Photoelectrochemistry in particulate systems. 6. Electron-transfer reactions of small cadmium sulfide colloids in acetonitrile

Small colloidal CdS particles (particle diameter < 25-42 A) have been prepared in acetonitrile and their absorption and emission properties characterized. A transient bleaching was observed when CdS colloids were subjected to bandgap excitation with a 355-nm laser pulse. The recovery of the bleaching which consisted of at least two components has been attributed to the recombination of trapped charge carriers and to the process of anodic corrosion. The red emission of CdS colloid can be quenched with an electron scavenger such as methylene blue. The quantum yield for the reduction of oxazine and thiazine dyes varied from 0.04 to 0.08 and was dependent on the reduction potential of the dye. The electron-transfer reactions of CdS colloids have been investigated by using nanosecond laser flash photolysis and microwave absorption techniques.