| With the development of science and technology, more and more chemical materials for industrial production were used, acetone as a kind of common organic solvents, it is widely used in the industries of paint, fibre, plastic, etc. After the human body inhaling acetone, it is dissolved in the bloodstream, anesthetizes the central nervous system, and can cause kidney damage, which is harmful to human health. Medical investigations have shown that the acetone concentration in exhaled breath from a healthy human body is lower than 0.8 ppm, while that for a diabetic patient is higher than 1.8 ppm, acetone has been classified as an important breath biomarker for noninvasive diagnosis of human type-1 diabetes. So it is necessary to develop a fast and convenient method for determining acetone vapor at very low concentrations in air. Now several gas sensors have been studied for their acetone sensing properties by various researchers. However, the problems of sensitivity, operating temperature, practicality and stability have not been solved. In order to detect whether acetone is exceed the standard fast and accurately, in this thesis, different systems molecular imprinting polymers (MIPs) powders based on Ag-LaFeO3 with specific recognition sites to acetone 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, 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 or MAC as functional monomer exhibit poor gas sensing properties; the ones prepared by MBA-Ag-LaFeO3-MIPs exhibit better gas sensing properties, the sensor with x=5:100 (x=acetone:N,N’-Methylenebisacrylamide, molar ratio) is the best. At the optimal operating temperature of 200℃, the response of the sensor to 2.5 ppm acetone is 14.7, and the response and recovery times are 80 s and 75 s, respectively.(2) Among SWCNTs-MEPs sensors, the ones prepared by SWCNTs-MBA-Ag-LaFeO3-MIPs exhibit better gas sensing properties, the sensor with 1.00% SWCNTs is the best. At the optimal operating temperature of 120℃, the response of the sensor to 2.5 ppm acetone is 18, and it also possesses excellent selectivity to acetone.(3) Among Graphene-MIPs sensors, the ones prepared by Graphene-MBA-Ag-LaFeO3-MIPs exhibit better gas sensing properties, the sensor with 0.4% Graphene is the best. At the optimal operating temperature of 110℃, the response of the sensor to 2.5 ppm acetone is 71.2, and the response and recovery times are 60 s and 65 s, respectively, it also possesses excellent selectivity to acetone.(4)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, recognition sites that complementary to acetone molecules were formed, which have more accessible sites, high recognition and binding ability for acetone 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 acetone gas sensors were fabricated by molecular imprinting technique. The optimal sensor showed a good sensitivity and an excellent selectivity to 2.5 ppm acetone. |
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