and channel number adjustment from 2 to 10 have been achieved.
Use of Raman spectroscopy and chemometrics to distinguish blue ballpoint pen inks.
de Souza Lins Borba, Flßvia; Honorato, Ricardo Saldanha; de Juan, Anna
The objective of this work is assessing whether the combination of Raman spectroscopy and chemometric tools is appropriate to differentiate blue ballpoint pen inks. Fourteen commercial blue ballpoint pen inks from different brands and models were studied and Raman spectra were obtained on ink lines written on A4 sulfite paper. First, a study of the best Raman configurations, in terms of laser intensity used and acquisition mode, was carried out to ensure sufficient spectroscopic quality without damaging the sample. Chemometric methods were applied first to improve the definition of spectral bands and to suppress fluorescence contributions from the signal. Once the spectra were suitably preprocessed, principal component analysis (PCA) and hierarchical cluster analysis (HCA) were applied to explore whether the different inks could be distinguished from their Raman spectra. Almost all inks could be gradually differentiated, through successive PCA analyses or looking at the different levels of the dendrogram structure provided by HCA. From these exploratory results, a tree structure was constructed based on PCA and HCA results in order to reflect the degree of similarity among ink classes. This tree structure was used as the basis to develop hierarchical classification models based on partial least squares-discriminant analysis (PLS-DA). Correct classification of inks was achieved by these PLS-DA models built and the most important regions to identify the ink classes were detected using the variable importance in projection plots (VIPs). The combination of Raman spectroscopy and chemometrics has been proven to be a promising fast non-destructive tool to differentiate among very similar ink types in documents. PMID:25679985
Detection and Quantitative Analysis of Chemical Species in Hanford Tank Materials Using Raman Spectroscopy Technology: FY94Florida State University Raman Spectroscopy Report
Reich, F.R.
This report provides a summary of work completed in FY-94 by FSU to develop and investigate the feasibility of using Raman spectroscopy with Hanford tank waste materials. Raman performance impacts from sample morphology, including the effects of absorption, particle size, density, color and refractive index, are discussed. An algorithm for relative species concentration measurement from Raman data is presented. An Algorithm for applying Raman to tank waste core screening is presented and discussed. A library of absorption and Raman spectra are presented that support this work.
The applications of near-infrared Fourier transform Raman spectroscopy to the analysis of polymorphic forms of cimetidine
NASA Astrophysics Data System (ADS)
Tudor, A. M.; Davies, M. C.; Melia, C. D.; Lee, D. C.; Mitchell, R. C.; Hendra, P. J.; Church, S. J.
Fourier transform (FT)-Raman spectroscopy, utilizing a near-infrared (Nd:YAG laser, at 1.064 ?m) source was used to characterise the three anhydrous polymorphic forms A, B and C of the drug cimetidine ( N?-cyano- N-methyl- N' -[2-[(5-methyl-1 H-imidazol-4-yl) methylthio]ethyl]guanidine). The FT-Raman spectra were free from fluorescence interference and had good signal-to-noise ratios. Each polymorph has a distinct spectrum, characterised by two regions, 1250-1050 cm -1 and 1500-1350 cm -1. This work demonstrates that it is possible to use FT-Raman spectroscopy to differentiate between polymorphic forms of the same compound.
Stochastic Liouville equations for femtosecond stimulated Raman spectroscopy
NASA Astrophysics Data System (ADS)
Agarwalla, Bijay Kumar; Ando, Hideo; Dorfman, Konstantin E.; Mukamel, Shaul
Electron and vibrational dynamics of molecules are commonly studied by subjecting them to two interactions with a fast actinic pulse that prepares them in a nonstationary state and after a variable delay period T, probing them with a Raman process induced by a combination of a broadband and a narrowband pulse. This technique, known as femtosecond stimulated Raman spectroscopy (FSRS), can effectively probe time resolved vibrational resonances. We show how FSRS signals can be modeled and interpreted using the stochastic Liouville equations (SLE), originally developed for NMR lineshapes. The SLE provide a convenient simulation protocol that can describe complex dynamics caused by coupling to collective bath coordinates at much lower cost than a full dynamical simulation. The origin of the dispersive features that appear when there is no separation of timescales between vibrational variations and the dephasing time is clarified.
Rapid Classification of Ordinary Chondrites Using Raman Spectroscopy
NASA Technical Reports Server (NTRS)
Fries, M.; Welzenbach, L.
Classification of ordinary chondrites is typically done through measurements of the composition of olivine and pyroxenes. Historically, this measurement has usually been performed via electron microprobe, oil immersion or other methods which can be costly through lost sample material during thin section preparation. Raman microscopy can perform the same measurements but considerably faster and with much less sample preparation allowing for faster classification. Raman spectroscopy can facilitate more rapid classification of large amounts of chondrites such as those retrieved from North Africa and potentially Antarctica, are present in large collections, or are submitted to a curation facility by the public. With development, this approach may provide a completely automated classification method of all chondrite types.
Identifying bacterial spores and anthrax hoax materials by Raman spectroscopy
NASA Astrophysics Data System (ADS)
Farquharson, Stuart; Brouillette, Carl R.; Smith, Wayne
The distribution of Bacillus anthracis spores through the US postal system in the autumn of 2001, initiated a secondary form of terror, the mailing of hoax materials. In the past three years nearly 20,000 letters containing harmless powders have been mailed, creating additional anxiety. Thus, there is a need for analyzers that can not only identify anthrax-causing spores to save lives, but also identify hoax materials to eliminate time-consuming and costly shutdowns. Recently, we established that Raman spectroscopy has the ability to identify both Bacilli endospores and hoax materials. Here we present Raman spectra of several Bacilli spores along with the dipicolinate salts, to further define the abilities of this technology to not only identify hoax materials, but also identify spores at the genus and species level.
[Comparison of discriminative methods of hypoglycemic drugs by Raman spectroscopy].
Gao, Qun; Zhang, Zhong-Hu; Lu, Feng
In the present paper, four kinds of cluster analysis methods were used in rapid, non-destructive discrimination of hypoglycemic tablets by the Raman spectroscopy technology. Nine kinds of hypoglycemic tablets, including 48 samples, were determined using a Raman spectrometer. The sample data were pretreated with the methods of frequency range cutting, baseline correction, smoothing and vector normalization, then were analyzed by K-means, hierachical cluster, self-organizing maps (SOM) and PCA-SOM respectively. The results demonstrated that SOM was better than K-means and hierachical cluster, and it provided the best discrimination when combined with PCA. The research offers a new approach to the rapid discrimination of different kinds of hypoglycemic tablets. PMID:23427547
Detection of nasopharyngeal carcinoma using deep NIR Raman spectroscopy
NASA Astrophysics Data System (ADS)
Li, J. H.; Li, W. T.; Zhang, G. H.
We compare depth information from below the mucosa of ex vivo tissue to diagnose nasopharyngeal carcinoma (NPC) by NIR Raman spectroscopy. Spectral diagnosis performed on a PCA-LDA model achieves a diagnostic sensitivity of 99.3% (149/150), 100% (150/150), 98% (147/150) and 96.7% (145/150), and a specificity of 96.7% (145/150), 96.7% (145/150), 96% (144/150) and 87.3% (131/150) from the surface to deeper levels using the zero separate lines, respectively. The spectra and discrimination results at different levels could reveal pathological development. Thus, the Raman spectra of deep level mucosa can be used to diagnose the stage of NPC from normal tissue.
Raman spectroscopy-based metabolomics for differentiating exposures to triazole fungicides using rat urine.
Cherney, Daniel P; Ekman, Drew R; Dix, David J; Collette, Timothy W
Normal Raman spectroscopy was evaluated as a metabolomic tool for assessing the impacts of exposure to environmental contaminants, using rat urine collected during the course of a toxicological study. Specifically, one of three triazole fungicides, myclobutanil, propiconazole, or triadimefon, was administered daily via oral gavage to male Sprague-Dawley rats at doses of 300, 300, or 175 mg/kg, respectively. Urine was collected from all three treatment groups and also from vehicle control rats on day six, following five consecutive days of exposure. Spectra were acquired with a CCD-based dispersive Raman spectrometer, using 785-nm diode laser excitation. To optimize the signal-to-noise ratio, urine samples were filtered through a stirred ultrafiltration cell with a 500 nominal molecular weight limit filter to remove large, unwanted urine components that can degrade the spectrum via fluorescence. However, a subsequent investigation suggested that suitable spectra can be obtained in a high-throughput fashion, with little or no Raman-specific sample preparation. For the sake of comparison, a parallel 1H NMR-based metabolomic analysis was also conducted on the unfiltered samples. Results from multivariate data analysis demonstrated that the Raman method compares favorably with NMR in regard to the ability to differentiate responses from these three contaminants. PMID:17718537
Optical diagnosis of malaria infection in human plasma using Raman spectroscopy.
