Microstructure-Controlled Metal And Complex Metal Oxide Functional Materials: Preparation, Structural And Their Properties

As we known, the properity of nanoscale materials can be tuned not only by composition, but also by their size, shape, dimension, exposed crystal faces and the combination behavior of the building units. Therefore, it is extremely important to be able to properly control the size and morphology of the nanomaterials. As an important class of inorganic functional materials, metal oxides have been widely used as semiconductors, magnetic materials, sensors, catalysts and catalyst supports, for their specific physicochemical. For the properties of metal oxides are highly size- and shape-dependent, increasing effort has been paid to regulate the composition, structure and morphologies of metal oxides with simple, green, economic, and affective preparation routes. In the present thesis, our research mainly focuses on the synthesis of microstructure-controlled metal oxides and their properties.As for the ZnAl2O4 spinel-like mixed metal oxides material fabricated by traditional high temperature ceramic method, the particles are apt to aggregation and sintering and lead to nonuniform of the product and low surface area. Therefore, we established a facile and green one-pot strategy to synthesize porous ZnAl2O4 without using any surfactants or post-treatment. The structural and textural properties of ZnAl2O4 spinels can be simply controlled by using different solvents. The obtained ZnAl2O4 processes large surface areas and high thermal stability. Meanwhile, Ag nanoparticle can be evenly dispersed on the interface of the porous ZnAl2O4 via a chemical reduction of silver salt by NaBH4. The resulting Ag/ZnAl2O4 nanocomposite catalysts show high catalytic activity and selectivity to o-CAN in the hydrogenation of o-CNB with restraining further dechlorination. This novel micro-/mesoporous ZnAl2O4 can prevent the oxidation and aggregation of Ag nanoparticles, and increase the thermal stability of the resulting catalyst.Based on the above results, we demonstrated an in situ crystallization method to directly fabricate ZnAl2O4 thin films on aluminum substrate with controlled surface nanostructures, which are composed of nanoparticles, nanorods and nanoswords, respectively. Such approach without using any templates or surfactants is of significant importance in industrial application as a consequence of low cost, benignancy to environment, synthetic convenience and scale production. The growth of ZnAl2O4 nanostructures is found to be greatly affected by the concentration of Zn2+ and urea under the solvothermal conditions. As-fabricated ZnAl2O4 films with specific surface topography are beneficial to obtain tunable hydrophobic or superhydrophobic properties. Furthermore, Ag nanoparticle can be evenly dispersed on the interface of the ZnAl2O4 film via a chemical reduction of silver salt by NaBH4, and the corresponding structured Ag/ZnAl2O4 film catalysts show excellent catalytic performance in the reduction of p-nitrophenol.A facile hydrothermal method was used to prepare macroporous NiFe2O4 thin films based on densely-packed uniform NiFe-LDH procedure films grown on sulfonated silicon substrates.The synthetic strategy principally involves the formation of two phase composite films containing desired nickel ferrite and nickel oxide phases, which is induced by sintering of NiFe-LDH precursor films and subsequent phase separation by a selective leaching of self-generated NiO template from the two-phase composite films. The microstructures such as particle sizes, spacing among particles, magnetism and surface hydrophobic property of as-fabricated NiFe2O4 films could be finely tuned by varying the Ni2+/Fe3+ molar ratio of the precursor films. The increasing Ni/Fe ratio in precursor films leads to reduced particle sizes and enlarged spacing among ferrite particles in NiFe2O4 films.At present, the most common route to fabricated CuO films with complex three-dimensional architectures are often under the presence of surfactants. However, the surfactants used often cover the active site of the CuO nanostructure which limits its applications in areas such as biosensor, field emission, lithium ion batteries. Here, we developed a new green synthetic route to three types of three-dimensional hierarchical CuO architectures with controlled flower-like morphologies onto copper by a facile solution-based approach in the presence of NaBH4 without using any surfactant or oxidant. The results indicated that NaBH4 acted as both alkaline agent and reductant for the formation of unusual CuO nanostructures. The morphology of CuO configurations on the substrate was diversified by governing the NaBH4 concentrations. A possible formation mechanism for the controlled organization of primary building units into three-dimensional flower-like architectures is proposed. Tunable hydrophobic/superhydrophobic surfaces of as-fabricated CuO architectures can be realized based on their special surface nano-/microstructures. Moreover, the flower-like CuO architecture can greatly enhance its catalytic performance in the oxidation of phenol. We also fabricated ZnO nano films/arrays directly on the zinc substrate via a facile solvothermal method in the presence of NaBH4 without using expensive substrate or the fabrication of ZnO nanoparticles layer on the substrate in advance. After adding appropriate amount of alcohol, single crystal ZnO nano arrays can be directly fabricated on the zinc substrate by a single step synthetic solvothermal route. The morphology of the ZnO films can be simply controlled by changing the volume ratio of water to ethanol. We also study the relationship between the surface morphology and the photoluminescence property. The result shows that the ZnO nano arrays process high UV/visible light discrimination ratio.