Generation of reactive oxygen species and charge carriers in plasmonic photocatalytic Au@TiO2 nanostructures with enhanced activityElectronic supplementary information (ESI) available: Experimental details, Fig. S1-S6. See DOI: 10.1039/c8cp01978a

The combination of semiconductor and plasmonic nanostructures, endowed with high efficiency light harvesting and surface plasmon confinement, has been a promising way for efficient utilization of solar energy. Although the surface plasmon resonance (SPR) assisted photocatalysis has been extensively studied, the photochemical mechanism, e.g. the effect of SPR on the generation of reactive oxygen species and charge carriers, is not well understood. In this study, we take Au@TiO 2 nanostructures as a plasmonic photocatalyst to address this critical issue. The Au@TiO 2 core/shell nanostructures with tunable SPR property were synthesized by the templating method with post annealing thermal treatment. It was found that Au@TiO 2 nanostructures exhibit enhanced photocatalytic activity in either sunlight or visible light ( λ > 420 nm). Electron spin resonance spectroscopy with spin trapping and spin labeling was used to investigate the enhancing effect of Au@TiO 2 on the photo-induced reactive oxygen species and charge carriers. The formation of Au@TiO 2 core/shell nanostructures resulted in a dramatic increase in light-induced generation of hydroxyl radicals, singlet oxygen, holes and electrons, as compared with TiO 2 alone. This enhancement under visible light ( λ > 420 nm) irradiation may be dominated by SPR induced local electrical field enhancement, while the enhancement under sunlight irradiation is dominated by the higher electron transfer from TiO 2 to Au. These results unveiled that the superior photocatalytic activity of Au@TiO 2 nanostructures correlates with enhanced generation of reactive oxygen species and charge carriers. Plasmonic Au@TiO 2 core/shell nanostructures exhibit significant enhancement in the generation of ROS, charge carriers and photocatalytic activity.