Competition between extinction and enhancement in surface enhanced Raman spectroscopy

TL;DR

This paper investigates the complex interplay between enhancement and extinction in surface enhanced Raman spectroscopy using metallic nanoparticles, revealing counterintuitive effects and providing a theoretical framework for optimization.

Contribution

It introduces an effective medium theory that explains the competition between enhancement and extinction in SERS, guiding optimal experimental conditions.

Findings

Raman signal vanishes at nanoparticle plasmon resonance.

Increasing nanoparticle concentration can decrease SERS signal off-resonance.

Optimal excitation wavelength and nanoparticle parameters are identified.

Abstract

Conjugated metallic nanoparticles are a promising means to achieve ultrasensitive and multiplexed sensing in intact three-dimensional samples, especially for biological applications, via surface enhanced Raman scattering (SERS). We show that enhancement and extinction are linked and compete in a collection of metallic nanoparticles. Counterintuitively, the Raman signal vanishes when nanoparticles are excited at their plasmon resonance, while increasing nanoparticle concentrations at off-resonance excitation sometimes leads to decreased signal. We develop an effective medium theory that explains both phenomena. Optimal choices of excitation wavelength, individual particle enhancement factor and concentrations are indicated.