Fabrication Of Sensing Device Based On Carbon Nanotube Film And Its Gas Sensing Properties

Gas detection plays a very important role in the various fields of atmospheric pollutionmonitoring, toxic gas leak, power transformer diagnosis, human health diagnosis. Gas sensorsbased on nanomaterials are also emerging in a large way as the recent trend indicates thepreference towards potential applications. Carbon nanotubes (CNTs) have attracted extensiveattention because of their unique physical, chemical and electrical properties, nowadays theyhave been used as one of the ideal materials for gas sensors. In order to realize a highlysensitive gas sensor, in this thesis, CNT-based films were deposited onto self-designedelectrodes as sensing materials, and its humidity and gas sensing properties werecharacterized and discussed. Furthermore, the electrical properties and gas sensingmechanism for the CNT-based sensors were investigated.A carbon nanotubes film-based sensor on the substrate of printed circuit board (PCB)with interdigital electrodes (IDE) was presented. For film fabrication, layer-by-layerself-assembly and drop-casting were used to deposit CNT film on IDE, the film morphologywas characterized by scanning electron microscope(SEM). The theoretical resistance formulaand gas absorption model of self-assembled CNT film were established based on the CNTfilm characterization. Finally, temperature influence on the film resistance as well as thelong-term stability behavior of the CNT films were studied. The electrical properties ofself-assembled CNTs film sensor were investigated through establishing exponentially andpolynomial models involved with number of self-assembled layers and IDE finger gap. Forhumidity sensing, a relative humitity(RH) environment was achieved by several saturatedaqueous solutions, the humidity sensing property of CNT film was characterized, and also the LiCl-doping CNT film was investigated, afterwards, the moisture-adsorption mechanism ofCNT film was discussed. The sensing properties of CNT films including sensitivity,response-recover property, and repeatability were characterized at room temperature whenexposed to ethanol, NH3and HCHO environment, respectively. In the end, a transfer model ofthe gas sensing system was proposed for the analysis of response time and gas diffusionprocess upon dynamic diffusion theory, and the response process to NH3and gas sensingmechanism of self-assembled CNT film was discussed.Base on “new materials-new properties-new devices-new mechanism”, this thesisinvestigated the preparation of carbon nanotube thin film device as well as its humidity andgas sensing properties. It not only provided a theoretical and experimental foundation fordeveloping portable high sensitive gas sensor with fast response and low cost, but also pushedforward the development of fields in public safety, environmental and industrial monitoring.