Investigation Of Indium Oxide Semiconductor Gas Sensor With High Sensing Performance

Environmental and health issues are increasingly becoming the focus of attention,and harmful gases are an important source of environmental pollution.Therefore,it is necessary to develop low-cost,high-performance gas sensors.In this paper,In₂O₃ was used as the research object,and In₂O₃ was synthesized by different methods or modified by doping and their gas sensing properties were studied.The main research includes:1)Ultra-sensitive H₂S sensors operated at room temperature were fabricated using Ag-In₂O₃ nanorod composites synthesized using sol-hydrothermal method followed by NaBH₄ reduction process.In₂O₃ was nanorod structures of¹10 nm in length and³5 nm in diameter.Ag nanoparticles with diameters from 10 to 15 nm homogeneously decorated on the surfaces of the In₂O₃ naonorods.XRD and XPS analysis proved that the Ag elements are existed as zero-valent metallic silver on the surface of the In₂O₃ nanorods.Ag nanoparticles could enhance the formation of chemisorbed oxygen species and interactions between H₂S molecules and oxygen species due to spill-over effect,and the electron transfer between Ag and In₂O₃ nanorods also enhanced the sensing properties.Therefore,the H₂S sensors based on the Ag-In₂O₃ nanorod composites showed significantly improved sensing performance than those based on the pure In₂O₃ nanorods.The optimized content of Ag nanoparticles is 13.6 wt%.The H₂S sensors made of 13.6 wt%Ag-In₂O₃ nanorod composites exhibited an ultra-highly response of 93719 to 20 ppm H₂S and a superior detection limit of 0.005 ppm at room temperature.The sensor also showed good reversibility,good selectivity,excellent reproducibility and stability for detection of H₂S gas.2)In₂O₃ nanorods were prepared using cetyltrimethyl ammonium bromide assisted solvothermal and subsequent calcination processes,and then used to make a gas sensor for both NO₂ and H₂S detection.The sensor showed good sensing properties for both NO₂ and H₂S at low operating temperatures,e.g.,the sensor's responses to 100 ppm NO₂ was 336 with fast response/recovery times of 18 s/31s measured at 100 ^oC,and its response to 60 ppm H₂S was 1461 with response/recovery times of 86 s/111 s at room temperature?RT?.The sensor showed superior detection limits of 0.001 ppm to NO₂?at100 ^oC?and 0.005 ppm to H₂S?at RT?,respectively.In addition,the sensor showed a good reversibility and long-term stability,as well as a good selectivity.Results showed that the change trends of sensing responses for H₂S and NO₂ gases were opposite,which provide a strategy for differentiation of sensing results for these two gases,and their different sensing mechanisms were discussed.3)Hydrogen gas sensors were fabricated using mesoporous In₂O₃ synthesized using hydrothermal reaction and calcination processes.They showed the best sensitivity for hydrogen at a working temperature of 260 ^oC with a high response of 18.0 toward 500ppm hydrogen,and fast response/recovery time?e.g.1.7 s/1.5 s for 500 ppm hydrogen?as well as a low detection limit down to 10 ppb.Using air as the carrier gas,the mesoporous In₂O₃ hydrogen gas sensors exhibited good reversibility and repeatability towards hydrogen.The good sensing performance of these hydrogen sensors is attributed to the formation of mesoporous structures,the large specific surface areas and numerous chemisorbed oxygen ions on the surfaces of mesoporous In₂O₃.