Laser-induced agglomeration of gold and silver nanoparticles dispersed in liquid

•Picosecond laser exposure leads to formation of elongated Au-Ag NPs.•Laser-induced fragmentation is followed by NPs agglomeration in form of nano-chains.•Aggregates consisting of both Au and Ag NPs are formed prior to alloy formation.•Laser-induced agglomeration is hypothetically assigned to excessive charge of NPs.

Evolution of size distribution function, morphology, and extinction spectra of Ag nanoparticles and Au-Ag nanoparticles mixture dispersed in liquids under picosecond laser exposure are experimentally studied. It is shown that picosecond laser exposure of dense aqueous solutions of NPs (above 1014 particles per ml) leads to formation of elongated agglomerates. Time dependence of the size distribution function is monitored during irradiation process and compared to optical spectra and Transmission Electron Microscope images. Exposure of Au-Ag nanoparticles mixture is shown to result in formation of NPs chains consisting of Au and Ag, or Au-Ag alloy NPs.

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