【作者】 刘立平；

【导师】 李亚栋；

【作者基本信息】 清华大学 ， 化学， 2010， 博士

【摘要】 半导体荧光纳米材料因其具有良好的光、电性能在发光器件,生物标记,太阳电池等领域有着广泛的应用前景。发展这些材料的合成方法,探寻其生长机理,从而制备具有特定尺寸大小、形貌、表面结构及单分散性的纳米材料,构建组装功能纳米材料体系,将对纳米材料最终进入实际应用具有重要的作用。本论文就II-IV族半导体荧光纳米材料的形貌及大小调控合成进行研究,并且对半导体材料在光电转换的应用进行了有益的探索。发展了一种利用溶液的酸碱性来制备单分散Se球的合成方法。利用前驱物Na₂SeSO₃对环境酸碱度的敏感性,通过调节溶液的pH值来制备具有不同尺寸大小的非晶态的Se球,并将所获得的单分散的Se球为模板,制备了具有核壳结构的Se@Ag₂Se球。利用非晶态Se球的不稳定性,将所获得的Se球置于乙醇溶液中,通过“固态-液态-固态”的生长过程制备稳定的六方相的单晶Se线。发展了一种室温注入法制备尺寸可调的CdSe纳米晶的方法。利用正相微乳体系在室温下制备得到CdSe纳米晶核,然后将其置于不同温度下进行晶化生长以及氧化刻蚀,得到荧光在红光到蓝紫光区域可调的CdSe纳米晶。在十八烯体系中,通过控制反应条件制备具有不同形貌的立方相结构的CdSe纳米颗粒。利用立方相CdSe材料其各个晶面不同的表面能以及各个晶面与表面活性剂分子吸附能的不同,控制反应温度,制备出单分散性良好的立方块状、球状、正四面体状以及分枝状结构的CdSe纳米颗粒。将制备的CdSe纳米颗粒与TiO₂纳米颗粒组装成胶体球结构,制成薄膜应用于PEC电池中。在半导体量子点敏化的TiO₂光电极薄膜中,一般是使用含有巯基的双亲分子将量子点与TiO₂连接起来,而这类双亲分子会在一定程度上降低电子在量子点与TiO₂之间的传输,因此在实验中,通过使用组装的方法将CdSe与TiO₂纳米颗粒连在起来,使CdSe镶嵌在TiO₂纳米颗粒中,不需要使用双亲分子进行连接。PEC结果显示,这类使用CdSe与TiO₂纳米颗粒组装起来的介孔材料,其PEC性能明显比用双亲分子连接的用CdSe敏化的TiO₂薄膜要好,展示出这类CdSe/ TiO₂复合介孔材料在光电转换应用中良好的应用前景。更多还原

【Abstract】 Fluorescent semiconductor materials have attracted much attention due to their unique optical and electrical properties which makes them have potential application in light-emitting diodes （LED）, biological labeling and solar cells. Preparation of nanomaterials with special-defined size, morphology, surface construction and diversity through simple and environmental friendly synthetic methods and the investigation of their growth mechanisms should be a crucial step to understand the relations between their structures and physical and chemical properties. In this dissertation, some explorations have been carried out on new simple and chemical green manipulated synthetic strategies for the II-VI group fluorescent semiconductor nanostructures, and their growth mechanisms and unique properties. And also, some research in solar cell field has been done for these prepared semiconductor nanomaterials.By utilizing the stability diversity of the Na₂SeSO₃ in different PH environment, Se power has been transformed to monodisperse amorphous Se （a-Se） spheres through the synthesis and dismutation of the Na₂SeSO₃. And the size of the a-Se can be adjusted by changing the pH value of the solution. Meanwhile, selenium nanowires are obtained through a“solid-solution-solid”process by dispersing the prepared Se spheres in ethanol solvent.A room temperature injection technique has been developed to synthesize the CdSe nanocrystal. The CdSe seed clusters are prepared at room temperature, and the CdSe nanocrystals with different sizes are obtained by a subsequent crystal growth process at different temperature after the injection. CdSe nanocrystals with fluorescent from green to red region can be adjusted by changing the growth temperature. The activity of the surfactant is found to be the crucial factor to control the growth rate of the nanocrystals. An effective oxidation route has been developed to etch the small size CdSe nanocrystals. By etching the CdSe nanocrystals, the fluorescent of the CdSe nanocrystals can be adjusted in blue-violet region. Zinc blende CdSe nanocrystals with different shape have been synthesized in octadecene solution by reacting Se powder and Cd（Ac）₂, the reaction temperature is found to be the key factor to control the final shape of the CdSe nanocrystal products as the temperature will affect the activity of the surfactant, and the thermodynamic property of the CdSe crystal is also one of the reason to affect the shape of the final products. By controlling the reaction temperature, CdSe nanocrystals with cube, sphere, tetrahedron and branched shape have been obtained. The shape controlled process here can give useful information to guide the control synthesis of other zinc blende structure nanocrystals.By using an emulsion-based bottom-up self-assembly method, CdSe/TiO₂ hybrid colloidal spheres have been synthesized and use as photoanode for photoelectrochemical （PEC） application. The PEC results show that the photoanode made from CdSe/TiO₂ hybrid colloidal spheres perform more active in PEC cells than the narmal CdSe-link-TiO₂ photoanode as the CdSe/TiO₂ hybrid colloidal spheres provide a better connection between the CdSe and TiO₂. This study illustrates the importance of fundamental structural control in influencing PEC properties of hybrid assembled nanostructures.更多还原