The Preparation Of Polypyrrole-based Composites And Their Gas Sensitivity To Nitrogen Dioxide

Nitrogen dioxide?NO₂?is an irritating gas that can cause respiratory infections,photochemical smog and acid rain,which is extremely harmful to the environment and the human body.Therefore,it is very important to develop the sensor with high sensitivity,good selectivity,fast response and low detection limit at room temperature.Polypyrrole has attracted extensive attention due to its excellent electrical conductivity,easy synthesis,and easy attachment to flexible films.However,the pure polypyrrole gas sensor has many disadvantages,mainly:the gas sensor's sensitivity,selectivity and detection limit are not ideal.In order to improve its sensor performance,doping PPy is a very effective method,mainly including metal oxide compound and functional polymer two methods.This article used two-step method to synthesize WO₃/PPy,one-step method to synthesize Fe₂O₃/PPy and BF₄/PPy composite materials.The amount of pyrrole monomer and oxidant added were investigated.X-ray diffraction?XRD?and other methods were used to characterize and analysis the materials,which to test the performance of the composite gas sensor.This article is mainly divided into the following three parts:?1?Using Na₂WO₄·2H₂O,C₆H₈O₇,and pyrrole monomers as raw materials,?NH₄?₂S₂O₈as oxidizing agent,C₃H₈O₃and distilled water as the solven,the WO₃/PPy composite was prepared at room temperature.When the moles of WO₃was 0.04 mmol,the WO₃/PPy composite sensor can detect 2 ppm of NO₂gas at 50 ?.?2?FeCl₃·6H₂O was used as oxidant and iron source,pyrrole monomer was used as raw material,and deionized water was used as solvent.Fe₂O₃/PPy composite was synthesized by simple one-step hydrothermal method.The Fe₂O₃/PPy composite material sensor can achieve ppb level detection of NO₂at 50 ?.The sensor showed good reproducibility and long-term stability.Similarly,the position of the Fermi level and the band gap of Fe₂O₃and PPy were analyzed using Kelvin probe and UV–vis absorption spectra to determine the direction of electron transfer.?3?Using NaBF₄and pyrrole monomer as raw materials,?NH₄?₂S₂O₈as oxidant,deionized water as solvent,one-step hydrothermal synthesis of BF₄^-/PPy composite.The composite material sensor had excellent selectivity to NO₂gas.It had good linear relationship and fast response recovery characteristics for 1 ppb?10 ppm NO₂.