PHOTOELECTROCHEMICAL PROPERTIES OF SIZE-QUANTIZED CDS MICROCRYSTALS MODIFIED WITH VARIOUS AMOUNTS OF VIOLOGEN-FUNCTIONALIZED THIOL

Size-quantized CdS microcrystals (Q-CdS) modified with various amounts of electroactive 1-decyl-1'-(3-mercaptopropyl)-4,4'-bipyridinium dibr omide (VSH) and electroinactive decanethiol were prepared. The surface -modified VSH was photoreduced by irradiation of Q-CdS to give both di meric and monomeric radical cations of the viologen, and the formation of the former was enhanced by increasing the amount of the surface-bo und VSH. Kinetic analyses revealed that the rate constants for the red uction of the surface-modified VSH and for the reoxidation of the prod uced radical cations were independent of the amount of the VSH, Q-CdS having the higher amount of VSH showed the higher activity for electro n transfer to methylene blue in solution, evidencing that the surface- bound viologen mediated electron transfers from Q-CdS to the electron acceptor in solution.