Spectroscopic evidence of a core-shell structure in the earlier formation stages of Au-Ag nanoparticles by pulsed laser ablation in water

Mixed Au-Ag nanoparticles were obtained by pulsed laser ablation of metallic targets, subsequently mixing and re-irradiating different volumes of each nano-colloid. The study of these colloids after different irradiation times, performed by spectral analysis in the plasmonic resonance ( PR) region, allows us to ascertain that solid solutions of Aginto Au nano-crystals are obtained after an initial formation of Au-core-Ag-shell nanoparticles. These findings are corroborated by fitting the PR spectra with a simulation model based on the Mie-Gans theory. X-ray photoelectron spectroscopy and transmission electron microscopy data support these results and their interpretation. (c) 2008 Elsevier B. V. All rights reserved.