Stability of colloidal solutions containing various surface-modified cadmium sulfide particles under stationary illumination

Abstract

Stability of the various colloidal solutions containing CdS particles with the surface modified by thiols such as thioglycerol (TG-CdS), mercaptophenyltetrazole (MPT-CdS), mercaptobenzimidazole (MBI-CdS), and mercaptoacetate (MA-CdS) (capped CdS particles) under the stationary illumination was studied by monitoring the changes in the absorption spectra to obtain knowledge about the influence of these capping agents on photocatalytic events such as electron and hole transfer processes at the capped semiconductor particle-solution interface. By the stationary illumination of the capped CdS particles, the photo-aggregation of the particles was observed in water and the photo-dissolution in organic solvents. The observed difference may be ascribed to the oxidative elimination of the capping agents from the CdS particles which occurs assisted by proton dissociation from the agents in water but not in organic solvents with aprotic nature. Addition of iodide which is known as a hole scavenger enhanced the photo-dissolution of both the capped and ordinary non-capped CdS particles, contrary to the expected photo-aggregation.