pH-Dependent photoinduced electron transfer at C-60-EDTA Langmuir-Blodgettfilm modified ITO electrode

The monolayer and multilayer films of an amphiphilic C-60-EDTA (C(60)EA) an d its tetramethyl ester (C60EM) were fabricated on semiconducting transpare nt ITO electrodes by the Langmuir-Blodgett (LB) technique. The photoelectri c response of the modified electrodes was measured under various conditions to explore possible mechanisms of the electron transfer in this Light harv esting and conversion system. The action spectrum of photocurrent implicate s the excited C(60)EA or C60EM as the photoactive species in the photoinduc ed electron transfer process. Anodic or cathodic photocurrent could be obse rved depending on the composition and concentration of redox agents in the solution and/or bias voltage applied. These results suggest that electron f low in either direction is energetically possible in the present photoelect ric chemical cell. When the pH in the solution was changed, the photocurren t of C(60)EA changed not only in its magnitude but also in its direction. E fficient photoinduced electron transfer was observed in the anodic directio n. The quantum yields for the photocurrent generation of C60EM and C(60)EA monolayer-ITO system are 4.80% and 3.80% under favorable conditions.