Kinetics of photoinduced changes in Ag nanoparticles deposited on an indium tin oxide surface

An enhancement of the UV-visible optical absorption spectra of Ag nanoparticles (NPs) deposited on indium tin oxide (ITO) surfaces of different resistance by a seed-mediated growth technique is presented. A bicolour coherent beam, obtained from a pulsed Nd: YAG laser providing a 1060-nm fundamental wavelength and a double-frequency one at 530 nm, was used. A significant change in the optical density is observed for Ag NPs on low-resistance ITO surfaces (approximate to 4 Omega/square), while almost nothing occurs with high-resistance ( approximate to 50 Omega/square surfaces). The spectral position of the maximal absorption at 440 nm is almost preserved in both cases. This result is explained in terms of a local photoinduced static field and surface-plasmon polaritons interacting with photoexcited phonons. A grating effect, arising from the coherent bicolour light forming a superstructure as for quantum crystals, could be another contribution.