Preparation Of Tungsten Trioxide-based Nanomaterials And Research On NO₂ Sensitivity

Nitrogen dioxide?NO₂?is mainly generated from internal combustion engines and industrial combustion plants and it has a great impact on the land and ecological environment.Besides,it is extremely harmful to human.Therefore,quantitative detection and control of NO₂ emissions is an urgent problem to be solved in today's society.as an important wide band gap n-type semiconductor,WO₃can be used for NO₂ detection.However,gas sensors based on WO₃ nanomaterials usually work at a high temperature?above 100°C?,which impedes the application of WO₃ in certain scenarios.In order to detect ppb-level NO₂ at a lower temperature,the solvothermal method is used to synthesize single-crystal WO₃ nanoparticles,WO₃nanowire cross-linking network structure and Au/WO₃ composites by adjusting the reaction conditions in this thesis.X-ray diffraction,X-ray photoelectron spectroscopy,scanning electron microscopy,and transmission electron microscopy were used to analyze the structure of the materials,and the materials were assembled into gas sensors to test gas sensing for NO₂ gas.The sensitive mechanism of NO₂ gaswas discussed in detail by XPS.This thesis is mainly divided into the following three parts:?1?WO₃ precursors were synthesized with a small amount of ILs addition using tungsten hexachloride?WCl₆?as the tungsten source,ethanol and glacial acetic acid as solvents and then calcined at 300?600°C and assembled into gas sensors.It is found that the gas sensor based on the material treated at 500°C shows good gas sensitivity to NO₂at the optimal working temperature of 50°C and the response to 10 ppm NO₂ gas can reach 63.9,with a recovery time of 363 s,and the minimum detection limit is 100 ppb.Even at room temperature,the response to 10 ppm NO₂ can reach 19.5.?2?WO₃ nanowires cross-linking network structure was in situ grown on the ceramic tube without seed and template by one-step solvothermal method with tungsten hexachloride as the tungsten source,anhydrous ethanol,glacial acetic acid,and ethylene glycol as the mixed solvents.Such thin film sensor shows better gas performance for the detection of NO₂ gas at the optimalworking temperature of 92°C.The response can reach132.8,the recovery time is 83.2 s,and the lowest limit of detection is 50 ppb.?3?Loading different mass fractions of Au nanoparticles on the WO₃ nanowire cross-linking network structure grown in situ can further improve the gas-sensitivity to NO₂.When the loading mass fraction of Au is 5 wt%,it shows the best gas-sensitivity to NO₂gas at 50°C,and the response to 10 ppm NO₂ is 4 times higher than that of WO₃ thin film sensor.