The Fabrication Of QCM Gas Sensors Based On Different Nanostructured Sensitive Films And Their Application In Constructing Artificial Nose System

In modern society, sensors have been widely used, and much more attention has been paid for developing high sensitive sensors. Due to the great progress achieved in nanoscience, fabricating improved gas sensors based on novel sensitive nanocomposites materials has arose much interesting of researchers. In this thesis, high sensitive QCM based gas sensors coated with different nanocomposites such as PANI/TiO2, PPy/TiO2 and GO/TiO2 were fabricated and developed. The composition, structure and morphology of the sensing materials were characterized by FT-IR, UV-vis, home-made QCM set, XRD, SEM, TEM, AFM, etc. Promising sensors with improved sensing properties have been selected out as potential sensor for constructing sensor array by comparing their performance toward different gases at different concentrations. The corresponding artificial nose system based on designed sensor array was constructed involves in optimized gas chamber, good conditioning circuit, and suitable data processing unit. To examine the efficiency of designed artificial nose system, it was used to determine ginseng ages, to distinguish the adulteration of Asian ginseng and American ginseng. There are three major parts in this room.(1) The QCM based gas sensor coated with nanostructured PANI/TiO2, PPy/TiO2, and GO/TiO2 hybrid materials by layer by layer self-assembly technology. It was found that the sensor performance is closely related to the thickness of sensitive film, and ultra-thin film of 10 bi layers, which presents the best sensing performance, was synthesized. The sensor behavior based on frequency data presenting higher sensitivity, more smooth curves and excellent reversibility than that based on resistance data, suggesting frequency signal is more efficient and useful. The PANI/TiO2 and PPy/TiO2 based gas sensors show strongly sensitive toward ammonia (NH3), but relative low sensitivity toward trimethylamine (TMA) and hydrogen sulfide (H2S), which indicating cross-sensitivity and excellent selectivity of fabricated PANI/TiO2 and PPy/TiO2 based gas sensors. In the application of evaluating storage time of mango, eggs and fish during one week storage, the as-resulting PANI/TiO2 and PPy/TiO2 based gas sensors represent accurate discrimination and classification.(2) For the GO/TiO2 based QCM gas senor, it was observed that the excellent sensitivity with remarkable frequency shift, fast response and good reversibility towards ppb scaled NH3 and TMA The sensing performance toward low concentration of typical volatile organic compounds (VOCs) were also tested. It was noted that the GO/TiO2 based gas senor shows highest sensitive to alkanes, with ketones and aldehydes followed by. Moreover, the excellent linearity in the function of gas concentration of selected volatile organic compounds was also observed. These results indicate the fabricated GO/TiO2 based QCM gas sensor is a promising gas sensor for detecting VOCs in low concentrations.(3) Nanostructured composites such as PANI/TiO2, PPy/TiO2 and GO/TiO2 based QCM gas sensors showed better sensing performance than those gas sensor only based on polymer or GO film, as is demonstrated by comparing sensor response towards different target gases under linearly increasing concentrations. Accordingly, total four potential sensors coated with different sensitive films (PANI/TiO2, PPy/TiO2, GO/TiO2 and GO) were selected out to construct sensor array. The corresponding artificial nose system were designed and completed and successfully applied in determining American ginseng and Asian ginseng and their adulteration, as well as discriminating different ginseng years. The results obtained from designed artificial nose system is comparably similar to that of GC-MS identification, which indicating its qualitative accuracy and efficiency, and potentially wide application in food industry. Moreover, the improved gas sensors coated with different functional sensitive films and the corresponding artificial nose system provide novel technical references for the development of invasive technologies.