几种无机氧化物纳米管的液相合成、生长机理及其应用研究

【作者】 禚林海；

【导师】 唐波；

【作者基本信息】 山东师范大学 ， 物理化学， 2008， 博士

【摘要】 如何合理控制纳米材料的定向生长,进而实现对其尺寸、维度、组成、晶体结构乃至物性的调控,对于深入研究结构与物性的关联,并最终实现按照人们的意愿来设计合成功能材料具有重要的意义。本论文的主要目的是探索无机氧化物纳米管的化学液相合成路线,发挥化学液相合成技术在控制材料的微结构、形貌和尺寸等方面的优势,探索在化学液相中制备纳米管的新方法,期望得到形貌和尺寸可控的纳米管,获得一些纳米管的制备和形貌控制等方面的规律,并开拓纳米管的应用研究。在本论文中,成功制备了氢氧化镁、氢氧化镍、氧化亚钴、四氧化三钴等纳米管,探讨了它们的生长机理;以氢氧化镍和氧化亚钴纳米管为模板,利用氢气还原方法得到了金属镍和钴的纳米管;进行了氢氧化镁纳米管吸附印染废水的试验;另外,我们还研究了四氧化三钴以及氧化亚钴纳米管作为催化剂,在催化过氧化氢氧化底物中的反应,发现上述两种纳米管具有过氧化物酶的活性。主要内容总结如下:1、以氨水为沉淀剂,得到了氢氧化物的前驱体,通过控制溶液的pH值、离子强度以及使用醇/水混合溶剂,经过溶剂热反应,得到了氢氧化镁、氢氧化镍、四氧化三钴、氧化亚钴纳米管。与已有文献相比,本方法具有通用性,方法简单的优点。到目前为止,氧化亚钴纳米管的合成还没有文献报道。2、对上述纳米管的结构进行了表征,通过HRTEM发现了这些纳米管中超结构的存在,推测可能是在形成过程中由于氧空位引起的。3、采用粉末衍射、电子显微镜等众多技术手段研究了产物的物相、形貌和结构;详细地研究了各反应参数对产物的形貌和尺寸的影响,深入探讨了这些纳米管的形成机制,发现纳米管的形成可以分为三个步骤:第一步:前驱体在高温高压下,重新溶解在混合溶剂中,随着饱和度的不断增加,溶解在溶剂中的前驱体又重新结晶,我们推测这个过程发生的驱动力与这些前驱体的层状结构以及它们的六方晶体结构有关;第二步:这些纳米片又发生了破裂,形成了一些小的纳米聚集体;第三步:这些小的纳米聚集体又组装成纳米管。4、以氢氧化镍和氧化亚钴纳米管为模板,利用氢气还原方法得到了金属镍和钴的纳米管。5、通过氢氧化镁纳米管吸附印染废水的试验,与商用氢氧化镁相比,发现纳米管的吸附能力较强。6、研究了四氧化三钴以及氧化亚钴纳米管做为催化剂,在催化过氧化氢氧化底物中的反应,对两种纳米管催化H₂O₂氧化TMB的动力学进行了研究。发现Co₃O₄、CoO纳米管在催化H₂O₂氧化TMB的反应中,催化机理与辣根过氧化物酶的催化机理类似,即Co₃O₄、CoO纳米管具有辣根过氧化物酶的活性。更多还原

【Abstract】 The main challenge in the area of nanotechnology is how to precisely control the sizes, dimensionalities, compositions and crystal structures in nanoscale, which may serve as a powerful tool for the tailoring of physical/chemical properties of materials in a controllable way. Solution-based chemical methods have some advantages in the controllable synthesis of nanomaterials in their structure, morphology and dimension. In this dissertation, valuable explorations have been carried out to prepare inorganic nanotubes including CoO, Co3O4, Ni（OH）2 and Mg（OH）2 nanotubes using solution-based chemical methods, as well as their formation mechanism and the novel properties of the as-obtained new-type nanostructures. The main points can be summarized as follows:1. CoO, Co3O4, Ni（OH）2 and Mg（OH）2 nanotubes were synthesized by solvothermal treatment of corresponding colloidal hydroxide. These nanotubes were characterized by powder X-ray diffraction （XRD）, selected area electron diffraction （SAED） and transmission electron microscopy （TEM）. Advantages of this method include that it is a simple and general process without the need for a catalyst, surfactant or template, which is low cost and the raw materials are readily available. Based on the above results, other metal hydroxides with layered structure are therefore potentially capable of forming nanotubes. To the best of our knowledge, no studies have been reported on the preparation of CoO nanotubes.2. Based on the above time-dependent morphological evolution evidence, the growth of these nanotubes can be divided into three steps. At first, these amorphous precursors would form some nanoplates during the first stage. The first step lasted for about 1 h, and then some of these nanoplates were dissolved again to form some small growth entities （such as atomistic species or cluster building blocks） in the second step. And subsequently, these small growth entities reorganized to from large aggregations till the tubular nanostructures formed.3. Some larger superstructures are found in CoO, Co₃O₄, Ni（OH）₂ nanotubes and are suggested to be caused by ordered oxygen vacancie during formation.4. Ni and Co nanotubes were synthesized using the as-obtained CoO and Ni（OH）₂ nanotubes as template.5. Decoloration of wastewater containing direct dye by using Mg（OH）₂ nanotubes is studied. The result showed that the absorbing capacity of Mg（OH）₂ nanotubes is larger than commerical Mg（OH）₂ materials.6. We report that CoO and Co3O4 nanotubes in fact possess an intrinsic enzyme imietic activity similar to that found in natural peroxides. To investigate the mechanism of the peroxidase activity of these nanotubes, we determined apparent steady-state kinetic parameters for the reaction. Within the suitable range of H2O2 concentrations typical Michaelis-Menten curves were observed for both CoO and Co₃O₄ nanotubes.更多还原