Modification Of Polypyrrole Materials And Gas Sensing Performance Investigation

The production and application of ammonia(NH₃)have been deeply integrated with industrial and agricultural activities.The highly toxic,combustible and explosive,and high environmental pollution of NH₃ bring a severe threat to the production safety and life and health.Herein,the research and development of new ammonia sensing materials are of great significance to realize the precise detection and management of NH₃.Compared with other polymer ammonia sensitive materials,polypyrrole(PPy)possesses the advantages of facile preparation,low cost of raw materials,excellent stability,high conductivity and low reduction potential,etc.Therefore,it can be considered as a kind of NH₃ sensing material with great potential application.This thesis focuses on the PPy modification strategy,preparation process,and gas sensing performance,et al.The details are as follows:SiO₂ nanospheres(SiO₂ NS)modified PPy film materials were prepared on flexible sponge and silk fiber substrates via chemical oxidation polymerization,respectively.Scanning electron microscope(SEM),X-ray diffraction(XRD)and Fourier infrared spectroscopy(FT-IR)analysis results indicate that the silk fiber is more favorable for growth of PPy than that of the sponge substrate.The surface of SiO₂ NS modified PPy film presents a concave and convex nano-microstructure with a large surface area,which benefits for NH₃ adsorption.The response value(73.25%)of SiO₂NS modified PPy@silk fiber sensor is five times higher than that of the sponge sensor(14.51%)for sensing 100 ppm NH₃,and it is about 13 times higher than that of the PPy sensor without SiO₂ NS modification.The sensor has good linearity(R²=0.971),gas selectivity,and mechanical bending stability(the response value reduces by 10.61%for sensing 25 ppm NH₃ after 200 bending-stretching cycles of test).Ga-In modified PPy composite materials were fabricated.SEM,XRD,and FT-IR analysis results show that there exists inferface interaction in the Ga-In/PPy composite materials.The Ga-In modified PPy composite materials exhibit a trend for forming nanofiber networked structure(fiber diameter is about 75?90 nm).The sensor sample has a response value of 103.57%for sensing 50 ppm NH₃ at room temperature,and the response-recovery time are 11 s and 55 s,respectively.The gas detection limit of the Ga-In modified PPy composite materials reach 1.69 ppm for NH₃.Moreover,it possesses good gas selectivity and linearity for NH₃ detection(R²=0.977).Tartrate modified PPy materials were prepared.FT-IR,XRD,and SEM analysises indicate that the tartrate involves in the formation process of the PPy molecular chain,and the interaction occurs at the molecular level.The addition of tartaric acid makes the accumulation of PPy particles looser.Through the analysis of PPy samples with addition of different tartrate,the modified PPy with 10 mol%tartaric exhibits relatively superior gas sensing performance,in which the response value(17.27%)is twice that of pure PPysample for sensing 5 ppm NH₃at room temperature.In addition,this modified PPy sample exhibits good response-recovery time(17/85 s)for sensing 50ppm NH₃ as well as good NH₃ selectivity.The limit of gas detection is less than 1 ppm.