Surface Enrichment of Ag Atoms in Au/Ag Alloy Nanoparticles Revealed by Surface-Enhanced Raman Scattering of 2,6-Dimethylphenyl Isocyanide

Abstract

Surface-enhanced Raman scattering (SERS) of 2,6-dimethylphenyl isocyanide (2,6-DMPI) has been investigated with Au/Ag alloy nanoparticles His the adsorbing substrate. UV/visible spectra suggest the formation of alloy nanoparticles is taking place, in conformity with the mole fractions of gold and silver used initially in preparing the alloy sols; according to transmission electron microscopic images, the alloy sols are composed of spherical particles with diameters of similar to 35 lam irrespective of their composition, front pure Ag to pure Au nanoparticles. We have confirmed that the SERS spectral feature of 2,6-DMPI oil pure Ag is distinctly different froth that on pure Au. Furthermore, the SERS spectral feature of 2,6-DMPI oil Au/Ag alloy particles, even with a nominal composition of 95% Au and 5% Ag (Au(0.95)Ag(0.05)), is the same as that on pure Ag. The present observation Supports our previous Contention that the outermost layers of the Au/Ag alloy nanoparticles are highly enriched in Ag atoms compared with their interiors. SERS is thus proven to he all invaluable tool for the surface analysis of alloy metals.