Semiconductor Photocatalysis: Size Control of Surface-Capped CdS Nanocrystallites and the Quantum Size Effect in Their Photocatalysis

Article abstract of DOI:10.1246/bcsj.68.752

Size-controlled CdS nanocrystallites were prepared by using thiophenol or hexanethiol as a capping reagent by controlling the ratio of Cd²⁺ to bis(trimethylsilyl) sulfide (S(TMS)2) as a source of the sulfide ion in reversed micelles.Their solubility and photocatalysis were examined.A series of size-controlled phenyl-capped CdS nanocrystallites catalyze the photoreduction of aromatic ketones in the presence of triethylamine as an electron donor under visible-light irradiation.The photocatalytic activity is affected by the particle size, i.e., the reducing power of the photogenerated electron on CdS nanocrystallites toward the ketones increases with decreasing the particle size.The enhancement of photocatalytic activity observed by reducing the particle size should be ascribed to not only a negative shift of the conduction band edge, but also suppression of the formation of surface defects.