Photoinduced electron transfer from synthetic chlorophyll analogue to fullerene C60 on carbon paste electrode

Upon a carbon paste electrode, fullerene C₆₀ and successively methyl pyropheophorbide-a (chlorin) were casted to prepare a chlorin–fullerene modified carbon paste electrode (CFE). Photocurrents on the CFE were produced by irradiating of visible lights (>510 nm) in an aqueous solution of 0.05 M ethylenediaminetetraacetic acid and 0.1 M Na₂SO₄ at pH 6.7. Larger anodic photocurrent was induced by the CFE than by the carbon paste electrodes modified with either the fullerene or the chlorin. In addition, the photocurrent of the CFE was dependent upon the amount of fullerene casted. The photocurrent action spectra of the CFE (at 300 mV vs. Ag/Ag⁺) showed that photoinduced electron transfer occurred from the excited state of the chlorin to the fullerene and/or from the chlorin to the photoexcited fullerene, and the electron of the fullerene anion radical produced was then shifted to the carbon paste. Upon irradiation of >375 nm lights, the anodic photocurrent of the CFE was enhanced by increase in the illuminated light power and reached 0.03 mA cm⁻² in the present system.