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基于一维结型纳米材料的新型爆炸物 蒸气电学传感方法研究
杨政
学位类型硕士
导师窦新存
2016-05-24
学位授予单位中国科学院大学
学位授予地点北京
学位专业材料物理与化学
关键词爆炸物检测 非制式爆炸物 光电检测 气敏 肖特基结
摘要

爆炸物检测作为打击恐怖主义的重要措施之一,正日益彰显出广阔的应用前景。基于电学传感器的气敏检测方法是一种被广泛应用于检测不同气体分子的方法,具有稳定性高、制备工艺成熟、结构简单和成本低廉等优点。使用气敏方法检测爆炸物蒸气具有非接触、采样简单、可靠性高等优点。近几年来,气敏检测技术在爆炸物检测领域得到长足发展。然而爆炸物的饱和蒸气压通常很低,尤其在开放环境中,其浓度更低。所以针对爆炸物蒸气检测的传感器必须具有极高的灵敏度、选择性以及快速的响应和恢复能力。单纯的化敏电阻传感器或场效应管在检测痕量爆炸物蒸气方面能力有限。因此,采用新方法或新策略,获得性能更加优异的传感器,才能使得高灵敏、选择性及快速的检测成为可能。本论文从光电-气敏检测方法和肖特基结传感器界面调控入手,对基于一维纳米材料的新型爆炸物蒸气电学传感方法进行研究。论文研究进展分为以下三个部分:1、基于CdS/ZnO核壳纳米线的硝基爆炸物分解产物光电-气敏检测(ppb级NO2)——间接实现对硝基爆炸物蒸气的检测。硝基爆炸物蒸气在光照下会有部分分解成氮氧化物,如NO2等。而NO2的性质与一些硝基爆炸物分子近似。因此,可以考虑从检测NO2入手来间接实现对硝基爆炸物的检测。CdS的带宽为2.4 eV,具有良好的光电性能;ZnO的带宽3.2 eV,具有良好的气敏性能,且与CdS能带结构匹配。CdS/ZnO核壳纳米线在光照下,CdS导带中的光生电子注入到ZnO导带中,并参与到ZnO壳层与NO2的电子交换反应中。由于核壳界面的异质结可以有效抑制光生电子-空穴对的复合,传感器灵敏度得以大幅提高,对NO2的检测限达到了2 ppb。同时,因为传感器的光电响应速度快、性质稳定,通过在气氛中进行光电响应曲线测试的方式,使得即时的光电-气敏检测成为可能。另外,该光电-气敏传感器对同一浓度NO2的响应大小随着施加光强的不同而发生明显变化。因此,可以通过改变光强调控传感器的气敏响应特性。该研究为构筑高灵敏度的光电-气敏传感器提供了参考,并且使得即时、光控的气敏检测成为可能。2、SiNWs/rGO肖特基结的TiO2界面调控及其对硝基爆炸物蒸气的检测性能研究——构建高选择性的肖特基结硝基爆炸物蒸气传感器。通过在SiNWs阵列表面修饰生长TiO2纳米颗粒以及旋涂rGO电极,构建了SiNWs/TiO2/rGO肖特基结硝基爆炸物蒸气传感器。在反向偏压下实现了对ppb级TNT、DNT和PNT,ppt级PA、RDX以及ppq级HMX 6种硝基爆炸物室温饱和蒸气的高灵敏检测。相应的检测限依次达到0.77 ppb、6.5 ppb、74 ppb、0.12 ppb、0.5 ppt和0.05 ppq。该结构中,SiNWs性质稳定,纳米线之间空隙多,有利于爆炸物分子的扩散;rGO具有优良的物理和化学性能,同时作为类金属可与SiNWs形成肖特基结,并起到吸附分子的作用;TiO2的界面调控既提高了肖特基结的势垒高度,又能够增大结区对硝基爆炸物的吸附能力,从而显著提高对硝基爆炸物蒸气的选择性检测。该肖特基结传感器对低浓度硝基爆炸物蒸气的响应大小与对10 ppm的干扰气体NO2和NH3的响应大小相当,表明其对硝基爆炸物蒸气具有良好的选择性。该研究不仅构建了基于肖特基结的高性能的爆炸物蒸气敏感材料,同时,其中的界面调制思想为开发具有高灵敏度和高选择性的传感器提供了新的思路。3、SiNWs/rGO肖特基结的ZnO界面调控及其对制式和非制式爆炸物蒸气的检测性能研究——构建全面、快速、灵敏的爆炸物蒸气传感器。由于TiO2对硝基爆炸物具有较高的吸附能力,难以实现对非制式爆炸物蒸气的检测。因此,需要选择其它氧化物作为肖特基结界面调控的材料。ZnO对不同气体均具有良好的响应,有助于检测非制式爆炸物。通过在SiNWs阵列表面包覆生长ZnO纳米晶构建SiNW/ZnO核壳纳米线结构,采用石墨烯转移方式构建了SiNWs/ZnO/rGO三元肖特基结。该结构传感器在反向偏压下,对5种制式爆炸物(TNT、DNT、PNT、PA和RDX)蒸气,以及3种非制式爆炸物(尿素、黑火药和硝铵)蒸气均具有良好响应,响应大小依次为4.4%、12.1%、19.0%、7.5%、-10.6%、21.7%、-20.4%和25.6%。同时,响应和恢复时间短,均小于5 s。与第二部分工作中旋涂构建石墨烯顶电极的方法相比,本部分中石墨烯转移构建顶电极的方法,使得形成的肖特基结具有更大的正负电流比,可充分发挥肖特基结在痕量传感检测方面的优势。

