Layer Layer Self-assembly Of Inorganic - Organic Nano-functional Composite Membrane

Inorganic-organic nanocomposite film materials with optical, electrical, and magnetic properties are one of the research focuses in contemporary materials science. My doctoral dissertation places emphasis on the preparation of polyoxometalate-based inorganic-organic nanocomposite films with interesting luminescent or electrically conductive properties. By means of the layer-by-layer self-assembly technique, ordered and stable inorganic-organic nanocomposite films consisting of europium-containing lanthanide polyoxometalates (including [Eu(P2W17O61)2]17-, [Eu(SiW11O39)2]13-, and [Eu(W5O18)2]9-) andpolyelectrolytes, a Keggin-type polyoxometalate [a-SiW12O40]4- and partially doped polyaniline, [a-SiW12O40]4- and two organic dyes (Rhodamine B and Rhodamine 6G), respectively, have been fabricated. In addition, ZnS nanoparticle-containing multilayer films have been prepared by combination of the layer-by-layer self-assembly technique with in situ chemical reaction. The composition, structure, and properties of the as prepared composite films have been characterized in detail by UV-vis, FTIR, and X-ray photoelectron spectra, ellipsometry, scanning electron microscopy, atomic force microscopy, transmission electron microscopy, fluorescence spectroscopy, and standard four-probe technique.The experimental results show that the above inorganic and organic components were incorporated into the composite films and their identities were preserved. The characteristic absorbances and film thicknesses of the films increased with the number of bilayers and also with the deposition solution concentrations. The composite films exhibited linear (or nearly linear), uniform, and regular layer-by-layer growth in a wide range of deposition solution concentrations. The films showed a uniform and smooth surface in a large area and good environmental and thermal stabilities. The ZnS nanoparticles were well-dispersed in the multilayerfilms with sizes of ca. 30-40nm. The composite films comprising europium-containing lanthanide polyoxometalates all exhibited the characteristic red light emissions of Eu3+ ion and the emission intensity increased with the number of bilayers. The films made up of Keggin-type [a-SiW12O40]4- polyanion and polyaniline had conductivities with a magnitude of 10-3 S cm-1. The composite films assembled from [a-SiW12O40]4- and dye molecules showed characteristic luminescence of the dyes and the emission intensity increased almost linearly with the number of bilayers. Moreover, extremely high luminescent intensity of the composite films can be obtained by using dye solutions with very low concentrations. Further, the multilayer films containing ZnS nanoparticles exhibited blue light emission resulting from ZnS nanoparticles.