Plasmon Enhanced Spectroscopy and Photocatalysis

TL;DR

This paper investigates how plasmon resonance enhances Raman scattering and facilitates charge transfer in molecules adsorbed on gold nanoparticles, combining computational methods with analysis of experimental phenomena.

Contribution

It provides a detailed computational study of plasmon-enhanced spectroscopy and photocatalysis, highlighting the role of adsorption sites and excitation energy.

Findings

Raman scattering enhancement factors of 3-15 due to chemical effects.

Larger plasmon resonance enhancements of 10^2-10^4 observed at 2.5 eV.

Charge transfer leading to negative ion formation upon plasmon excitation.

Abstract

This study examines the Raman scattering and charge transfer properties of molecules adsorbed on the surface of a tetrahedral Au$_{120}$ nanoparticle based on the time-dependent density functional tight-binding (TD-DFTB) method. We study Raman scattering (SERS) enhancements for pyridine where the molecule is adsorbed either on the tip (V complex) or surface (S complex) of the nanoparticle. The scattering intensity is enhanced by a factor of 3-15 due to chemical effects while significantly larger enhancements (in the order of 10$^2$-10$^4$) are observed for plasmon resonance excitation at an energy of 2.5 eV depending on the adsorption site. Furthermore, we demonstrate charge transfer between the nanoparticle and a fullerene-based molecule after pulsed excitation of the plasmon resonance which shows how plasmon excitation can lead to negative molecular ion formation. All of these results are consistent with earlier studies using either TD-DFT theory or experimental measurements.