Photoinduced Electron Transfer between the Anionic Porphyrins and Viologens in Titania Nanosheets and Monodisperse Mesoporous Silica Hybrid Films

Photoinduced electron transfer between an anionic porphyrin derivative (tetrakis(p-carboxyphenyl)porphyrin; H2TCPP4-) and an electron accepting methyl viologen (MV2+) was investigated in two different nanoscale configurations, i.e., layered titania nanosheet (TNS) photocatalysts and ammonium-functionalized monodisperse mesoporous silica (AMMSS) particles. Cationic MV2+ intercalated within the TNS interlayers while anionic H2TCPP4- was accommodated within AMMSS nanocavities to form (MV2+-TNS)/(H2TCPP4--AMMSS) hybrid films. Upon irradiation with UV light and excitation of the TNS in the (MV2+-TNS)/(H2TCPP4--AMMSS) hybrid films, the consumption of H2TCPP4- and the formation of a one-electron reduced MV2+ (MV+center dot) were simultaneously observed. No consumption of H2TCPP4- was observed when an electrically insulating poly(styrene) (PS) was also introduced at the interface. These results suggest that photoinduced electron transfer occurred at the interface between the TNS and the AMMSS.