电纺氧化锡基纳米纤维材料的制备及其丙酮传感性能研究

发布时间：2018-01-05 13:11

本文关键词：电纺氧化锡基纳米纤维材料的制备及其丙酮传感性能研究　出处：《吉林大学》2017年博士论文　论文类型：学位论文

【摘要】：为了应对日益严重的空气污染,研究对于以丙酮为代表的挥发性有机空气污染物具有优良敏感性质的高效率气体传感器具有十分重要的意义。SnO_2基敏感材料在气体传感研究领域中一直扮演着比较重要的角色,在环境污染物气体的检测和易燃易爆气体的报警等领域具备巨大的应用潜力。与传统的零维和二维纳米材料相比,一维纳米材料由于其自身独特的结构和特性,在快速识别信号和电子传输等方面具有很大优势,因而在纳米传感器研究领域受到格外重视。静电纺丝是一种成本较为低廉、操作较为简单的制备一维纳米材料的方法。该方法得到的一维纳米纤维,其组成和结构可以便捷地进行精确设计和调控,较大的比表面积为气体分子在材料表面提供了更多的反应活性位点,有利于提高气体响应;纳米纤维较大的宏观长度和长径比,也十分有利于电信号的快速传递,从而获得快速的响应恢复特性。本论文采用静电纺丝技术制备了一系列SnO_2基一维纳米纤维材料,通过采用掺杂、构筑异质结以及贵金属负载等方法对纳米纤维的组成结构进行定向设计调控来提高气体传感特性,并深入研究这些材料作为丙酮敏感材料所表现出来的性能,建立组成结构和性能之间的关系,从而为进一步拓展一维纳米纤维在环境监测和保护领域的应用奠定基础。主要内容分为以下三部分:1.金属离子掺杂是目前应用最广泛的可以有效提高金属氧化物半导体气体传感性能的方法之一。我们基于纳米纤维的独特结构以及组成可控的特点,以高分子PVP为模板,利用静电纺丝结合高温后处理技术制备了一系列碱土金属离子掺杂的SnO_2纳米纤维,并研究了它们对于丙酮的传感性能,详细地讨论了不同碱土金属离子的掺杂机制。首先,我们以电纺SnO_2纳米纤维作为本征材料,选择Sr~(2+)对其进行间隙掺杂,通过碱土金属掺杂对于SnO_2晶体生长的抑制作用对SnO_2纳米纤维的晶粒尺寸进行调控,从而进一步影响改善其气体传感性能。当Sr~(2+)掺杂量为1 at%时,纳米纤维的晶粒尺寸最小;相应地,丙酮传感性能此时最佳,对100 ppm丙酮的响应值(~25)为纯SnO_2纳米纤维的2倍,响应时间和恢复时间均为6 s左右,且兼具优秀的选择性和稳定性。为了进一步验证碱土金属掺杂对于SnO_2纳米纤维的气体传感性能的提高作用,我们又选择了另外一种比Sr~(2+)半径稍小的碱土金属离子Ca~(2+)对SnO_2纳米纤维进行微量掺杂。当Ca~(2+)掺杂量为0.8 at%时,纳米纤维对丙酮的传感性能最佳,对100 ppm丙酮的响应值(~27)为纯SnO_2纳米纤维的2.3倍;响应时间约为6 s,恢复时间约为3 s,选择性和稳定性也较为优异。通过对这些提高的传感性能的研究和探讨,发现除了碱土金属抑制剂对于晶粒生长的控制作用外,部分Ca~(2+)在掺杂过程中替代Sn~(4+)位点而导致的晶格缺陷和氧空位同样在气敏性能的增强中发挥着重要作用。2.在气体敏感材料中构建异质结同样是一种提高半导体气体传感性能的重要方法。我们充分利用纳米纤维结构组成可控的特点,通过静电纺丝技术将不同的纳米异质结引入SnO_2纳米纤维中,并研究了不同异质组分比例对丙酮的传感性能所造成的影响,详细地讨论了异质结增强气体传感性能的作用机理。首先,我们以高分子PVP为模板,运用静电纺丝结合高温后处理技术制备了组分分布均匀的p-Cr_2O_3/n-SnO_2复合纳米纤维,并详细考察了其丙酮敏感性能。实验结果表明Cr_2O_3/SnO_2 p-n异质结的引入极大地改善了SnO_2纳米纤维的丙酮传感性能,以100 ppm丙酮为目标气体,当Cr_2O_3组分在复合纤维中的含量为3 at%时,Cr_2O_3/SnO_2复合纳米纤维的响应(~46,280 oC)最大,为纯SnO_2纳米纤维响应(~12,300 o C)的3.8倍;响应时间仅为4s,恢复时间约为5s;对丙酮的饱和浓度(20,000 ppm)大大超过纯SnO_2纳米纤维(5,000 ppm),抗湿性、选择性和稳定性优异。为了研究同型异质结对于气敏性能的影响,我们又运用静电纺丝技术制备了n-Cd O/n-SnO_2复合纳米纤维,并详细考察了其丙酮传感性能。实验结果表明相比于纯SnO_2纳米纤维,CdO/SnO_2异质结复合纳米纤维表现出显著提高的丙酮敏感特性。对于性能最出色的Cd O含量为5 at%的CdO/SnO_2复合纳米纤维,其对100 ppm丙酮的响应(~50,280 o C)为纯SnO_2纳米纤维(~12,300 o C)的4.2倍;响应时间约为6 s,恢复时间仅为5 s;对丙酮的饱和浓度(20,000 ppm)大大超过纯SnO_2纳米纤维(5,000 ppm),抗湿性、选择性和稳定性优异。3.本体材料负载贵金属已经被证明是一种提高气体响应和降低工作温度的有效方法,但目前大部分这方面工作所使用的都是多步后处理方法,即先制备本体材料,再通过浸渍、沉积、溅射等方法在材料表面修饰贵金属,过程较为繁琐且材料利用率较低。由于静电纺丝的各组分前驱体是在溶液相中混合均匀的,因此这种一步直接的方法制备出的一维纳米材料各组分分布均匀,对于提高性能和降低贵金属负载的成本十分有利。我们基于静电纺丝技术,以高分子PVP为模板制备了负载Au的SnO_2基复合纳米纤维,通过引入Au成功降低了对丙酮的操作温度,并进一步提高了响应特性。首先,我们将Au引入到SnO_2纳米纤维中,得到的Au/SnO_2复合纳米纤维对于丙酮的操作温度大幅降低,响应明显提升;在220 oC的最佳工作温度下对100 ppm丙酮的响应值达到了57,响应时间为8.5 s,恢复时间为7 s;丙酮饱和浓度达到了30,000 ppm,经60天长期放置后依旧能够保持响应信号的稳定。此外,对Au/SnO_2肖特基结和贵金属催化剂在性能增强中所起的作用也进行了讨论。随后,针对Au/SnO_2复合纳米纤维的丙酮选择性不够特别突出的问题,我们通过引入第三方非本征稀土金属氧化物Eu2O3,利用Eu2O3和Au的协同作用成功地改善了丙酮选择性;所制备的Eu_2O_3/Au/SnO_2复合纳米纤维在200 o C的最佳工作温度下对100 ppm丙酮的响应值达到了65,响应时间为11.7 s,恢复时间为6.5 s;丙酮检测下限达到了ppb级,饱和浓度为30,000 ppm,可测浓度范围更宽,且重复稳定性优异。
[Abstract]:In order to cope with the increasingly serious air pollution, high efficiency gas sensor has excellent sensitive properties for volatile organic air pollutants using acetone as the representative of the significance of.SnO_2 based sensitive materials plays a very important role has been more important in the research field of gas sensing, have great application potential in the field of environmental pollutants detection alarm gas flammable and explosive gases. Compared with the traditional zero and two dimensional nano materials, nano materials because of its unique structure and characteristics, has great advantages in the rapid identification of electronic signals and transmission, which has been in the field of nano sensor attention. Electrospinning is a relatively inexpensive, preparation method one dimensional nano materials. The operation is relatively simple one-dimensional nanofibers obtained by this method, the composition and structure