Luminescent multilayer film based on mixed-addenda polyoxometalates and polyethyleneimine by layer-by-layer assembly

A luminescent multilayer film has been fabricated from mixed-addenda polyoxometalate anion [Eu(SiW4Mo7O39)2]13- (EuSiWMo) and polyethyleneimine (PEI) through electrostatic layer-by-layer self-assembly (LBL). The fabrication processes of the film have been monitored by UV-Vis absorption spectra. The results indicated that the composite film was formed by the alternate adsorption of EuSiWMo and PEI, and the layer growth was linear and highly reproducible from layer-to-layer. The elemental composition of the film was obtained from X-ray photoelectron spectrum (XPS). The data of XPS confirmed the presence of the expected elements. The film was smooth and homogeneous as indicated by atomic force microscopy images (AFM). The close-packed nanoclusters of the conglomeration of EuSiWV anions, with a mean grain size of ca. 60 nm, are distributed on the surface uniformly. The mean interface roughness estimated by AFM is about 3.8 nm in an area of <F>2.0×2.0</F> μm2. The film exhibited characteristic emission bands of rare-earth ions, consisting with those of the solid sample. In addition, the electrochemical behavior of the film was investigated by cyclic voltammetry, indicating that the electrochemical property of EuSiWMo was fully maintained in the LBL film. [Copyright &y& Elsevier]