Study Of QCM Gas Sensors Based On Conducting Polymers

As a convenient method to detect gases, gas sensors are widely used in many fields, such as environment monitoring, industry and agriculture production, food safety, medical diagnosis, military and public safety. Combining gas sensor arrays with artificial intelligence, artificial olfaction systems overcome the shortcomings of single gas sensor, expand the usage of gas sensors and requiremuch improvement on the performances of gas sensors. Therefore, it is very important to research and develop the gas sensors with high sensitivity, short response time, good repeatability, small volume, low operating temperature and power consumption.This thesis reviewed the research on gas sensors, and compared different kinds of gas sensors from the view point of sensing material and detecting method. To meet the urgent demands of detecting of trimethylamine in food assay, environment monitoring and medical diagnosis, this thesis studied some gas sensors based on conducting polymer and QCM (Quartz Crystal Microbalance) technology.After introducting the principle, configuration and characteristics of QCM, the author developed a low cost QCM testing system to investigate the performances of the sensors in all later experiments.Secondly, the author prepared polypyrrole using emulsion polymerization method as well as water soluble polyaniline by adding a small amount of surfactant. Both knids of materials are used as sensing film of QCM trimethylamine gas sensors, respectively. The sensitivity, response time, recover time, repeatability, selectivity and life-span of these sensors were investigated. The results show that these sensors work stably at room temperature. The method to prepare these QCM gas sensors has many advantages, such as easy operation, no strict condition requirement, rapid fabrication and low cost.Furthermore, polyaniline-TiO₂ nanocomposite was prepared with chemical oxide method by adding a small amount of TiO₂ sol-gel, and the effect of TiO₂ nano-particle on gas sensing performance of polyaniline investigated. The Experimental results shown that polyaniline-TiO₂ nanocomposite had better thermal resistance than water soluble polyaniline. The reason why two materials have different thermal resistance are discussed, which is meaningful for gas sensing material design and modification.