The Study And Preparation Of Tungsten Oxide Nanostructure Gas Sensor Via The Morphology-Controllable Solvothermal Synthesis

In recent years,the NO_X gas produced by industrial waste gas,combustion and auto mobile tail gas not only caused pollution to the environment but also posed a serious threat to human health.As one member of numerous NO_X sensitive materials,WO₃ shows its great potential as a gas sensing material because of high performance,low price,low power consumption,etc.In order to further improve the gas sensing properties of WO₃ nanostructure gas sensors,a great deal of scientific research have been carried out on the morphology control,noble metal doping,composite structure and so on.As a simple and low-cost method,the solvothermal method is very important for the morphology-controllable synthesis of tungsten oxide nanostructures.WO₃ nanostructure with various novel morphologies were synthesized by adjusting the solvothermal reaction conditions,the effects of solvothermal conditions?solvent,temperature and water content in the reaction solution?on the morphology of WO₃ nanostructure and the gas response of NO₂ were mainly investigated.The nano structures of all samples were characterized by transmission electron microscopy?TEM?,X-ray diffraction?XRD?and field emission scanning electron microscopy?SEM?.In addition,the NO₂ gas response,response recovery characteristics and gas selectivity were tested along with the changing of NO₂ concentration and operating temperature.Finally,the mechanism of growth and gas response were also explored.The results obtained are as follows:Solvothermal reaction conditions changed the morphology of WO₃ nanostructures to a large extent,By changing the content of water?0-23.1vol.%?,reaction temperature?170-200oC?and reaction solvent?Ethylene glycol?Ethanol?Isopropanol and n-Propanol?,the WO₃ nanosheets nanorods,nanoblocks and so on were synthesized.The optimum operating temperature of the sample was very low,about 50 or 100oC,at the same time,it also possessed excellent NO₂ gas response and selectivity.With the increase of the water content in the solvent,the morphology of the nanostructure changed from the pure nanosheet to the nanorods;as the amount of water reached a certain amount?23.1 vol.%?,the morphology was almost completely changed to nanorods.The gas response toward 1 ppm NO₂ can be as high as 62.1 at100oC,the response and recovery time were respectively 80 s and 196 s;When thereaction temperature was low,the morphology of the prepared nanostructure was nanoparticles,with the increasing of the reaction temperature,the nanosheet structure appeared,when the temperature reached 200oC,the nanorods became the main structure,its highest gas response was 51.2,the response and recovery time toward different concentrations?0.1-3 ppm?NO₂ were respectively 61-145 s and 42-155 s;As the reaction solvent was a single variable,WO₃ nanoblocks,nanosheets and nanorods were synthesized in different reaction solvents,and all the samples have high gas response?2 8.1-82.9?,fast response time?27-83 s?and recovery time?95-212 s?.