Shvalagin V. Spectral and photochemical properties of metal-semiconductor nanocomposites based on ZnO and CdS.

Factors affecting the size of ZnO and CdS nanocrystals in aqueous and alcoholic colloidal solutions, as well as their stability towards the aggregation have been studied. It has been shown, that the irradiation of colloidal ZnO and CdS solutions in the presence of electronodonors and metal ions (Ag(I), Cu(II), Cd(II), Ni(II), In(III) and others) results in the reduction of the metals and formation of metal-semiconductor nanocomposites. The effects of spacial exiton confinement and photoinduced cathodic polarization of ZnO and CdS nanoparticles on the rates of photochemical metal ions reduction in the presence of these semiconductors have been revealed and interpreted. Spectral and photochemical properties of the metal-semiconductor nanocomposites formed have been investigated, the effect of the irradiation on the parameters of the surface plasmon resonance absorption bands in electronic spectra of the composites has been studied. Increased photocatalytic activity of metal-semiconductor nanocomposites as compared to individual semiconductor nanoparticles in the reduction of Cu(II) to metal (ZnO/Ag composite), nitrobenzene to aniline (ZnO/Cu nanocomposite) in alcohols as well as hydrogen evolution from aqueous sodium sulfite solutions (CdS/Me, Me = Ni, Co, Cd, Fe etc.) has been found.