Direct observation of charge separation on Au localized surface plasmons

Plasmonic nano-structures of d(10) metals are suggested to be the future of photo-voltaics and photo-catalysis under solar irradiation, thanks to their large light absorption cross-section, versatility, and stability. We investigated the impact of continuous plasmon excitation at 532 nm on the density of states of gold nanoparticles, and found an increase of the unoccupied density of d states of gold nanoparticles at the Fermi level, consistent with the formation of electron-hole pairs. Some of those electrons have sufficient energy to overcome the Schottky barrier, and be injected into the TiO2 conduction band. The results confirm that d(10) metal plasmonic structures can act as light sensitizers and photo-catalysts.