【作者】 徐梽川；

【导师】 力虎林； 高鸿钧；

【作者基本信息】 兰州大学 ， 分析化学， 2008， 博士

【摘要】 近十年来纳米材料的合成方法有了长足的发展,特别是在纳米颗粒的合成方面,液相合成法已经成为了最重要的方法之一。液相法合成纳米颗粒,即在液相溶液中通过化学反应将可溶性的金属化合物共沉淀为不溶性的固体小颗粒,它包括共沉积法、溶胶凝胶法和微乳法等。该方法具有效率高,适用范围广,合成颗粒质量好等优点。本文综述了液相法合成纳米颗粒的最新进展,同时以氧化铁、金和二氧化钛等材料为研究对象,研究了几种液相合成法在金属及金属氧化物纳米颗粒制备中的应用。主要内容如下:1)通过对高温液相共沉积法的研究,发现大量的表面活性剂可以起到溶剂的作用,从而代替溶剂。表面活性剂作为溶剂,不仅可以简化合成方法,而且可以有效控制纳米结构的化学组成、形貌以及尺寸。本文介绍了一种较为简单的高温液相法,该方法适用于金属、合金以及金属氧化物等纳米结构的制备。利用油酸油胺作为表面活性剂和溶剂,通过控制反应温度和升温速率,可以有效控制金属配合物在反应体系中的热分解过程,得到的纳米结构尺寸均匀,表面包覆有油酸和油胺,不团聚,分散均匀,可以自发的排列成有序的纳米结构。使用透射电镜、X衍射仪、紫外可见分光光度计、振动样品磁强计等物理方法研究了纳米颗粒的光学和磁学等性质,发现纳米结构的物理性质与尺寸和形貌密切相关,为进一步研究纳米颗粒的实际应用提供了实验基础。2)介绍了一种非常简单的制备金纳米颗粒的方法。通过对液液两相法的研究,发现能够得到尺寸均匀的金纳米颗粒的关键因素是合成后的热处理过程。该过程一般采用加热有机试剂硫醇的均相溶液,通过金纳米颗粒之间的消化融合使其颗粒尺寸均匀。将硫醇包覆的金纳米颗粒加热至高温且保持在该温度状态下一段时间,就能够得到尺寸均匀的金纳米颗粒。这一实验现象说明制备硫醇包覆金纳米颗粒的方法并不是唯一的,任何使用硫醇为表面活性剂的制备方法都可以用来制备尺寸均匀的金纳米颗粒。根据这一原理,本文提出一种只使用三种化学试剂的液相制备方法。该方法不仅操作简单,而且制备的金纳米颗粒尺寸非常均匀,可以作为研究纳米颗粒自组装原理的模型材料。通过缓慢挥发不同浓度的金纳米颗粒溶液,得到了二维和三维的超晶格纳米颗粒阵列。3)以表面活性剂为软模板,加入的金纳米颗粒为种子,在水溶液中制备了金纳米棒。通过控制种子溶液的加入量,可以有效控制纳米棒的长度和宽度。一般情况下,加入的种子的量越多,得到的纳米棒就越短。使用透射电镜、扫描电镜、X衍射仪、X衍射线能谱、紫外可见分光光度计、光学显微镜等物理检测设备,对制备的纳米棒以及其自组装阵列进行了研究。发现由于纳米棒的纵向表面积较横向表面积大,因此造成纵向方向上的表面张力非常显著,在其自组装过程中,纵向方向上的表面张力吸引纳米棒相互靠近且平行相接,形成“枕木”式平行结构。在自组装的过程中,纳米棒与球形颗粒选择性的相互分离,最后分布在基底上不同的区域内。4)利用溶胶凝胶法和水热法分别制备了二氧化钛纳米颗粒和纳米管。通过金属配合物与二氧化钛表面羟基的化学反应,在液相中将金属配合物组装在二氧化钛纳米结构的表面,进一步高温灼烧去除有机配体,得到了表面具有过渡金属搀杂的二氧化钛纳米结构。过渡金属搀杂可以有效提高二氧化钛的电荷分离率,从而提高光催化性能。过渡金属原子搀杂在催化剂表面(反应界面),不仅起到电荷分离中心的作用,还可以减少分离后的电荷再次复合的几率。更多还原

【Abstract】 The methodology study on nanosized materials has received significant progresses in the past ten years. Particularly, regarding the synthetic methods for nanoparticles, wet chemical process has been one of the most important methods. The wet chemical method involves the chemical reaction, in which the dissolved metallic compounds are reduced or precipitated into undissolved solid particles in a small size. The method usually has a high yield for production of high quality nanoparticles and is capable of producing many kinds of nanoparticles. This thesis addressed the recent progresses of wet chemical synthesis of nanoparticles and studied the synthetic methods of iron oxide, gold and titanium dioxide nanoparticles. The details are shown as follows:1) The thermal decomposition of metallic organic compounds in a high boiling point solvent may produce high quality nanoparticles. This method was studied in this thesis for synthesize magnetic nanoparticles. The effects of surfactants and solvents were investigated during the synthesis. The size and shape of magnetic nanoparticles were controlled by changing concentration of surfactants and reaction temperature. TEM, XRD, VSM, UV-vis were used for characterizations of magnetic nanoparticles.2) A facile synthesis of high quality gold nanoparticles is developed and introduced here. Take an inside view of the typical two phase method, it can be found that the key factor for producing uniform sized gold nanoparticles is the thermal treatment after synthesis. Removing solvent and heating thiol capped gold nanoparticles will result in a shape and size evolution of gold nanoparticles toward high uniformity. This result indicates that the synthetic method for thiol capped gold nanoparticles can be varied to many. Based on this principle, a step-by-step method is developed to produce high quality gold nanoparticles. This method only uses three chemicals and can be performed easily. By controlling the concentration of gold nanoparticles, 2D and 3D close packing structures were observed in as-prepared gold nanoparticles.3) Using seed mediated method produced gold nanorods with different aspect ratio in aqueous solution. The aspect ratio of gold nanorods is controlled by varying seeding amounts. In general, more seeds were added into growth solution, smaller aspect ratio is obtained. TEM, SEM, XRD, and UV-vis are employed to characterize gold nanorods and self-assembly structures. It is observed that the capillary force between nanorods plays an important role in the formation of highly ordered packing structures. The gold nanorods prefer to align side by side to form a ribbon-like structure. Due to the shape effect, the nanorods separate automatically from the mixture of nanorods and nanospheres.4) Titanium dioxide nanoparticles and nanotubes are prepared by wet chemical methods. The titanium dioxide nanostructures were further modified by doping transition metal ions to improve its Photocatalytic activity. The transition metal ions act as a charge separation center to trap the electrons on the surface of titanium dioxide and help catalyst improve its catalysis efficiency.更多还原