Surface-Enhanced Raman Scattering in Noble-Metal Nanoparticles : a Microscopic Approach

Abstract

Nanoparticles, surface plasmon, Raman scatteringWe present a microscopic model for surface-enhanced Raman scattering (SERS) from molecules adsorbed on small noble-metal nanoparticles. We demonstrate that, in nanometer-sized particles, SERS is determined by a competition between two distinct quantum-size effects : Landau damping of surface plasmon resonance and reduced screening near nanoparticle surface. The first mechanism comes from the discreteness of energy spectrum in a nanoparticle and leads to a general decrease in SERS. The second mechanism originates from the different effect of confining potential on sp-band and d-band electron states and leads to relative increase in SERS. We calculate numerically the spatial distribution of local field near the surface and the enhancement factor for different nanoparticles sizes.