Bilal, Muhammad; Saleem, Muhammad; Amanat, Samina Tufail; Shakoor, Huma Abdul; Rashid, Rashad; Mahmood, Arshad; Ahmed, Mushtaq
We present the prediction of malaria infection in human plasma using Raman spectroscopy. Raman spectra of malaria-infected samples are compared with those of healthy and dengue virus infected ones for disease recognition. Raman spectra were acquired using a laser at 532 nm as an excitation source and 10 distinct spectral signatures that statistically differentiated malaria from healthy and dengue-infected cases were found. A multivariate regression model has been developed that utilized Raman spectra of 20 malaria-infected, 10 non-malarial with fever, 10 healthy, and 6 dengue-infected samples to optically predict the malaria infection. The model yields the correlation coefficient r(2) value of 0.981 between the predicted values and clinically known results of trainee samples, and the root mean square error in cross validation was found to be 0.09; both these parameters validated the model. The model was further blindly tested for 30 unknown suspected samples and found to be 86% accurate compared with the clinical results, with the inaccuracy due to three samples which were predicted in the gray region. Standard deviation and root mean square error in prediction for unknown samples were found to be 0.150 and 0.149, which are accepted for the clinical validation of the model. PMID:25588165
Optical diagnosis of malaria infection in human plasma using Raman spectroscopy
NASA Astrophysics Data System (ADS)
Bilal, Muhammad; Saleem, Muhammad; Amanat, Samina Tufail; Shakoor, Huma Abdul; Rashid, Rashad; Mahmood, Arshad; Ahmed, Mushtaq
We present the prediction of malaria infection in human plasma using Raman spectroscopy. Raman spectra of malaria-infected samples are compared with those of healthy and dengue virus infected ones for disease recognition. Raman spectra were acquired using a laser at 532 nm as an excitation source and 10 distinct spectral signatures that statistically differentiated malaria from healthy and dengue-infected cases were found. A multivariate regression model has been developed that utilized Raman spectra of 20 malaria-infected, 10 non-malarial with fever, 10 healthy, and 6 dengue-infected samples to optically predict the malaria infection. The model yields the correlation coefficient r2 value of 0.981 between the predicted values and clinically known results of trainee samples, and the root mean square error in cross validation was found to be 0.09; both these parameters validated the model. The model was further blindly tested for 30 unknown suspected samples and found to be 86% accurate compared with the clinical results, with the inaccuracy due to three samples which were predicted in the gray region. Standard deviation and root mean square error in prediction for unknown samples were found to be 0.150 and 0.149, which are accepted for the clinical validation of the model.
Trace detection of explosives and their precursors by surface enhanced Raman spectroscopy
NASA Astrophysics Data System (ADS)
Almaviva, S.; Botti, S.; Cantarini, L.; Palucci, A.; Puiu, A.; Rufoloni, A.; Landstrom, L.; Romolo, F. S.
Surface Enhanced Raman Spectroscopy measurements on some common military explosives were performed with a table-top micro-Raman system integrated with a Serstech R785 minispectrometer. Serstech R785 is a miniaturised spectrometer suitable for Raman and NIR measurements. Integration of R785 in our table-top system aims to the realization of a portable SERS detector, able to perform in-situ measurements. SERS Spectra were obtained exciting the substance of interest with a 785 nm diode-laser, while these substances were deposited starting from commercial solutions on commercial SERS substrates, to improve the detection sensitivity. The amount of the sampled substance was determined through the analysis of images of the substrate covered with the residue of explosive. In fact, once the solvent is completely evaporated, the residue of explosive was observed to be uniformly distributed on the substrate surface. Images acquired with a Scanning Electron Microscope provided further details of the deposition process showing that a fraction of the active SERS sites are completely covered with the analyte while other sites appear to be empty; from the analysis of the images the sampled quantity was estimated to be about 200 pg. The main Raman features of each substance were clearly identified, the spectral resolution was sufficiently high to clearly distinguish spectra belonging to different substances.
Correlating computational docking predictions with Raman spectroscopy for ?-lactoglobulin-porphyrin complexes
NASA Astrophysics Data System (ADS)
Parker, James; Brancaleon, Lorenzo
Computational molecular docking simulations (Dock and AutoDock) may provide a wealth of structural information related to the bound configuration of protein-ligand complexes, but they require verification to ensure their results correctly predict the bound complex. Resonance Raman spectroscopy data has been collected to correlate normal mode vibrations observed in the bound configurations to computationally generated structures in order to determine the best match between the in silico model and experiment. This methodology was used to determine the bound structures at an atomistic level of ?-lactoglobulin (BLG) and meso-tetrakis (p-sulfonatophenyl) porphyrin (TSPP) in aqueous solutions at pH 7 and 9. Comparisons of Raman spectra of TSPP before and after binding to BLG yield line shifts that are generated by the noncovalent binding of the ligand to the protein. Previous studies have shown that the Tanford transition in BLG, which occurs above pH 7.9, destabilizes the protein, allowing it to undergo a laser-induced structural change when bound to TSPP and illuminated by at least 0.3 J of laser energy. By examining the structures at pHs above and below the transition, we hope to reveal the mechanism of action that initiates the laser-induced changes in the protein. Future studies will use the computed bound configuration as an initial condition for molecular dynamics simulations of the laser-protein-complex interaction to predict the final state of the protein after irradiation.
Impulsive rotational Raman scattering of N2 by a remote "air laser" in femtosecond laser filament.
Ni, Jielei; Chu, Wei; Zhang, Haisu; Zeng, Bin; Yao, Jinping; Qiao, Lingling; Li, Guihua; Jing, Chenrui; Xie, Hongqiang; Xu, Huailiang; Cheng, Ya; Xu, Zhizhan
We report on experimental realization of impulsive rotational Raman scattering from neutral nitrogen molecules in a femtosecond laser filament using an intense self-induced white-light seeding "air laser" generated during the filamentation of an 800Ānm Ti:sapphire laser in nitrogen gas. The impulsive rotational Raman fingerprint signals are observed with a maximum conversion efficiency of ?0.8%. Our observation provides a promising way of remote identification and location of chemical species in the atmosphere by a rotational Raman scattering of molecules. PMID:24978965
Technology Transfer Automated Retrieval System (TEKTRAN)
In this study, we investigated a potential of FT-Raman spectroscopy as a method for cereal food classification and the result was compared to the NIR. Particularly, we focused on the problem of improving the performance of linear calibration algorithms in the presence of high non linearity. To impro...
Micro-Raman imaging spectroscopy of suspended graphene
NASA Astrophysics Data System (ADS)
Simpson, J. R.; Hight Walker, A. R.
The recent observationootnotetextK. I. Bolotin et al., Solid State Commun. 146, 351 (2008). of ultrahigh mobility, >200,000,s-1, in suspended and annealed graphene underscores the importance of environmental effects on graphene electronic properties. We compare the Raman spectra of graphene and chemically modified graphite oxide both in contact with and suspended above substrate surfaces. Graphene samples were prepared using micromechanical cleavage and chemically modifiedootnotetextJ. T. Robinson et al., Nano Lett. 8, 3441 (2008). graphite flakes on silicon substrates with a thin, 300,nm, silicon oxide coating. Reactive ion etching patterns the substrates with circular holes, approximately 3-7,m in diameter, etched through the oxide layer. We present spatially-resolved Raman spectra obtained in a scanning, confocal microscope configuration using 632.8,m and 514.5,m laser excitation.
Raman spectroscopy of the N-C-O symmetric (?3) and antisymmetric (?2) stretch fundamentals in HNCO
NASA Astrophysics Data System (ADS)
Brown, Steven S.; Berghout, H. Laine; Crim, F. Fleming
We report the first gas-phase Raman spectra of the N-C-O stretching fundamentals in isocyanic acid. Using stimulated Raman excitation to prepare vibrationally excited molecules, we record spectra via two different techniques, photoacoustic Raman spectroscopy and action spectroscopy. The former detects the sound wave generated as the Stokes laser tunes through resonances and deposits heat in the gas sample. The latter detects transitions by photodissociating the vibrationally excited states prepared in the vibrational excitation step and detecting the photofragments by laser induced fluorescence. In analogy with the stretching modes in CO2, the N-C-O symmetric stretch (?3) Raman fundamental in HNCO is strong while the antisymmetric stretch (?2) is weak, although neither is symmetry forbidden. Both vibrational states are strongly perturbed. The symmetric stretch interacts with combination states that contain two quanta of bending excitation, and the antisymmetric stretch interacts with several different combination states. Both Raman spectra have strong QQ branch rotational structure in which the band origins for different K sublevels in this near-prolate symmetric top follow no simple pattern. Photodissociation of the vibrationally excited states demonstrates the influence of the initial state preparation on the rotational resonances, photofragment appearance thresholds, and Franck-Condon factors in the transition to a dissociative excited electronic state.
Continuous Wave Stimulated Raman Spectroscopy Inside a Hollow Core Photonic Crystal Fiber
NASA Astrophysics Data System (ADS)
Domenech, Jose L.; Cueto, Maite
Hollow-core photonic crystal fibers (HCPCF) have raised new opportunities to study light-matter interaction. Dielectric or metallic capillaries are intrinsically lossy, making poor light guides. In contrast, HCPCFs can guide light quite efficiently, due to the band-gap effect produced by an array of smaller channels which surrounds a central hollow core with a few ?m diameter. The tight confinement of light inside the core, that can be filled with gases, as well as a long interaction length, enhance multiple nonlinear phenomena, making it possible to devise new ways to do low signal level spectroscopy, as is the case of high resolution stimulated Raman spectroscopy (SRS). A. Owyoung demonstrated high resolution continuous wave SRS in 1978. Shortly afterwards, seeking higher sensitivity, he developed the quasi-continuous SRS technique (a high peak power pump laser, interacting with a low power cw probe laser). That variant remains today the best compromise between resolution and sensitivity for gas-phase Raman spectroscopy. In this work, we show the possibility of fully cw stimulated Raman spectroscopy, using a gas cell built around a HCPCF to overcome the limitations posed by the weakness of the stimulated Raman effect when not using pulsed sources. The interaction length (1.2 m), longer than that of a multiple pass refocusing cell, and the narrow diameter of the core (4.8 ?m), can compensate for the much lower laser powers used in the cw set-up. The experimental complexity is considerably reduced and the instrumental resolution is at the 10's of MHz level, limited, with our fiber, by transit time effects. At present, we have demonstrated the feasibility of the experiment, a sensitivity enhancement of ś 6000 over the single focus regime, and a spectral resolution better than 0.005 wn in the unresolved Q-branch of the ?_1 component of the Fermi dyad of CO_2 at 1388 wn. Other examples of rotationally resolved spectra will be shown: the Q branch of O_2 at 1555 wn, and the 2?_2 component of the Fermi dyad of CO_2 at 1285 wn. P. St. Russell, Science {299}, 358, 2003. A.Owyoung, C. W. Patterson, R S. McDowell, Chem. Phys. Lett. {59}, 156, 1978
FT-Raman, surface-enhanced Raman spectroscopy and theoretical investigations of diclofenac sodium
NASA Astrophysics Data System (ADS)
Iliescu, T.; Baia, M.; Kiefer, W.
