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纳米TiO2及其异质结对爆炸物气氛的检测性能研究
周文义
学位类型硕士
导师窦新存
2015-05-28
学位授予单位中国科学院大学
学位授予地点北京
学位专业有机化学
关键词爆炸物检测 气敏 光电 传感器阵列 二氧化钛
摘要

爆炸物检测对于反恐防暴和维护国家安全具有重要意义。目前,爆炸物检测的研究对象主要集中在制式爆炸物,而对恐怖分子常用的非制式爆炸物的检测缺乏系统研究。基于纳米材料的气敏传感器具有体积小、能耗低、灵敏度高、响应快等优点,在痕量检测中占有重要地位。TiO2 纳米线被证明是一种对三硝基甲苯(TNT)等制式爆炸物具有检测性能的传感材料,然而,其在爆炸物检测方面缺乏系统研究。本文从调控TiO2 纳米结构以提升其对爆炸物气氛的响应入手,系统研究了CdS/TiO2 核壳结构纳米线、晶面调控的TiO2 纳米线,以及形貌不同的TiO2 纳米片对制式及非制式爆炸物气氛的检测性能,实现了从单个传感器对爆炸物气氛响应的增强,到传感器阵列对爆炸物气氛的定性识别,取得的创新性成果如下:一、设计制备了CdS/TiO2 核壳纳米线并首次利用催化-气敏机理实现了对TNT 气氛检测性能的提升。通过控制低浓度的钛酸四丁酯(TBOT)无水乙醇溶液的水解速率,在CdS 纳米线表面生长了均匀、连续、结晶性好的TiO2 纳米颗粒,从而得到了CdS/TiO2 核壳纳米线异质结结构。该异质结结构增强了电子-空穴对的分离、提高了电子传输及材料的可见光吸收能力。通过控制TiO2 的负载量,可以实现对异质结吸附能力、光催化能力以及光电转换能力的调控。优化负载量的CdS/TiO2 核壳纳米线能够在弱光照射下检测TNT 气氛,检测限达到2 ppb。其原因可以归结为其优异的吸附能力、光催化能力以及光激发生成的大量光生载流子参与到与气氛的电子交换过程中。该工作利用光催化-气敏机理及光电方法增强了对爆炸物气氛的检测灵敏度,为该机理提供了实验佐证。二、通过调控TiO2 纳米线的晶面,实现了对6 种制式及6 种非制式爆炸物气氛检测性能的提升。使用F 离子作为调控剂,水热法制备了不同暴露晶面的板钛矿型TiO2(TiO2-B)纳米线,测试了其对DNT、PNT、RDX、NT、PA、TNT6 种制式爆炸物原料及KClO3、KNO3、KMnO4、S、NH4NO3、Urea 6 种非制式爆炸物原料的响应。相比于普通TiO2 纳米线,F 离子调控的TiO2 纳米线的气敏性能得到显著提升,对上述12 种爆炸物的响应依次提升4.8 倍、2.4 倍、4 倍、从无到13.5%、6 倍、6 倍、3.5 倍、2 倍、从无到14.8%、13.5 倍、1.5 倍、从无到117 倍。气敏响应提升的原因可以归结为F 离子调控的TiO2 纳米线表面暴露的(110)晶面更多,从而促进了材料与气氛的电子交换。该工作为TiO2 纳米线结构气敏性能的提升提出了新的思路。三、通过F 离子调控,实现了对TiO2 纳米片的形貌调控,构建了由7 个传感器组成的传感器阵列,实现了对6 种制式及6 种非制式爆炸物的识别检测。使用F 离子作为晶面调控剂,通过水热方法制备出一系列不同形貌的TiO2 纳米片。HF 的量对TiO2 纳米片的形貌具有至关重要的作用。随着HF 量的增多,纳米片逐渐长大。不同形貌的TiO2 纳米片对爆炸物气氛的响应不同,成为构建传感器阵列的基础。7 种传感器组成的传感器阵列能够实现对12 种爆炸物的识别检测,从而弥补了单个传感器不能实现对不同种类爆炸物进行识别的缺点。该工作利用同种材料的形貌调控造成的响应差异,首次实现了定性判别制式及非制式爆炸物,为爆炸物传感器阵列的发展做出了有力的实验尝试。

其他摘要
Explosives detection is of vital importance to the national security. The previous research mainly focused on the detection of military explosives, and there is no systematical investigation on the detection of improvised explosives. Nanomaterials-based gas sensor is an important explosives detection method due to the small size, low energy consumption, high and rapid response. TiO2 nanowires are proved to be an efficient sensing material towards Trinitrotoluene (TNT) detection. However, a comprehensive study on the detection of explosives vapors is lacking. This thesis aims to tailor the structure of TiO2 nanomaterials and boost the sensing performance towards explosives vapors. CdS/TiO2 core/shell nanowires, TiO2 nanowires with crystal facets controlled and TiO2 nanosheets with different morphologies were systematically studied. Through this study, not only the sensing performance of a single sensor is enhanced, but the function of explosives species recognition is realized. The innovative achievements are summarized as following: 1) CdS/TiO2 core/shell nanowires were designed and prepared and the sensing performance towards TNT vapor was enhanced by the photocatalysis-gas sensing mechanism for the first time. Ultra-low concentration Tetra-n-butyl Titanate (TBOT) in ethanol solution was used to control the hydrolysis rate. Uniform, continuous and highly crystalline TiO2 nanoparticles were grown on the surface of CdS nanowires. The separation efficiency of electron-hole pairs, the charge transfer property and the visible light absorption performance were greatly enhanced by the formation of the