Dendritic Effects on Structure and Photophysical and Photoelectrochemical Properties of Fullerene Dendrimers and Their Nanoclusters

Multifullerene-terminated dendrimers Gn (n = 1-5) were synthesized and structural, photophysical, and photoelectrochemical properties were studied for the fullerene dendrimers and their nanoclusters. The fullerene dendrimers formed clusters when toluene solutions of the fullerene dendrimers were injected into acetonitrile. Dynamic light scattering and atomic force and scanning electron microscopic measurements on these clusters revealed that the cluster size decreased with increasing the generation number of the dendrimers. The negatively charged clusters were deposited electrophoretically onto a nanostructured SnO2-coated ITO electrode by applying DC voltage to the electrode. Photoelectrochemical measurements were carried out in acetonitrile dissolved 0.5 M LiI and 0.01 M I2 with the standard three electrodes containing the fullerene dendrimer-modified SnO2 working electrode, a platinum wire as a counter electrode, and I-/I3- as a reference electrode. An incident photon-to-photocurrent efficiency of the dendrimer photoelectrochemical devices increased with increasing the generation number. Such a close relationship between the structure and photophysical and photoelectrochemical properties of the fullerene dendrimers and their nanoclusters will provide knowledge of photophysics regarding photoactive molecular assemblies with dendritic architectures.