Raman and surface-enhanced Raman (SER) spectroscopies have been applied to the vibrational characterization of diclofenac sodium (DCF-Na). Theoretical calculations (DFT and ab initio) of two DCF-Na conformers have been performed to find the optimized structure and computed vibrational wavenumbers of the most stable one. SER spectra in silver colloid at different pH values have been also recorded and analyzed. Good SER spectra have been obtained in acidic and neutral environments, proving the chemisorption of the DCF-Na molecule on the silver surface. In the investigated pH range the carboxylate anion has been bonded to the silver surface through the lone pair oxygen electrons. The phenyl rings' orientation with respect to the silver surface changed on passing from acidic to neutral pH from a tilted close to flat to a more perpendicular one.
Continuous-wave anti-Stokes Raman laser based on phase-matched nondegenerate four-wave mixing.
Zaitsu, Shin-ichi; Imasaka, Totaro
We demonstrate phase-matched nondegenerate four-wave mixing (FWM) in a high-finesse optical cavity using a gaseous Raman-active medium pumped by two independent continuous-wave lasers. Efficient upconversion is achieved for pump beams at different wavelengths under phase-matched conditions by optimizing the total dispersion of the hydrogen-filled optical cavity. The independent control of the pump-beam polarizations leads to further enhancement of the upconversion efficiency arising from a larger Raman gain than that in degenerate FWM. This approach offers a promising alternative for a narrow-linewidth tunable light source for highly precise laser spectroscopy. PMID:25531612
Thermal degradation of organic material by portable laser Raman spectrometry
NASA Astrophysics Data System (ADS)
Som, Sanjoy M.; Foing, Bernard H.
Raman spectrometry has been established as an instrument of choice for studying the structure and bond type of known molecules, and identifying the composition of unknown substances, whether geological or biological. This versatility has led to its strong consideration for planetary exploration. In the context of the ExoGeoLab and ExoHab pilot projects of ESA-ESTEC & ILEWG (International Lunar Exploration Working Group), we investigated samples of astrobiological interest using a portable Raman spectrometer lasing at 785 nm and discuss implications for planetary exploration. We find that biological samples are typically best observed at wavenumbers >1100 cm-1, but their Raman signals are often affected by fluorescence effects, which lowers their signal-to-noise ratio. Raman signals of minerals are typically found at wavenumbers <1100 cm-1, and tend to be less affected by fluorescence. While higher power and/or longer signal integration time improve Raman signals, such power settings are detrimental to biological samples due to sample thermal degradation. Care must be taken in selecting the laser wavelength, power level and integration time for unknown samples, particularly if Raman signatures of biological components are anticipated. We include in the Appendices tables of Raman signatures for astrobiologically relevant organic compounds and minerals.
Stimulated Raman scattering of laser dye mixtures dissolved in multiple scattering media
NASA Astrophysics Data System (ADS)
Yashchuk, V. P.; Komyshan, A. O.; Tikhonov, E. A.; Olkhovyk, L. A.
Stimulated Raman scattering (SRS) of a mixture of rhodamine 6G and pyrromethene 605 laser dyes in vesicular films is studied. It is shown that a peculiar interaction of dyes occurs under conditions of multiple scattering of light from vesicles. This interaction manifests itself as SRS excitation of one of the dyes by random lasing of the other dye, provided that the random lasing spectrum overlaps the Stokes lines of the first dye. In addition, there is energy transfer between molecules of these dyes if their luminescence and absorption spectra overlap. The results obtained confirm that the mechanism of SRS from laser dyes in multiple scattering media is similar to that in coherent-active Raman spectroscopy. These results extend the possibility of determining the vibrational spectrum of dye molecules from their secondary radiation in these media.
CONTRIBUTED ARTICLE 117. Use of in situ Fiber-Optic Raman Spectroscopy to Replace
Myrick, Michael Lenn
CONTRIBUTED ARTICLE 117. Use of in situ Fiber-Optic Raman Spectroscopy to Replace Calorimetry. Abstract A method for real time determination of the percent cure of epoxies via in-situ fiber-optic Raman to be reliable to +/- 0.82% in the 40-90% cure range. Key words: Process monitoring, fiber optic, Raman
Micro-Raman Spectroscopy of Algae: Composition Analysis and Fluorescence Background Behavior
ARTICLE Micro-Raman Spectroscopy of Algae: Composition Analysis and Fluorescence Background performed using Stokes Raman scattering for compositional analysis of algae. Two algal species, Chlorella while acquiring Raman signals from the algae. The time dependence of fluorescence background is char
Advances in instrumentation are making Raman spectroscopy the tool of choice for an increasing number of chemical applications. For example, many recalcitrant industrial process monitoring problems have been solved in recent years with in-line Raman spectrometers. Raman is attr...
FEATURE ARTICLE Single Molecule Raman Spectroscopy at the Junctions of Large Ag Nanocrystals
FEATURE ARTICLE Single Molecule Raman Spectroscopy at the Junctions of Large Ag Nanocrystals Jiang because of fundamental spectroscopic issues. The invention of modern confocal single molecule techniques Raman scattering (SERS) in compact clusters of 30-70 nm Ag nanocrystals has shown single molecule Raman
Transcutaneous monitoring of steroid-induced osteoporosis with Raman spectroscopy
NASA Astrophysics Data System (ADS)
Maher, Jason R.; Inzana, Jason; Takahata, Masahiko; Awad, Hani A.; Berger, Andrew J.
Although glucocorticoids are among the most frequently prescribed anti-inflammatory agents used in the treatment of rheumatoid arthritis, extended exposure to this steroid hormone is the leading cause of iatrogenic osteoporosis. Recently, Raman spectroscopy has been utilized to exploit biochemical differences between osteoporotic and normal bones in order to predict fracture risk. In this presentation, we report the results of ongoing research in our laboratory towards the clinical translation of this technique. We will discuss strategies for the transcutaneous acquisition of spectra from the tibiae of mice that are of sufficient quality to generate accurate predictions of fracture risk.
Elucidating Viral Protein Structures and Assembly Mechanisms by Raman Spectroscopy
NASA Astrophysics Data System (ADS)
Thomas, George J.
Morphogenesis of icosahedral viruses involves the initial assembly of a precursor shell from a small number of virally encoded proteins, including the principal protein component of the shell. Structural details of precursor shells and transformation into the mature virion architecture are rigorously controlled along the in-vivo assembly pathway. Efficient assembly usually involves, in addition to constituent proteins of the shell, a virally encoded scaffolding protein to ensure the appropriate shell dimensions and assembly rate. The use of Raman spectroscopy to probe structures, molecular mechanisms and thermodynamics of assembly of the DNA bacterial viruses P22 and HK97 will be described.
Applications Of Stimulated Raman Scattering To Short Wavelength Lasers
NASA Astrophysics Data System (ADS)
Trainor, Daniel W.
The Raman process has been extensively used with short wavelength excimer lasers almost since excimers were first made to lase in the mid 70's.(1,2,3) Operating in the ultraviolet, they are used to perform a variety of research and development tasks, as well as participate in a variety of commercial activities. They represent a major laser market and are available commercially around the world.
Coherent control of stimulated Raman scattering using chirped laser pulses
Umstadter, Donald
will eliminate Raman forward scattering for a plasma density that is 1% of the critical density. The predicted and relativistic nonlinear optics.6 Many of these applications depend critically on the amount of laser energy or eliminate SRS.14 From the previous discussion on bandwidth mismatch and density gradients, one might think
Fluorescent properties and spontaneous Raman spectroscopy of new ketocyanine probes in organic solvents
NASA Astrophysics Data System (ADS)
Nemkovich, N. A.; Sobchuk, A. N.; Khodasevich, I. A.
We have used fluorescence spectroscopy and spontaneous Raman spectroscopy to study the characteristics of two ketocyanine dyes: 2,5-di[(E)-1-(4-diethylaminophenyl)methylidene]-1-cyclopentanone (CPET) and 2-[(E)-1-(4-diethylaminophenyl)methylidene]-5-{(E)-1-[4-(4,7,10,13-tetraoxa-1-azacyclopentadecalin) phenyl]methylidene}-1-cyclopentanone (CPMR) in organic solvents. The position of their electronic spectra depends strongly on the polarity of the solvent. We measured the dipole moments of the dyes in the equilibrium ground state and the Franck-Condon excited state. In mixtures of neutral nonpolar toluene with aprotic polar dimethylsulfoxide, we observe inhomogeneous broadening of the electronic spectra for the indicated compounds, due to fluctuations in solution of the intermolecular interaction energy. The time-resolved characteristics of fluorescence obtained suggest formation of an intermolecular hydrogen bond between the dye and the surrounding medium in a toluene-ethanol mixture. We measured the Raman spectra of CPET and CPMR in different organic solvents. The most intense lines in the 1582 1591 cm-1 region can be assigned to stretching of the phenyl rings of the molecules; the lines in the 831 842 cm-1 region can be assigned to a cyclopentanone ring mode; the lines at 1186 1195 cm-1 can be assigned to stretching of the =C-C-bond of the phenyl ring and rocking of the H atoms of the phenyl ring. We have observed that the position and width of the lines for the stretching vibrations of the ketocyanines depend substantially on the polarity of the surrounding medium. The studied dyes can be used as probes for studying different biological systems by site-selective laser spectroscopy and Raman spectroscopy. The fact that these two methods can be used simultaneously for diagnostics of biosystems is an important advantage of ketocyanine dyes compared with other known probes.
