Immobilization of photosynthetic pigments into silica-surfactant nanocomposite films

Highly transparent silica-surfactant nanocomposite films containing photosynthetic pigments have been successfully formed through the solubilization of chlorophyll a (Chl a) into surfactant micelles. The UV-vis absorption spectra indicated that a large amount of Chl a were transformed into pheophytin a in the films. These photosynthetic pigments were well dispersed in the surfactant assemblies and their chlorin rings were exposed to the surface of silica layers. Even under an air atmosphere, the photostability of immobilized pigments was largely improved in comparison with that in a homogeneous Chl a solution. Because both Chl a and pheophytin a molecules are effective for the photosensitive charge separation, the present film system is very suitable for heterogeneous immobilizing media for photosynthetic pigments from the viewpoint of in vitro biomimetic devices for solar energy conversion.