多孔SnO₂纳米材料与CNTs基复合纳米材料的制备及其气敏性能研究

【作者】 肖元化；

【导师】 唐新村；

【作者基本信息】 中南大学 ， 有机化学， 2010， 硕士

【摘要】 随着人类对自身生存环境要求的提高,人类对有毒和可燃气体的检测、监控、报警的要求也就越来越高。而有毒气体和可燃气体的检测则依赖于高品质的气敏传感器的开发。如何从根本上改善气敏传感器的灵敏度与选择性,实现对待测物的低检测极限和定性识别依然是目前传感器研究的热点之一。气敏材料是气敏传感器的核心部件,因此气敏材料的合成及其气敏性能的研究显得越发重要。纳米材料的出现以及纳米科技的发展为传感器性能的改善提供了新的契机。近年来,具有多孔结构的半导体氧化物纳米材料以及碳纳米管(CNTs)基复合材料因其具有更大的活性表面积而倍受关注。因此合成具有多孔结构的半导体氧化物纳米材料与CNTs基复合纳米材料来制作气敏元件,对提高传感器敏感性能具有非常重要的意义。针对以上问题,本文主要研究了以几个部分：(1)采用一种简单的溶剂热途径,使用DMF与水的混合物作为溶剂,通过改变DMF与水的体积比,制备了多孔的SnO2纳米片、纳米球与空心核壳球状结构。分别采用透射射电镜(TEM)、红外光谱(FT-IR)、比表面积孔径分析仪和X射线衍射(XRD)等分析测试手段对样品的形貌、晶相组成及微观结构特征进行了表征。气敏性能测试表明3种结构的气敏材料,都展示了较好的气敏性能,其中SnO2纳米片则展示了对乙醇蒸汽较好的选择性,SnO2多孔球则显示了对丙酮、甲苯、四氢呋喃和二氯甲烷蒸汽更高的灵敏度,而SnO2空心核壳结构显示对乙醇,甲醇蒸汽最高的灵敏度。(2)采用简单的阳离子表面活性剂诱导原位聚合方法成功制备了新颖的具有针状结构的聚苯胺(PANI)包覆多壁碳纳米管(MWCNTs)的分级纳米结构材料。分别采用红外光谱(FT-IR)、紫外可见(UV-Vis)、扫描电镜(SEM)、透射电镜(TEM)、热重(TG)、气敏测试等分析测试手段对PANI/MWCNT的组成、形貌、微观结构特征、热稳定性和气敏测性能进行了表征和测试。结果表明,在MWCNTs上均匀包覆了约20nm厚的针状PANI,该材料制备的气敏元件在室温下对NH3的灵敏度,重复性明显好于单纯PANI,灵敏度也高于相关文献报道合成的非针状PANI包覆的PNAI/MWCNT。(3)使用硫代乙酰胺,醋酸镉为原料在60℃条件下,通过超声辅助湿法合成了CdS/MWCNT纳米复合物。采用扫描电镜(SEM)、透射电镜(TEM)、X射线能谱(EDS)、选区电子衍射(SAED)和X射线衍射(XRD)等分析测试手段对样品的形貌、晶相组成及微观结构特征进行了表征。结果表明：CdS纳米粒子为立方相的,均匀的包覆在多壁碳纳米管(MWCNTs)上,厚度约为30-40nm。气敏性能测试,表明该材料对乙醇蒸汽展示高的灵敏度与好的选择性。更多还原

【Abstract】 In recent years, with the fast development of science and technology, it provides tremendous convenience to human beings. But at the same time, it has seriously polluted the enviroment. Owing to the toxic and flammable gases threat to our health and wealth, human beings call for a high-qualiy environment. So it becomes more and more important in the study of gas sensor to detect and inspect the toxic and flammable gases. Recently nanomaterials and nanotechnology provide new opportunities for improving the performance of gas sensors.In the past several decades, the sensing properties of porous nanomaterials semiconductor metal oxide nanomaterials and CNT-basd nanocomposites have been widely investigated. Owing to the existence of the large activated surface areas, it could cause the detected gas samples to easily diffuse and interact with sensing materials. Therefore, the syntheses of porous nanomaterials and CNT-basd nanocomposites would be of importance for improving gas sensing properties. Aiming at solving the problem mentioned above, the follows:(1) Porous nanosheets, nanospheres and hollow core-shell nanosperes of SnO2 have been prepared via a solvethermal approach in DMF/water solution by changing the ratio of DMF to total mixture volume. These nano-materials have been thoroughly characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) and nitrogen adsorption-desorption. The gas-sensing properties of samples were studied. Results show all the SnO2-based gas sensors are realized the detection of organic vapors with high sensitivity and short response-recovery time. But the obtained SnO2 porous nanosheet exhibit high selectivetity to ethanol vapor and the SnO2 hollow core-shell structures exhibit high sensitivity to ethanol and methanol vapors, while the SnO2 porous nanospheres exhibit high sensitivity to acetone, toluene, tetrahydrofuran and dichloromethane vapors.(2) We described here a simple approach to the synthesis of hierarchical polyaniline/multiwalled carbon nanotube (MWCNT) nanocables by in situ chemical polymerization directed by the cationic surfactant cetyltrimethylammonium bromide (CTAB). Morphological and structural characteristics, thermal stability, as well as gas-sensing properties of the hybrid nanocomposites were characterized by using various techniques; including Fourier transform infrared spectroscopy (FT-IR), UV-visible absorption spectra (UV-vis), scanning electron microscopy (SEM), transmission electronmicroscopy (TEM), thermogravimetric analyzer and gas-sensing measurement. The results indicate that the as-prepared PANI/MWCNT is uniform with needle-like PANI shell with the thickness as about 20nm. The sensors based on PANI/MWCNT nanocomposites and pure PANI was tested for ammonia gas. The results show that the as-prepared PANI/MWCNT nanocomposites sensors have higher sensitivity and repeatability, and better response/reproducibility towards ammonia at room temperature. Compare with reported PANI/MWCNT with no needle-like PANI, the as-prepared PANI/MWCNT also exhibits the higher sensitivity.(3) A convenient method of sonochemical route in an aqueous solution is reported to synthesize CdS/MWCNT with thioacetamide and cadmium acetate as raw materials at 60℃. The obtained samples are characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDS) and selected area electon diffraction (SAED). The results indicate that the as-prepared CdS/MWCN are uniform with cubic CdS shell thickness of about 30-40 nm. The applications in gas sensors for the SnO2 nanomaterials reveal that the obtained CdS/MWCNT nanocomposites exhibit high sensitivity and better selectivity to ethanol vapors.更多还原