Single fiber laser based wavelength tunable excitation for CRS spectroscopy
Su, Jue; Xie, Ruxin; Johnson, Carey K.; Hui, Rongqing
We demonstrate coherent Raman spectroscopy (CRS) using a tunable excitation source based on a single femtosecond fiber laser. The frequency difference between the pump and the Stokes pulses was generated by soliton self-frequency shifting (SSFS) in a nonlinear optical fiber. Spectra of C-H stretches of cyclohexane were measured simultaneously by stimulated Raman gain (SRG) and coherent anti-Stokes Raman scattering (CARS) and compared. We demonstrate the use of spectral focusing through pulse chirping to improve CRS spectral resolution. We analyze the impact of pulse stretching on the reduction of power efficiency for CARS and SRG. Due to chromatic dispersion in the fiber-optic system, the differential pulse delay is a function of Stokes wavelength. This differential delay has to be accounted for when performing spectroscopy in which the Stokes wavelength needs to be scanned. CARS and SRG signals were collected and displayed in two dimensions as a function of both the time delay between chirped pulses and the Stokes wavelength, and we demonstrate how to find the stimulated Raman spectrum from the two-dimensional plots. Strategies of system optimization consideration are discussed in terms of practical applications. PMID:23950620
Few-layer epitaxial graphene grown on vicinal 6H-SiC studied by deep ultraviolet Raman spectroscopy
Kenji Kisoda; Susumu Kamoi; Noriyuki Hasuike; Hiroshi Harima; Kouhei Morita; Satoru Tanaka; Akihiro Hashimoto
Few layer epitaxial graphenes (1.8-3.0 layers) grown on vicinal 6H-SiC (0001) were characterized by deep ultraviolet Raman spectroscopy. Shallow penetration depth of the probe laser enabled us to observe G-peak of graphene without subtraction of the SiC substrate signal from observed spectra. The G-peak was greatly shifted to higher frequency compared to that of graphite due to in-plane compressive stress
Mineralogical and Raman spectroscopy studies of natural olivines exposed to different planetary environments
NASA Astrophysics Data System (ADS)
Weber, I.; B÷ttger, U.; Pavlov, S. G.; Jessberger, E. K.; H³bers, H.-W.
New lander missions to bodies of our solar system are coming up and thus new techniques are desirable for the in-situ investigation of planetary surface and near surface materials. During the last decade Raman spectroscopy has been developed to become an excellent laboratory tool for fast petrological and mineralogical investigation of terrestrial and extraterrestrial rocks. Consequently, Raman spectroscopy has successfully been proposed for operation on planetary surfaces. In the joint ESA and Roscosmos mission ExoMars a Raman Laser Spectrometer (RLS) will for the first time be applied in space to identify minerals and organic compounds in Martian surface rocks and soils. The present study aims to investigate the possible response of various environmental conditions to Raman spectra in preparation for the ExoMars mission, as well as other space missions in future. For our study we selected five natural olivines with different forsterite (Mg2SiO4) and fayalite (Fe2SiO4) compositions. Olivine as an important rock forming mineral of the Earth upper mantle and an abundant mineral in Martian meteorites is one of the key planetary mineral. The spectra were taken in various environmental conditions that include vacuum down to 10-6 mbar, 8 mbar CO2 atmosphere, and temperatures ranging between room temperature and~8 K resembling those on Mars as well as on the Moon and on asteroids. We have found that forsterite shows only small temperature-related shifts in Raman spectra at very low temperatures indicating relatively weak changes in the lattice modes. Fayalite demonstrates, in addition to temperature dependent changes in the lattice modes found for forsterite, modification of Raman spectra at low Stokes frequencies. This is an effect in the SiO4 internal modes that most probably is caused by the high amount of iron in the mineral structure, which triggers antiferromagnetic transition at low temperatures. No influence of a CO2 atmosphere on Raman spectra for the investigated rock-forming minerals has been observed at any pressure from ambient 1 bar down to a few mbar.
Defect characterization in graphene and carbon nanotubes using Raman spectroscopy.
Dresselhaus, M S; Jorio, A; Souza Filho, A G; Saito, R
This review discusses advances that have been made in the study of defect-induced double-resonance processes in nanographite, graphene and carbon nanotubes, mostly coming from combining Raman spectroscopic experiments with microscopy studies and from the development of new theoretical models. The disorder-induced peak frequencies and intensities are discussed, with particular emphasis given to how the disorder-induced features evolve with increasing amounts of disorder. We address here two systems, ion-bombarded graphene and nanographite, where disorder is represented by point defects and boundaries, respectively. Raman spectroscopy is used to study the 'atomic structure' of the defect, making it possible, for example, to distinguish between zigzag and armchair edges, based on selection rules of phonon scattering. Finally, a different concept is discussed, involving the effect that defects have on the lineshape of Raman-allowed peaks, owing to local electron and phonon energy renormalization. Such effects can be observed by near-field optical measurements on the G' feature for doped single-walled carbon nanotubes. PMID:21041218
Tackling field-portable Raman spectroscopy of real world samples
NASA Astrophysics Data System (ADS)
Shand, Neil C.
A major challenge confronting first responders, customs authorities and other security-related organisations is the accurate, rapid, and safe identification of potentially hazardous chemicals outside a laboratory environment. Currently, a range of hand portable Raman equipment is commercially available that is low cost and increasingly more sophisticated. These systems are generally based on the 785nm Stokes shifted Raman technique with many using dispersive grating spectrometers. This technique offers a broad range of capabilities including the ability to analyse illicit drugs, explosives, chemical weapons and pre-cursors but still has some fundamental constraints. 'Real world' samples, such as those found at a crime scene, will often not be presented in the most accessible manner. Simple issues such as glass fluorescence can make an otherwise tractable sample impossible to analyse in-situ. A new generation of portable Raman equipment is currently being developed to address these issues. Consideration is given to the use of longer wavelength for fluorescence reduction. Alternative optical designs are being tested to compensate for the signal reduction incurred by moving to longer wavelengths. Furthermore, the use of anti-Stokes spectroscopy is being considered as well as investigating the robustness and portability of traditional Fourier Transform interferometer designs along with future advances in detector technology and ultra small spectrometers.
Surface-Sensitive Raman Spectroscopy of Collagen I Fibrils
Gullekson, Corinne; Lucas, Leanne; Hewitt, Kevin; Kreplak, Laurent
Collagen fibrils are the main constituent of the extracellular matrix surrounding eukaryotic cells. Although the assembly and structure of collagen fibrils is well characterized, very little appears to be known about one of the key determinants of their biological functionŚnamely, the physico-chemical properties of their surface. One way to obtain surface-sensitive structural and chemical data is to take advantage of the near-field nature of surface- and tip-enhanced Raman spectroscopy. Using Ag and Au nanoparticles bound to Collagen type-I fibrils, as well as tips coated with a thin layer of Ag, we obtained RamanĀspectra characteristic to the first layer of collagen molecules at the surface of the fibrils. The most frequent Raman peaksĀwere attributed to aromatic residues such as phenylalanine and tyrosine. In several instances, we also observed Amide I bands with a full width at half-maximum of 10¢30Ācm?1. The assignment of these Amide I band positions suggests the presence of 310-helices as well as ?- and ?-sheets at the fibril's surface. PMID:21463598
Adiabatic Tip-Plasmon Focusing for Nano-Raman Spectroscopy
Berweger, Samuel; Atkin, Joanna M.; Olmon, Robert L.; Raschke, Markus Bernd
True nanoscale optical spectroscopy requires the efficient delivery of light for a spatially nanoconfined excitation. We utilize adiabatic plasmon focusing to concentrate an optical field into the apex of a scanning probe tip of {approx}10 nm in radius. The conical tips with the ability for two-stage optical mode matching of the surface plasmon polariton (SPP) grating-coupling and the adiabatic propagating SPP conversion into a localized SPP at the tip apex represent a special optical antenna concept for far-field transduction into nanoscale excitation. The resulting high nanofocusing efficiency and the spatial separation of the plasmonic grating coupling element on the tip shaft from the near-field apex probe region allows for true background-free nanospectroscopy. As an application, we demonstrate tip-enhanced Raman spectroscopy (TERS) of surface molecules with enhanced contrast and its extension into the near-IR with 800 nm excitation.
Low-Resolution Raman-Spectroscopy Combustion Thermometry
NASA Technical Reports Server (NTRS)
Nguyen, Quang-Viet; Kojima, Jun
A method of optical thermometry, now undergoing development, involves low-resolution measurement of the spectrum of spontaneous Raman scattering (SRS) from N2 and O2 molecules. The method is especially suitable for measuring temperatures in high pressure combustion environments that contain N2, O2, or N2/O2 mixtures (including air). Methods based on SRS (in which scattered light is shifted in wavelength by amounts that depend on vibrational and rotational energy levels of laser-illuminated molecules) have been popular means of probing flames because they are almost the only methods that provide spatially and temporally resolved concentrations and temperatures of multiple molecular species in turbulent combustion. The present SRS-based method differs from prior SRS-based methods that have various drawbacks, a description of which would exceed the scope of this article. Two main differences between this and prior SRS-based methods are that it involves analysis in the frequency (equivalently, wavelength) domain, in contradistinction to analysis in the intensity domain in prior methods; and it involves low-resolution measurement of what amounts to predominantly the rotational Raman spectra of N2 and O2, in contradistinction to higher-resolution measurement of the vibrational Raman spectrum of N2 only in prior methods.
Achieving molecular selectivity in imaging using multiphoton Raman spectroscopy techniques
Holtom, Gary R. (BATTELLE (PACIFIC NW LAB)); Thrall, Brian D. (BATTELLE (PACIFIC NW LAB)); Chin, Beek Yoke (BATTELLE (PACIFIC NW LAB)); Wiley, H Steven (BATTELLE (PACIFIC NW LAB)); Colson, Steven D. (BATTELLE (PACIFIC NW LAB))
In the case of most imaging methods, contrast is generated either by physical properties of the sample (Differential Image Contrast, Phase Contrast), or by fluorescent labels that are localized to a particular protein or organelle. Standard Raman and infrared methods for obtaining images are based upon the intrinsic vibrational properties of molecules, and thus obviate the need for attached flurophores. Unfortunately, they have significant limitations for live-cell imaging. However, an active Raman method, called Coherent Anti-Stokes Raman Scattering (CARS), is well suited for microscopy, and provides a new means for imaging specific molecules. Vibrational imaging techniques, such as CARS, avoid problems associated with photobleaching and photo-induced toxicity often associated with the use of fluorescent labels with live cells. Because the laser configuration needed to implement CARS technology is similar to that used in other multiphoton microscopy methods, such as two -photon fluorescence and harmonic generation, it is possible to combine imaging modalities, thus generating simultaneous CARS and fluorescence images. A particularly powerful aspect of CARS microscopy is its ability to selectively image deuterated compounds, thus allowing the visualization of molecules, such as lipids, that are chemically indistinguishable from the native species.
