【作者】 李新平；

【导师】 于丽； 郑利强；

【作者基本信息】 山东大学 ， 物理化学， 2010， 硕士

【摘要】 纳米结构的空心材料由于具有较大的内部空间以及具有一定厚度的纳米尺度的壳层,可作为药物载体,在医学和制药学领域应用很广。此外,空心材料与块材相比还具有比表面积大、密度小等特性,可作为轻质填料、催化剂、隔热材料等。由于空心材料独特的结构及优异的性能,其研究受到人们广泛的关注。目前空心材料的制备方法多采用模板法,为了避免杂质的引进以及反应过程的复杂,发展非模板方法制备空心材料是纳米材料研究的一个重要方面。近年来,研究单分散性能优异的胶体球的制备是胶体化学领域颇受挑战的主题,通过自组装的方法,胶体球作为基本单元被广泛应用于制备光子晶体。高度单分散的具有高折射指数胶体球,是形成宽带光子晶体的理想的基本单元。CdS,作为一种重要的半导体材料,具有优异的光电转化性能和发光性能,随着尺寸的减小以及形貌的变化,CdS纳米结构的禁带宽度发生明显的变化,表现出不同于块材的、更加优异的光电性能,因而在催化、非线性光学、光吸收、传感器和磁性材料等新材料方面有广阔的应用前景。本文利用水热法对空心结构及单分散的胶体球进行了控制合成,并分别从材料制备,性质分析、反应条件、反应机理等方面进行了系统的研究,初步研究了CdS纳米空心球光催化降解亚甲基蓝的效率。论文的具体研究内容如下：(1)离子液体辅助水热法制备CdS纳米空心球目前CdS空心材料的制备多采用模板法。本文首次采用离子液体辅助的非模板方法制备了尺寸约为130 nm的CdS纳米空心球,反应过程简单可重复。研究了反应物摩尔比、温度、添加剂等条件对CdS纳米空心球形成的影响。经过研究发现,反应物摩尔比对产物形貌有较大的影响,只有在S过量的情况下,才能形成结构较好的空心球；较低或较高的反应温度均不能形成结构完善的CdS空心球；此外添加剂六亚甲基四胺(HMT)与聚乙烯吡咯烷酮(PVP)对于空心球的形成二者缺一不可,二者共同影响球形结构的形成；离子液体1-丁基-3-甲基咪唑六氟磷酸盐([bmim][PF6])对于空心结构的形成起着至关重要的作用,当不添加离子液体时得不到空心结构。通过对不同反应时间段产物形貌的考察,初步认为CdS纳米空心球的形成机理为奥氏熟化作用。此外,研究了CdS空心球光催化亚甲基蓝降解的效率,经研究表明,CdS空心球由于具有较高的比表面积,因此能够有效的催化亚甲基蓝降解。(2)水热法制备CdS胶体球CdS胶体颗粒由于具有较大的折射指数及特殊的光学、磁学等性能,在光子晶体领域具有潜在的应用价值。在本文中以CdCl2和硫代乙酰胺(TAA)为反应物,以HMT和PVP为添加剂,通过两种添加剂的协同作用,提出了一种简便快速水热反应方法,制备了分散性能良好的CdS胶体球。通过改变添加剂的浓度,可以实现对产物尺寸的调节。深入研究了PVP及HMT在产物形成过程中所起的作用。通过对比两个极端试验以及比较不同添加剂浓度下产物形貌图,认为在产物形成过程中HMT通过与Cd2+形成络合剂,控制单体的释放速度,从而影响产物的形貌；PVP有双重作用,既作为保护剂又作为增粘剂,影响晶面及颗粒的生长。更多还原

【Abstract】 Inorganic materials with hollow structures have recieved considerable attention in recent years, owing to their unique chemicophysical properties including high specific surface area, good permeability, and special optical/electrical/magnetic properties. Many applications could be realized using hollow materials, such as catalysis, nanoscale chemical reactors, encapsulation and controlled release of bioactive agents, photonic devices, lightweight fillers and acoustic insulators. Among the methods employed for the preparation of hollow nanostructures, hard or soft template-assisted synthesis has been most widely investigated. Compared with template-assisted methods involving multistep procedures, a one pot template-free method for controlled preparation of hollow nanostructures with rationally designed parameters is highly attractive. On the other hand, monodispersed colloidal spheres have been extensively exploited as building blocks to fabricate photonic crystals by self-assembly. Of the various colloidal nanocrystals, semiconductor types, especially metal sulfides, have been the most studied due to their high refractive index and excellent optical, magnetic, and optoelectronic properties that can be further exploited to produce photonic crystals with tunable or switchable band gaps. As a semiconductor with important wide band gap (2.4 eV at room temperature), CdS is useful for many important applications such as light emitting diodes, flat panel displays, solar cells, photo-catalysts, and thin film transistors. Since the properties of the material greatly depend on their morphological features, nanostructured CdS with different sizes and morphologies has been fabricated and characterized, among which the hollow structure and colloidal spheres have received particular attention. Herein, firstly, we present an ionic liquid assisted hydrothermal method for the preparation of CdS hollow nanospheres, and investigate the effect of the reaction parameters on the formation of CdS hollow nanospheres, and a hollowing growth mechanism involve Ostwald ripening is proposed. Secondly, we demonstrate that CdS colloidal spheres could be prepared by a facile hydrothermal method.1. Template-free synthesis of CdS hollow nanospheres based on an ionic liquid assisted hydrothermal process and their application in photocatalysis.Until now, the synthesis of hollow CdS has been largely based on the use of templates. It is the first time for the preparation of CdS hollow nanospheres in high yield with a template-free ionic liquid (IL) assisted hydrothermal route in the presence of polyvinylpyrrolidone (PVP) and hexamethylenetetramine (HMT). Structural characterization by TEM, SEM, SAED, and XRD indicates that the CdS hollow nanospheres are polycrystalline consisting of some smaller nanoparticles. The formation of such nanospheres is attributed to the preferential adsorption of PVP molecules on the CdS crystal nuclei. The small crystal nuclei aggregated to form solid nanoparticles that are protected by the adsorption of HMT molecules on certain faces of nanoparticles. The solid nanoparticles experienced a localized Ostwald ripening process and finally the CdS hollow nanospheres are obtained. The reaction temperature, the molar ratios of Cd/S, the concentration of capping agents (PVP and HMT) and IL [bmim][PF6] were found to be crucial for the formation of CdS hollow nanospheres. These hollow structured materials can be used as efficient photocatalysts for the degradation of MB. The CdS hollow nanospheres with near band emission, may find promising applications in microelectronic and photovoltaic devices. Importantly, the ionic liquid (IL) assisted hydrothermal route may be a versatile method to prepare hollow nanomaterials.2. Facile synthesis and properties of uniformed CdS colloidal spheresDue to high refractive index and excellent properties of luminescence and photochemistry, CdS could be used as building blocks for the fabrication of wide band photonic crystals. In our study, we developed a facile one-pot hydrothermal approach for the synthesis of uniform CdS colloidal spheres with tunable sizes, by changing the concentrations of capping agents PVP and HMT. To the best of our knowledge, this is the first report that CdS colloidal spheres could be prepared with such a rapid method. Only by changing the concentrations of PVP and HMT, the sizes of the product can be tuned from 70 um to approximately 200 nm. Comparative experiments reveal that synergistic effect of HMT and PVP are crucial for the formation of colloidal spheres. Meanwhile, the nearly uniformed CdS colloidal spheres could serve as an ideal building block for the fabrication of wide band gap photonic crystals.更多还原