Photochromism of Titanium Oxide Gels Prepared by the Salt-Catalytic Sol-Gel Process

Photochromism for the monolithic gel of titanium oxide prepared by the catalytic sol-gel process was observed. When hydrazine monohydrochloride was used as a catalyst, an intense blue color development was observed with the formation of Ti3+ on the irradiation of UV light (< ca. 350 nm). The degree of coloration and the recovery time were strongly affected by a kind of salt catalysts although the color was independent. Presence of active salt catalysts in the gel was indispensable for color development.