摘要
随着科技的不断发展，纳米科学已成为十分热门的研究领域，其应用范围不断扩大。纳米材料在分析化学中的应用已经成为现代分析化学发展的最重要的前沿领域之一。碳纳米管(Carbon nanotubes，CNTs)是优良的一维纳米材料，由于其独特的力学性能，电学性能和极高的纵横比，使CNTs在纳米电子器件、催化剂载体、电极材料、储氢材料、高效吸附剂等方面的应用广泛。纳米SnO_2是n型宽禁带半导体材料，具有优异的气敏特性和光电性能，作为一种新型功能材料应用于气敏和湿敏元件、电极材料、光学玻璃、催化剂、功能陶瓷等方面。
本论文针对碳纳米管和纳米SnO_2的应用开展了两部分研究工作。
一、采用氧化性酸对多壁碳纳米管(Multi-walled carbon nanotubes，MWCNTs)进行了纯化与短切，在碳纳米管表面引入羧基，提高了碳纳米管的水溶性，并用扫描电镜(SEM)和透射电镜(TEM)对其进行表征。将制备的水溶性羧基化碳纳米管作为增敏剂，用方波溶出伏安法测定痕量镉，发现其增敏效果显著。随后讨论了吸附溶出的机理，对富集时间、富集电位、镉的浓度、HCl加入量的影响及部分离子干扰等进行试验，并对含镉水样进行测定。试验结果发现：Cd~(2+)在-0．65V左右出现灵敏溶出峰，峰电流在Cd~(2+)浓度为2．0×10~(-9)～1．0×10~(-8) mol／L时呈现良好的线性关系，检出限为1．0×10~(-10) mol／L，回收率为94％～103％。
二、以离子液体和水为混合溶剂结合水热技术制备了尺寸可控的SnO_2纳米材料。采用X射线衍射(XRD)、透射电镜(TEM)、高分辨透射电镜(HRTEM)、选区电子衍射(SAED)和X射线能谱分析仪(EDS)等现代表征手段对产物进行表征。
本文考察了反应温度、反应时间和离子液体浓度等实验条件对纳米SnO_2粉体的晶体结构、粒度及分散性的影响，并对合成机理进行了初步的探讨。结果表明：在水热温度240℃、反应时间20h、离子液体的浓度为2．65mol／L时得到的粉体结晶性好、粉体颗粒大小在8-10nm左右、并具有良好的分散性。纳米级二氧化锡基体的量子尺寸效应和表面效应使得二氧化锡传感器气敏性能优化。将制备的SnO_2纳米材料制作成气敏传感器，可实现对环境中H_2、CO、NO_2、C_2H_2、H_2S、天然气等还原性气体的检测。
With the continuous development of science and technology, nano-science has been widely used in various fields and become a very popular research area. Especially in recent years, the application of nanomaterials in the analytical chemistry has become one of the most important frontier in the modern analytical chemistry. Carbon nanotubes (CNTs) are an excellent kind of one-dimensional nanomaterials. Because of their outstanding chemical, physical and mechanical properties, CNTs have been applied in many fields, such as emission electron sources, scanning probes, chemical sensors, field-effect transistors nano-electronic devices, and so on. Tin oxide (SnO_2) is an n-type, wide bandgap semiconductor. Because of its unique gas sensitivity and photoelectric properties, tin oxide has been widely used for various electrochemical and catalytic applications, such as gas-sensing and humidity sensor, electrode material, optical glass, catalysts, ceramics and so on.
In this paper, we have mainly done two parts of research work with respect to the applications of carbon nanotubes and nanocrystal SnO_2.
1. MWCNTs were treated with the oxidized acid to generate pure and unentangled MWCNTs with carboxylic groups on it, and the modified MWCNTs were characterized by scanning electron microscope(SEM) and transmission electron microscope (TEM). The resulting MWCNTs have excellent solubility in water and were used as a sensitizing agent which has significant effect on the square wave anodic stripping voltammetric measurement of trace cadmium. Possible adsorption and stripping mechanism were discussed. The electrochemical response was characterized with respect to accumulation time, cadmium concentration, supporting electrolyte, influence of hydrochloric acid added and possible interferences. The method was successfully applied to determine trace cadmium in water sample. The results show that a sensitive stripping peak potential of cadmium is about -0.65V, and the peak current is linear with the concentration of Cd~(2+) in the range of 2.0×10~(-9)-1.0×10~(-8) mol/L. The detection limit is 1.0×10~(-10) mol/L, and the recovery is 94 %-103 %.
2. Here we report the preparation of size controllable SnO_2 nanomaterials using ionic liquid and distilled water as the component solvent by hydrothermal method. The phases, morphology, microstructure and composition of the products were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), high resolution transmission electron microscope (HRTEM), selected area electron diffraction (SAED) and energy-distersive X-ray spectroscopy (EDS) and so on.
The influences of the hydrothermal temperature, ionic liquid's concentration and hydrothermal time on crystal structure, morphology and paricle size were discussed. The experimental results indicated that SnO_2 powder exhibits well crystallinity with size of 8-10nm and good dispersivity. The optimized conditions for the preparation of SnO_2 are at 220-240℃of the hydrothermal temperature, 2.65mol/L of the ionic liquid's concentration and 20 hours of the hydrothermal time. The quantum size effect and surface effect of nanostructures of SnO_2 can optimize the gas sensitivity of the sensor. The resulting SnO_2 nanomaterials can be used in the preparation of gas sensor for determining reductive gases in environment such as H_2, CO, NO_2, C_2H_2, H_2S and natural gas.
引文
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