Nanostructured artificial photosynthesis

We have proposed a novel strategy for artificial photosynthesis where porphyrins and fullerenes are assembled as building blocks into nanostructured artificial photosynthetic systems by the help of self-assembled monolayers. Photodynamical studies on porphyrin-fullerene-linked systems revealed that fullerenes accelerate photo-induced electron transfer and charge-shift and slow down charge recombination, which is in sharp contrast with the modalities of conventional two-dimensional aromatic acceptors such as quinones and imides. We proposed and demonstrated, for the first time, that such electron transfer properties are attributable to the small reorganization energies of fullerenes, which make it possible to optimize artificial photosynthetic multistep charge separation. The multistep electron transfer strategy was combined with our finding that fullerenes have small reorganization energies, which are well-suited for the construction of light energy conversion systems as well as artificial photosynthetic models. Highly efficient photosynthetic energy and electron transfers were realized at gold and indium-tin oxide (ITO) electrodes modified with self-assembled monolayers of porphyrin-fullerene-linked systems. Porphyrin-modified gold nanoclusters were found to have potential as artificial photosynthetic materials and photonic molecular devices. These results provide basic principles and concepts for the development of nanostructured artificial photosynthetic materials as well as molecular devices. (C) 2003 Japanese Photochemistry Association. Published by Elsevier Science B.V. All rights reserved.