A nanosized composite film based on polyoxometalate anion [Eu(SiW10VO39)(2)](15-) (EuSiWV) and polyethyleneimine (PEI) has been synthesized by layer-by-layer (LBL) self-assembly. The components and growth processes of the film have been determined by X-ray photoelectron spectra and ultraviolet-visible absorption spectra. The results showed that the composite film was formed by the alternate adsorption of EuSiWV and PEI, and the deposition process was quantitative and highly reproducible from layer to layer. Atomic force microscopy images indicated that the surface of the film was relatively uniform and smooth. The EuSiWV salt aggregated into nanoclusters with approximately 10 nm mean grain size, distributing on the surface uniformly. The surface roughness was approximately 2.4 nm. Fluorescence properties of the film were consistent with those of the solid sample, exhibiting obvious activity of fluorescence and incarnating the characteristic luminescence of Eu3+. In addition, the electrochemical behavior of the film has also been investigated, demonstrating that the electrochemical property of EuSiW10V was fully maintained in the LBL film. (C) 2003 Elsevier B.V. All rights reserved.