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.
Optically transparent poly(methyl methacrylate) films incorporated with CdS quantum crystallites are prepared by using pyridine-soluble phenyl-capped CdS microcrystallites (av. 2–8 nm). The morphology of the CdS in the films is characterized by UV-vis spectroscopy and TEM, and the film doped with av. 8-nm CdS is found to have large third-order nonlinearity by degenerate four-wave mixing technique.
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