Demonstration of stable raman fibre laser with asymmetrical laser cavity including broadband chirped FBG
NASA Astrophysics Data System (ADS)
Im, Young-Eun; Chun, Kyungwon; Kim, Hangeul; Hann, Swook; Kim, Dong-Hwan; Chung, Youngjoo; Park, Chang-Soo
We experimentally and theoretically demonstrated a novel technique to generate a stable multi-wavelength Raman fibre laser (RFL) based on an asymmetrical all-fibre Raman laser cavity by using a broadband chirped fibre Bragg grating (CFBG). The output power variations from detuning the center wavelength of in/out reflectors are studied with symmetrical and asymmetrical RFL cavities. The RFL output with asymmetrical cavity is more stable than that of symmetrical cavity.
The Development of Combined Raman Spectroscopy-Optical Coherence Tomography and Application for Skin Cancer Diagnosis
Chetan Patil
Optical spectroscopy and imaging have shown promise for performing rapid, non-invasive disease detection and diagnosis in vivo. Independently, Raman Spectroscopy (RS) has demonstrated the ability to perform diagnosis of epithelial cancers such the cervix with excellent overall classification accuracy due to the inherent biochemical specificity of the technique, however relating features of tissue morphology with techniques such as Raman mapping
Integrated AWG spectrometer for on-chip optical coherence tomography and Raman spectroscopy
B. I. Akca; N. Ismail; F. Sun; A. Driessen; K. W÷rhoff; M. Pollnau; Ridder de R. M; V. D. Nguyen; J. Kalkman; Leeuwen van T. G
Silicon oxynitride-based arrayed waveguide grating (AWG) spectrometers were designed for on-chip spectral-domain optical coherence tomography (OCT) systems and Raman spectroscopy of the skin. A novel geometrical layout for Raman spectroscopy was introduced to reduce loss. Measurements show that integrated optics has a good potential for miniaturizing current OCT systems
Evaluation of fiber optic probes for in-vivo Raman spectroscopy
Martin G. Shim; Brian C. Wilson; Eric Marple; Michael L. Wach
Raman spectroscopy has been sued for the analysis of biological tissue. Preliminary studies, which have been performed ex vivo, indicate that potentially useful diagnostic information may be obtained from the spectra. A new fiber optic-based in vivo Raman system has been constructed which can obtain spectra in vivo from tissue in less than 30 s. Unfortunately, tissue spectroscopy is hindered
High-Speed Linear Raman Spectroscopy for Instability Analysis of a Bluff Body Flame
NASA Technical Reports Server (NTRS)
Kojima, Jun; Fischer, David
We report a high-speed laser diagnostics technique based on point-wise linear Raman spectroscopy for measuring the frequency content of a CH4-air premixed flame stabilized behind a circular bluff body. The technique, which primarily employs a Nd:YLF pulsed laser and a fast image-intensified CCD camera, successfully measures the time evolution of scalar parameters (N2, O2, CH4, and H2O) in the vortex-induced flame instability at a data rate of 1 kHz. Oscillation of the V-shaped flame front is quantified through frequency analysis of the combustion species data and their correlations. This technique promises to be a useful diagnostics tool for combustion instability studies.
An amplified femtosecond laser system for material micro-/nanostructuring with an integrated Raman microscope.
Zalloum, Othman H Y; Parrish, Matthew; Terekhov, Alexander; Hofmeister, William
In order to obtain new insights into laser-induced chemical material modifications, we introduce a novel combined approach of femtosecond pulsed laser-direct writing and in situ Raman microscopy within a single experimental apparatus. A newly developed scanning microscope, the first of its kind, provides a powerful tool for micro-/nanomachining and characterization of material properties and allows us to relate materials' functionality with composition. We address the issues of light delivery to the photomodification site and show the versatility of the system using tight focusing. Amplified femtosecond pulses are generated by a Ti:sapphire laser oscillator and a chirped-pulse regenerative amplifier, both pumped by a diode-pumped frequency doubled neodymium-doped yttrium orthovanadate (Nd:YVO(4)) laser operating at 532 nm. Results of Raman spectroscopy and scanning electron microscopy images of femtosecond laser micro-/nanomachining on the surface and in the bulk of single-crystal diamond obtained from first trials of this instrument are also presented. This effective combination could help to shed light on the influence of the local structure fluctuations on controllability of the laser processing and the role of the irradiation in the ablation processes ruling out possible imprecisions coming from the use of the two independent techniques. PMID:20515154
Towards Single-Shot Detection of Bacterial Endospores via Coherent Raman Spectroscopy
NASA Astrophysics Data System (ADS)
Pestov, Dmitry; Wang, Xi; Ariunbold, Gombojav; Murawski, Robert; Sautenkov, Vladimir; Sokolov, Alexei; Scully, Marlan
Recent advances in coherent anti-Stokes Raman scattering (CARS) spectroscopy hold exciting promise to make the most out of now readily available ultrafast laser sources. Techniques have been devised to mitigate the nonresonant four-wave-mixing in favor of informative Raman-resonant signal. In particular, a hybrid technique for CARS (see Science 316, 265 (2007)) brings together the advantages of coherent broadband pump-Stokes excitation of molecular vibrations and their time-delayed but frequency-resolved probing via a spectrally narrowed and shaped laser pulse. We apply this technique to the problem of real-time detection of warfare bioagents and report single-shot acquisition of a distinct CARS spectrum from a small volume of B. subtilis endospores (ś10^4 spores), a harmless surrogate for B. anthracis. We study the dependence of the CARS signal on the energy of the ultrashort preparation pulses and find the limit on the pulse energy fluence (ś0.2 J/cm^2), imposed by the laser-induced damage of the spores.
Optical trapping and Raman spectroscopy of solid particles.
Rkiouak, L; Tang, M J; Camp, J C J; McGregor, J; Watson, I M; Cox, R A; Kalberer, M; Ward, A D; Pope, F D
The heterogeneous interactions of gas molecules on solid particles are crucial in many areas of science, engineering and technology. Such interactions play a critical role in atmospheric chemistry and in heterogeneous catalysis, a key technology in the energy and chemical industries. Investigating heterogeneous interactions upon single levitated particles can provide significant insight into these important processes. Various methodologies exist for levitating micron sized particles including: optical, electrical and acoustic techniques. Prior to this study, the optical levitation of solid micron scale particles has proved difficult to achieve over timescales relevant to the above applications. In this work, a new vertically configured counter propagating dual beam optical trap was optimized to levitate a range of solid particles in air. Silica (SiO2), ?-alumina (Al2O3), titania (TiO2) and polystyrene were stably trapped with a high trapping efficiency (Q = 0.42). The longest stable trapping experiment was conducted continuously for 24 hours, and there are no obvious constraints on trapping time beyond this period. Therefore, the methodology described in this paper should be of major benefit to various research communities. The strength of the new technique is demonstrated by the simultaneous levitation and spectroscopic interrogation of silica particles by Raman spectroscopy. In particular, the adsorption of water upon silica was investigated under controlled relative humidity environments. Furthermore, the collision and coagulation behaviour of silica particles with microdroplets of sulphuric acid was followed using both optical imaging and Raman spectroscopy. PMID:24803083
Raman spectroscopic differentiation of beef and horse meat using a 671 nm microsystem diode laser
NASA Astrophysics Data System (ADS)
Ebrahim, Halah Al; Sowoidnich, Kay; Kronfeldt, Heinz-Detlef
A non-invasive Raman spectroscopic approach for meat species identification and quality detection was successfully demonstrated for the two closely related species beef and horse. Fresh beef and horse muscles were cut and ice-stored at 5 ░C, and time-dependent Raman measurements were performed daily up to 12 days postmortem. Applying a 671 nm microsystem diode laser and a laser power of 50 mW, spectra were recorded with integration times of 1-4 s. A pronounced offset of the Raman spectra was observed between horse and beef, with high fluorescence background for horse compared to beef for all days of storage. Principal components analysis was applied for data evaluation revealing a clear distinction between beef and horse meat which can be attributed to differences in the myoglobin content of both species. Furthermore, separations according to aging and spoilage for the two species could be identified simultaneously. Therefore, Raman spectroscopy might be an efficient test method for meat species identification in combination with spoilage detection.
Detection of bacterial endospores by means of ultrafast coherent Raman spectroscopy
NASA Astrophysics Data System (ADS)
Pestov, Dmitry Sergeyevich
This work is devoted to formulation and development of a laser spectroscopic technique for rapid detection of biohazards, such as Bacillus anthracis spores. Coherent anti-Stokes Raman scattering (CARS) is used as an underlying process for active retrieval of species-specific characteristics of an analyte. Vibrational modes of constituent molecules are Raman-excited by a pair of ultrashort, femtosecond laser pulses, and then probed through inelastic scattering of a third, time-delayed laser field. We first employ the already known time-resolved CARS technique. We apply it to the spectroscopy of easy-to-handle methanol-water mixtures, and then continue building our expertise on solutions of dipicolinic acid (DPA) and its salts, which happen to be marker molecules for bacterial spores. Various acquisition schemes are evaluated, and the preference is given to multi-channel frequency-resolved detection, when the whole CARS spectrum is recorded as a function of the probe pulse delay. We demonstrate a simple detection algorithm that manages to differentiate DPA solution from common interferents. We investigate experimentally the advantages and disadvantages of near-resonant probing of the excited molecular coherence, and finally observe the indicative backscattered CARS signal from DPA and NaDPA powders. The possibility of selective Raman excitation via pulse shaping of the preparation pulses is also demonstrated. The analysis of time-resolved CARS experiments on powders and B. subtilis spores, a harmless surrogate for B. anthracis, facilitates the formulation of a new approach, where we take full advantage of the multi-channel frequency-resolved acquisition and spectrally discriminate the Raman-resonant CARS signal from the background due to other instantaneous four-wave mixing (FWM) processes. Using narrowband probing, we decrease the magnitude of the nonresonant FWM, which is further suppressed by the timing of the laser pulses. The devised technique, referred to as hybrid CARS, leads to a single-shot detection of as few as 104 bacterial spores, bringing CARS spectroscopy to the forefront of potential candidates for real-time biohazard detection. It also gives promise to many other applications of CARS, hindered so far by the presence of the overwhelming nonresonant FWM background, mentioned above.
