Photoelectrochemical properties of dye-containing langmuir-blodgett films prepared by polyion complex technique

The ionic-complex monolayer was formed at the air-water interface when a cationic amphiphile, such as a dialkylammonium amphiphile, an azobenzene amphiphile, and an azobenzene amphiphile having a viologen head, were spread on an aqueous subphase containing rose bengal and poly(vinyl sulfate). The pressure-area isotherm of the complex monolayer was expanding with increasing the concentration of the rose bengal. The polyion complex monolayer was deposited as a Y type LB film on an ITO electrode. The adsorption isotherms examined by the spectroscopic measurement show that the amount of the adsorbed dye is in proportion to its concentration of the subphase. A large sensitized cathodic photocurrent of ITO electrode was observed when the rose bengal incorporated in the dialkylammonium LB film was irradiated with visible light. But in the azobenzene LB films, the sensitization of the rose bengal was strongly suppressed. The excited state of the rose bengal is assumed to be quenched by the viologen and the azobenzene triplet.