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

Sensitive materials for gas sensors include inorganic oxide semiconductor materials and organic conductive polymer materials.The oxide semiconductor sensitive material represented by SnO₂ and ZnO has been developed rapidly because of its fast response,low cost and high sensitivity.However,the oxide semiconductor has the disadvantages of poor selectivity and high working temperature,the organic conductive polymer is sensitive materials can be carried out at room temperature for gas detection,but low response,slow response and other shortcomings affect its development.The results show that the combination of inorganic semiconducting oxide material and organic conductive polymer material can greatly improve the gas sensing properties of materials.Organic/inorganic composite sensitive materials have attracted the attention of researchers.In this paper,SnO₂ nanofibers were prepared by electrospinning,and the PPy/SnO₂ nanofiber were prepared by chemical oxidation polymerization.The morphology of SnO₂,the doping of the metal element,the polymerization conditions and content of PPy will make effect on the gas-sensing properties of the composites.Specific research work is as follows:1.The pure SnO₂ nanofibers were prepared by electrospinning.The effects of the contents of stannous chloride,polyvinylpyrrolidone?PVP?,N-N dimethylformamide?DMF?and anhydrous ethanol in the precursor solution were investigated.Proportioning of the precursor solution and the sintering process will make effect on the morphology of the SnO₂ nanofiber.SnO₂ nanofibers can be either columnar or tubular.In the case of stannous chloride,N-N dimethylformamide and anhydrous ethanol,when the amount of PVP is small and the heating rate is low,the prepared SnO₂ nanofibers are solid,When the amount of PVP is big and the heating rate is high,the prepared SnO₂ nanofibers are hollow.The sensitivity of SnO₂ nanofibers and nanotube fibers to ethanol was investigated.The sensitivity of SnO₂ nanofibers to 100 ppm alcohol was 2.6,the sensitivity of SnO₂ nanofiber to 100 ppm alcohol was 40,and the gas sensitivity of SnO₂ nanofiber fibers to ethanol to be superior to SnO₂ nanofibers.2.The p-type conductive polymer PPy film was coated on the surface of SnO₂ nanofibers by gas phase chemical polymerization and liquid phase chemical polymerization.The gas-sensing properties of the p-type conductive polymer PPy and n-type semiconductor SnO₂ were studied.The results show that the sensitivity of PPy/SnO₂ composites obtained by gas phase polymerization for 5 min to NO is 2.8,which is higher than that of gas phase polymerization for 2 min and 10 min.The sensitivity of PPy/SnO₂ composites prepared by liquid phase chemical polymerization to 5ppmNO was 8.7.The gas sensing properties of PPy/SnO₂ composites prepared by liquid phase chemical polymerization are better than that of gas phase chemical polymerization.The results show that the selectivity and sensitivity of the PPy/SnO₂ composites obtained by the liquid phase chemical polymerization method are greatly improved compared with the pure SnO₂ nanofibers,and the working temperature of the gas sensing test is greatly reduced.It was also found that the electrical properties of PPy/SnO₂ composite nanofibers will achieve n-type to p-type transitions when the mass ratio of PPy is 20%.3.PPy/SnO₂ composites make as the channel materials of the field effect transistor to determine the electrical properties of composites at room temperature and 120°C to determine the electrical properties of composites at different temperatures.In addition,the experiment also investigated the i-t characteristic curve of the PPy/SnO₂ composites at 120°C to detect the gas-sensing properties of the composites for NO.The results show that when the VDS is 40 V and the VGS is 50 V,the PPy/SnO₂ composites can be used to study the effect of PPy/SnO₂ composites on the 20 ppm NO.The average sensitivity is at 7.03.4.The gas-sensitive response of the semiconductor material is mainly a surface reaction process,it is affected by the surface adsorption and surface chemical reaction.the sensitivity of the nanofiber was improved by the metal element doping of SnO₂ nanofibers.The sensitivity of 10% In-SnO₂ nanofibers to 500 ppm alcohol was 70.The sensitivity of La-SnO₂ nanofibers to 500 ppm alcohol was 89,The sensitivity of 1% Sb-SnO₂ nanofibers to 500 ppm alcohol reached 56,the sensitivity of pure SnO₂ nanofibers to 500 ppm alcohol reached 55,and the sensitivity of La-SnO₂ nanofibers to alcohol was much higher than that of pure SnO₂.The La-SnO₂ nanofibers were used as channel materials to construct the bottom gate FETs to test the electrical properties of La-SnO₂.La-SnO₂ and PPy were combined to test the electrical properties and gas-sensing properties of the prepared materials.It was found that the sensitivity of the material to NO could be improved by adjusting the Source-drain voltage and the gate voltage.