Friday, September 30, 2011

Colloidal quantum dots: Performance boost next-generation solar cell technology

Researchers from the University of Toronto (U of T), the King Abdullah University of Science & Technology (KAUST) and Pennsylvania State University (Penn State) have created the most efficient solar cell ever made based on colloidal quantum dots (CQD).

The discovery is reported in the latest issue of Nature Materials.

Quantum dots are nanoscale semiconductors that capture light and convert it into an energy source. Because of their small scale, the dots can be sprayed on to flexible surfaces, including plastics. This enables the production of solar cells that are less expensive to produce and more durable than the more widely-known silicon-based version. In the work highlighted by the Nature Materials paper, the researchers demonstrate how the wrappers that encapsulate the quantum dots can be shrunk to a mere layer of atoms.

"We figured out how to shrink the passivating materials to the smallest imaginable size," states Professor Ted Sargent, corresponding author on the work and holder of the Canada Research Chair in Nanotechnology at U of T.

A crucial challenge for the field has been striking a balance between convenience and performance. The ideal design is one that tightly packs the quantum dots together. The greater the distance between quantum dots, the lower the efficiency.

However the quantum dots are usually capped with organic molecules that add a nanometer or two. When working on a nanoscale, that is bulky. Yet the organic molecules have been an important ingredient in creating a colloid, which is a substance that is dispersed in another substance. This allows the quantum dots to be painted on to other surfaces.

To solve the problem, the researchers have turned to inorganic ligands, which bind the quantum dots together while using less space. The result is the same colloid characteristics but without the bulky organic molecules.

"We wrapped a single layer of atoms around each particle. As a result, they packed the quantum dots into a very dense solid," explains Dr. Jiang Tang, the first author of the paper who conducted the research while a post-doctoral fellow in The Edward S. Rogers Department of Electrical & Computer Engineering at U of T.

The team showed the highest electrical currents, and the highest overall power conversion efficiency, ever seen in CQD solar cells. The performance results were certified by an external laboratory, Newport, that is accredited by the US National Renewable Energy Laboratory.

"The team proved that we were able to remove charge traps -- locations where electrons get stuck -- while still packing the quantum dots closely together," says Professor John Asbury of Penn State, a co-author of the work.


"This finding proves the power of inorganic ligands in building practical devices," states Professor Dmitri Talapin of The University of Chicago, who is a research leader in the field. "This new surface chemistry provides the path toward both efficient and stable quantum dot solar cells. It should also impact other electronic and optoelectronic devices that utilize colloidal nanocrystals. Advantages of the all-inorganic approach include vastly improved electronic transport and a path to long-term stability."

"At KAUST we were able to visualize, with incredible resolution on the sub-nanometer length scale, the structure and composition of this remarkable new class of materials," states Professor Aram Amassian of KAUST, a co-author on the work.

"We proved that the inorganic passivants were tightly correlated with the location of the quantum dots; and that it was this new approach to chemical passivation, rather than nanocrystal ordering, that led to this record-breaking colloidal quantum dot solar cell performance," he adds.

As a result of the potential of this research discovery, a technology licensing agreement has been signed by U of T and KAUST, brokered by MaRS Innovations (MI), which will will enable the global commercialization of this new technology.


Story Source:

The above story is reprinted (with editorial adaptations ) from materials provided by University of Toronto, via EurekAlert!, a service of AAAS.

Journal Reference:

Jiang Tang, Kyle W. Kemp, Sjoerd Hoogland, Kwang S. Jeong, Huan Liu, Larissa Levina, Melissa Furukawa, Xihua Wang, Ratan Debnath, Dongkyu Cha, Kang Wei Chou, Armin Fischer, Aram Amassian, John B. Asbury, Edward H. Sargent. Colloidal-quantum-dot photovoltaics using atomic-ligand passivation. Nature Materials, 2011; DOI: 10.1038/nmat3118

Lasers could be used to detect roadside bombs

 A research team at Michigan State University has developed a laser that could detect roadside bombs -- the deadliest enemy weapon encountered in Iraq and Afghanistan.

The laser, which has comparable output to a simple presentation pointer, potentially has the sensitivity and selectivity to canvas large areas and detect improvised explosive devices -- weapons that account for around 60 percent of coalition soldiers' deaths. Marcos Dantus, chemistry professor and founder of BioPhotonic Solutions, led the team and has published the results in the current issue of Applied Physics Letters.


"Having molecular structure sensitivity is critical for identifying explosives and avoiding unnecessary evacuation of buildings and closing roads due to false alarms," he said.

Since IEDs can be found in populated areas, the methods to detect these weapons must be nondestructive. They also must be able to distinguish explosives from vast arrays of similar compounds that can be found in urban environments. Dantus' latest laser can make these distinctions even for quantities as small as a fraction of a billionth of a gram.

The laser beam combines short pulses that kick the molecules and make them vibrate, as well as long pulses that are used to "listen" and identify the different "chords." The chords include different vibrational frequencies that uniquely identify every molecule, much like a fingerprint. The high-sensitivity laser can work in tandem with cameras and allows users to scan questionable areas from a safe distance.

"The laser and the method we've developed were originally intended for microscopes, but we were able to adapt and broaden its use to demonstrate its effectiveness for standoff detection of explosives," said Dantus, who hopes to net additional funding to take this laser from the lab and into the field.


Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by Michigan State University.

Journal Reference:

Marshall T. Bremer, Paul J. Wrzesinski, Nathan Butcher, Vadim V. Lozovoy, Marcos Dantus. Highly selective standoff detection and imaging of trace chemicals in a complex background using single-beam coherent anti-Stokes Raman scattering. Applied Physics Letters, 2011; 99 (10): 101109 DOI: 10.1063/1.3636436

A guiding light for new directions in energy production: Optofluidics could help solve the energy challenge

The science of light and liquids has been intimately entwined since Léon Foucault discovered the speed of light in 1862, when he observed that light travels more slowly in water than in air. This physical harmony between the two materials is now being harnessed to collect and drive light to where it can be the most useful. October's issue of Nature Photonics focuses on optofluidics, the study of microfluidics -- the microscopic delivery of fluids through extremely small channels or tubes -- combined with optics. In a review written by Demetri Psaltis, Dean of EPFL's School of Engineering, he and his co-authors argue that optofluidics is poised to take on one of this century's most important challenges: energy.

