溶剂和离子调控纳米ZnO自组装的研究

发布时间：2018-03-22 22:20

  本文选题：自组装　切入点：溶剂　出处：《南京大学》2017年硕士论文　论文类型：学位论文

【摘要】：纳米材料的自组装是当今纳米科学领域的研究热点之一,这是因为自组装不仅是纳米材料的一种生长机制,而且可以用于构造具有特定集体性质的纳米超结构。自组装是一个十分复杂的过程,会受制于多种因素,包括自组装单元的形状,电偶极矩、磁偶极矩、氢键、范德瓦耳斯力等各种驱动力,以及外加电场、磁场、光等的调节。目前,关于自组装机理的研究仍然在不断深入地开展着。我们考虑,在溶液中,溶剂和离子是两种重要的物质,并且与纳米晶之间存在吸附/脱吸附、氢键、静电力等多种相互作用,因而可以推断它们会对溶液中纳米材料的自组装产生重要影响。本文以碱式醋酸锌纳米片到ZnO的转变与自组装过程为例,系统研究了溶剂和离子对纳米材料自组装的影响。为了避免多种化学物质共存带来的复杂性,我们采用两步法来构建纯净而简单的反应条件,即首先制备出碱式醋酸锌纳米片作为前驱物,然后考察其在各种纯净溶剂或盐溶液中的转变与自组装过程。我们首先研究了蒸馏水、乙醇、甲醇等三种极性质子溶剂和蒸馏水-乙醇混合溶剂的影响,然后研究了 COOH-,NO3-,CO32-,Cl-,SO42-等多种阴离子和阳离子的影响。我们从同一种前驱物出发,调控生长出了多种形貌结构的ZnO,包括量子点、纳米球、纳米片、圆柱、圆锥、棱台,以及前所未有的三棱柱、四棱柱和五棱柱。这些结果有力证明了溶剂和离子对纳米材料自组装过程的调控作用实验表明,蒸馏水、甲醇、乙醇等质子溶剂对碱式醋酸锌纳米片的作用不仅仅是提供一个分散环境,更重要的是可以促进其分解,并将诱导所生成ZnO的自组装过程。在该过程中,溶剂的物理化学性质和结构都会起到重要作用。例如,溶剂的极性一方面会影响溶液中溶剂与纳米晶之间以及纳米晶与纳米晶之间的作用力;另一方面会影响溶液中各种离子的溶解度,从而影响各种离子在纳米晶表面的吸附过程,并最终影响到纳米晶之间的作用力和自组装。而溶剂的局域结构会影响溶剂中离子的分布,并可作为纳米颗粒自组装的模板。我们发现,离子对纳米材料自组装的影响与它们和纳米晶之间的结合力密切相关:如果离子与纳米晶的结合力较强,那么离子将可能会与纳米材料发生化学反应;如果离子与纳米晶的结合力较弱,那么离子也会吸附到纳米晶的特定晶面,从而影响纳米材料在各晶面上的自组装。在上述研究过程中,我们调控生长出了多种形貌结构的ZnO,这些样品各具特点,具有广泛的应用价值。例如,所制备的ZnO量子点能够发射很强的绿光,可以用于生物成像;而所制备的ZnO孪生圆柱和孪生棱台能够强烈散射可见光,如果旋涂到太阳能电池的电极板上,则可以有效提高光捕获能力,从而提高能量转换效率。
[Abstract]:Self-assembly of nanomaterials is one of the hotspots in the field of nanoscience, because self-assembly is not only a growth mechanism of nanomaterials. And it can be used to construct nanostructures with specific collective properties. Self-assembly is a very complex process that is subject to a variety of factors, including the shape of the self-assembled unit, the electric dipole moment, the magnetic dipole moment, the hydrogen bond. All kinds of driving forces such as van der Waals force, as well as the regulation of electric field, magnetic field, light, etc. At present, the study of self-assembly mechanism is still going on in depth. Solvents and ions are two important substances, and there are many interactions with nanocrystals, such as adsorption / desorption, hydrogen bond, hydrostatic power, etc. Therefore, it can be inferred that they will have an important effect on the self-assembly of nanomaterials in solution. In this paper, the conversion and self-assembly process from basic zinc acetate to ZnO is taken as an example. The effects of solvents and ions on the self-assembly of nanomaterials were systematically studied. In order to avoid the complexity caused by the coexistence of various chemical substances, we used a two-step method to construct pure and simple reaction conditions. That is to say, the basic zinc acetate nanoparticles were prepared as precursors, and then their transformation and self-assembly in various pure solvents or salt solutions were investigated. The effects of three polar proton solvents such as methanol and distilled water-ethanol mixed solvents on the effects of various anions and cations such as COOH-no _ 3-CO _ (32) O _ (2) O _ (2) O _ (2) O _ (2) O _ (2) and CO _ (32) O _ (2) O _ (2) O _ (2) were studied. Zno has grown in a variety of morphologies, including quantum dots, nanospheres, nanochips, cylinders, cones, prisms, and unprecedented triangular prisms. Four prism and five prism. These results strongly demonstrate the effects of solvents and ions on the self-assembly process of nanomaterials. Experiments show that distilled water, methanol, The effect of proton solvents, such as ethanol, on basic zinc acetate nanoparticles is not only to provide a dispersed environment, but also to promote its decomposition and induce the self-assembly process of the resulting ZnO. The physical and chemical properties and structure of the solvent play an important role. For example, the polarity of the solvent will affect the force between the solvent and the nanocrystalline and between the nanocrystalline and the nanocrystalline. On the other hand, it will affect the solubility of the ions in the solution, thus affecting the adsorption process of the ions on the nanocrystalline surface. The local structure of the solvent will affect the distribution of ions in the solvent and can be used as a template for the self-assembly of nanoparticles. The effect of ions on the self-assembly of nanomaterials is closely related to the adhesion between them and nanocrystals: if the binding force between ions and nanocrystals is strong, then ions may react with nanomaterials; If the binding force between ions and nanocrystals is weak, then ions will also adsorb to the specific crystal planes of nanocrystals, which will affect the self-assembly of nanomaterials on each crystal plane. We have controlled and grown a variety of ZnO with different morphology and structure. These samples have their own characteristics and have wide application value. For example, the ZnO quantum dots can emit strong green light and can be used in biological imaging. The ZnO twin cylinder and the twin prism can scatter the visible light strongly. If the solar cell is rotated on the electrode plate, the optical capture ability can be improved effectively and the energy conversion efficiency can be improved.
【学位授予单位】：南京大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O614.241;TB383.1
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本文编号：1650666