Photoinduced Charge Transfer from a Semiconductor to a Metal Probed at the Single-Nanoparticle Level

Decorating semiconductors with noble metals may significantly enhance the efficiency of photocatalysis. Probing photoinduced charge transfer (PICT) between semiconductors and noble metals at the single-nanoparticle level is of crucial importance for the rational design of photocatalytic systems, because it helps extract individual structure–function relationships that would be lost in ensemble measurements. Herein, we systematically investigate the PICT behavior of an individual gold nanorod (Au NR) on a TiO2 single crystal under UV laser irradiation by single-nanoparticle scattering spectroscopy. We quantitatively correlate the shift of the surface plasmon resonance (SPR) frequency of a single Au NR with the number of photogenerated electrons under UV laser irradiation. Our results show that the PICT process is accompanied by the desorption of surface oxygen and the formation of oxygen vacancies (VO) in TiO2. Our research may shed light on the essence of PICT on semiconductor–metal nanostructures for more efficient photocatalytic energy conversion.