"By directing the light and concentrating where it can be most efficiently used, we could greatly increase the efficiency of already existing energy producing systems, such as biofuel reactors and solar cells, as well as innovate entirely new forms of energy production" explains Psaltis. "EPFL is the world leader in optofluidics, our institution is in a position to develop truly efficient and disruptive energy sources."

Sunlight is already used for energy production besides conventional solar panels. For example, it is used to convert water and carbon dioxide into methane in large industrial biofuel plants. Prisms and mirrors are commonly employed to direct and concentrate sunlight to heat water on the roofs of homes and apartment buildings. These techniques already employ the same principles found in optofluidics -- control and manipulation of light and liquid transfer -- but often without the precision offered by nano and micro technology.

A futuristic example: Optofluidic solar lighting system

How can we better exploit the light that hits the outside of a building? Imagine sunlight channelled into the building An optofluidic solar lighting system could capture sunlight from a roof using a light concentrating system that follows the sun's path by changing the angle of the water's refraction, and then distribute the sunlight throughout the building through light pipes or fibre optic cables to the ceilings of office spaces, indoor solar panels, or even microfluidic air filters. Using sunlight to drive a microfluidic air filter or aliment an indoor solar panel -- which would be protected from the elements and last longer -- is a novel way to use solar energy to supplement non-renewable resources.

In such a system, it would be essential to deviate from the secondary devices such as air filtrage and solar panels to maintain a comfortable constant light source for ceiling lighting -- the flickering of the light source due to a cloud passing over would be intolerable. In order to modulate these different channels to maintain a constant light source, a system using electrowetting could deviate light from one channel into another both easily and inexpensively. A droplet of water sits on the outer surface of light tube. A small current excites the ions in the water, pushing them to the edge of the droplet and expanding it just enough for it to touch the surface of another tube. This expanded droplet then creates a light bridge between the two parallel light tubes, effectively moderating the amount of light streaming through either one.

Up-scaling for industrial use




Story Source:

The above story is reprinted (with editorial adaptations ) from materials provided by Ecole Polytechnique Fédérale de Lausanne, via EurekAlert!, a service of AAAS.

Journal Reference:

David Erickson, David Sinton, Demetri Psaltis. Optofluidics for energy applications. Nature Photonics, 2011; DOI: 10.1038/nphoton.2011.209

New method to grow synthetic collagen unveiled: New material may find use in reconstructive surgery, cosmetics, tissue engineering


"Our work is significant in two ways," said Rice's Jeffrey Hartgerink, the lead author of a new paper about the research in Nature Chemistry. "Our final product more closely resembles native collagen than anything that's previously been made, and we make that material using a self-assembly process that is remarkably similar to processes found in nature."

Collagen, the most abundant protein in the body, is a key component of many tissues, including skin, tendons, ligaments, cartilage and blood vessels. Biomedical researchers in the burgeoning field of regenerative medicine, or tissue engineering, often use a combination of stem cells and collagen-like materials in their attempts to create laboratory-grown tissues that can be transplanted into patients without risk of immunological rejection.

Animal-derived collagen, which has some inherent immunological risks, is the form of collagen most commonly used in reconstructive and cosmetic surgery today. Animal-derived collagen is also used in many cosmetics.

Despite the abundance of collagen in the body, deciphering or recreating it has not been easy for scientists. One reason for this is the complexity collagen exhibits at different scales. For example, just as a rope is made of many interwoven threads, collagen fibers are made of millions of proteins called peptides. Like a rope net that can trap and hold items, collagen fibers can form three-dimensional structures called hydrogels that trap and hold water.

"Our supramolecules, fibers and hydrogels form in a similar way to native collagen, but we start with shorter peptides," said Hartgerink, associate professor of chemistry and of bioengineering.

With an eye toward mimicking collagen's self-assembly process as closely as possible, Hartgerink's team spent several years perfecting its design for the peptides.

Hartgerink said it's too early to say whether the synthetic collagen can be substituted medically for human or animal-derived collagen, but it did clear the first hurdle on that path; the enzyme that the body uses to break down native collagen also breaks down the new material at a similar speed.

A faculty investigator at Rice's BioScience Research Collaborative, Hartgerink said scientists must next determine whether cells can live and grow in the new material and whether it performs the same way in the body that native collagen does. He estimated that clinical trials, if they prove warranted, are at least five years away.

The paper's co-authors include Rice graduate students Lesley O'Leary, Jorge Fallas, Erica Bakota and Marci Kang. The research was funded by the National Science Foundation, the Robert A. Welch Foundation and the Norman Hackerman Advanced Research Program of Texas.

Story Source:

The above story is reprinted (with editorial adaptations ) from materials provided by Rice University.

Journal Reference:

Lesley E. R. O'Leary, Jorge A. Fallas, Erica L. Bakota, Marci K. Kang, Jeffrey D. Hartgerink. Multi-hierarchical self-assembly of a collagen mimetic peptide from triple helix to nanofibre and hydrogel. Nature Chemistry, 2011; DOI: 10.1038/nchem.1123



New material synthesized: Graphene nanoribbons inside of carbon nanotubes

Physicists from Umea University (Sweden) and Finland have found an efficient way to synthesize graphene nanoribbons directly inside of single-walled carbon nanotubes.

The result was recently published in the journal Nano Letters.








"This creates an enormous potential for a wide range of applications. We can prepare hybrids that combine graphene and nanotubes in all possible combinations in the future," says Talyzin.




Story Source:

The above story is reprinted (with editorial adaptations ) from materials provided by Umea University.

Journal Reference:

Alexandr V. Talyzin, Ilya V. Anoshkin, Arkady V. Krasheninnikov, Risto M. Nieminen, Albert G. Nasibulin, Hua Jiang, Esko I. Kauppinen. Synthesis of Graphene Nanoribbons Encapsulated in Single-Walled Carbon Nanotubes. Nano Letters, 2011; 110902093500003 DOI: 10.1021/nl2024678

Thursday, September 29, 2011

New light on detection of bacterial infection: Polymers fluoresce in the presence of bacteria


When contained in a gel and applied to a wound, the level of fluorescence detected will alert clinicians to the severity of infection. The polymers are irreversibly attached to fragments of antibiotics, which bind to either gram negative or gram positive bacteria -- both of which cause very serious infections -- informing clinicians as to whether to use antibiotics or not, and the most appropriate type of antibiotic treatment to prescribe. The team also found that they could use the same gels to remove the bacteria from infected wounds in tissue engineered human skin.

