Research On Performance And Characteristics Of Visible Light-assisted Gas Sensor Based On ZnO Nanorods

With the development of human society,the increasing air pollution will bring more demands for environmental monitoring and more working conditions for gas sensors.The traditional ceramic gas sensor has the disadvantages such as high working temperature and high energy consumption,which greatly limits its broad applications.At present,the light assisted resistance gas sensor shows the more advantages than the traditional metal oxide semiconductor resistance gas sensor in gas detection.At the same time,it uses light instead of heating to reduce the working temperature,and finally realizes gas detection at room temperature.Furthermore,the structure design of the sensor is simplified without the limitation of working temperature,which is very beneficial to the integration of the sensor.These advantages make the light assisted gas sensor have great application prospects.Therefore,the room temperature gas sensors based on ZnO nanorods have been prepared,and their light assisted theory,nanostructure modification,and composite material modification and studied in detail.The main work of this paper is as follows:?1?A visible light assisted gas sensor based on ZnO nanorods has been developed.By doping precious metals,the advantages of local surface plasmon resonance effect in light absorption can be exerted.By optimizing the synthesis process of sensitive materials,excellent performance was obtained.Visible light assisted gas sensor achieve such purpose as low cost,high efficiency,and room temperature detection for toxic and harmful gases.At the same time,the sensitivity mechanism of the sensor is studied.ZnO nanorod array thin films modified with Au nanoparticles were prepared on the interdigital electrode by a low-temperature hydrothermal method,and NO₂ gas sensors with a resistive structure were obtained.Due to the adsorption of NO₂ gas molecules on sensitive materials,the resistance value of the film will change with the concentration of the gas after the gas is adsorbed.Therefore,the change in the gas concentration can be tested by the change in the resistance of the sensor.Compared with pure ZnO sensors,Au-doped ZnO sensors have a significantly improved response to NO₂,and also increased the absorption of visible light.Results showed that a gas sensor under the concentration of gold doped in 2 mL HAuCl₄·xH₂O aqueous solution and 495nm light wavelength has the highest response,the highest sensitivity and the best repeatability to NO₂.?2?Nowadays,the study of multi-component composite materials is not common,among which the interaction is a difficult problem.In this paper,we first prepared a small amount of Au nanoparticles modified ZnO nanorods,and then composite them with few-layer MoS₂ nanosheet by ultrasound,and finally obtain ternary composite materials.Under the visible light irradiation,NO₂ gas at ppb level can be detected.First of all,the composite of 1-D and 2-D materials can produce a high porosity hierarchical structure,rather than a dense structure,in order to improve the specific surface area,which is conducive to gas molecular diffusion and adsorption desorption process in gas detection.At the same time,a few layer MoS₂nanosheet can enhance the absorption of UV-Vis light,and improve the separation ability and lifetime of photogenerated carriers.Finally,the heterojunction between the narrow band gap p-type MoS₂ and the wide band gap n-type ZnO can effectively tune the depletion layer to the optimal carrier loss,thus improve the test response performance of the device.The results showed that the gas sensor with the highest response and the best repeatability to NO₂ gas was obtained under 495nm light,and its maximum sensitivity can reach 25.9302 ppm^-1.