其他摘要

As an important strategy to meet the demands of counter-terrorism, there is a vast potential for the development of the detection methods of explosives. The gas sensing method based on electrical sensors is one of the most commonly used approaches for the detection of different gas-phase species. It has advantages such as high stability, mature preparation technology, simple structure and low cost. Gas sensing method has the merits of non-contacting, simple sampling and high reliability to detect explosive vapors.Recently, the gas sensing method has undergone a qualitative change in the field of explosives detection. However, due to the ultralow vapor pressure of explosives in the open environment, the development of sensors with high sensitivity and selectivity, fast response and recovery processes is of great urgency. Actually, the present chemiresistors or FETs have very limited sensing capability towards explosive vapors detection. Thus, to make the sensitive, selective and rapid detection of explosive vapors possible, more advanced strategies are needed to construct electrical sensors with excellent properties.This study covers two strategies concerning electrical explosives sensors: the optoelectronic gas sensing method and the interface modulation of Schottky junction. Thus, new electrical gas sensing methods towards explosive vapors detection based on 1D junction nanomaterials were developed. Research progresses presented here can be divided into the following three sections:1. The detection of the decomposition product of nitro-explosives (ppb level NO2) using CdS/ZnO core/shell nanowires - an indirect realization of nitro-explosive vapors detectionThe nitro-explosive vapors can be decomposed into nitric oxides, such as NO2, which has similar properties with some nitro-explosives. Therefore, the optoelectronic detection of trace NO2 can be applied to realize the indirect detection of nitro-explosives. CdS is a semiconductor with a bandgap of ~2.4 eV and it has excellent optoelectronic properties. While ZnO with a bandgap of ~3.2 eV is widely used as the gas sensing material. Through the construction of heterojunction between CdS and ZnO , not only the light-induced electrons in CdS can inject into the conduction band of ZnO, but also the recombination of light-induced electron and hole pairs could be hindered. It is considered that the light-induced electrons would participate in the charge exchange reaction with NO2, resulting in the enhanced sensitivity. The detection limit of the sensor is down to 2 ppb. Furthermore, the gas sensing behaviors can be modulated by changing the light intensity. Thus, the CdS/ZnO core/shell nanowire structure will facilitate a unique gas sensor and shine light on optoelectronic gas sensing, and at the same time, make the instant and light-controlled gas sensing possible. 2. Fabrication of Schottky sensors with high selectivity towards nitro-explosive vapors through interface modulation of SiNWs/rGO using TiO2A high-performance SiNWs array/TiO2/rGO Schottky sensor is fabricated via the decoration of TiO2 nanoparticles onto the SiNWs and spin-coating of rGO. The sensitive detection of trace nitro-explosives vapors like ppb level TNT, DNT and PNT, ppt level PA and RDX and ppq level HMX is obtained under a reverse bias. The detection limits for TNT, DNT, PNT, PA, RDX and HMX are 0.77 ppb, 6.5 ppb, 74 ppb, 0.12 ppb, 0.5 ppt and 0.05 ppq, respectively. In this structure, the SiNWs have a long-term stability and the gaps between the nanowires are beneficial for molecules diffusion. RGO not only help to form the Schottky junction with SiNWs and , but also help to adsorb explosive molecules. The insertion of TiO2 not only increases the Schottky barrier height, but also enhances the adsorption energy. An excellent selectivity was shown even compared with NO2 and NH3 of 10 ppm. The interface modulation concept illustrated here presents a new sensing method that can be applied to the ultrasensitive detection of trace molecules.3. Fabrication of Schottky sensors with comprehensive, rapid and sensitive detection towards explosive vapors through interface modulation of SiNWs/rGO using ZnODue to the good selectivity towards nitro-explosives shown by TiO2 modulation, the SiNWs array/TiO2/rGO Schottky sensor is not suitable for the detection of improvised explosives. Thus, a suitable oxide needs to be selected for surface/interface modulation. ZnO is an excellent sensing material towards different kinds of gases including military explosives and improvised explosives. It is expected that the interface modulation by the insertion of ZnO is beneficial for the detection of a variety of explosives. In this section, the ternary Schottky junction sensor was obtained with the growth of ZnO nanocrystals on SiNWs array and the transfer of rGO sheets on the array. This sensor shows a fast and ultrasensitive characteristic for the detection of the vapors of five military explosives TNT, DNT, PNT, PA and RDX, and three improvised explosives, urea, BP and AN. The responses towards TNT, DNT, PNT, PA, RDX, urea, BP and AN are 4.4%, 12.1%, 19.02%, 7.5%, -10.6%, 21.72.%, -20.4% and 25.6%, respectively. Furthermore, all the response times and recovery times are less than 5 s. Compared with the spin-coating method in Section 2, the graphene transfer method showing here is more beneficial for the construction of Schottky junction between rGO and vertical nanowire array, and thus can fully utilize the superiority of Schottky junction in trace detection field.

文献类型学位论文
条目标识符http://ir.xjipc.cas.cn/handle/365002/4593
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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杨政. 基于一维结型纳米材料的新型爆炸物 蒸气电学传感方法研究[D]. 北京. 中国科学院大学,2016.
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