表面活性剂辅助的纳米材料的控制合成和机理研究

【作者】 周广军；

【导师】 吕孟凯；

【作者基本信息】 山东大学 ， 材料学， 2006， 博士

【摘要】 近年来，随着纳米科技的发展，发现与合成新型的、高质量、性能优异的纳米结构材料成为多学科交叉研究的热点。本论文中，我们选择了几种重要的无机物，包括铬酸盐、钨酸盐、硫化铅以及银、铜和钯等金属，利用表面活性剂辅助的水溶液方法，成功合成了包括纳米棒、空心纳米球、枝晶、星状纳米颗粒、纳米立方块以及金属核-壳结构等多种形态的纳米和微米结构，系统研究了它们的形成机理和发光特性。 在第一章中，我们简要介绍了纳米科技领域的发展状况及研究现状，概括了几种通常使用的纳米材料制备方法，如水溶液法、非水溶液法、水热／溶剂热法以及模板法等，阐述了表面活性剂在纳米材料制备中的作用与应用。 作为半导体化合物，PbS由于具有窄的带隙能（0.41ev）和大的激子波尔半径（18nm），而成为一种重要的半导体材料。在第二章中，我们利用表面活性剂辅助的水溶液回流法成功地合成了单晶PbS纳米和微米结构，包括星状枝晶、多角的颗粒、去角的立方块（十四面体）和纳米立方块。星状PbS枝晶具有新颖结构：沿晶体的<100>方向生长出6个形态和大小均等的“枝”，每个“枝”具有一个“主干”，每个“主干”上又生长出4排相互垂直的“分枝”，每排“分枝”由相互平行的“纳米棒”组成，每个“纳米棒”垂直于“主干”。典型的PbS枝晶是在以下条件下合成的：分别以Pb（AC）₂和硫代乙酰胺（TAA）作为反应的前躯体，摩尔比Pb（AC）₂／TAA=2／1，初始反应温度80℃，100℃回流30分钟，表面活性剂为3g CTAB／100mL。去角的立方块（十四面体）具有丰富的{100}面，具体的典型合成条件为：摩尔比Pb（AC）₂／TAA=1／3，初始反应温度40℃，100℃回流12小时。通过对PbS结构演化的系统研究，我们提出了PbS纳米—和微米结构形成的机理。具有面心立方结构的PbS纳米结构的形状主要是由晶体沿<100>和<111>方向生长速率的比值R决定的。在PbS成核的早期阶段，Pb（AC）₂／TAA摩尔比和初始反应温度影响R值，并影响PbS的最终形态。在现有的实验条件下，我们可以通过调节Pb（AC）₂／TAA摩尔比、初始反应温度和反应时间控制PbS纳米晶的形态，通过形态演化的系统研究，该方法有望用于其它具有面心立方结构更多还原

【Abstract】 With the development of nanotechnology, the synthesis of novel and high quality inorganic nanomaterials with unique chemical and physical property has become a major interdisciplinary reseach area in recent years. In this thesis, we selected several kinds of inorganic materials, including chromate salts, tungstate salts, sulfide lead, and metals such as silver, copper, and palladium. Various morphologies such as nanorods, hollow nanospheres, dendrites, star-shaped nanocubes, and metallic core-shell nanostructures, have been successfully synthesized via surfactant-assist process. The formation mechanisms were proposed and their optical properties were investigated. In Chapter 1, we briefly introduced the history and recent work in the field of nanotechnology. Some kinds of methods for th synthesis of nanomaterials, such as aqueous-phase, nonaqueous-phase, hydrothermal / solvothermal methods, and templated method, have been introduced clearly. The role and application of the surfactant in the synthesis of nanomaterials were also illustrated in this chapter.As one of the semiconductor compounds, PbS is an important π-π semiconductor material with a narrow band gap energy （0.41 ev） and large excition Bohr radius （18 nm）. In Chapter 2, well-defined single-crystalline PbS nano- and microstructures including dendrites, multipods, truncated nanocubes, and nanocubes were synthesized in high yield by a simple solution route. Novel star-shaped PbS dendrites with six symmetric arms along the <100> direction, each of which shows one trunk （long axis） and four branches （short axes）, have been achieved using Pb（AC）2 and thioacetamide（TAA） as precursors, under the molar ratio Pb（AC）₂/TAA=2/1, at initial reaction temperature 80℃, refluxing for 30 min at 100℃, in presence of cetyltrimethylammonium bromine （CTAB）. The "nanorods" in each branch are parallel to each other in the same plane, and are perpendicular to the trunk. The truncated nanocubes mainly bounded by {100} plane were prepared under the different Pb（AC）2/TAA molar ratio, at initial reaction temperature 40℃, refluxing for12 h at 100 ℃. Based on the systematic studies on their shape evolution, a possible更多还原