Preparation And Gas Sensing Properties Of PPy/Oxide Semiconductor Composite Nanofibers

Inorganic oxide semiconductor such as SnO2, ZnO etc., as the gas sensing material has the advantages of high sensitivity, quick response and recovery, but the high temperature, poor selectivity restrict its further development. Meanwhile, organic conducting polymers such as polypyrrole (PPy), polyaniline (PANI) as gas sensing material has low working temperature, high conductivity, but the response of slow recovery, sensitivity and low defects influence the development of space. Recently, organic/inorganic composite gas-sensing materials have gradually become the focus of attention, and have been rapidly development. In this paper, PPy/oxidation semiconductor composite nanofibers with core-shell structures were prepared by electrospinning and in-situ vapor/liquid chemical oxidative polymerization, and the gas sensing properties were studied. The effects of inorganic phase change and their change of the polymerization conditions on the morphology and sensing properties of the composite were discussed. The main conclusions are as follows:1. PPy/Co3O4 composite nanofibers were prepared by electrospinning and in-situ vapor phase chemical oxidation polymerization. The effects of polymerization time on the morphology and sensing properties of composite nanofibers were discussed. The results indicate that when the PPy thickness of PPy/Co3O4 composite nanofibers is about 6 nm, the composite nanofibers at room temperature for H2S show excellent sensing properties. Compared with the pure PPy, the sensitivity and the recovery performance of the composite nanofibers are improved, and the detection limit can reach 100ppb.2. PPy/SnO2 composite nanofibers were prepared by electrospinning and in-situ vapor phase chemical oxidation polymerization. The effects of polymerization time on the sensing properties of composite nanofibers were discussed. The results show that when the polymerization time is 3 min, the PPy/SnO2 composite nanofibers at room temperature for NO2 show good sensing properties. The sensitivity can reach 0.2 when the concentration of NO2 is 300 ppb. The sensitivity of the composite nanofibers is 9 times that of pure PPy, and has good revovery and stability.3. PPy/Sb doped SnO2 composite nanofibers were prepared by ectrospinning and in-situ vapor phase chemical oxidation polymerization. The PPy and Sb element were confirmed by Raman spectrum. Gas sensing test results show that the working temperature of the two kinds of composites after Sb doping for NO2 is 90℃. Compared with PPy/SnO2 composite nanofibers, the resistance of composite nanofibers decreased significantly after Sb doping. The NO2 detection range is increased as much as 300 ppm, and the response and recovery time is significantly shortered.4. SnO2 hollow nanofibers were prepared by electrospinning method, and the PPy/SnO2 composite hollow nanofibers were prepared by in-situ liquid phase chemical oxidation polymerization with different polymerization time. The morphology and structure of the composite nanofibers were characterized by SEM, TEM and FTIR. The results show that the diameter of PPy/SnO2 hollow nanofibers is 300-400 nm and the thickness of PPy shell layer is about 40 nm when the polymerization time is 2 h. The PPy/SnO2 composite nanofibers under the polymerization conditions at room temperature for NO2 has good selectivity, and the response and recovery time is 20 s and 50 s, respectively. Compared with the PPy/SnO2 compostie nanofibers prepared by in-situ vapor phase chemical oxidation polymerization, the response and recovery time is significantly shortened.