Synthesis And Properties Of Metal Oxide Based Micro-/Nanostructures

The goal of this dissertation is to explore the controllable synthesis ofinorganic micro-/nanostructures in solution phase by applying a simplecoordination chemistry principle, developing the effective methodologyto control both the phase and morphology of the final products. Moreover,the corresponding structure-dependent properties of the as-obtainedinorganic micro-/nanostructures were also investigated in this dissertation.The details are summarized briefly as follows:1. Highly uniform three-dimensional-Ni（OH）₂hierarchicalarchitectures based on nanoslices were successfully synthesized on alarge scale in a water-in-oil microemulsion of cetyltrimethylammoniumbromide （CTAB）/water/cyclohexane/glycerol with Ni（HCOO）₂·2H₂Oserved as both a nickel source and a weak alkaline source. The phaseformation of-Ni（OH）₂takes advantage of the hydrolyzation of HCOO-in Ni（HCOO）₂·2H₂O precursor. The size and morphology of-Ni（OH）₂can be tuned through varying the experimental parameters. As-obtained3D-Ni（OH）₂possesses high electrochemical sensitivity to H₂O₂, andthe microstructures had a noticeable influence on their sensitivities, whichindicate potential applications in the field of electrochemical sensingdevices.2. The mesoporous MgO nanosheets with uniformly distributedmesoporosity and high specific surface area of102.8m²/g were simplysynthesized on a large scale by calcination of hexagonal Mg（OH）₂nanosheet precursor, which was prepared using1,6-hexanediamin-assisted solution approach. The as-prepared mesoporousMgO nanosheets were used to construct a cheap, easy andenvironmentally-friendly electrochemical sensor on glassy carbonelectrode for the simultaneous and selective electrochemicaldetermination of four toxic metal ions of Hg（Ⅱ）, Cu（Ⅱ）, Pb（Ⅱ） and Cd（Ⅱ）in an aqueous solution, which exhibits high sensitivity and selectivity.The DPV responses of the sensor toward separate measurements of Hg（Ⅱ）, Cu（Ⅱ）, Pb（Ⅱ） and Cd（Ⅱ） at different concentrations show thelinear detection range was0.005–1.71,0.01–2.13,0.01–2and0.01–0.21M. The simultaneous and selective determination of these species in thequaternary mixtures presents the linear responses in the range of0.005–1.71,0.01–1.92,0.01–1.76and0.01–0.2M. The favorableperformance makes this sensor extremely attractive for onsiteenvironmental monitoring of heavy metal ions.3. Needle-like ZnO nanorods （ZnO-NRs）/Ag nanoparticles （Ag-NPs）heterostructure with tunable silver contents have been successfullydesigned and constructed via two-step hydrothermal approach using zincfoil as both substrate and reactant. The as-fabricated heteroarchitecturedcomposite was Ag-NPs with size range about30to50nm in diameterassembled uniformly on the surface of needle-like ZnO-NRs, severalmicrometers long and about480nm wide near the half height of thenanorods. Through the variation of silver nitrate concentration, the silvercontent on the ZnO-NRs can be controllably tuned, which further greatlyaffected the photocatalytic performance of the decomposition of arepresentative dye pollutant of rhodamine B and there is optimum amountof secondary Ag-NPs. This facile method developed here also can beextended to construct other ZnO-based noble metal or semiconductorheterostructures on zinc substrate.