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Monitoring the dispersion and agglomeration of silver nanoparticles in polymer thin films using localized surface plasmons and Ferrell plasmons

The ability to disperse metallic nano-objects in a given matrix material is an important issue for the design and fabrication of functional materials. A means to monitor the spatial distribution of the nano-dopants is highly desirable but often possible only a posteriori and with destructive techniques. Here we present a spectroscopic characterization based on different plasmonic responses of silver nanoparticles, their agglomerates, and finally the percolated silver film. We demonstrate its usefulness for the specific case of their dispersion in layer-by-layer polymeric films but the method is extendable to any other host material transparent in the visible/near UV range. Individual silver nanoparticles display the well-known localized surface plasmon resonance around 400 nm, which is red-shifted upon inter-particle coupling. The transition regime between weakly coupled particles and fully percolated metal films is, however, much harder to evidence unambiguously. We show here how to monitor this transition using the so-called Ferrell plasmon, a plasmonic mode of the thin film in the mid-UV, and excitable only under oblique irradiation but without specific coupling precautions. We can thus follow the entire transition from isolated to coupled and finally to fully agglomerated nanoparticles by optical spectroscopy.The ability to disperse metallic nano-objects in a given matrix material is an important issue for the design and fabrication of functional materials. A means to monitor the spatial distribution of the nano-dopants is highly desirable but often possible only a posteriori and with destructive techniques. Here we present a spectroscopic characterization based on different plasmonic responses of silver nanoparticles, their agglomerates, and finally the percolated silver film. We demonstrate its usefulness for the specific case of their dispersion in layer-by-layer polymeric films but the method is extendable to any other host material transparent in the visible/near UV range. Individual silver nanoparticles display the well-known localized surface plasmon resonance around 400 nm, which is red-shifted upon inter-particle coupling. The transition regime between weakly coupled particles and fully percolated metal films is, however, much harder to evidence unambiguously. We show here how to monitor this transiti...