Professor Sheila MacNeil, an expert in tissue engineering and wound healing, explained: "The polymers incorporate a fluorescent dye and are engineered to recognise and attach to bacteria, collapsing around them as they do so. This change in polymer shape generates a fluorescent signal that we´ve been able to detect using a hand-held UV lamp."

"The availability of these gels would help clinicians and wound care nurses to make rapid, informed decisions about wound management, and help reduce the overuse of antibiotics," added project lead Dr Steve Rimmer.



The research is the result of a three-year project which started in 2006, part-funded by the Engineering and Physical Sciences Research Council (EPSRC) and the Defence Science and Technology Laboratory (Dstl) -- an agency of the Ministry of Defence, interested in the medical application of the research in battlefield conditions, and a subsequent EPSRC funded PhD studentship.

The team is also investigating whether using a sophisticated technique called fluorescence Non Radiative Energy Transfer (NRET) to generate the light signal could enable a highly refined sensor technology that could have applications in other areas.



Story Source:

The above story is reprinted (with editorial adaptations ) from materials provided by University of Sheffield.

'Inexhaustible' source of hydrogen may be unlocked by salt water, engineers say


"This system could produce hydrogen anyplace that there is wastewater near sea water," said Bruce E. Logan, Kappe Professor of Environmental Engineering. "It uses no grid electricity and is completely carbon neutral. It is an inexhaustible source of energy."

Microbial electrolysis cells that produce hydrogen are the basis of this recent work, but previously, to produce hydrogen, the fuel cells required some electrical input. Now, Logan, working with postdoctoral fellow Younggy Kim is using the difference between river water and seawater to add the extra energy needed to produce hydrogen.

Their results, published Sept. 19 in the Proceedings of the National Academy of Sciences, "show that pure hydrogen gas can efficiently be produced from virtually limitless supplies of seawater and river water and biodegradable organic matter."

Logan's cells were between 58 and 64 percent efficient and produced between 0.8 to 1.6 cubic meters of hydrogen for every cubic meter of liquid through the cell each day. The researchers estimated that only about 1 percent of the energy produced in the cell was needed to pump water through the system.

The key to these microbial electrolysis cells is reverse-electrodialysis or RED that extracts energy from the ionic differences between salt water and fresh water. A RED stack consists of alternating ion exchange membranes -- positive and negative -- with each RED contributing additively to the electrical output.

"People have proposed making electricity out of RED stacks," said Logan. "But you need so many membrane pairs and are trying to drive an unfavorable reaction."

For RED technology to hydrolyze water -- split it into hydrogen and oxygen -- requires 1.8 volts, which would in practice require about 25 pairs of membrane sand increase pumping resistance. However, combining RED technology with exoelectrogenic bacteria -- bacteria that consume organic material and produce an electric current -- reduced the number of RED stacks to five membrane pairs.

Previous work with microbial electrolysis cells showed that they could, by themselves, produce about 0.3 volts of electricity, but not the 0.414 volts needed to generate hydrogen in these fuel cells. Adding less than 0.2 volts of outside electricity released the hydrogen. Now, by incorporating 11 membranes -- five membrane pairs that produce about 0.5 volts -- the cells produce hydrogen.

"The added voltage that we need is a lot less than the 1.8 volts necessary to hydrolyze water," said Logan. "Biodegradable liquids and cellulose waste are abundant and with no energy in and hydrogen out we can get rid of wastewater and by-products. This could be an inexhaustible source of energy."

Logan and Kim's research used platinum as a catalyst on the cathode, but subsequent experimentation showed that a non-precious metal catalyst, molybdenum sulfide, had a 51 percent energy efficiency. The King Abdullah University of Science and Technology supported this work.

Story Source:

The above story is reprinted (with editorial adaptations ) from materials provided by Penn State.

Journal Reference:

Younggy Kim, Bruce E. Logan. Hydrogen production from inexhaustible supplies of fresh and salt water using microbial reverse-electrodialysis electrolysis cells. Proceedings of the National Academy of Sciences, 2011; DOI: 10.1073/pnas.1106335108

Scientists solve long-standing plant biochemistry mystery





















Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by DOE/Brookhaven National Laboratory.

Journal Reference:


Researchers power line-voltage light bulb with nanotube wire

 Cables made of carbon nanotubes are inching toward electrical conductivities seen in metal wires, and that may light up interest among a range of industries, according to Rice University researchers.

A Rice lab made such a cable from double-walled carbon nanotubes and powered a fluorescent light bulb at standard line voltage -- a true test of the novel material's ability to stake a claim in energy systems of the future.

The work appears this week in the Nature journal Scientific Reports.

Highly conductive nanotube-based cables could be just as efficient as traditional metals at a sixth of the weight, said Enrique Barrera, a Rice professor of mechanical engineering and materials science. They may find wide use first in applications where weight is a critical factor, such as airplanes and automobiles, and in the future could even replace traditional wiring in homes.

The cables developed in the study are spun from pristine nanotubes and can be tied together without losing their conductivity. To increase conductivity of the cables, the team doped them with iodine and the cables remained stable. The conductivity-to-weight ratio (called specific conductivity) beats metals, including copper and silver, and is second only to the metal with highest specific conductivity, sodium.

Yao Zhao, who recently defended his dissertation toward his doctorate at Rice, is the new paper's lead author. He built the demo rig that let him toggle power through the nanocable and replace conventional copper wire in the light-bulb circuit.

Zhao left the bulb burning for days on end, with no sign of degradation in the nanotube cable. He's also reasonably sure the cable is mechanically robust; tests showed the nanocable to be just as strong and tough as metals it would replace, and it worked in a wide range of temperatures. Zhao also found that tying two pieces of the cable together did not hinder their ability to conduct electricity.

