| In this dissertation, four different kinds of oxide, including γ-AlOOH, γ-Al2O3, CO3O4and CeO2, have been successfully synthesized by choosing non-hydrolytic, calcination and template approach, respectively. These strutures have been characterized by X-ray diffraction (XRD), X-ray energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), Ultraviolet-visible spectrometer (UV-vis), Fourier transform infrared Spectroscopy (FT-IR), laser Raman scattering spectroscopy, fluorescence spectroscopy. Some new and interesting physicochemical properties are found in the obtained nanostructures. The main results are as follows:1. For the first time, novel porous y-AlOOH nanostrips were formed in the mixed system of oleic acid, dodecylamine, urea and1-octadecene. From the various literature studied, it is noticed that the most common strategy for synthesizing AlOOH is generally conducted in aqueous or aqueous-organic solvents to disperse reactants where water is used for hydrolysis. However, as aluminum alkoxide is very reactive to water and precipitates quickly, the morphology of alumina is difficult to control and the nanoparticles are easy to aggregate. The nonhydrolytic approach is an attractive alternative to conventional aqueous solvents for well-defined boehmite nanostructure formation. Water was not added to this one-pot reaction process directly, instead, the in situ generated water through the intermediate step likely fuels the reactions. Thus the controlled hydrolysis would decrease the reaction rate and facilitate the formation of a well-defined nanostructure instead of precipitate. In previous studies, urea generally was used to manipulate the pH during the process of preparing γ-AlOOH under hydrothermal conditions. While in our studies, urea acted as porogen.2. Porous δ-Al2O3and γ-Al2O3strips could be obtained by thermal decomposition of γ-AlOOH precursor at different temperature. γ-Al2O3nanostrips could catalyze the oxidation of alizarin dramatically. Furthermore, the silver nanoparticles, a relatively cheap and rich metal, were successfully supported on the porous γ-Al2O3to form Ag/γ-Al2O3composite. The size of the Ag NCs was mainly in the range of10-12nm. The prepared Ag/γ-AlO3displayed superior catalytic activity in the hydrogenation of nitroaromatics compared with bare γ-Al2O3nanostrips, pure Ag NCs, Ag/Al2O3(amorphous) and Ag/γ-Al2O3(amorphous). The excellent catalytic performance of the nanocomposites could be attributed to the strong synergistic interaction of Ag NCs with γ-Al2O3nanostrips.3. Monodisperse hollow CO3O4spheres were fabricated by a facile and low-cost soluble-starch-assisted method. XRD analysis and X-ray photoelectron spectroscopy showed that the obtained samples were pure cube phase product. Raman experimental results revealed that the obtained hollow CO3O4spheres exhibited different vibration and scattering features compared with that of bulk-counterparts. Two optical band gaps (1.5eV and2.0eV) for the CO3O4samples could be calculated from the UV-vis absorption spectrum. Electrochemical properties of the CO3O4electrodes were carried out using galvanostatic charge-discharge measurements.4. Novel CeO2nanosuare slice and Ag/CeCh nanocomposites were successfully prepared with (NH4)2Ce(NO3)6as raw material in the mixed system of oleic acid, dodecylamine and1-octadecene. The size of CeO2nanosuare slice is quite small, only about7nm. XRD analysis and X-ray photoelectron spectroscopy(XPS) showed that the obtained samples were pure Ag/CeO2nanocomposites. No Ag2O by-product was detected in the obtained samples. Styrene was epoxidized by air under mild conditi ons using Ag/CeO2as catalyst. |
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