PHOTOCHEMICAL FORMATION OF COLLOIDAL SILVER IN THE PRESENCE OF BENZOPHENONE

An aqueous silver perchlorate-sodium dodecylsulfate (SDS)-benzophenone (BP) solution was photolyzed with either UV or near-UV light. Irradia tion with 253.7 nm light, which was absorbed by both BP and silver ion s, brought about the formation of colloidal silver and the photobleach of BP. Peptization of colloidal silver agglomerates after prolonged i rradiation was ascribed to electron injection from the benzophenone ke tyl radical (BPK). The formation of colloidal silver and the photoblea ch of BP were also caused by irradiation with 365 nm light, which was absorbed solely by BP (sensitized reaction). A simple reaction scheme was introduced and the initial rates for the sensitized photoreduction of silver ions and the photobleach of BP were expressed in closed for ms. Suitable combinations of the kinetics parameters and the extinctio n coefficient of colloidal silver were proposed in order to interpret the dependences of the initial rates on the reactant concentrations.