Photochemistry of semiconductor colloids. 22. Electron ejection from illuminated cadmium sulfide into attached titanium and zinc oxide particles

摘要: Colloidal solutions of CdS containing colloidal TiO, or ZnO were illuminated with visible light. The fluorescence (decay time -50 ns) was quenched by Ti02, several Ti02 particles being required per particle. rate photoanodic corrosion in aerated solution drastically increased the presence In deaerated methanol and Cd2+ ions, cadmium metal formed when present. Methyl viologen reduced a quantum yield close to one, while it reacted about ten times more slowly absence These effects are explained terms improved charge separation rapid electron injection from into conduction band attached particles. Electron less efficient occurred only case Q-CdS (very small having greater gap). injected electrons caused blue shift absorption threshold ZnO. photocatalytic action suspended semicon- ductor is based on generation positive holes which rapidly move surface initiate redox processes. efficiency often contacting semiconductor particle another semiconductor. Typical examples platinized ti- tanium dioxide' sulfide2 as well Ru02-covered Ti02.3 Serpone et al. reported few years ago that H2 H2S powder light aqueous slightly powder! effect an due transfer increase 20%, Le., little above could be internal scattering additive. present paper, experiments transparent additives described. Efficient excited part "sandwich" colloids observed three methods observation: (1) With use colloid fluoresces high yield, quenching added studied. (2) Redox processes, such reduction excess ions methyl dissolution CdS, initiated illumination influence investigated. (3) additive, accompanied typical changes spectrum have recently been other deposition particles.s-6