Porphyrin monolayer-modified gold clusters as photoactive materials

Porphyrin monolayer-modified gold clusters (three-dimensional system) have been prepared successfully. Their electrochemical and photophysical properties have been compared to those of the corresponding two-dimensional system of self-assembled monolayers (SAMs) of the porphyrin as well as the bis(porphyrin) disulfide reference in solutions. In particular, the time-resolved single-photon counting fluorescence studies have indicated that the undesirable quenching of the porphyrin excited singlet state via energy transfer to the gold surface of the three-dimensional system is much suppressed, as compared to the quenching of the porphyrin SAMs on the two-dimensional flat gold surface. Thus, the present systems have a variety of potential utility for development of the artificial photosynthetic materials, photocatalysts, and chemical and biochemical sensors using fluorescent chromophore-monolayer modified gold clusters.