Prearation And Gas Sensing Properties Of Tungsten Disulfide And Its Nanocomposites

Gas sensors play an important role in industry,agriculture,biological,medical treatment and daily life.As the core of the gas sensors,the performance of the gas sensing material directly determines the performance of the gas sensor.Gas sensors based on metal oxide semiconductors are widely used due to their advantages of simple preparation,low cost,high response,etc.However,the high operating temperatures leads to high energy consumption and safety issues.Therefore,the development of gas-sensing materials with good gas-response at room temperature is a breakthrough in solving this problem.WS₂ is an important transition metal disulfides（TMDs）,which has a layered structure similar to graphene.Its specific surface area is large and the bandgap is adjustable.It has great potential application in gas sensors.At present,WS₂ based gas sensors devices are mainly made by stripping and CVD.The preparation methods have poor repeatability,the obtained film has a small area and the gas sensor has poor stability.For these problems,we have prepared WS₂ nanosheets with a thickness of about 5 nm by a method of combining hydrothermal Synthesis with Thermal decomposition and studied its gas sensing performance.In order to improve the gas-sensing property of WS₂ nanosheets,the WS₂-SnO₂ composites were preared by semiconductor mental oxide SnO₂ and their gas-sensing properties were studied.The specific research contents are as follows:1.The WS₂ nanomaterials were prepared by a combination of hydrothermal and thermal decomposition methods,the morphologies of the products were analyzed by SEM,XRD and TEM.The effects of CTAB,hydrothermal time and pH on WS₂nanomaterial products were further investigated.When the CTAB is 136.7 mmol/L,PH=8 and the hydrothermal time is 72 h,an ultra-thin WS₂ nanosheets having a three-dimensional network structure were obtained,and the thickness of the nanosheet was⁵ nm.2.The gas sensor based on WS₂ nanosheets is prepared,the gas sensitivity test results show that it has respond to NH₃,NO and NO₂ at room temperature and has high response to low concentration of NO and NO₂ gas.The device’s response to1ppm NH₃ gas is up to 13.6%.The response of 0.2 ppm NO is 24.9%,the response of 0.1 ppm NO₂ gas is 9.3%.In addition,the gas sensing mechanism of WS₂nanosheets were analyzed and the influence of humidity on the response of NO₂ gas was studied.3.The WS₂ nanosheets were composited with SnO₂ by hydrothermal synthesis to improve the response,selectivity and response/recovery time of WS₂ to NO gas.The test results show that the gas-sensitivity of WS₂ can be improved by compounding with semiconducting metal oxides.The optimal operating temperature for gas sensors based on WS₂-SnO₂ composites is 75°C.In the atmosphere of 0.2ppm NO gas,the sensitivity of the gas sensor was 9.6%,but it was up to 2185.6%at15 ppm,the response and recovery time were significantly improved.