Magnetic field effects on photoelectrochemical reactions of modified electrodes with C60-phenothiazine nanoclusters

Magnetic field effects on the photoelectrochemical reactions of photosensitive electrodes modified with C60 nanoclusters were examined, intended for the development of nanodevices where photofunctions were controllable with magnetic field. Mixed clusters of a C60 derivative (C60N+) containing a positive charge and methylphenothiazine (MePH) were prepared by dissolving them in the THF-H2O mixed solvent. Diameters of the clusters were estimated to be ca. 100 nm from dynamic light scattering and AFM measurements. Photofunctional electrodes with the nanoclusters of C60N+ and MePH were fabricated on the electrodes modified with a self-assembled monolayer of HS(CH2)2SO3−Na+ on a gold substrate. The photocurrent action spectrum of the cluster-modified electrode strongly indicates that the photocurrents are ascribed to the photoexcitation of the nanoclusters of C60N+. Furthermore, the photocurrents increased with increasing an external magnetic field, typically 3% at 0.5 T. The profile of magnetic field dependence on the photocurrents is in good agreement with the results on the dynamics of radical pair in the nanoclusters of C60N+ and MePH in the THF-H2O mixed solvent. This is suggested that the magnetic field effects are ascribable to the contribution of triplet radical pair that are generated by photoinduced intermolecular electron-transfer from MePH to triplet excited state of nanocluster of C60N+, and are explained in terms of spin-lattice relaxation mechanism in radical pair mechanism.