The few centimeters of cable demonstrated in the present study seems short, but spinning billions of nanotubes (supplied by research partner Tsinghua University) into a cable at all is quite a feat, Barrera said. The chemical processes used to grow and then align nanotubes will ultimately be part of a larger process that begins with raw materials and ends with a steady stream of nanocable, he said. The next stage would be to make longer, thicker cables that carry higher current while keeping the wire lightweight. "We really want to go better than what copper or other metals can offer overall," he said.

The paper's co-authors are Tsinghua researcher Jinquan Wei, who spent a year at Rice partly supported by the Armchair Quantum Wire Project of Rice University's Smalley Institute for Nanoscale Science and Technology; Robert Vajtai, a Rice faculty fellow in mechanical engineering and materials science; and Pulickel Ajayan, the Benjamin M. and Mary Greenwood Anderson Professor of Mechanical Engineering and Materials Science and professor of chemistry and chemical and biomolecular engineering.

The Research Partnership to Secure Energy for America, the Department of Energy and Air Force Research Laboratory supported the project.

Story Source:


Journal Reference:

Yao Zhao, Jinquan Wei, Robert Vajtai, Pulickel M. Ajayan, Enrique V. Barrera. Iodine doped carbon nanotube cables exceeding specific electrical conductivity of metals. Scientific Reports, 2011; 1 DOI: 10.1038/srep00083

Wednesday, September 28, 2011

Nuclear detector: New materials hold promise for better detection of nuclear weapons

 Northwestern University scientists have developed new materials that can detect hard radiation, a very difficult thing to do. The method could lead to a handheld device for detecting nuclear weapons and materials, such as a "nuclear bomb in a suitcase" scenario.

"The terrorist attacks of 9/11 heightened interest in this area of security, but the problem remains a real challenge," said Mercouri G. Kanatzidis, who led the research. "We have designed promising semiconductor materials that, once optimized, could be a fast, effective and inexpensive method for detecting dangerous materials such as plutonium and uranium."

Kanatzidis is a Charles E. and Emma H. Morrison Professor of Chemistry in the Weinberg College of Arts and Sciences. He also holds a joint appointment at Argonne National Laboratory.

The Northwestern materials perform as well as materials that have emerged from five decades of research and development, Kanatzidis said.

To design an effective detector, Kanatzidis and his team turned to the heavy element part of the periodic table. The researchers developed a design concept to make new semiconductor materials of heavy elements in which most of the compound's electrons are bound up and not mobile. When gamma rays enter the compound, they excite the electrons, making them mobile and thus detectable. And, because every element has a particular spectrum, the signal identifies the detected material.

The method, called dimensional reduction, will be published in the Sept. 22 issue of the journal Advanced Materials.

In most materials, gamma rays emitted by nuclear materials would just pass right through, making them undetectable. But dense and heavy materials, such as mercury, thallium, selenium and cesium, absorb the gamma rays very well.

The problem the researchers faced was that the heavy elements have a lot of mobile electrons. This means when the gamma rays hit the material and excite electrons the change is not detectable.

"It's like having a bucket of water and adding one drop -- the change is negligible," Kanatzidis explained. "We needed a heavy element material without a lot of electrons. This doesn't exist naturally so we had to design a new material."

Kanatzidis and his colleagues designed their semiconductor materials to be crystalline in structure, which immobilized their electrons.

The materials they developed and successfully demonstrated as effective gamma ray detectors are cesium-mercury-sulfide and cesium-mercury-selenide. Both semiconductors operate at room temperature, and the process is scaleable.

"Our materials are very promising and competitive," Kanatzidis said. "With further development, they should outperform existing hard radiation detector materials. They also might be useful in biomedicine, such as diagnostic imaging."

The work was a Northwestern team effort, involving three professors and their research groups. Kanatzidis made the materials; Bruce W. Wessels, the Walter P. Murphy Professor of Materials Science and Engineering in the McCormick School of Engineering and Applied Science, measured and evaluated the materials; and Arthur J. Freeman, a Charles E. and Emma H. Morrison Professor of Physics and Astronomy in Weinberg, provided theoretical predictions of the materials' performance.

In addition to Kanatzidis, Wessels and Freeman, other authors include John Androulakis, Sebastian C. Peter, Hao Li, Christos D. Malliakas, John A. Peters, Zhifu Liu, Jung-Hwan Song and Hosub Jin.

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Story Source:

The above story is reprinted (with editorial adaptations ) from materials provided by Northwestern University, via EurekAlert!, a service of AAAS.

Journal Reference:

John Androulakis, Sebastian C. Peter, Hao Li, Christos D. Malliakas, John A. Peters, Zhifu Liu, Bruce W. Wessels, Jung-Hwan Song, Hosub Jin, Arthur J. Freeman, Mercouri G. Kanatzidis. Dimensional Reduction: A Design Tool for New Radiation Detection Materials. Advanced Materials, 2011; DOI: 10.1002/adma.201102450

Ground glass solution for cleaner water

 British science has led to a use for waste glass that cannot be recycled that could help clean up polluted waterways by acting as an ion-exchange filter to remove lead, cadmium and other toxic metals.

Details are published in a forthcoming issue of the International Journal of Environment and Waste Management.

Only a fraction of waste glass bottles and jars can be recycled, partly because much of the glass is coloured, brown or green, and partly because the market sustains only a limited weight of recyclable glass. Millions of tonnes of waste container glass are generated across Europe. As such, large amounts of waste glass, purportedly for recycling, are shipped to China and elsewhere to be ground up and used as hardcore filling materials for road building.

Now, Nichola Coleman of the University of Greenwich, London, has developed a simple processing method for converting waste container glass, or cullet, into the mineral tobermorite. Tobermorite is hydrated calcium silicate, silicate being the main material that can be extracted from glass. In the form produced, the phase-pure 11-angstrom form -- the mineral can be used as an ion-exchange material that can extract toxic lead and cadmium ions from industrial effluent, waste water streams or contaminated groundwater.

To make the tobermorite, Coleman simply heats a mixture of ground cullet, lime (as a calcium source) and caustic soda (sodium hydroxide solution) to 100 Celsius in a sealed Teflon container. Initial tests show that uptake of lead and cadmium from solution are rather slow, so Coleman suggests that, at this stage of development, the synthetic mineral might best be used in the in situ remediation of groundwater rather than in industrial ex situ effluent filtration processes. The concept is now being extended to create other classes of ion exchange filter from unrecyclable and low-quality waste glass.

