荧光素衍生物LB膜对TiO_2电极的光敏化作用

Photosensitization of the LB Films of Fluorescein Derivatives on n-TiO_2 Film Electrode

合成了三种荧光素长碳链衍生物，通过LB技术将它们组装成单分子薄膜，修饰在用溶胶-凝胶法制备的TiO2透明电极上，研究了这些LB膜的结构和特性及它对TiO2的光增感作用．并对其光敏化机理作了阐述．

The photoelectrochemical semiconductive films of the n-type TiO2 prepared from tetrabutyl titanate through sol-gel method by dip-coating technique has been investigated. In order to sensitize this kind of uniform transparent TiO2 films, dye modification is one of the effective ways. Three kinds of fluorescein surfactant derivatives containing long hydrocarbon chains were synthesized and could form good quality LB films. The behavior of the monolayer of fluorescein derivatives on subphase, their periodic structure,the absorption spectra and chemically modified electrode of the LB films have been investigated. It was found that the monolayer on air-water interface was stable, and its collapse pressure was up to 50 mN·m-1, and the average area occupied by each fluorescein derivative molecules in the monolayer is in good agreement with the theoretical calculation. The monolayer thickness was measured to be 21-24A by the X-ray diffeaction technique. By the absorption spectra and fluorescence spectra, it was proved that the LB films of fluorescein surfactant derivatives were successfully transferred onto the TiO2 film electrode which was prepared with SnO2-coated glass plate by sol-gel method, and were in direct contact with the semiconductor. The photocurrents and quantum yields of both the TiO2 film electrode modified with fluorescein adsorbate and the LB films are greater than that of the bare one around the maximum absorption of dyes (400-00nm). This photosensitization can be explained by a energy model for the electron injjection.