Raman tensor and domain structure study of single-crystal-like epitaxial films of CaCu3Ti4O12 grown by pulsed laser deposition.
Ahlawat, Anju; Mishra, Dileep K; Sathe, V G; Kumar, Ravi; Sharma, T K
The local domain structure of a strain free, 150 nm thick, epitaxially grown single crystalline thin film of CaCu(3)Ti(4)O(12) is probed by polarized Raman spectroscopy. The polarization dependence of the Raman intensities of the observed bands as a function of varying angle between the domain axes and the polarization vector of the scattered laser photon is measured. Theoretical formulations involving the Raman tensor are presented, which enable determination of the domain structure from the observed polarized Raman spectra, and a single-crystal-like domain structure is found. The Raman tensor elements and domain orientation direction were determined by fitting the observed Raman intensities with theoretical calculations and by carrying out Raman mapping of the film. Our data show an absence of twin domain structure and twin domain boundaries in the single-crystal-like epitaxial thin films of CaCu(3)Ti(4)O(12). PMID:23197270
Raman tensor and domain structure study of single-crystal-like epitaxial films of CaCu3Ti4O12 grown by pulsed laser deposition
NASA Astrophysics Data System (ADS)
Ahlawat, Anju; Mishra, Dileep K.; Sathe, V. G.; Kumar, Ravi; Sharma, T. K.
The local domain structure of a strain free, 150 nm thick, epitaxially grown single crystalline thin film of CaCu3Ti4O12 is probed by polarized Raman spectroscopy. The polarization dependence of the Raman intensities of the observed bands as a function of varying angle between the domain axes and the polarization vector of the scattered laser photon is measured. Theoretical formulations involving the Raman tensor are presented, which enable determination of the domain structure from the observed polarized Raman spectra, and a single-crystal-like domain structure is found. The Raman tensor elements and domain orientation direction were determined by fitting the observed Raman intensities with theoretical calculations and by carrying out Raman mapping of the film. Our data show an absence of twin domain structure and twin domain boundaries in the single-crystal-like epitaxial thin films of CaCu3Ti4O12.
Er/Tm:fiber laser system for coherent Raman microscopy.
Coluccelli, Nicola; Kumar, Vikas; Cassinerio, Marco; Galzerano, Gianluca; Marangoni, Marco; Cerullo, Giulio
We present a novel architecture for a fiber-based hybrid laser system for coherent Raman microscopy, combining an amplified Er:fiber femtosecond oscillator with a Tm:fiber amplifier boosting the power of the 2-?m portion of a supercontinuum up to 300 mW. This is enough to obtain, by means of nonlinear spectral compression, sub-20-cm(-1) wide pump and Stokes pulses with 2500-3300??cm(-1) frequency detuning and average power at the 100-mW level. Application of this system to stimulated Raman scattering microscopy is discussed. PMID:24875984
Water quantification in silicate glasses and melts using Raman spectroscopy
NASA Astrophysics Data System (ADS)
Le Losq, Charles; Neuville, Daniel
Water plays a fundamental role in the dynamics and evolution of magmas in the deep interior and during volcano eruptions. In particular, extraction of magma can change drastically as a function of dissolved water content. In addition to temperature, pressure and main chemical components, volatiles exert a strong influence on the physical properties of magmas. However their speciation, which is pressure and temperature dependent, must be understood to fully assess their effects on the properties of magmas. Therefore we need to quantify the proportion and speciation of volatile in silicate melts. To quantify water content in silicate glass or lava, bulk analysis like fire loss or water extraction are very well used and accurate, but they are destructive and a sufficient quantity of material is needed. Raman spectroscopy allows to measure water contents of hydrous silicate glasses. It offers several advantages in the study of natural silicate glasses like pumice: (i) the high spatial resolution of 1-2 ?m, (ii) the non-destructive nature of this analysis and (iii) sample preparation is not necessary. Two parts can be distinguished on Raman spectra of a hydrated silicate glass: the low wave-number region, which correspond to vibrations of the silicate network (0-1500 cm-1), and the high wave-number region which correspond to the OH- stretching vibration and H2O molecular vibration (3100 -3750 cm-1). Behrens et al. (2006) have shown that water content of a glass can be determined making a ratio between these two parts. However, their calibrations are SiO2 dependent. We present now a new chemical independent internal calibration. Using cubic-spline baseline to fit the bases of silicate peaks in the low wave-number region of Raman spectra allows us to take into account the changes in this region induced by chemical variations in our set of glasses (basaltic to rhyolitic). That allows us to study basaltic glasses or rhyolitic glasses with the same calibration line. Ref.: Behrens H., Roux J., Neuville D. R., Siemann M., 2006, Quantification of dissolved H2O in silicate glasses using confocal microRaman spectroscopy, Chemical Geology 229, 96-112.
Non-destructive Identification of Individual Leukemia Cells by Optical Trapping Raman Spectroscopy
Chan, J W; Taylor, D S; Lane, S; Zwerdling, T; Tuscano, J; Huser, T
Currently, a combination of technologies is typically required to assess the malignancy of cancer cells. These methods often lack the specificity and sensitivity necessary for early, accurate diagnosis. Here we demonstrate using clinical samples the application of laser trapping Raman spectroscopy as a novel approach that provides intrinsic biochemical markers for the noninvasive detection of individual cancer cells. The Raman spectra of live, hematopoietic cells provide reliable molecular fingerprints that reflect their biochemical composition and biology. Populations of normal T and B lymphocytes from four healthy individuals, and cells from three leukemia patients were analyzed, and multiple intrinsic Raman markers associated with DNA and protein vibrational modes have been identified that exhibit excellent discriminating power for cancer cell identification. A combination of two multivariate statistical methods, principal component analysis (PCA) and linear discriminant analysis (LDA), was used to confirm the significance of these markers for identifying cancer cells and classifying the data. The results indicate that, on average, 95% of the normal cells and 90% of the patient cells were accurately classified into their respective cell types. We also provide evidence that these markers are unique to cancer cells and not purely a function of differences in their cellular activation.
Graphene nanoribbons from unzipped carbon nanotubes: atomic structures, Raman spectroscopy, and electrical properties.
Xie, Liming; Wang, Hailiang; Jin, Chuanhong; Wang, Xinran; Jiao, Liying; Suenaga, Kazu; Dai, Hongjie
We investigated the atomic structures, Raman spectroscopic and electrical transport properties of individual graphene nanoribbons (GNRs, widths ~10-30 nm) derived from sonochemical unzipping of multiwalled carbon nanotubes (MWNTs). Aberration-corrected transmission electron microscopy (TEM) revealed a high percentage of two-layer (2 L) GNRs and some single-layer ribbons. The layer-layer stacking angles ranged from 0░ to 30░ including average chiral angles near 30░ (armchair orientation) or 0░ (zigzag orientation). A large fraction of GNRs with bent and smooth edges was observed, while the rest showed flat and less smooth edges (roughness ?1 nm). Polarized Raman spectroscopy probed individual GNRs to reveal D/G ratios and ratios of D band intensities at parallel and perpendicular laser excitation polarization (D(?)/D(?)). The observed spectroscopic trends were used to infer the average chiral angles and edge smoothness of GNRs. Electrical transport and Raman measurements were carried out for individual ribbons to correlate spectroscopic and electrical properties of GNRs. PMID:21678963
Oral pathology diagnosis by means of micro-Raman spectroscopy on biopsies and blood serum
NASA Astrophysics Data System (ADS)
Zenone, F.; Lepore, M.; Perna, G.; Carmone, P.; Delfino, I.; Gaeta, G. M.; Capozzi, V.
Pemphigus vulgaris is a chronic, autoimmune, blistering disease of the skin and mucous membranes with a potentially fatal outcome. In this case micro-Raman spectroscopy (?-RS) can provide a powerful tool for a not invasive analysis of biological tissue for biopsy and in vivo investigation. Based on the evaluation of molecular vibration frequencies, the ?-RS is able to detect the main molecular bonds of protein constituents, as the C-H and C-C ones. Changes in frequency or in the relative intensity of the vibration modes revealed by ?-RS can be related to changes of chemical bond and of protein structure induced by pathology. Quantitative information on the intensity variation of specific Raman lines can be extracted by Partial Least Square (PLS) analysis. ?-RS was performed on some samples of oral tissue and blood serum from informed patients affected by pemphigus vulgaris (an oral pathology) at different pathology stages. The spectra were measured by means of a Raman confocal microspectrometer apparatus using the 633 nm line of a He- Ne laser source. The main protein bonds are clearly detectable in the considered samples giving important information on the integrity and on the state of tissue and blood serum components (lipids and proteins), and consequently on the occurrence of pathology.
Pulsed-laser-excited Raman spectra of shock compressed triaminotrinitrobenzene
NASA Astrophysics Data System (ADS)
Trott, Wayne M.; Renlund, Anita M.
Pulsed-laser-excited Raman scattering methods were used to examine sustained shock compression of 1,3,5-triamino 2,4,6-trinitrobenzene (TATB) at an optical window interface. Records of vibrational frequency shifts and line shape changes were obtained under variable and well-controlled shock loading using a 63 mm-diameter compressed gas gun to provide a planar impact geometry. To facilitate interpretation of the shock data. Raman spectra of TATB samples at elevated temperatures and ambient pressure were also acquired. Raman modes identified with the nitro and amino groups in TATB exhibit complex behavior arising from interactions associated with the extensive intra- and intermolecular hydrogen bonding network in this material. The distinct (and frequently competing) effects of pressure and temperature on these modes are discussed in relation to the known insensitivity of TATB to shock initiation.
