【作者】 太惠玲；

【导师】 蒋亚东；

【作者基本信息】 电子科技大学 ， 光学工程， 2008， 博士

【摘要】 作为气体传感器的核心，气敏材料正在由单一材料向复合材料发展。导电聚合物/无机纳米复合材料综合了导电聚合物和无机纳米材料的各自优点，在气敏特性方面拥有许多优异的性能。本论文运用原位自组装技术制备了一系列导电聚合物/无机纳米复合薄膜，并运用多种方法对其进行了表征和分析；设计并制备了平面微叉指电极式器件结构，深入研究了导电聚合物/无机纳米复合薄膜传感器的NH₃气敏性能。将不同的导电聚合物/无机纳米复合薄膜应用于微气体传感器阵列，同时与人工神经网络模式识别技术相结合构成气体辨识系统，初步实现了对多气体的定性分析。其主要内容归纳如下：1．室温条件下，运用原位自组装技术制备了聚吡咯（PPy）和聚吡咯/二氧化钛（PPy/TiO₂）气敏薄膜，并首次研究了PPy/TiO₂纳米复合薄膜的NH₃敏特性。光谱分析表明，PPy和TiO₂在形成纳米复合材料时二者之间存在一定的相互作用；热失重（TG）分析表明，PPy/TiO₂纳米复合材料较纯PPy材料的热稳定性好；形貌分析发现，PPy/TiO₂纳米复合材料呈典型的核-壳结构，其复合薄膜比单一的PPy薄膜生长地更均匀、致密，且颗粒粒径更小，这使得复合薄膜具有更大的比表面积及更多的表面活性位，结构缺陷减少，纳米粒子吸附能力增强，从而使得复合薄膜的敏感性能优于纯的PPy薄膜，这与气敏特性研究结果一致。当TiO₂溶胶浓度为0．1 wt％，薄膜沉积时间为20 min时，PPy/TiO₂纳米复合薄膜传感器的敏感性能最佳。建立了PPy基气体传感器微观气敏响应模型，并根据该模型计算出PPy和PPy/TiO₂气敏薄膜与NH₃气体之间的平衡常数分别为1．18×10^-2和1．32×10^-2。2．运用原位自组装法制备了聚苯胺（PANI）和聚苯胺/二氧化钛（PANI/TiO₂）薄膜，并研究了其NH₃敏性能。实验发现，在PANI链增长初期插入基片可获得光滑透明的薄膜；PANI/TiO₂纳米复合薄膜传感器能够有效探测较低浓度的NH₃（1 ppm），且其敏感性能明显优于纯的PANI薄膜，这是因为PANI/TiO₂复合薄膜的多孔纳米纤维网状结构更有利于气体的吸附和扩散，同时在TiO₂表面形成的正电荷消耗层造成了复合薄膜对NH₃气体活化能和物理吸附焓的降低。掺杂酸种类和聚合温度对PANI/TiO₂复合薄膜的形貌及气敏性能有一定的影响。结果表明，在10℃下以盐酸为掺杂酸制备的PANI/TiO₂复合薄膜传感器对NH₃（23-141 ppm）的响应时间达到2 s，恢复时间小于60 s，其灵敏度值与NH₃浓度具有良好的线性相关性；该传感器同时具有较好的重复性、选择性和稳定性。温度对该传感器的响应特性有较大影响，其对NH₃的灵敏度值随温度的升高呈倒数关系减小，而环境湿度的影响则相对较小。3．采用软模板法制备了聚苯胺/氧化铟（PANI/In₂O₃）、聚苯胺/氧化锡（PANI/SnO₂）和聚苯胺/多壁碳纳米管（PANI/MWNT）复合薄膜，并研究了其NH₃敏感性能；重点研究了阳离子表面活性剂十四烷基三甲基溴化铵（TTAB）和非离子表面活性剂聚氧乙烯（20）失水山梨醇单月桂酸酯（Tween-20）对PANI/In₂O₃纳米复合薄膜形貌及气敏特性的影响。X射线衍射分析（XRD）和形貌分析发现，TTAB和Tween-20在一定程度上减小了In₂O₃纳米颗粒的团聚，使得复合薄膜具有更致密的纳米纤维网状结构，且纳米纤维直径更小；但不同浓度的TTAB造成了不同的PANI/In₂O₃复合薄膜形貌和敏感性能，这一现象可能与TTAB在水介质中形成的超分子结构有关。气敏特性研究表明，采用TTAB且TTAB与纳米粉体的物质的量为0．5时，制备的复合薄膜具有最高的灵敏度，但其响应及恢复时间增长，这可能是由于致密的薄膜表面在一定程度上阻碍了气体分子的吸附和解析。基于Langmuir吸附模型建立了PANI及其复合薄膜传感器对NH₃气体的吸附/解吸附动力学方程，拟合结果与实际响应曲线有较好的一致性。4．采用4个半导体气体传感器分立元件构建了气体传感器阵列，并分别与基于误差反向传播算法（BP算法）的BP神经网络和自组织竞争网络相结合，实现了对40-1000 ppm浓度范围内CO和H₂气体的定量与定性分析。在此基础上，首次以PANI及PANI/无机纳米复合薄膜微传感器单元构成原始气体传感器阵列，并运用分步聚类分析对该阵列进行了优化，最终选取了PANI、PANI/TiO₂、PANI/In₂O₃和PANI/MWNT等4个薄膜微传感器单元构成优化阵列；将该优化阵列与概率神经网络（PNN）相结合构成气体辨识系统，完成了一定浓度范围内的NH₃、CO和H₂单一气体的定性识别。更多还原

