Fabrication and photoelectrochemical properties of electron donor-acceptor assemblies via titanium oxide interlayers

Ultrathin molecular films consisting of electron donor (D)-acceptor (A) pairs via titanium oxide coordinative bonding have been fabricated on an indium-tinoxide electrode, by using the techniques of self-assembly and surface sol-gel process. Porphyrin and tris (2,2′-bipyridine) ruthenium (II) were used as D, while viologen as A, respectively. The degree of assembling of D and A were characterized by electrochemical and absorption measurements. In the case of the porphyrin-viologen pair, photocurrent generation based on photoinduced electron-transfer was realized, and multilayer formation of porphyrin increased the photocurrents. On the other hand, the ruthenium (II) complex-viologen pair showed very poor photocurrent responses, probably due to much poorer light absorptivity as compared with porphyrin.