Regime for a Self-ionizing Raman Laser Amplifier
D.S. Clark; N.J. Fisch
Backward Raman amplification and compression at high power might occur if a long pumping laser pulse is passed through a plasma to interact resonantly with a counter-propagating short seed pulse [V.M. Malkin, et al., Phys. Rev. Lett. 82 (1999) 4448-4451]. One critical issue, however, is that the pump may be unacceptably depleted due to spontaneous Raman backscatter from intrinsic fluctuations in the amplifying plasma medium prior to its useful interaction with the seed. Premature backscatter may be avoided, however, by employing a gaseous medium with pump intensities too low to ionize the medium, and using the intense seed to produce the plasma by rapid photoionization as it is being amplified [V.M. Malkin, et al., Phys. Plasmas (2001)]. In addition to allowing that only rather low power pumps be used, photoionization introduces a damping of the short pulse which must be overcome by the Raman growth rate for net amplification to occur. The parameter space of gas densities, laser wavelengths, and laser intensities is surveyed to identify favorable regimes for this effect. Output laser intensities of 10(superscript ''17'') W/cm(superscript ''2'') for 0.5 mm radiation are found to be feasible for such a scheme using a pump of 10(superscript ''13'') W/cm(superscript ''2'') and an initial seed of 5 x 10(superscript ''14'') W/cm(superscript ''2'') over an amplification length of 5.6 cm in hydrogen gas.
Human erythrocytes analyzed by generalized 2D Raman correlation spectroscopy
NASA Astrophysics Data System (ADS)
Wese?ucha-Birczy?ska, Aleksandra; Kozicki, Mateusz; Czepiel, Jacek; ?abanowska, Maria; Nowak, Piotr; Kowalczyk, Grzegorz; Kurdziel, Magdalena; Birczy?ska, Malwina; Biesiada, Gra?yna; Mach, Tomasz; Garlicki, Aleksander
The most numerous elements of the blood cells, erythrocytes, consist mainly of two components: homogeneous interior filled with hemoglobin and closure which is the cell membrane. To gain insight into their specific properties we studied the process of disintegration, considering these two constituents, and comparing the natural aging process of human healthy blood cells. MicroRaman spectra of hemoglobin within the single RBC were recorded using 514.5, and 785 nm laser lines. The generalized 2D correlation method was applied to analyze the collected spectra. The time passed from blood donation was regarded as an external perturbation. The time was no more than 40 days according to the current storage limit of blood banks, although, the average RBC life span is 120 days. An analysis of the prominent synchronous and asynchronous cross peaks allow us to get insight into the mechanism of hemoglobin decomposition. Appearing asynchronous cross-peaks point towards globin and heme separation from each other, while synchronous shows already broken globin into individual amino acids. Raman scattering analysis of hemoglobin ōwrappingö, i.e. healthy erythrocyte ghosts, allows for the following peculiarity of their behavior. The increasing power of the excitation laser induced alterations in the assemblage of membrane lipids. 2D correlation maps, obtained with increasing laser power recognized as an external perturbation, allows for the consideration of alterations in the erythrocyte membrane structure and composition, which occurs first in the proteins. Cross-peaks were observed indicating an asynchronous correlation between the senescent-cell antigen (SCA) and heme or proteins vibrations. The EPR spectra of the whole blood was analyzed regarding time as an external stimulus. The 2D correlation spectra points towards participation of the selected metal ion centers in the disintegration process.
Silica-coated gold nanostars for surface-enhanced resonance Raman spectroscopy mapping of integrins in breast cancer cells
NASA Astrophysics Data System (ADS)
Fenn, Michael B.; Roki, NikÜa.; Bashur, Chris
Surface-Enhanced Resonance Raman Spectroscopy (SERRS) has great potential for improving cancer research and diagnosis. Capable of sub-femtomolar detection, and a high degree of multiplexing, SERRS is an attractive new technique for studying cancer biology. We have developed PEGylated silica-coated gold nanostars that can be tuned to match the Raman laser-light source wavelength, providing high-level SERRS/SERS enhancement when combined with various reporter molecules. Furthermore, the particles were conjugated with cyclo-RGDf/k peptide to investigate integrin expression of breast cancer cells using high-speed Raman mapping. We propose that this may provide a better understanding of the role of integrins in breast cancer invasiveness.
Ten deep blue to cyan emission lines from an intracavity frequency converted Raman laser
NASA Astrophysics Data System (ADS)
Geskus, Dimitri; Jakutis-Neto, Jonas; Pask, Helen M.; Wetter, Niklaus U.
Here we report on the generation of ten deep blue to cyan laser emission lines using an intracavity frequency converted Raman laser. The fundamental laser field of the intracavity Raman laser is based on the 3 level transition of a Nd:YLF laser crystal, providing a short wavelength at 903 or 908 nm. When combined with generation of a Stokes shifted field via intracavity stimulated Raman scattering (SRS) by a KGW Raman crystal, enables generation of laser emission in the deep blue to cyan wavelength regime via additional nonlinear frequency conversion. Output at several blue-green wavelengths was achieved, with quasi continuous wave (qcw) output powers of up to 1W. A detailed study of the spectral behavior of the underlying Raman laser processes revealed strong spectral broadening of the fundamental laser line at 908 nm to a width of up to 4 nm. The effect of the spectral broadening on the overall laser efficiency is analyzed.
Raman Scattering of Intense Laser Light Propagating In Water
NASA Astrophysics Data System (ADS)
Manka, Charles; Susman, Yael; Jones, Theodore
The Laboratory for Underwater Hydrodynamics at the Naval Research Laboratory produces "detonation product free" subsurface bubbles by focusing a short energetic laser pulse into water. The dynamic interaction of these bubbles with adjacent surfaces is of great interest. The propagation of these intense laser pulses in water is of interest as well. We present evidence of the Raman scattering of converging 527nm laser light from NRL's PHAROS laser (Nd:glass frequency doubled). The wavelength of the observed Stokes line matches well with values found in the literature and with qualitative observations of "red flashes" reported when intense doubled YAG lasers were propagated into water. However, only one of two Stokes components mentioned in the literature is observed. We believe that the appearance of the Stokes line is an indicator for the onset of filimentation as the converging light becomes more intense.
Excited-state Raman spectroscopy with and without actinic excitation: S1 Raman spectra of trans-azobenzene
NASA Astrophysics Data System (ADS)
Dobryakov, A. L.; Quick, M.; Ioffe, I. N.; Granovsky, A. A.; Ernsting, N. P.; Kovalenko, S. A.
We show that femtosecond stimulated Raman spectroscopy can record excited-state spectra in the absence of actinic excitation, if the Raman pump is in resonance with an electronic transition. The approach is illustrated by recording S1 and S0 spectra of trans-azobenzene in n-hexane. The S1 spectra were also measured conventionally, upon n?* (S0 ? S1) actinic excitation. The results are discussed and compared to earlier reports.
Classification of oral cancers using Raman spectroscopy of serum
NASA Astrophysics Data System (ADS)
Sahu, Aditi; Talathi, Sneha; Sawant, Sharada; Krishna, C. Murali
Oral cancers are the sixth most common malignancy worldwide, with low 5-year disease free survival rates, attributable to late detection due to lack of reliable screening modalities. Our in vivo Raman spectroscopy studies have demonstrated classification of normal and tumor as well as cancer field effects (CFE), the earliest events in oral cancers. In view of limitations such as requirement of on-site instrumentation and stringent experimental conditions of this approach, feasibility of classification of normal and cancer using serum was explored using 532 nm excitation. In this study, strong resonance features of ?-carotenes, present differentially in normal and pathological conditions, were observed. In the present study, Raman spectra of sera of 36 buccal mucosa, 33 tongue cancers and 17 healthy subjects were recorded using Raman microprobe coupled with 40X objective using 785 nm excitation, a known source of excitation for biomedical applications. To eliminate heterogeneity, average of 3 spectra recorded from each sample was subjected to PC-LDA followed by leave-one-out-cross-validation. Findings indicate average classification efficiency of ~70% for normal and cancer. Buccal mucosa and tongue cancer serum could also be classified with an efficiency of ~68%. Of the two cancers, buccal mucosa cancer and normal could be classified with a higher efficiency. Findings of the study are quite comparable to that of our earlier study, which suggest that there exist significant differences, other than ?- carotenes, between normal and cancerous samples which can be exploited for the classification. Prospectively, extensive validation studies will be undertaken to confirm the findings.
Frame-Transfer Gating Raman Spectroscopy for Time-Resolved Multiscalar Combustion Diagnostics
NASA Technical Reports Server (NTRS)
Nguyen, Quang-Viet; Fischer, David G.; Kojima, Jun
Accurate experimental measurement of spatially and temporally resolved variations in chemical composition (species concentrations) and temperature in turbulent flames is vital for characterizing the complex phenomena occurring in most practical combustion systems. These diagnostic measurements are called multiscalar because they are capable of acquiring multiple scalar quantities simultaneously. Multiscalar diagnostics also play a critical role in the area of computational code validation. In order to improve the design of combustion devices, computational codes for modeling turbulent combustion are often used to speed up and optimize the development process. The experimental validation of these codes is a critical step in accepting their predictions for engine performance in the absence of cost-prohibitive testing. One of the most critical aspects of setting up a time-resolved stimulated Raman scattering (SRS) diagnostic system is the temporal optical gating scheme. A short optical gate is necessary in order for weak SRS signals to be detected with a good signal- to-noise ratio (SNR) in the presence of strong background optical emissions. This time-synchronized optical gating is a classical problem even to other spectroscopic techniques such as laser-induced fluorescence (LIF) or laser-induced breakdown spectroscopy (LIBS). Traditionally, experimenters have had basically two options for gating: (1) an electronic means of gating using an image intensifier before the charge-coupled-device (CCD), or (2) a mechanical optical shutter (a rotary chopper/mechanical shutter combination). A new diagnostic technology has been developed at the NASA Glenn Research Center that utilizes a frame-transfer CCD sensor, in conjunction with a pulsed laser and multiplex optical fiber collection, to realize time-resolved Raman spectroscopy of turbulent flames that is free from optical background noise (interference). The technology permits not only shorter temporal optical gating (down to <1 s, in principle), but also higher optical throughput, thus resulting in a substantial increase in measurement SNR.