"The cullet-derived sorbent could be used in reactive barriers to prevent the lateral migration of pollutants in groundwater, rather than as a remediation material for waterways," says Coleman. "Heavy metal-contaminated land and groundwater are global problems, arising from industrial and military activities and also from the natural leaching of heavy metal-bearing minerals," she adds.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Inderscience, via AlphaGalileo.

Journal Reference:

Nicola J Coleman. 11 A tobermorite ion exchanger from recycled container glass. International Journal of Environment and Waste Management, 2011; 8 (3/4): 366-382



Microspiders: Polymerization reaction drives micromotors






More information: Ayusman Sen, A Polymerization-Powered Motor, Angewandte Chemie International Edition, … ie.201103565

Provided by Wiley (news : web)

Insect gut microbe with a molecular iron reservoir



Microbacterium arborescens is a bacterium, which can be found in the guts of herbivorous . The Department of Bioorganic Chemistry at the Max Planck Institute for studies interactions between insects and which live in their digestive system. What is the advantage for both, insects and microbes? How strongly do they depend on each other? Do microbes play a role in mediating interactions between herbivorous insects and host plants? In the course of the experiments to answer these questions the scientists came across an enzyme they had isolated from M. arborescens, a resident in the gut of the Beet Armyworm Spodoptera exigua. It was called N-acyl amino acid hydrolase (AAH) because of its catalytic function: it catalyzes the synthesis and of conjugates of the amino acid glutamine with . The N-acyl glutamines enter the infested plant via oral secretions and intestinal contents of the larvae and trigger the plant's defense responses.


Fe2+ + H2O2 › Fe3+ + OH- + •HO (Fenton's Reaction)

The highly reactive hydroxyl radical •HO damages especially the DNA and thus causes dangerous mutations of the genetic material. In cooperation with Kornelius Zeth from the Institute for Developmental Biology in Tuebingen the researchers succeeded in analyzing the iron transport mechanisms by means of crystallization and X-ray structure determination.

Longitudinal section through the pore along with a representation of the iron uptake mechanism. Entering Fe(II)ions, surrounded by 6 water molecules (spatial representation in the box on the right below), are oxidized to Fe(III)ions with a simultaneous loss of their hydrate shell. The Fe(III) is stored as Fe2O3 in the center of the macromolecule. Credit: Kornelius Zeth, MPI Tuebingen




Provided by Max-Planck-Gesellschaft (news : web)



J. Mark Powell, Ph.D., described the results of three studies undertaken to determine how adding plant substances called "tannins" to cow feed affects the emission of ammonia from dairy barn floors and farm fields fertilized with mixtures of cow manure and urine.

"For , cow urine is the source of the ammonia emission problem," said Powell, who is with the U.S. Department of Agriculture (USDA) Agricultural Research Service (ARS). "Dairy cows excrete large amounts of urine, about 3.5 gallons daily for each cow. That's almost 1,300 gallons per year. And there are about 10 million dairy cows in the United States alone. Cows usually are fed a high-protein diet, and they produce various nitrogen compounds when they digest protein. They release the excess nitrogen mainly in their urine, and enzymes convert it into ammonia."


The ammonia problem originates with the nitrogen-rich protein in cow feed. Cows' digestive systems are inefficient, and barely one-third of the nitrogen in their feed ends up in milk. The rest exits in urine and feces. The nitrogen in urine is in the form of urea, and enzymes contained in cow manure on the barn floor quickly convert it into ammonia gas.

Tannins apparently reduce urea production by allowing more protein to escape digestion in the stomach and enter the cow's intestines, where it's used to produce milk protein.




Provided by American Chemical Society (news : web)

Tuesday, September 27, 2011

Chemical research could help solve radioactive waste concerns


Researchers in the Department of Chemistry have discovered a class of that can selectively extract extremely radioactive components - ‘minor actinides' - that remain after spent fuel has been reprocessed, making the eventual waste far less radiotoxic. The minor actinides can potentially be fed back into nuclear reactors, providing extra energy and, in turn, be converted to non-radioactive products.

The UK nuclear power industry produces about 10,000 megawatts of power each year. Although the vast bulk of the spent fuel from a reactor can be reprocessed and fed back into the fuel cycle, a residue, consisting of corrosion products, lanthanides and minor actinides, must be sent to storage.

For every 500kg of spent fuel, there is 15kg of waste, of which the minor actinides, such as americium, curium and neptunium, constitute less than 1kg. However, these present an extreme hazard as they are intensely radioactive and long-lived nuclides that cause serious concern when it comes to storing them for more than 100,000 years.

Professor Laurence Harwood, who led the research at Reading, said: "The minor actinides are highly radioactive and have half lives up to millions of years. If these can be removed they could be used as fuel in the new generation of nuclear reactors that will come on-stream around 2025 and converted to non-radioactive material.  Being able to separate out the minor actinides even now already makes storage simpler and reduces the security risk as well.

"Our research has produced molecules capable of removing 99.9%of the minor actinides left after reprocessing , ensuring much smaller levels of radioactive waste would accrue and remain hazardous for a much shorter period of time; a few hundred years, rather than effectively forever."

More information: The research, ‘Highly efficient separation of actinides from lanthanides by a phenanthroline-derived bis-triazine ligand', can be viewed at http://centaur.rea … 0000170.html

Provided by University of Reading

First chemical complex consisting of rare earth metals and boron atoms produces unexpected results

Boron is an intriguing member of the periodic table because it readily forms stable compounds using only six electrons—two fewer than most other main-group elements. This means that chemists can easily add boron to unsaturated hydrocarbons, and then use electron-rich atoms, such as oxygen, to change organoborons into versatile units such as alcohols and esters. Recently, researchers found that combining transition metals with boron ligands produces catalysts powerful enough to transform even fully saturated hydrocarbons into new organic functionalities with high selectivity.

Now, Zhaomin Hou and colleagues from the RIKEN Advanced Science Institute in Wako have made another breakthrough in this field: they have created the first-ever complexes between ligands and rare earth metals1. Because these novel chemical combinations display a surprising ability to incorporate molecules such as carbon monoxide into their frameworks, they have potential applications that range from synthesizing organic substrates to controlling noxious emissions.

are hot commodities because they are vital for products in high demand such as smartphones and electric cars (Fig. 1). However, full chemical studies of these elements are only in their infancy since they are difficult to handle under normal conditions. 

