Plasmon-induced oxidation of gold nanoparticles on TiO2 in the presence of ligands.

The mechanism of plasmon-induced charge separation of gold nanoparticles (Au NPs) on TiO2 was investigated with the help of anionic ligands. Au NPs are oxidized in the presence of KX (X = SCN, Br or Cl), chiefly via direct oxidation to [AuX4](-). The reactivity of Au NPs depends on the solution pH, the type of anion ligands and the excitation wavelength, suggesting that the photopotential of Au NPs during plasmon-induced charge separation depends on both the flatband potential of TiO2 and the energy of irradiated photons. The results indicate that the reactivity and efficiency of the plasmon-induced charge separation and accompanying reactions can be tuned and optimized by changing those factors.