The Investigation For Synthesis And Properties Of Low Dimensional Functional Oxides Nanomateriais

Due to their unique physical and chemical properties, low-dimensional metal oxide nanomaterials show signifaicant research value and wide applications in the fields of catalysis, optoelectronics, sensing, magnetics, electrochemistry and bio-medicine, etc. Preparation of nanomaterials with well-defined size, morphology, dimensionality through novel synthetic approaches and fabrication of functional systems with nanostructures, should have crucial influence on their real applications. In this dissertation, the investigation was focused on the two kinds of important metal oxides—vandium oxides and magnetite, and valuable explorations have been carried out on new solution-based manipulated synthetic strategies, surface modification and novel properties for above functional metal oxide nanostructures along with the connection between composition, structure and properties of these nanomaterials. At the same time, the structure formation mechanism was also discussed. The main contents and results were listed as follows:1. We developed a green, environmental friendly and facile method for the preparation of metastable VO2. Namely, belt-like VO2 (B) nanomaterials were successfully synthesized via a hydrothermal approach using mild, low-cost and non-toxic glucose as reducing agent, and the related experimental parameters were optimized. The results revealed that the belt-like VO2 (B) nanomaterials with uniform morphology and fine crystaline could be obtained at 180℃for 24 h when the molar ratio of V2O5 and glucose was maintained at the ratio of 1:1. Compared with other methods, this route is more milder, greener. Furthermore, the as-synthesized products were very pure with high productivity. Therefore, it is particularly fit for the synthesis of VO2 (B) nanomaterials on a large scale. In addition, the structure-directing roles played by polyhydroxy groups in the formation of belt-like VO2 (B) under hydrothermal conditions were discussed basically in comparison with the control experiments of other kinds of polyhydroxy. 2. Vanadium oxide nanotubes (VOx-NTs) modified by highly dispersed Ag nanoparticles (Ag/VOx-NTs) have been firstly synthesized via a facile silver-mirror reaction at room temperature and ambient pressure. The relevant experimental parameters were optimized. It was confirmed that the optimum concentration of AgNO3 solution to synthesize well modified Ag/VOx-NTs is about 0.1%. The Ag/VOx-NTs composite obtained from optimum conditions was used as sample in the test of antibacterial properties. Escherichia coli (E.coli), one of the most frequent species inhibiting in water, was employed as standard strains. The corresponding antibacterial tests demonstrated the as-synthesized Ag/VOx-NTs exhibited strong antibacterial activity against E.coli. Additionally, fine Co-doped vanadium oxide nanotubes were prepared successfully via a modified sol-gel process followed by hydrothermal reaction. It was found Co atoms could enter the crystalline lattice of VOx-NTs when Co doping level was relatively low, and the Co-doped VOx-NTs still preserved the nanotubular structure. However, if the Co content reach or exceed 10 mol%, only partial Co atom could enter the crystalline lattice of VOx-NTs. Small fragments appear with the doped nanotubes. The above work enriched the investigations of functional VOx-NTs.3. Pd nanoparticles with average diameter of 8-10nm were successfully supported on the Fe3O4 hollow nanospheres via a facile sonochemical reduction process. The as-obtained Pd/Fe3O4 composite was used as electrocatalyst for methanol oxidation in alkaline media. The results showed that the Pd/Fe3O4 compodite exhibited noticeable electrocatalytic activity and good stability towards methanol oxidation. To further improve the electrocatalytic performance of Pd/Fe3O4 composite, a new method was provided. In this route, Fe3O4 hollow nanospheres pretreated with dilute HCl solutions were firstly employed as supports and simple chemical reduction was then introduced. The Pd/Fe3O4 catalyst synthesized in this way showed enhanced electrocatalytic activity and better stability towards methanol oxidation in comparition with relevant literatures and the Pd/Fe3O4 obtained from sonochemical reduction process. 4. Well dispersed Fe3O4 nanoparticles with narrow size range were firstly fabricated by a solvothermal route without the present of surfactants or polymers. The influence of different experimental conditions towards the purity, morphology and yield of the FesO4 nanoparticles was investigated by changing experimental parameters, such as temperature, time, molar ratio of glycerol and water, alkaline source. The relevant experimental parameters were optimized. The dispersibility of the products in different solvents as well as the magnetic properties was also studied. The results indicated the as-obtained Fe3O4 nanoparticles held weak amphiphilic behavior, and had better dispersibility in polar solvents. In addition, the products exhibited nearly superparamagnetic properties, indicating it would have promising applications in biomedical field. While K2CO3 was replaced by EDA, highly dispersed Fe3O4 nanocrystalline (30-40nm) with irregular morphology of hexahedron was obtained under the similar conditions. The corresponding tests confirmed that this product dispersed easily in polar solvents, and possesed soft ferromagnetic properties.