Plasmon Enhanced Spectroscopy and Photocatalysis

This study examines the Raman scattering and charge transfer properties of molecules adsorbed on the surface of a tetrahedral Au₁₂₀ nanoparticle based on the time-dependent density functional tight-bonding (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 10²-10⁴) 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.