Photocurrent Switching Effects in TiO2 Modified with Ruthenium Polypyridine Complexes

Selected ruthenium complexes [Ru(trpy)L], [Ru(bpy)2L], and [Ru(dcbpy)2L] were chemisorbed onto the surface of nanocrystalline titanium dioxide. The ligands (L) were Cl ions or cyanodithioimidocarbonate (C2N2S2), so the type of linkage with the TiO2 surface was different in each case. The resulting materials were sensitive to visible light. Photoelectrochemical studies revealed significant, potential-dependent photosensitization in the 300–650 nm window. In addition, the direction of the photocurrent could be switched from cathodic to anodic and vice versa by application of adequate external potential. Further photoelectrochemical, spectroscopic and theoretical studies allowed prediction of the possible mechanism of current switching. The photoelectrochemical properties of those materials allow construction of optoelectronic ternary logic devices.