of Convenient to carry out precise design and control of large surface area for gas molecules on the surface of the material provides more reactive sites, improve the gas response; macroscopic length nanofibers and larger length diameter ratio, also very fast to signal transmission, to obtain fast response characteristics. In a series of SnO_2 based one-dimensional nanofibers were fabricated by electrospinning, by doping, construct heterojunction and noble metal loading method of the structure on the nanometer fiber directional regulation design to improve gas sensing properties, performance and in-depth study of these materials as acetone sensitive material, the relationship between the establishment of structure and performance, so as to lay the foundation for further development of application of one-dimensional nano fiber in the field of environmental monitoring and protection. The main content is divided into the following The three part: 1. metal ion doping is currently the most widely used can be one method of metal oxide semiconductor gas sensing performance effectively. Our unique structure of nano fiber and characteristics of controllable composition based on polymer PVP as template by electrospinning combined with high temperature postprocessing technology for SnO_2 nano fiber series of alkaline earth metal ions doped the preparation and study their sensing properties for acetone, different doping mechanism of alkaline earth metal ions were discussed in detail. First, we use the electrospun SnO_2 nanofibers as intrinsic materials, Sr~ (2+) doping on the gap, the alkaline earth metal doped SnO_2 crystal growth inhibitory effect of grain size on SnO_2 nano fiber regulation, so as to further improve the gas sensing performance. When Sr~ (2+) doped with 1 at%, grain size of nano fiber Inch minimum; accordingly, acetone sensing performance at best, in response to 100 ppm of acetone (~25) value was 2 times of pure SnO_2 nanofibers, the response time and recovery time was about 6 s, and has excellent selectivity and stability. In order to improve the effect of further verification of the gas sensing performance of alkaline earth metal doping on SnO_2 nano fiber, we chose another than Sr~ (2+) alkaline earth metal ions Ca~ radius smaller (2+) micro doping on SnO_2 nano fiber. When Ca~ (2+) doped with 0.8 at%, nano fiber to acetone sensing performance is the best response to the value of 100 ppm acetone (~27) is 2.3 times that of pure SnO_2 nanofibers; the response time is about 6 s, the recovery time is about 3 s, selectivity and stability are excellent. Through the research and Discussion on the sensing performance improvement, found that in addition to grain growth inhibitor for alkaline earth metal The control effect, part of the Ca~ (2+) instead of Sn~ during doping (4+) lattice defects and oxygen vacancies caused the same sites in enhanced gas sensing properties play an important role in the construction of.2. gas sensitive material in the heterojunction is also an important method to improve the performance of semiconductor gas sensing characteristics we. Make full use of nano fiber structure controllable, via electrospinning of different nano heterostructures into SnO_2 nanofibers, and studied the influence of different heterogeneous groups caused by the sensing performance ratio of acetone, discussed in detail the heterojunction enhancement mechanism of the gas sensing performance. First, we take PVP as the polymer the use of templates, electrospinning with high temperature postprocessing technology for p-Cr_2O_3/n-SnO_2 composite nanofibers uniformly distributed components were prepared, and a detailed study of its acetone sensitive