According to Hou, typical methods to prepare transition metal–boron complexes—halogen or metal exchange reactions, for example—seemed unsuitable for rare earth metals. Instead, the team used a vigorous lithium–boron compound to handle the reactive rare earth precursors, producing previously unseen scandium–(Sc–B) and gadolinium–boron (Gd–B) complexes in good yields, but not without difficulty. “Rare earth–boron compounds are air- and moisture-sensitive and sometimes thermally unstable,” says Hou. “They therefore require great care in isolation and handling.”

To determine whether or not the Sc–B complex could act as a nucleophile—an important electron-donating reagent in organic chemistry—the team reacted it with N,N,-diisopropylcarbodiimide, a molecule that easily accepts to change into an amidinate salt. X-ray analysis revealed that initially, the carbodiimide became incorporated between Sc and carbon ligands on the rare earth metal, but extra quantities of the reagent became incorporated between the Sc–B bond. Furthermore, adding carbon monoxide to this mixture also caused a rare earth–boron insertion, accompanied by an unexpected rearrangement into a cyclic structure. 

Because chemists rely on insertion reactions to efficiently transform ligands into a diverse range of products, these findings should enable development of brand new synthetic techniques—opportunities that Hou and his team are actively pursuing.

More information: Li, S., et al.  Rare earth metal boryl complexes: Synthesis, structure, and insertion chemistry. Angewandte Chemie International Edition 50, 6360–6363 (2011). 

Provided by RIKEN (news : web)

New material shows promise for trapping pollutants


Chemists at the University of California, Santa Cruz, have now developed a new type of material that can soak up negatively-charged pollutants from water. The new material, which they call SLUG-26, could be used to treat polluted water through an ion exchange process similar to water softening. In a water softener, weakly attached to a negatively-charged resin are exchanged for the hard-water minerals, which are held more tightly by the resin. SLUG-26 provides a positively-charged substrate that can exchange a nontoxic negative ion for the negatively-charged pollutants.



The researchers are currently focusing on the use of SLUG-26 to trap the radioactive metal technetium, which is a major concern for long-term disposal of radioactive waste. Technetium is produced in nuclear reactors and has a long half-life of 212,000 years. It forms the negative ion pertechnetate in and can leach out of solid waste, making groundwater contamination a serious concern.




Provided by University of California - Santa Cruz (news : web)

Early detection of plant disease

Each year, plant viruses and fungal attacks lead to crop losses of up to 30 percent. That is why it is important to detect plant disease early on. Yet laboratory tests are expensive and often time-consuming. Researchers are now developing a low-cost quick test for use on site.

The farmer casts a worried gaze at his potato field: where only recently a lush green field of plants was growing, much of the has now turned brown – presumably the result of a fungal disease. Usually, by the time the disease becomes visible, it is already too late. The course of the disease is then so advanced that there is little the farmer can do to counteract the damage done. To determine early on whether and how severely his are diseased, he would have to submit samples to a laboratory on a regular basis. There, researchers usually employ the ELISA method, a conventional detection method based on an antibody-antigen reaction. “These tests are expensive, though. It also takes up to two weeks before the farmer has the results of the tests. And by then, the disease has usually spread out across the entire field,” explains Dr. Florian Schröper of the Fraunhofer Institute for Molecular Biology and Applied Ecology IME in Aachen, Germany.

Researchers at the IME are now working on a new quick test that is to provide the farmer a low-cost analysis right there in the field. At the heart of the test is a magnetic reader devised by scientists at the Peter Grünberg Institute of the Forschungszentrum Jülich. The device has several excitation and detection coils arrayed in pairs. The excitation coils generate a high- and low-frequency magnetic field, while the detection coils measure the resulting mixed field. If magnetic particles penetrate the field, the measuring signal is modified. The result is shown on a display, expressed in millivolts. This permits conclusions about the concentration of magnetic particles in the field.

Researchers are making use of this mechanism to track down pathogens. “What we detect is not the virus itself but the magnetic particles that bond with the virus particles,” Schröper notes. These are first equipped with antibodies so that these can specifically target and dock onto the pathogens. This way, essentially there is a virus particle “stuck” to each magnetic particle. To ensure that these are in proportion to one another, researchers use a method that functions similarly to the ELISA principle. They introduce plant extract into a tiny filtration tube filled with a polymer matrix to which specific antibodies were bound. When the plant solution passes through the tube, the virus particles are trapped in the matrix. Following a purification step, the experts add the magnetic particles modified with antibodies. These, in turn, dock onto the antigens in the matrix. A subsequent purification step removes all of the unbound particles. The tube is then placed in an appliance in the magnet reader to measure the concentration of . The researchers have already achieved promising results in initial tests involving the grapevine virus: the measured values reached a level of sensitivity ten times that of the ELISA method. Currently, Schröper and his team are working to expand their tests to other pathogens such as the mold spore Aspergillus flavus.

The mobile mini-lab needs to be made more user-friendly, however, before it is ready for widespread use in the field. Rather than grapple with measurements in millivolts, farmers should be able to consult the display and determine directly how severe the level of crop disease is. If possible, the scientists also want to reduce the number of analytical steps, and hence the detection time involved.

Provided by Fraunhofer-Gesellschaft (news : web)

Monday, September 26, 2011

Scientists pinpoint shape-shifting mechanism critical to protein signaling

In a joint study, scientists from the California and Florida campuses of The Scripps Research Institute have shown that changes in a protein's structure can change its signaling function and they have pinpointed the precise regions where those changes take place.

The new findings could help provide a much clearer picture of potential drugs that would be both effective and highly specific in their biological actions.

The study, led by Patrick Griffin of Scripps Florida and Raymond Stevens of Scripps California, was published in a recent edition of the journal Structure.

The new study focuses on the ß2-adrenergic receptor, a member of the G protein-coupled receptor family. G protein-coupled convert extracellular stimuli into intracellular signals through various pathways. Approximately one third of currently marketed drugs (including for diabetes and heart disease) target these receptors.

Scientists have known that when specific regions of the receptor are activated by neurotransmitters or hormones, the structural arrangement (conformation) of the receptor is changed along with its function.

