Multilayer films (PW12-AA)(n) (PW12 = PW12O403-, AA = azure A, n is the number of PW12-AA bilayers) were prepared on solid slides via a layer-by-layer (LbL) self-assembly method. The growth of the films was characterized by UV-vis spectra, FUR spectra, and atomic force microscopy (AFM). The results show that the deposition process is linear and reproducible from layer to layer and the PW12 is intact during the self-assembly process. AFM images indicate that the film surface is smooth and uniform. Moreover, the photocatalytic property of the films was investigated by the decomposition of methyl orange (MO) under visible light irradiation (lambda > 420 nm). The multilayer films show photocatalytic activity for the degradation of MO under visible light irradiation using a xenon lamp and sunlight. The kinetics of the photodecomposition follows the first-order reaction. (C) 2010 Elsevier Inc. All rights reserved.