Formation of filament structures of noble-metal nanoparticles in transparent dielectrics under the action of continuous laser radiation

The formation of filamentary structures (up to 5 mm in length and 5–90 mm thick) of gold and silver nanoparticles (NPs) was studied in porous Vycor glass and polymer material (crosslinked oligouretanmetakrilate) doped with appropriate organic and inorganic precursors of these metals (H[AuCl4] · 4H2O, AgNO3, Ag(hfac)COD) under the action of continuous laser radiation in the visible wavelength range of 5–100 mW power. The formation of such structures along the direction of a laser beam was observed both in the course of laser exposure and after it ended. The mechanism of self-assembling of filaments from metal NPs is rationalized by the photolysis of precursor molecules in the zone of irradiation, the release of metal atoms, and their assembly into NPs. The very process of particle assembly in the filaments are ordered by the effects of self-focusing of laser radiation on a micro lens arising in the matter and channeling it into a medium with a varying refractive index. The features of formation of filamentary structures in the matrices under laser irradiation with different wavelengths are discussed.