【作者】 刘军枫；

【导师】 李亚栋；

【作者基本信息】 清华大学 ， 化学， 2007， 博士

【摘要】 金属氧化物纳米材料在催化、光电、气敏、磁性以及锂电池等领域有着广泛的应用前景。发展新的合成方法,探索其生长机制,从而获得具有特定尺寸、形貌、维度、单分散性等的纳米材料,对于深入系统地研究纳米材料与性能的关系,并进一步实现纳米材料的组装,构建功能纳米结构体系,最终使纳米材料进入应用领域具有重要意义。本论文就功能氧化物纳米材料的液相调控合成与其相关性质进行了研究,对纳米材料的形成机制、材料尺寸形貌等与性能之间的关系进行了有益探索。发展了水热合成钒氧化物单晶纳米带的新方法,在对不同价态钒氧化物晶体结构差异进行了系统分析后,通过设计合理的化学反应,实现了对五氧化二钒、二氧化钒单晶纳米带的控制合成,验证了层状结构与纳米带形成的相关性。基于五氧化二钒晶体本身的层状结构特点和纳米带的特殊性,设计制备了具有较高选择性和稳定性的气敏传感器。另外,对于VO2(B)纳米带的电磁学性质的研究为其在纳米器件上的潜在应用提供了实验依据。设计了水-油界面溶剂热反应体系,合成了稀土离子掺杂的荧光LaVO4单分散胶体纳米晶,并进一步将此方法发展为稀土钒酸盐胶体纳米晶的通用合成方法。基于单分散LaVO4纳米晶良好的成膜性以及下转换荧光性质,将其应用于染料敏化太阳能电池中,明显地提高电池了的性能。以具有特定形貌和晶面的LaVO4纳米晶为载体,单分散Au溶胶为活性Au,设计制备了新型催化剂。建立了表面活性剂辅助的水热及溶剂热合成方法,通过选用合适的表面活性剂及控制单体浓度,获得了一系列不同晶形及形貌的BiVO4微/纳米晶,研究了晶体结构与生长行为的相关性。通过对水热体系pH值的调控成功制备了具有特殊形貌、取向的KNbOx纳米结构,并研究了KNbO3合成中的溶剂效应。采用水热法制备了多种形貌确定的Fe2O3纳米晶,对其催化性能的研究结果显示催化活性不仅与催化剂粒子的大小有关,而且与其晶面有密切联系。采用溶剂热法合成了单分散TiO2纳米晶,并进一步采用微乳体系将具有疏水表面的TiO2纳米晶组装成具有亲水表面的胶体球。此胶体球高温退火可形成介孔材料,具有优异的催化性能。此方法为单分散纳米晶的进一步应用打下了基础。更多还原

【Abstract】 Metal oxide nanomaterials have exhibited promising applications in catalysis, sensing, optics, magnetism and batteries. Preparation of nanomaterials with well-defined size, morphology, dimensionality and diversity through novel synthesis approaches and investigations of their formation mechanism should be a key precondition to reveal the relations between the structures and properties, assemble the nanocrystals into superstructures and pave the way to the real applications. In this dissertation, valuable explorations have been carried out on new solution-based manipulated synthetic strategies for functional metal oxide nanostructures along with their formation mechanisms and novel properties, emphasizing on the relationship between crystal symmetry and morphology manipulation as well as the connection between properties and size/morphology of nanomaterials.A rational low-temperature hydrothermal synthetic way has been developed to selectively prepare vanadium oxide nanobelts with different valent status. The formation mechanism is investigated in details and believed to be closely related to their layered structure. A highly selective and stable ethanol sensor was designed based on the intrinsical layered structure of vanadium pentoxides and the advantages of nanobelts. The investigation on the electrical transport and magnetic properties of vanadium dioxide nanobelts shows their potential applications in nanodevices.A synthesis and self-assembly approach assisted with oleic acid molecules is developed to fabricate luminescent Ln3+ doped LaVO4 nanocrystals (NCs) and rare earth vanadates. A transparent luminescent film of uniform nanocrystals, which could absorb UV light and down-convert it to visible light, prepared by coating approach could greatly improve the cell performance when applied in dye-sensitized solar cells. Catalytically active gold catalysts have been designed via monodispersed gold colloids on LaVO4 nanocrystals with controlled size as more well-defined nanocatalysts. The use of rare earth vanadates as supports for active gold catalysts opens up new routes in the research work for high performance catalysts.Bismuth vanadate micro/nanocrystals with different morphologies were synthesized by surfactant assisted hydrothermal/solvothermal methods. The studies on the crystal growth reveal the relationship between the crystal structures and the morphology. Low dimensional potassium niobate nanostructures with different compositions were achieved by simply controlling pH value of the hydrothermal system. It was found that the solvent plays an important role in the phase control of the KNbO3 nanocrystals.Study on the catalysis properties of iron oxide nanocrystals with different size and morphology showed that the catalytical activities were influenced not only by the size and BET of the materials, but also by the crystal planes due to the facts that the reactivity, coming from different active sites on certain reactions, varies with crystal planes. Redispersible TiO2 nanocrystals with hydrophobic surface were prepared by controlled solvothermal reactions, followed by a newly developed microemulsion-based method to assemble the nanocrystals to colloidal spheres with hydrophilic surface. Mesoporous spheres, which are expected to show excellent properties in applications such as catalysis, could then be achieved by annealing of colloidal spheres.更多还原