Room Temperature NO₂ Gas Sensor Based On ZnO/Graphene

With the rapid development of society,the government and the public pay more and more attention to environmental protection.Meanwhile,the sensor technology closely related to the exploration environment is also developing rapidly,which together promote the environmental monitoring section to become one of the first services in the vertical field of the Internet of Things.In the field of environmental monitoring,the amount of NO₂ gas emissions in the air has increased dramatically due to the large amount of combustion of chemical fuels.NO₂ is extremely harmful to the environment and human health.Therefore,it is of great significance to develop a gas sensor that can effectively detect the NO₂ in the environment.Traditional metal oxide sensors have entered the development bottleneck due to shortcomings such as poor conductivity and high energy consumption.The graphene gas sensor can respond well to NO₂ at room temperature,but it still has shortcomings such as poor stability and long response time,and the gas sensitivity characteristics need to be improved.In this thesis,high performance NO₂gas sensors based on ZnO/Graphene were prepared by constructing a heterojunction and modifying metal nanoparticles.The gas sensing mechanism of composite materials was studied.The main research contents include:?1?Different proportions of zinc oxide microrods/graphene composites were synthesized by hydrothermal method,and the gas sensing property of graphene-based NO₂ gas sensor was improved by constituting heterojunction.The experimental results show that rGO has a relatively uniform coating and connection of zinc oxide microrods,and has no significant effect on the morphology of zinc oxide during the composite process.The gas sensitivity test found that the composite material has more excellent room temperature NO₂ gas sensitivity than the pure reduced graphene oxide.Among them,ZnO rods-2%rGO showed the best gas sensitivity.The gas sensor has a response value of 3.35 for 30 ppm NO₂ gas,response time/recovery response time of 90/215 s,and good repeatability and selectivity..At the same time,we explored the gas sensing mechanism of zinc oxide/graphene composites based on the above experimental phenomena.?2?Ag-ZnO rods-2%rGO and Au-ZnO rods-2%rGO ternary composite products were prepared by hydrothermal method.Morphological structure analysis found that graphene encapsulated and connected zinc oxide and metal nanoparticles.At room temperature,Ag-ZnO rods-2%rGO,Au-ZnO rods-2%rGO have a response to NO₂ of 2.311 and 2.852,and Au-ZnO rods-2%rGO has a higher specific gravity than Ag-ZnO rods-2%rGO.Response and faster response time,recovery response time.Compared to ZnO rods-2%rGO,the two gas sensing materials have higher response and shorter recovery response time in low concentration NO₂ gas.?3?Different proportions of zinc oxide nanoparticles/graphene composites were synthesized by hydrothermal method.Structural characterization results show that graphene affects the agglomeration of zinc oxide nanoparticles and coats them,while zinc oxide particles inhibit the stacking of graphene.The gas sensitivity test results show that the synthesized ZnO NPs-1%rGO,ZnO NPs-2%rGO,ZnO NPs-3%rGO ZnO NPs-1%rGO has the best room temperature NO₂ gas sensitivity,which the response is 5.21 and the response/recovery time is 198/144 s.In addition,the composite material has good recognition ability and test stability for NO₂ gas.The excellent gas sensitivity of the composite material is derived from the stronger synergy between the smaller particles of zinc oxide and graphene.