heterojunction structure. The gas adsorbing ability, photocatalytic activity and the photoelectric properties were tuned by the amount of the loaded TiO2 nanoparticles. The CdS/TiO2 heterostructure with the optimal amount of loaded TiO2 nanoparticles could detect TNT vapor under weak light illumination and the limit of detection could reach as low as 2 ppb. This good sensitivity can be attributed to the excellent gas adsorbing ability, the nice photocatalytic performance and the efficient interaction between the abundant photoinduced electrons and TNT vapor. This work utilizes the photocatalysis-gas sensing mechanism and the optoelectronic detection method to boost the sensing performance towards explosives vapors, and provides experimental evidence for this mechanism. 2) The gas sensing performance of TiO2 nanowires for six different military explosives vapors (DNT, PNT, RDX, NT, PA, TNT) and six improvised explosives vapors (KClO3, KNO3, KMnO4, S, NH4NO3, urea) were improved by regulating the crystal facets on the surface of TiO2 nanowires using F- as the regulating agent via hydrothermal reaction. Compared with the pristine TiO2 nanowires without crystal facets regulation, the gas sensing properties of the TiO2 nanowires with crystal facets regulated improved dramatically. The responses for the above explosives increased for 4.8 times, 2.4 times, 4 times, 13.5%, 6 times, 6 times, 3.5 times, 2 times, 14.8%, 13.5 times, 1.5 times and 117 times. The reason can be attributed to the exposed (110) facet of the F-regulated TiO2 nanowires, which could promote the electrons transfer between the sensing material and the target molecules, thus boost the gas sensing responses. This work provides a new strategy for enhancing the gas sensing properties of TiO2 nanowires. 3) A series of TiO2 nanosheets with different morphologies were successfully prepared via the hydrothermal reaction with the help of F-. A gas sensor array based on the series of TiO2 nanosheets was fabricated and this sensor array can identify the six military explosives vapors and six improvised explosives vapors successfully. The morphologies of the nanosheets were controlled by adjusting the concentration of HF in the reaction mixture. The size of the TiO2 nanosheets grew larger with the increase of the amount of HF. Furthermore, TiO2 nanosheets with different morphologies result in different responses towards explosives vapors, which is the basis of the explosives vapors identification. An individual gas sensor can only detect explosives vapors but cannot recognize them, while the gas sensor array composed of seven gas sensors here can efficiently conquer this fault and can realize the recognition of explosives vapors. This work utilizes the response differences resulted by the morphology controlling process in a single material and realizes the recognition of different explosives, which is an important attempt for the development of explosives sensor array.
文献类型学位论文
条目标识符http://ir.xjipc.cas.cn/handle/365002/4264
专题环境科学与技术研究室
作者单位中国科学院新疆理化技术研究所
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周文义. 纳米TiO2及其异质结对爆炸物气氛的检测性能研究[D]. 北京. 中国科学院大学,2015.
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