| With the development of science and technology, more and more chemical materials for industrial production and daily life were used and more and more species and quantities of poisonous gas were produced in the production process. Among these gases methanol gas is highly toxic and often fatal to body's blood system and nervous system, especially on optic nerve and retina. So it is necessary to develop a fast and convenient method for determining methanol vapor at very low concentrations in air. Now several gas sensors have been studied for their methanol sensing properties by various researchers. However, the problems of sensitivity, operating temperature, practicality and stability have not been solved. In order to detect whether indoor methanol is exceed the standard fast and accurately, in this thesis, different systems molecular imprinting polymers (MIPs) powders based on Ag-LaFeO3/LaFeO3 with specific recognition sites to methanol were fabricated by molecular imprinting technique. The composition, structure, micromorphology, and gas sensing properties (including sensitivity, selectivity, optimal operating temperature, response-recovery character and continuous monitoring property) of these MIPs powders were characterized by XRD, Raman spectroscopy, TEM, FT-IR and gas sensor tester. And the impact of different preparation conditions and modification methods on sensors performance was studied. The main results were summarized as following:(1) Among Ag-LaFeO3-MIPs sensors, the ones prepared by using AM as functional monomer exhibit poor gas sensing properties; the ones prepared by MAA-Ag-LaFeO3powders-MIPs exhibit better gas sensing properties, the sensor with x=1:4 (x=methanol:methyl acrylic acid, molar ratio) is the best. At the optimal operating temperature of 130 ?, the response of the sensor to 1 ppm methanol is 41, and the response and recovery times are 40 s and 50 s, respectively.(2) Among LaFeO3-MIPs sensors, the sensor prepared by Methanol-MAA-LaFeO3sol-MIPs with x=6:10 (x=MAA:LaFeO3, molar ratio) is the best. At the optimal operating temperature of 130?, the response of the sensor to 1 ppm methanol is 21, and it also possesses good selectivity to methanol.(3) Among SWCNTs-MIPs sensors, the ones prepared by using powders as crosslinking agent exhibit poor gas sensing properties; the ones prepared by SWCNTs-MAA-Ag-LaFeO3soi-MIPs exhibit better gas sensing properties, the sensor with 1.00% SWCNTs is the best. At the optimal operating temperature of 90?, the response of the sensor to 1 ppm methanol is 19.6, and it also possesses excellent selectivity to methanol.(4) The compounds composed of LaFeO3 and MIPs have even better gas sensing properties. The operating temperature based on the sensor is 110? and the sensitivity to 1 ppm methanol based on the sensor with best properties is 17.2. It has excellent selectivity to methanol. and the response and recovery times are 67 s and 75 s, respectively.(5)The gas sensing mechanism of MIPs:the template molecule is allowed to interact with functional monomers via hydrogen-bond firstly, and then functional monomers is subsequently copolymerized with the cross-linker to form metal carbonyl. Finally, after removal of the template methanol, recognition sites that complementary to methanol molecules were formed, which have more accessible sites, high recognition and binding ability for methanol and result in the improvement of the selectivity and response of the sensor.The novelties of this work are mainly reflected in sensor performance and preparation method:the MIPs powders based on Ag-LaFeO3/LaFeO3 methanol gas sensors were fabricated by molecular imprinting technique. The optimal sensor showed a good sensitivity and an excellent selectivity to 1 ppm methanol. |
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