Effects of elemental composition variations of Keggin polyoxometalates on photocurrent generation of their layer-by-layer self-assembled films with a hemicyanine dye.

A series of layer-by-layer electrostatically self-assembled films consisting of one of three Keggin-type polyoxometalates (POMs) of [BW 12 O 40 ] 5− , [PW 12 O 40 ] 3− and [PMo 12 O 40 ] 3− , and a hemicyanine of ( E )-1,1′-methylenebis(4-(4-(dimethylamino)styryl)pyridinium)bromide (H 1 Br 2 ) are prepared. The UV–vis absorption spectroscopy showed that the films were uniformly deposited with the visible absorption bands for the hemicyanine being bathochromically shifted with respect to the H 1 Br 2 aqueous solution to different extents depending on POMs. The (POMs/H 1 ) n films exhibited stable photocurrents that were differed by over 7 folds depending on POMs as irradiated with white light. The effects of applied bias voltages, electron acceptor added in the electrolyte, and layer numbers of the films, irradiated light intensities, and the compositions of POMs on photocurrent generation of the films were discussed. [ABSTRACT FROM AUTHOR]