Effects of Sensitizers on the Photosensitivity of Chemically Modified Al₂O₃ Gel Films

Abstract

The effects of acetophenone and benzophenone on the photosensitivity of Al₂O₃ gel films chemically modified with benzoylacetone have been studied. Benzophenone was found to accelerate the dissociation of remaining chelate rings and densification of the gel films on UV-irradiation, whereas acetophenone was little effective. To get insight on the mechanism of sensitization by benzophenone, the effects of excitation wavelength were studied using two different excimer lasers: KrF (249nm) and XeF (351nm), nearly corresponding to the π-π* (252nm) and n-π* (335nm) transitions of benzophenone, respectively. The photolysis rate of the chelate rings in the benzophenone-containing gel films was the same as that of the undoped films for KrF (249nm) laser irradiation, while it was higher than the latter for XeF (351nm) laser irradiation. It was also found that the photolysis rate of the chelate rings was decreased by drying the gel films for a given amount of benzophenone. These findings indicate that the sensitization by benzophenone is associated with the excitation of n-π* transition of benzophenone and the abstraction of H atom from residual i-PrOH solvent in the gel films. Furthermore, the fine-patterning characteristics of modified Al₂O₃ gel films containing benzophenone were examined.