EFFECT OF IMMOBILIZED ELECTRON RELAY ON THE INTERFACIAL PHOTOINDUCED ELECTRON-TRANSFER AT A LAYERED INORGANIC-ORGANIC COMPOSITE FILM ON GOLD

A layered composite film of CdS nanoparticles and a 1,6-hexanedithiol self-assembled monolayer (SAM) fabricated on a gold substrate was modi fied with 11-ferrocenylundecanethiol (FcC(11)SH), which is expected to act as an electron relay, by immersion into its hexane solution. X-ra y photoelectron spectroscopy and electrochemical measurements revealed that FcC(11)S(H) is mainly located on the gold surface, and partly on the CdS nanoparticle layer. The FcC(11)SH modification induced a sign ificant difference in the photoelectrochemical characteristics of the composite film. The photocurrent increased and decreased at potentials more positive and negative than the redox potential of the ferrocene moiety, respectively, leading to a positive shift in the onset potenti al for the photoinduced anodic current. A change in the transient phot oresponse was also observed. Efficient electron transfer by the ferroc ene moiety immobilized between the gold substrate and the CdS nanopart icle layer accounts reasonably for the behavior mentioned above. (C) 1 998 Elsevier Science S.A. All rights reserved.