Effects of Clay Nanosheets on the Photostability of Cationic Porphyrin.

The photodecomposition behavior of cationic porphyrin ZnTMAP 4+ (zinc tetrakis-( N , N , N -trimethylanilinium-4-yl) porphyrin) in water and complexed with clay nanosheets was investigated by light irradiation to the Soret band of ZnTMAP 4+ . The decomposition of ZnTMAP 4+ was observed by UV-visible absorption spectroscopy. While the decomposition quantum yield ( ϕ dec ) was 3.4 × 10 -4 in water, that was 9.4 × 10 -7 on the exfoliated clay nanosheets. It was revealed that the photostability of ZnTMAP 4+ was stabilized by the complex formation with clay. When ZnTMAP 4+ was intercalated between the stacked clay nanosheets, ϕ dec was further decreased to 4.9 × 10 -7 . The photostability increased by 361 times and 693 times for the exfoliated and stacked state, respectively. These results indicate that the flat clay surface has the potential to control intra- and intermolecular photochemical reactions.