【Abstract】 As the nucleus of gas sensors,the gas-sensing material is changing from thesimplex material to the composite material.Conducting polymer/inorganic materialnanocomposites combine the advantages of conducting polymers and inorganicnano-materials,which endows the nanocomposite with excellent gas-sensingcharacteristics.In this dissertation,a series of conducting polymer/inorganic materialnanocomposite ammonia （NH₃） gas-sensing thin films were fabricated by an in-situself-assembly approach,which were characterized and analyzed with different methods.The planar micro-interdigital electrodes were designed and prepared,and the deep anddetailed investigation on their NH₃ gas-sensing properties was carried out.Furthermore,the discrimination of gas species was achieved by the gas recognition system composedof the gas sensor array with different nanocomposite thin films and the patternrecognition technique of the artificial neuron network （ANN）.The main results are asfollows:1.Polypyrrole （PPy） and polypyrrole/titanium dioxide （PPy/TiO₂） gas sensitivethin films were developed by an in-situ self-assembly method at room temperature.NH₃gas sensitive properties of the PPy/TiO₂ nanocomposite thin film was firstlyinvestigated.Spectrum analyses indicated that some kind of interaction did take placebetween PPy and TiO₂ nanoparticles.Thermogravimetric analysis （TG） showed that thePPy/TiO₂ nanocomposite material exhibited an enhancement of thermal stabilitycompared with pure PPy.The morphology analyses revealed that,a typical core-shellstructure could be found in the PPy/TiO₂ nanocomposite material,and the PPy/TiO₂nanocomposite thin film with the smaller size of nanoparticles was more uniform andcompact,which resulted in larger surface area and more active sites,decreasingstructural defects and greater selective adsorption.This explained why the gas-sensingcharacteristics of the PPy/TiO₂ nanocomposite thin film were superior to a pure PPythin film.The optimum gas-sensing properties of PPy/TiO₂ nanocomposite thin filmsensors were obtained with 0.1 wt% colloidal TiO₂ under 20 min deposition.Themicroscopic gas-sensing model for the PPy gas sensor was developed,and based on this model,the equilibrium constants of PPy and PPy/TiO₂ sensitive thin films for NH₃ were1.18×10^-2 and 1.32×10^-2,respectively.2.Polyaniline （PANI） and polyaniline/titanium dioxide （PANI/TiO₂） thin filmswere fabricated,and NH₃ gas sensitivity was examined.It was found that smooth andtransparent thin films could be produced when the substrate was dipped into the reactionsolution at the initial stage of polymerization.The PANI/TiO₂ nanocomposite thin filmsensor exhibited good detecting ability to lower NH₃ gas concentration （1 ppm） andsuperior gas-sensing properties than a pure PANI thin film,which was attributed to theporous structure with an interconnected network of nanofibers that enhanced theadsorption and diffusion of gas molecules,and it was also supposed that a positivelycharged depletion layer on the surface of TiO₂ nanoparticles may cause a decrease of theactivation energy and enthalpy of physisorption for NH₃ gas.The doping acid and thepolymerization temperature had effects on the morphology and gas sensitivities ofPANI/TiO₂ nanocomposite thin film.The experimental results showed that,the responsetime of the sensor prepared using HCl as the doping acid at 10℃was 2 s,and therecovery time was less than 60 s when it was exposed to NH₃ （23-141 ppm）.Thesensitivity was linear to the concentrations of NH₃.The sensor also had goodreproducibility,selectivity and long-term stability.The sensitivity of PANI/TiO₂nanocomposite thin film sensor decreased reciprocally with the increase of thetemperature,and the influence of humidity on the response was much less than that oftemperature.3.Polyaniline/indium oxide （PANI/In₂O₃）,polyaniline/tin oxide （PANI/SnO₂） andpolyaniline/multi-walled carbon nanotube （PANI/MWNT） nanocomposite thin filmswere prepared by a soft-template technique,and their NH₃ gas-sensing performanceswere studied.The effects of a cationic surfactant,tetradecyltrimethylammoniumbromide （TTAB） and a non-ionic surfactant,poly （ethylene oxide） （20） sorbitanmonolaurate （Tween-20） on the morphology and gas-sensing properties of PANI/In₂O₃nanocomposite thin film were studied.X-ray diffraction spectrometry （XRD） andmorphology analyses showed that TTAB and Tween-20 prevented In₂O₃ nanoparticlesfrom aggregating to some extent,and hence the nanocomposite thin films by thesoft-template method had more compacted network structure with smaller diameter ofnanofibers.However,different concentrations of TTAB might induce different morphologies and sensitive characteristics of PANI/In₂O₃ thin films,which might berelated with the super-molecule structure of TTAB in the water-dispersed medium.Thegas-sensing characteristics showed that the nanocomposite thin film was the mostsensitive when TTAB/nanoparticles molar ratio was 0.5,but the response/recovery timeof sensors increased,which was postulated that the compact surface of the film affectedthe adsorption and desorption of gas molecules to a certain extent.The NH₃adsorption/desorption kinetics equation of PANI and its nanocomposite thin filmsensors based on the Langmuir adsorption model was established,which revealedeffective by comparing its predictions to experimental curves.4.The quantitative and qualitative analyses of CO and H₂ gases in the range of40-1000 ppm were accomplished by the combination of a gas-sensing array with fourseparate commercial semiconductor gas sensors and back-propagation neural network（BPNN） and self-organized competitive network.The original gas sensor array wasdeveloped with PANI and PANI/inorganic nanocomposite thin film micro-gas sensorsfor the first time,which was optimized by the step-clustering analysis.The optimizedarray was composed of PANI,PANI/TiO₂,PANI/In₂O₃ and PANI/MWNTnanocomposite thin film sensors.A gas recognition system composed of the optimizedarray and probabilistic neuron network （PNN） was developed,which distinguished NH₃,CO and H₂ within a certain concentration range.更多还原