Resonance Raman spectroscopy of volatile organics -- Carbon tetrachloride
Barletta, R.E.; Veligdan, J.T. [Brookhaven National Lab., Upton, NY (United States). Dept. of Advanced Technology
Volatile organic chemicals are a class of pollutants which are regulated at very low levels by the EPA. Consequently a need exists as a part of site remediation efforts within DOE to develop technologies which will allow for the in situ monitoring of these chemicals. Resonance Raman spectroscopy is a potential technique to accomplish this if the resonance enhancement is sufficiently high. Carbon tetrachloride was selected as a test case. Measurements under resonance conditions at 248 nm showed an enhancement factor of 2 {times} 10{sup 4}. Using this value an estimate of the sensitivity for both in situ and remote monitoring of CCl{sup 4} was made. It was concluded that resonance Raman could be used to detect these chemicals at levels of regulatory interest. Future effort directed towards the development of a suitable probe as well as a field-portable system would be desirable. Such effort could be directed towards the solution of a particular monitoring problem within a DOE waste remediation project. Once developed, however, it should be easily generalized to the analysis of other VOC`s in other environments.
Lignin Radicals in the Plant Cell Wall Probed by Kerr-Gated Resonance Raman Spectroscopy
Barsberg, S°ren; Matousek, Pavel; Towrie, Mike; J°rgensen, Henning; Felby, Claus
Lignin radicals are crucial intermediates for lignin biosynthesis in the cell wall of vascular plants. In this work they were for the first time, to our knowledge, selectively observed in wood cell walls by laser-based Kerr-gated resonance Raman spectroscopy, and the observations were supported by density functional theory prediction of their vibrational properties. For dry wood cells a lignin radical Raman band is observed at 1570 cm?1 irrespective of species. For wet beech cells they were generated in situ and observed at 1606 cm?1. DFT/B3LYP/6-31+G(d) modeling results support that in beech they are formed from syringyl (S) phenolic moieties and in spruce from guaiacyl (G) phenolic moieties. The observed lignin radical band is predicted as G is ?1597 cm?1 and S is ?1599 cm?1, respectively, and is assigned the (Wilson notation) ?8a phenyl ring mode. The RR band probes lignin radical properties, e.g., spin density distribution, and these respond to charge polarization or hydrogen bonding to proximate water molecules. These observations can be crucial for an understanding of the factors that control cell wall structure during biosynthesis of vascular plants and demonstrate the unique potential of RR spectroscopy of lignin radicals. PMID:16443659
Raman spectroscopy of hot hydrogen above 200 GPa
NASA Astrophysics Data System (ADS)
Howie, Ross T.; Dalladay-Simpson, Philip; Gregoryanz, Eugene
It has been theorized that at high pressure the increased energy of the zero-point oscillations in hydrogen would destabilize the lattice and form a ground fluid state at 0 K (ref.Ā). Theory has also suggested that this fluid state, representing a new state of matter, might have unusual properties governed by quantum effects, such as superfluidity or superconductivity. Here, by combining Raman spectroscopy and in situ high-temperature, high-pressure techniques, we demonstrate that above 200 GPa a new phase transition occurs as temperature is increased, for example 480 K at 255 GPa. If the transformation is interpreted as melting, it would be the lowest melting temperature of any material at these high pressures. We also find a new triple point between phases I and IV and the new phase, and demonstrate that hydrogen retains its molecular character around this point. These data may require a significant revision of the phase diagram of hydrogen above 200 GPa.
Probing diseased skin with FT-Raman spectroscopy
NASA Astrophysics Data System (ADS)
Carter, Elizabeth A.; Williams, Adrian C.; Barry, Brian W.; Edwards, Howell G.
Healthy and abnormal human skin has been examined using Fourier transform (FT) Raman spectroscopy. The molecular basis of alternations in this tissue have been proved with the aim of providing a tool to aid in clinical diagnosis of skin disorders. Intact human stratum corneum show spectral features of keratin and the lipids. Spectra from callus and psoriatic tissue show that the keratin component is essentially intact and is similar to that in the normal tissue. However, the abnormal skin shows that the keratin component is essentially intact and is similar to that in the normal tissue. However, the abnormal skin shows a significant depletion of the lipoidal component, which correlates with clinical observations of an increase in permeability and the hyper-proliferative nature of these conditions. Verrucal tissue again shows some alterations to the lipoidal fraction of the tissue.
Combining hyperspectral imaging and Raman spectroscopy for remote chemical sensing
NASA Astrophysics Data System (ADS)
Ingram, John M.; Lo, Edsanter
The Photonics Research Center at the United States Military Academy is conducting research to demonstrate the feasibility of combining hyperspectral imaging and Raman spectroscopy for remote chemical detection over a broad area of interest. One limitation of future trace detection systems is their ability to analyze large areas of view. Hyperspectral imaging provides a balance between fast spectral analysis and scanning area. Integration of a hyperspectral system capable of remote chemical detection will greatly enhance our soldiers' ability to see the battlefield to make threat related decisions. It can also queue the trace detection systems onto the correct interrogation area saving time and reconnaissance/surveillance resources. This research develops both the sensor design and the detection/discrimination algorithms. The one meter remote detection without background radiation is a simple proof of concept.
An intracavity, frequency-doubled self-Raman vortex laser.
Lee, Andrew J; Zhang, Chunyu; Omatsu, Takashige; Pask, Helen M
We demonstrate intracavity frequency doubling of the self-Raman field generated within a diode end-pumped, solid state Nd:GdVO(4) vortex laser. A maximum output power of 727 mW is generated at 586 nm with an overall diode-to-yellow conversion efficiency of 4%. Conservation of orbital angular momentum is observed under intracavity frequency doubling, with the topological charge of the yellow beam being twice that of the Stokes beam. PMID:24663879
Application to the optical coherent tomography of fiber Raman laser
M. Higashihata; K. Tochigi; Y. Nakata; T. Okada
This paper describes the development of a broad-band light source for the use in an optical coherence tomographic system. The broad-band light was generated via stimulated Raman scattering in a single-mode SiO2 optical fiber pumped by a conventional nano-second solid state laser. A band-width of approximately 400 nm was obtained using a 500 m long single-mode SiO2 optical fiber with
Backward Raman amplification of laser pulses in randomly inhomogeneous plasmas
NASA Astrophysics Data System (ADS)
Malkin, Vladimir; Solodov, Andrey; Fisch, Nathaniel
Current experiments on backward Raman amplification (BRA) of laser pulses in plasmas deal with strong enough random inhomogeneities in plasma concentrations capable of substantially modifying linear and even nonlinear stages of BRA. We present a simple BRA theory taking into account modifications caused by the random inhomogeneities. We show that the modified linear theory is not inconsistent with recent BRA experiments. We also give quantitative conditions for entering nonlinear BRA regimes, modified by the presence of the inhomogeneities.
Raman Spectroscopy for Mineral Identification and Quantification for in situ Planetary Surface Analysis: A Point Count Method
NASA Technical Reports Server (NTRS)
Haskin, Larry A.; Wang, Alian; Rockow, Kaylynn M.; Jolliff, Bradley L.; Korotev, Randy L.; Viskupic, Karen M.
Quantification of mineral proportions in rocks and soils by Raman spectroscopy on a planetary surface is best done by taking many narrow-beam spectra from different locations on the rock or soil, with each spectrum yielding peaks from only one or two minerals. The proportion of each mineral in the rock or soil can then be determined from the fraction of the spectra that contain its peaks, in analogy with the standard petrographic technique of point counting. The method can also be used for nondestructive laboratory characterization of rock samples. Although Raman peaks for different minerals seldom overlap each other, it is impractical to obtain proportions of constituent minerals by Raman spectroscopy through analysis of peak intensities in a spectrum obtained by broad-beam sensing of a representative area of the target material. That is because the Raman signal strength produced by a mineral in a rock or soil is not related in a simple way through the Raman scattering cross section of that mineral to its proportion in the rock, and the signal-to-noise ratio of a Raman spectrum is poor when a sample is stimulated by a low-power laser beam of broad diameter. Results obtained by the Raman point-count method are demonstrated for a lunar thin section (14161,7062) and a rock fragment (15273,7039). Major minerals (plagioclase and pyroxene), minor minerals (cristobalite and K-feldspar), and accessory minerals (whitlockite, apatite, and baddeleyite) were easily identified. Identification of the rock types, KREEP basalt or melt rock, from the 100-location spectra was straightforward.
Raman Spectroscopy for Mineral Identification and Quantification for in situ Planetary Surface Analysis: A Point Count Method
NASA Astrophysics Data System (ADS)
Haskin, Larry A.; Wang, Alian; Rockow, Kaylynn M.; Jolliff, Bradley L.; Korotev, Randy L.; Viskupic, Karen M.
Quantification of mineral proportions in rocks and soils by Raman spectroscopy on a planetary surface is best done by taking many narrow-beam spectra from different locations on the rock or soil, with each spectrum yielding peaks from only one or two minerals. The proportion of each mineral in the rock or soil can then be determined from the fraction of the spectra that contain its peaks, in analogy with the standard petrographic technique of point counting. The method can also be used for nondestructive laboratory characterization of rock samples. Although Raman peaks for different minerals seldom overlap each other, it is impractical to obtain proportions of constituent minerals by Raman spectroscopy through analysis of peak intensities in a spectrum obtained by broad-beam sensing of a representative area of the target material. That is because the Raman signal strength produced by a mineral in a rock or soil is not related in a simple way through the Raman scattering cross section of that mineral to its proportion in the rock, and the signal-to-noise ratio of a Raman spectrum is poor when a sample is stimulated by a low-power laser beam of broad diameter. Results obtained by the Raman point-count method are demonstrated for a lunar thin section (14161,7062) and a rock fragment (15273,7039). Major minerals (plagioclase and pyroxene), minor minerals (cristobalite and K-feldspar), and accessory minerals (whitlockite, apatite, and baddeleyite) were easily identified. Identification of the rock types, KREEP basalt or melt rock, from the 100-location spectra was straightforward.