Research Of ZnO-based Room Temperature No₂ Gas Sensor

With the rapid development of China's economy and society,the consumption of fossil fuel continues to increase.Nitrogen oxides?NO_x?produced by fossil fuel combustion are the main causes of air pollution such as acid rain,photochemical smog and smog,and also causes respiratory diseases,cancer and other diseases,seriously damaging human health.Therefore,achieving rapid and accurate detection of NO_x,especially NO₂,is of great significance for environmental monitoring and governance,and protection of people's health.There are various detection methods for NO₂.However,gas sensors have been widely concerned because of their advantages such as high sensitivity,good selectivity,low price,and small size.Among them,the NO₂ sensor based on oxide semiconductor has the characteristics of all solid state,simple structure,low detection limit,etc.It has great potential in the detection of low concentration or ultra-low concentration NO₂ in the atmosphere.Therefore,it has become one of the hot spots in gas sensor research.Oxide semiconductor gas sensors usually work at 100-400?,which not only consumes much power,but also easily detonates the gas to be measured.In order to build the environmental monitoring Internet of Things or develop a portable NO₂ detector,it is necessary to reduce the power consumption of the oxide semiconductor NO₂ sensor.Therefore,it is very important to reduce the operating temperature of the NO₂ sensor.In this paper,oxide semiconductor is used to detect NO₂,ZnO,a typical N-type oxide semiconductor,is selected as the sensing material,and the micro-nano structure of ZnO is adjusted to optimize its sensing characteristics of NO₂ while reducing the operating temperature of the sensor.The main research contents are as follows:1.The ZnO nanoflowers were prepared by hydrothermal method.The results of material structure characterization indicated that the average diameter of ZnO nanoflowers was 0.9-1?m,which was composed of tapered nanorods with a diameter of 250-400 nm.The thick film of ZnO nanoflower was formed on the interdigital electrode to fabricate the NO₂ gas sensor.The gas sensing characteristic test results of the sensor showed that the response value of the sensor to 1ppm NO₂ was as high as128.6 at room temperature,and it had good stability.In addition,the room temperature sensitive mechanism of the sensor was discussed.2.The porous flower-like ZnO was prepared by hydrothermal method.The characterization results showed that the diameter of the porous flower-like ZnO was about 4?m,and it was composed of porous nanosheets with a thickness between 20-30 nm.The relevant gas sensitivity test found that the response value of the sensor to500ppb NO₂ is 77.5 at room temperature.The good gas-sensing properties can be attributed to the large specific surface area and porosity of porous flower-like ZnO,which increases the active sites of gas adsorption/reaction and promotes the reaction between NO₂ gas and sensitive materials.