Preparation And Low Temperature Gas Sensing Properties Of Composites Based On Conducting Polymer

The performance of gas sensor depends on the property of sensing materials.There are a few questions among sensing materials such as high operating temperature.To overcome these drawback and enhance the performance of gas sensor,the gas-sensing materials based on conductive polymer have been studied in this paper.1.PTh/rGO has been prepared by in situ chemical oxidative polymerization.The as-prepared materials utilized the room temperature gas sensing property of polymer and large surface area,good electron transferring ability of rGO.The structure and gas sensor performance of PTh/rGO have been investigated,the gas sensor based on PTh/rGO showed a high sensitivity and good selectivity towards NO₂ at room temperature.2.The gas sensor based on metal oxide has many advantages such as high sensitivity,good stability and quick response,but the operating temperature of metal oxide is high.To lower the operating temperature of metal oxide,PTh/rGO/WO₃ and PPy/r GO/In₂O₃ have been successfully synthesized by hydrothermal route and in situ chemical oxidative polymerization.These composites were characterized by FESEM,TEM,BET,FTIR and XRD,and the gas sensing of these composites has been tested.Result indicates that ternary composites have high sensitivity,good selectivity and short response time at room or low temperature.3.PANI/TiO₂/GO ternary composite has been prepared by means of two step method including the TiO₂/GO binary composite and in situ oxidative polymerization of aniline.To enhance the stability of the ternary composite TiO₂ with thermally stable bulk reduction states and GO are conjugated by amide bond.The sensor based on ternary composite exhibited high sensitivity,high selectivity and short recover time towards NH₃ at room temperature.4.The gas sensing performance of conductive polymer/metal oxide under UV illumination has been investigated in the paper.The process of preparation consisted of three steps,firstly,the precursors of Zn₅（CO₃）₂（OH）₆ nanosheets and ZnO₂ were prepared,secondly,ZnO nanosheets and ZnO nanoparticle including oxygen vacancy were obtained by calcination under 400 ℃,in the end,PANI/ZnO nanosheets and PTh/ZnO nanoparticle were gained by in situ oxidative polymerizaton.The characterization and gas sensing test have been done for thesetwo binary composites.It is found that these two composites have high sensitivity,good selectivity towards alcohol,and good stability at room temperature.There is synergistic effect between ZnO and polymer under UV illumination.5.The low or room temperature gas sensing mechanism of these composites has been discussed.Conductive polymer（PANI、PTh、PPy）can detect gases at room temperature,gas sensors based on metal oxide have good stability,high sensitivity,short response time and recover time,reduced grapheme oxide have large surface area and excellent in-plane conductivity.Considering the synergistic effect among these three types of gas sensing materials and combination of the merits of them,ternary composites and binary composites have been prepared,and gas sensors based on them were fabricated for toxic gases detection.There were three advantages,⑴three dimensional hybrid structure provides many channels for gas diffusion and many active sites for surface reaction,⑵ rGO has excellent electrical properties and can facilitate transport of holes and electrons between metal oxide and rGO,⑶metal oxide is n type semiconductor,polymer,GO and rGO are p type semiconductors,there are p-n junction at the interface between them,electron transfer can take place by means of p-n junction.