Photo-induced electron migrations in the nano-cavities of mesoporous silica sensitized by a cationic porphyrin dye.

Photo-induced redox reactions in a hybrid film of a cationic porphyrin dye (H2TMPyP) accommodated within a transparent mesoporous silica (MPS) film spin-coated on an FTO electrode have been investigated for such applications as the construction of efficient solar energy storage devices and novel light-stimulated sensors. In this system, anodic and cathodic photocurrents were observed under bias voltages of +0.3 V and -0.4 V, respectively. The action spectrum of the photocurrents corresponded well with the absorbance of the H2TMPyP molecules in the visible light region. Control experiments showed no photocurrents for the mesoporous silica without H2TMPyP. Our investigations showed that the H2TMPyP molecules function not only as a sensitizer but also as a mediator for electron migrations within mesoporous nano-cavities.