"While it's accepted that these receptors adopt multiple conformations and that each conformation triggers a specific type of signaling, the molecular mechanism behind that flexibility has been something of a black box," said Griffin, who is chair of the Scripps Research Department of Molecular Therapeutics and director of the Scripps Florida Translational Research Institute. "Our findings shed significant light to it."

The study describes in structural detail the various regions of the receptor that are involved in the changes brought about by selective ligands (ligands are molecules that bind to proteins to form an active complex), which, like a rheostat, run the gamut among activating the receptor, shutting it down, and reversing its function, as well as producing various states in between.

To achieve the results described in the study, the team used hydrogen-deuterium (HDX) mass spectrometry to measure the impact of interaction of various functionally selective ligands with the ß2-adrenergic receptor. A mass spectrometer determines the mass of fragments from the receptor by measuring the mass-to-charge ratio of their ions. HDX has been used to examine changes in the shape of proteins and how these shape changes relate to function. The approach is often used to characterize protein-protein interactions that are critical for signal transduction in cells and to study protein-folding pathways that are critical to cell survival.

"At this early stage in understanding GPCR structure and function, it is important to view the entire receptor in combination with probing very specific regions," said Stevens, who is a professor in the Scripps Research Department of Molecular Biology. "Hydrogen-deuterium exchange mass spectrometry has the right timescale and resolution to asked important questions about complete receptor conformations in regards to different pharmacological ligand binding. The HDX data combined with the structural data emerging will really help everyone more fully understand how these receptors work."

"Using the HDX technology we can study the intact receptor upon interaction with ligands and pinpoint regions of the receptor that have undergone change in position or flexibility," Griffin said. "By studying a set of ligands one can start to develop patterns that are tied to activation of the receptor or shutting it down. Once we get a picture of what a functional ligand looks like, it might be possible to develop a drug to produce a highly selective therapeutic effect."

More information: "Ligand-Dependent Perturbation of the Conformational Ensemble for the GPCR b2 Adrenergic Receptor Revealed by HDX," Structure.

Provided by The Scripps Research Institute (news : web)

Need for new magnet materials drives ORNL research

Increasing demand and a shrinking supply of rare earth elements for magnets creates a perfect opportunity for a research team from Oak Ridge National Laboratory and the University of Minnesota. The goal is to create a recipe for a replacement that doesn't use scarce ingredients.

"Worldwide demand for rare earths is expected to exceed supply by some 40,000 tons annually by the end of this decade," said Larry Allard, a researcher in ORNL's Materials Science and Technology Division. "In the past, 95 percent of that material has been supplied to the world by China, but in recent years China has begun limiting exports and by 2015 is expected to become a net importer."

The prospect of not having enough rare earth elements such as neodymium and dysprosium for magnets looms large for industries that need them for products we count on every day.

Most people never give it a second thought, but magnets are used in everything from the motors that power hybrid vehicles and electric windows to windmills, computers and hundreds of items that touch our lives every day. The traction drive components of a Toyota Prius, for example, use about 2 pounds of magnet materials while a 3-megawatt windmill uses 550 pounds. Today's automobiles and light trucks each use between 70 and 150 magnets to operate the speedometer, odometer, gas gauge, antilock brake systems, air bag sensors, fuel pumps and dozens of other systems.

In the home, magnets are even more common as they are found in door chimes, security systems, personal computers, printers, telephones, furnaces and air conditioning systems, garage door openers, refrigerators, freezers, workshop tools, hair dryers and electric shavers. It's difficult to imagine a world with no magnets. From an economics and national security perspective, it would be catastrophic.

That's why researchers like Allard, Edgar Lara-Curzio and Mike Brady of ORNL and Jian-Ping Wang of the University of Minnesota are focused on developing magnets made from abundant and inexpensive materials. Of specific interest is an iron nitride compound with a specific phase that potentially exhibits the highest saturation magnetization ever reported for a material.

"This is a critical parameter related to the highest degree to which a material can be magnetized," said Allard, who noted that this particular iteration of the iron-nitrogen compound has values up to 18 percent higher than the best commercial alloy, iron cobalt. The problem is that this material is metastable and exhibits relatively low coercivity, which means it can be demagnetized easily. The best permanent magnets - such as those made of neodymium-iron-boride - score high in these areas.

Working with Wang, Allard, Lara-Curzio and Brady will devise a method of producing this pure phase iron nitride compound and use specialized modeling methods to better understand the role of alloying additions that might stabilize the material so it retains its magnetic properties. Through their efforts, the researchers hope to better understand the magnetic behavior of the "alpha double prime" phase by correlating microstructure at the atomic level to processing and magnetic behavior.

Once researchers have answered these questions, their goal is to make bulk quantities of the material and move toward their ultimate goal of replacing neodymium-iron-boride magnets for automotive and other energy technology uses. This work with the University of Minnesota builds on previous work with Wang in which ORNL researchers were able to characterize iron nitride films with demonstrated potential. Allard noted that the Spallation Neutron Source made it possible to perform polarized neutron reflectometry, a test performed by Valeria Lauter to determine magnetic property.

In a separate effort, ORNL's David Parker hopes to computationally screen dozens of materials and then mix elements that emerge as promising candidates in a way to create a compound that will behave like rare earth elements. This material must also be scalable, retain its magnetic properties under varying conditions and meet cost-performance criteria. Parker noted that often the compounds identified as having desirable properties consist of elements with greatly differing melting points, stabilities and other traits and can prove very difficult to controllably manufacture. That's where ORNL's unique capabilities come into play.

"We have a suite of conventional and novel processing approaches to try to make the computationally predicted compounds, including a range of powder consolidation and gas reaction approaches," said Parker, who noted that there's nothing "sacred" about .

"Their main advantage is that due to their large nuclear charge, spin-orbit coupling is very strong and serves to fix the magnetization direction of the unpaired electrons," Parker said. "Other heavy elements may play the same role."

By employing strategic computational screening and ORNL's specialized microscopy and characterization skills, Allard and Parker believe they can make great strides toward solving a problem of national importance.

Provided by Oak Ridge National Laboratory (news : web)

Old fruit peel are the new healthy snacks

Old fruit peel are the new healthy snacks


A snapshot of Fruit-Peelo. Credit: UiTM

Japanese food researchers Noriham Abdullah, Marina Zulkifli, Mohd Hilmi Hassan, Wan Nur Zahidah Wan Zainon and Nur Ilmiah Alimin have developed a new healthy snack out of fruit peels to fulfil a growing need for fast, on-the-go health food.

