Photoelectrochemical responses of optically transparent electrodes modified with Langmuir-Blodgett films consisting of surfactant derivatives of electron donor, acceptor and sensitizer molecules

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A novel electrochemical photodiode was fabricated by depositing complex Langmuir-Blodgett (LB) films which consists of an electron acceptor (A), a sensitizer (S) and an electron donor (D) surfactant derivative. In these surfactant molecules, violegen, pyrene and ferrocene moieties act as A, S and D units respectively. By arranging these three units on a gold optically transparent electrode regularly in space normal to the electrode surface, e.g. A/S/D or D/S/A, the photoinitiated vectorial flow of electrons could be achieved and was detected as photocurrents in a photoelectrochemical cell. The photocurrents had opposing directions depending on the spatial arrangements of A, S and D units in the film and the direction was in accordance with the energy level profile across the LB film. The photodiode function was also achieved by aligned amphiphatic triads which contain three functional units in each molecule.