【作者】 梁鑫；

【导师】 李亚栋；

【作者基本信息】 清华大学 ， 化学， 2009， 博士

【摘要】 稀土化合物纳米材料在催化、光学、生物分析等诸多领域有着广泛的应用前景。发展稀土化合物纳米材料的控制合成方法、探索其生长机制、深入研究其结构形貌与性能之间的关联具有重要的意义。本论文就液相调控合成稀土化合物纳米材料进行研究,探讨了稀土化合物纳米材料的结构、形貌和性质之间的关联,构建了乙二醇溶剂热体系合成稀土化合物及其复合功能材料纳米晶和纳米空心结构的新方法。通过油酸辅助的水热体系制备了不同形貌和晶体结构的NaYF4纳米晶;发展了水热法合成多枝状NaYF4纳米晶和NH4Ln2F7纳米空心球的方法。以稀土复合氟化物为模型,详细研究了反应参数对纳米晶的形貌和成相规律的影响,探讨了镧系收缩对稀土复合氟化物的晶体结构、物理性质和纳米晶形貌的影响;探索和总结了纳米晶的成核、生长以及相转变过程中的本质的物理化学规律。设计和发展了一种不添加其他表面活性剂,以乙二醇和水为混合溶剂,在溶剂热的条件下合成单分散稀土正钒酸盐纳米晶的新方法。将乙二醇溶剂热合成方法由稀土正钒酸盐纳米晶体系扩展到二氧化铈及其复合氧化物纳米晶体系。通过在体系中引入短链有机酸,制备了一系列不同形貌的CeO2的纳米结构(球型、多面体型、介孔纳米球、空心纳米球)。以CeO2纳米球为前驱体,构建了铈锆氧和铈钛氧固溶体空心球结构,提出并验证了空心球基于柯肯达尔效应的形成机制。CeO2及其复合氧化物是重要的助催化材料,采用本方法制备的一系列CeO2基纳米材料具有较高的比表面积和良好的热稳定性,在催化领域具有可期待的应用前景。进一步将乙二醇溶剂热合成方法的应用范围由稀土化合物纳米晶扩展到稀土复合功能纳米材料的合成。利用浓硝酸氧化乙二醇和催化乙二醇缩合的反应,发展了一步法制备多功能稀土有机无机杂化胶囊的新方法。该杂化胶囊具有可进行化学修饰和表面包覆的功能性表面,并表现出特征的光学和磁学特性,在生物分析、药物传送等领域具有一定的应用前景。将银离子在乙二醇中还原反应与其串联起来,构建了一系列银和稀土有机无机复合纳米结构;以其为前驱物,发展了一种制备银和稀土氧化物复合纳米空心球的新方法。更多还原

【Abstract】 Rare earth compounds nanomaterials have intensive potential in various fields, such as catalysis, optics, biology analysis, and so on. Developing synthetic routes for rare earth compounds nanomaterials, exploring the formation mechanisms and investigating the relationship among the crystal structure, morphology and properties of nanomaterials have great significance. This dissertation explored new solution-based synthetic strategies for rare earth nanomaterials, emphasizing the relationship between structure and shape/properties manipulation of nanomaterials, and new strategies based on glycol systems for preparation of functional rare earth compounds and composites nanocrystals and hollow structures.NaYF4 nanocrystals with various morphologies and crystal structures have been synthesized via a hydrothermal approach assisted with oleic acid. Synthesis approaches have been developed for multi-armed NaYF4 nanocrystals and NH4Ln2F7 hollow spheres. By taking complex rare earth fluorides as an ideal system, we have carried out careful investigations on the influences of reaction parameters on the morphologies and phases of nanocrystals, explored the influence of lanthanide contraction on crystals structures, shape/properties of complex rare earth fluorides, discussed and summed up the underlying rules of the nucleation, growth and phase transition process of nanocrystals.Designing and developing a new surfactant free solvothermal synthetic strategy for monodisperse rare earth orthovanadate nanocrystals, with the use of glycol and water as mixed solvent.The glycol solvothermal method has been extended from rare earth orthovanadate to the system of ceria and related composite oxides. Series of CeO2 nanomaterials with controllable morphologies (spheres, polyhedrons, mesoporous spheres and hollow spheres) have been fabricated by introducing short-chain organic acids. By taking CeO2 as precursors, we constructed Ce1-xZrxO2 and Ce1-xTixO2 solid-solution hollow spheres. The formation mechanism based on kirkendall effect was proposed and verified. Ceria and related composite oxides are important catalytic promoters. As-prepared CeO2-based nanomaterials have high surface area and good thermal stability, which would have promising application potentials in the field of catalysis.For a further step, the application fields of this glycol-based solvothermal method were stretched from rare earth compound nanocrystals to functional rare earth composite nanomaterials. A one-step synthesis strategy for functional rare earth organic/inorganic hybrid capsules has been developed by using the reaction between strong oxidizing acid (HNO3) and glycol ethylene. The hybrid capsules have functional surface. And some distinctive optical and magnetic characteristics were found on the capsules, which would be of promising potentials in the fields such as biology analysis and drug deliver. Associating the reaction of Ag+ ions in glycol with this method, series of Ag and rare earth composites nanostructures have been constructed. By taking it as precursor, a new synthetic method for Ag and rare earth oxides composites hollow spheres have been developed.更多还原