properties. The results of experiments The Cr_2O_3/SnO_2 p-n heterojunction into acetone and greatly improve the sensing properties of SnO_2 nano fiber, 100 ppm acetone as the target gas, when the content of Cr_2O_3 component in the composite fiber is 3 at%, the response of Cr_2O_3/SnO_2 composite nanofibers (~46280 oC), in response to pure SnO_2 nanofibers (~12300 o C 3.8 times); response time is only 4S, the recovery time is about 5S; the saturated concentration of acetone (20000 ppm) significantly more than the pure SnO_2 nanofibers (5000 ppm), moisture resistance, selectivity and excellent stability. In order to study the heterojunction effect on gas sensing properties, we use technology the electrospun n-Cd O/n-SnO_2 composite nanofibers were prepared and investigated with the acetone sensing performance. Experimental results show that compared to pure SnO_2 nanofibers, CdO/SnO_2 heterojunction composite nanofibers showed a significantly higher sensitivity of acetone The content of O Cd. For the best performance of CdO/SnO_2 composite nano fiber 5 at%, its response to 100 ppm acetone (~50280 o C) for pure SnO_2 nanofibers (~12300 o C) 4.2 times; the response time is about 6 s, the recovery time is only 5 s; on the saturated concentration of acetone (20000 ppm) significantly more than the pure SnO_2 nanofibers (5000 ppm), moisture resistance, excellent selectivity and stability of.3. bulk materials supported noble metal has been proved to be an effective method to improve the gas response and reduce the temperature, but the use of most of this work is the processing method of multi step, i.e. preparation of bulk materials, through impregnation deposition, sputtering method in material surface modification of precious metals, the process is more complicated and the material utilization rate is relatively low. Because each electrospinning precursor is divided evenly mixed in the solution phase, so that the one step direct method One dimensional nano materials prepared were divided evenly distributed, to improve the performance and reduce the cost of the precious metal load is very favorable. We electrospinning technology based on SnO_2 composite nanofiber supported Au templates for preparation of polymer PVP, by introducing Au successfully reduced to acetone operating temperature, and further improve the response characteristics. Firstly, we introduce the Au into SnO_2 nanofibers, Au/SnO_2 nanofibers obtained for acetone operating temperature significantly reduced, significantly enhance the response; at the optimal temperature under 220 oC in response to 100 ppm acetone value reached 57, the response time is 8.5 s, the recovery time was 7 s; the saturated concentration of acetone reached 30000 ppm, after 60 days after long period of storage is still able to maintain the stability of the response signal. In addition, the Au/SnO_2 Schottky junction and noble metal catalyst in the performance enhancement of it Are discussed. Then, the Au/SnO_2 composite nanofibers acetone selective enough prominent problem, we introduce third extrinsic rare earth metal oxide Eu2O3, successfully improved the selectivity of acetone by the synergistic effect of Eu2O3 and Au; in response to 100 ppm acetone optimum temperature for Eu_2O_3/Au/SnO_2 composite nanofibers prepared in 200 o C value reached 65, the response time is 11.7 s, the recovery time is 6.5 s; the detection limit of acetone reached ppb and the saturation concentration of 30000 ppm, measured concentrations of a wide range of heavy and complex stability is excellent.

【学位授予单位】：吉林大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TQ340.64

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