Microscopic theory of surface-enhanced Raman scattering in noble-metal nanoparticles

TL;DR

This paper develops a microscopic model for SERS in noble-metal nanoparticles, emphasizing quantum-size effects and surface plasmon resonance, and calculates local field distributions and enhancement factors.

Contribution

It introduces a quantum-mechanical approach to analyze how size-dependent effects influence SERS enhancement in small noble-metal nanoparticles.

Findings

Quantum-size effects significantly modify electromagnetic enhancement in small particles.

Landau damping and reduced screening compete to determine SERS magnitude.

Calculated local field distributions vary with nanoparticle size.

Abstract

We present a microscopic model for surface-enhanced Raman scattering (SERS) from molecules adsorbed on small noble-metal nanoparticles. In the absence of direct overlap of molecular orbitals and electronic states in the metal, the main enhancement source is the strong electric field of the surface plasmon resonance in a nanoparticle acting on a molecule near the surface. In small particles, the electromagnetic enhancement is strongly modified by quantum-size effects. We show that, in nanometer-sized particles, SERS magnitude is determined by a competition between several quantum-size effects such as the Landau damping of surface plasmon resonance and reduced screening near the nanoparticle surface. Using time-dependent local density approximation, we calculate spatial distribution of local fields near the surface and enhancement factor for different nanoparticles sizes.