pH-Dependent photoinduced electron transfer at C60-EDTA Langmuir-Blodgett film modified ITO electrode

The monolayer and multilayer films of an amphiphilic C-60-EDTA (C(60)EA) and its tetramethyl ester (C60EM) were fabricated on semiconducting transparent ITO electrodes by the Langmuir-Blodgett (LB) technique. The photoelectric response of the modified electrodes was measured under various conditions to explore possible mechanisms of the electron transfer in this Light harvesting and conversion system. The action spectrum of photocurrent implicates the excited C(60)EA or C60EM as the photoactive species in the photoinduced electron transfer process. Anodic or cathodic photocurrent could be observed depending on the composition and concentration of redox agents in the solution and/or bias voltage applied. These results suggest that electron flow in either direction is energetically possible in the present photoelectric chemical cell. When the pH in the solution was changed, the photocurrent of C(60)EA changed not only in its magnitude but also in its direction. Efficient photoinduced electron transfer was observed in the anodic direction. 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.