There is a growing body of evidence suggesting health conscious consumers are becoming more experimental in selecting their healthier snacks alternatives. In response to this, a team of researchers from the Faculty of Applied Sciences used cheap and abundant agricultural by-products, such as mango and guava peels, to produce a leathery, bite size snacks called Fruity-Peelo.

Fruit peels contain high levels of polyphenols, carotenoids and other which offer various health benefits. In addition, utilisation of such by-products is a promising measure from an environmental as well as an economic point of view.

Dr. Noriham Abdullah, the lead researcher, says that Fruity-Peelo is a tasty convenience snack with long shelf life that contains healthy compounds such as antioxidants, dietary fibres and Vitamin C.

The growing concerns over climbing obesity levels, combined with efforts to rejuvenate the image of the on-the-go healthy , have further improved Fruity Peelo’s prospect to fulfil a growing demand for convenience snacks that are healthy, quick and unique.

Provided by Universiti Teknologi MARA



The secret to their low cost estimates actually lie in their newly developed method for making hydrogen, which they use to make their ammonia. They say that by using a new kind of transformer that Fleming built, they can reduce the number of cells necessary for electrolysis to such a degree that they can produce hydrogen at almost half the cost of traditional electrolysis methods.

To make the ammonia, the hydrogen produced is pumped into a compression chamber where a piston squeezes it, causing it to heat up; in this case to 400C°. The result is then allowed to escape into another compartment where a reaction is set off by an iron oxide catalyst. This makes the hydrogen grow even hotter to the point where it begins creating ammonia. The ammonia and leftover is then allowed to cool down and decompress in yet a third compartment, and in so doing causes another piston to move back and forth creating energy that is fed back into the system to help lower electric consumption. Then, the ammonia is chilled to -75C° and pumped into a tank for use.

Cars already on the road can use ammonia as an additive without modification (up to 10%) and flex cars could be, according to Fleming, easily modified to use ammonia in conjunction with ethanol, allowing for a mixture of 85% ammonia.

This is all still new technology of course, and apparently no one else has yet verified the claims of the duo, so until that happens, everyone will just have to wait and see if everything they say pans out. One thing not mentioned is the smell; the strong odor of gasoline at service stations is bad enough, it’s difficult to imagine the exceedingly noxious odor of permeating the air of such places instead.

More information: via Newscientist


Artificial light-harvesting method achieves 100% energy transfer efficiency



“In order to realize an artificial light-harvesting system, almost 100% efficiency is necessary,” Takagi told “Since light-harvesting systems consist of many steps of , the total energy transfer efficiency becomes low if the energy transfer efficiency of each step is 90%. For example, if there are five energy transfer steps, the total energy transfer is 0.9 x 0.9 x 0.9 x 0.9 x 0.9 = 0.59. In this way, an efficient energy transfer reaction plays an important role in realizing efficient sunlight collection for an artificial light-harvesting system.”

As the researchers explain in their study, a natural LHS (like those in purple or plant leaves) is composed of regularly arranged molecules that efficiently collect sunlight and carry the excitation energy to the system’s reaction center. An artificial LHS (or “artificial leaf”) attempts to do the same thing by using functional dye molecules.


“A molecular arrangement with an appropriate intermolecular distance is important to achieve nearly 100% energy transfer efficiency,” Takagi said. “If the intermolecular distance is too near, other reactions such as electron transfer and/or photochemical reactions would occur. If the intermolecular distance is too far, deactivation of excited dye surpasses the energy transfer reaction.”



As the researchers demonstrated, the regular arrangement of the molecules leads to an excited energy of up to 100%. The results indicate that porphyrin dye and clay host materials look like promising candidates for an artificial LHS.


More information: Yohei Ishida, et al. “Efficient Excited Energy Transfer Reaction in Clay/Porphyrin Complex toward an Artificial Light-Harvesting System.” Journal of the American Chemical Society. DOI:10/1021/ja204425u


Sunday, September 25, 2011



Overcoming these deficiencies with a unique approach, a team based at Kyoto University has designed an inexpensive new material capable of quick and accurate detection of a specific gas under a wide variety of circumstances. Moreover, in addition to being reusable, the compound gives off variable degrees of in correspondence with different gas concentrations, providing for development of easy to use monitoring devices.

The findings, published in a recent issue of , describe the use of a flexible (porous coordination polymer, or PCP) that transforms according to changes in the environment. When infused with a fluorescent reporter molecule (distyrylbenzene, or DSB), the composite becomes sensitive specifically to , glowing with varying intensity based on changing concentrations of the gas. Lead author for the paper was Dr. Nobuhiro Yanai of the university's Graduate School of Engineering.

"The real test for us was to see whether the composite could differentiate between carbon dioxide and , which have similar physiochemical properties," explains Assoc. Prof. Takashi Uemura, also of the Graduate School of Engineering. "Our findings clearly show that this PCP-DSB combination reacts very differently to the two gases, making accurate CO2 detection possible in a wide variety of applications."

In its natural state, DSB is a long, flat molecule, which emits a blue light. When adsorbed by the PCP framework, DSB molecules twist, causing the entire PCP structure to also become skewed. In this condition, the glow of DSB diminishes significantly.

"On this occasion we observed that the presence of CO2 causes the DSB molecules to revert to their flat, brightly fluorescent form, while also returning the PCP grid to its usual state," adds Professor and deputy director Susumu Kitagawa of the university's Institute for Integrated Cell-Material Sciences (iCeMS). "And importantly, these steps can be reversed without causing any significant changes to the composite, making possible the development of a wide variety of specific, inexpensive, reusable gas detectors."

More information: "Gas detection by structural variations of fluorescent guest molecules in a flexible porous coordination polymer" by Nobuhiro Yanai, Koji Kitayama, Yuh Hijikata, Hiroshi Sato, Ryotaro Matsuda, Yoshiki Kubota, Masaki Takata, Motohiro Mizuno, Takashi Uemura, and Susumu Kitagawa, Nature Materials, Published online on September 4, 2011.

Provided by Kyoto University