Multi Polyoxometalates Preparation And Characterization Of The Multi-function Film

The studies on inorganic-organic composite films of polyoxometalateshave drawn more and more attention owing to their potential applicationsin luminescence, photochromism, magnetism, electrics and catalysis. Thiswork deals with the preparation of the polyoxometalate-basedinorganic-organic film materials with multifunctions. Theinorganic-organic luminescent nanocomposite films of{PEI/(EuSiWV/PEI)n}, {PEI/(EuSiWMo/PEI)n}, and {PEI/(PSS/PEI/PMo12/Ru(bpy))n} were prepared by layer-by-layer technology. Thebiologically active films of {PDDA(SiW11Co P2O7)n} and{PDDA(SiW11CoPO4)n}based on polyoxometalates with pendant surfaceligands, were prepared by layer-by-layer method, too. The charge-transfersalts conducting thin films of (ET)5VW5O19 and (ET)11P2W18O62 werefabricated by electrochemical process. The components, structures andproperties of these films were characterized by ultraviolet-visibleabsorption spectra, X-ray photoelectron and Raman spectra, scanningelectron microscopy, atomic force microscopy, transmission electronmicroscopy, fluorescence spectroscopy, and cyclic voltammetry. These measurements showed that the above-mentionedinorganic-organic components were incorporated into the composite filmsand their original structures and properties remained in the films. Thegrowth processes of the assembled films were quantitative and highlyreproducible from layer to layer. The surfaces were smooth and weredispersed with uniform spherical particles. The films of{PEI/(EuSiWV/PEI)n} and {PEI/(EuSiWMo/ PEI)n} showed thecharacteristic luminescence of Eu3+. In addition, compared with the solidpolyoxometalates, the transition of nonradiative reduced, and thus theexcitation energy was more efficiently transferred from LMCT levels toEu3+ levels, which improved the fluorescence efficiency. The film of{PEI/(PSS/PEI/PMo12/Ru(bpy))n} presented the behavior of thephotoluminescence of Ru(bpy) and emitted red light excited by visiblelight. The films based on polyoxometalates with pendant surface ligandswere used to immobilize the DNA molecules through the surface pendantgroups, which possessed potential biological activity. All these iiself-assembly films exhibited favorable electrochemical behaviors ofpolyoxometalates. Furthermore, the conductivity of theoe charge transfersalt films vertical to the surface of the substrate fell into semiconductorcategory with the order of magnitude of 10－3Scm-1.