title: Influences of acid on molecular forms of fluorescein and photoinduced electron transfer in fluorescein-dispersing sol-gel titania films.
abstract: Fluorescein-dispersing titania gel films were prepared by the acid-catalyzed sol-gel reaction using a titanium alkoxide solution containing fluorescein. The molecular forms of fluorescein in the films, depending on its acid-base equilibria, and the complex formation and photoinduced electron transfer process between the dye and titania surface were investigated by fluorescence and photoelectric measurements. The titanium species were coordinated to the carboxylate and phenolate-like groups of the fluorescein species. The quantum efficiencies of the fluorescence quenching and photoelectric conversion were higher upon excitation of the dianion species interacting with the titania, i.e. the dye-titania complex. This result indicated that the dianion form was the most favorable for formation of the dye-titania complex exhibiting the highest electron transfer efficiency. Using nitric acid as the catalyst, the titania surface bonded to the fluorescein instead of the adsorbed nitrate ion during the steam treatment. The dye-titania complex formation played an important role in the electron injection from the dye to the titania conduction band.
authors: Department of Environmental Science and Technology, Graduate School of Science and Technology, Shinshu University, Nagano, Japan.
authors: Hiromasa
authors: H
authors: Nishikiori
authors: Rudi Agus
authors: RA
authors: Setiawan
authors: Kyohei
authors: K
authors: Miyashita
authors: Katsuya
authors: K
authors: Teshima
authors: Tsuneo
authors: T
authors: Fujii