Research On Nitrogen Dioxide Sensor Stem From ZnO Heterojunction

With the rapid socio-economic development,the living standard of residents has gradually improved while the motor vehicle holdings have increased rapidly,leading to a significant increase in tailpipe emissions.Nitrogen dioxide,as a typical air pollutant in motor vehicle exhaust,is highly toxic and irritating.It is also one of the causes of the formation of acid rain,atmospheric haze and photochemical smog pollution,causing great damage to people’s physical and mental health and the natural environment.Therefore,it is particularly important to be able to detect nitrogen dioxide in real time and accurately.At present,the equipment for detecting nitrogen dioxide in the environment is large,expensive and complicated to operate,which can no longer meet the detection needs in the current situation.The semiconductor metal oxide gas sensor is one of the means to achieve effective detection of nitrogen dioxide in the environment because of its small size,low cost and simple operation.Zinc oxide（ZnO）,as a wide band gap semiconductor metal oxide,not only has excellent electrical properties but also exhibits excellent gas-sensitive properties,and is widely used in the development of semiconductor metal oxide gas sensors.Although ZnO gas sensors have many advantages mentioned above,they still suffer from low sensitivity and high lower detection limit.In this paper,the sensitization methods of modulating the microstructure and constructing heterojunctions are used to enhance the gas-sensitive performance of ZnO sensors for NO₂ detection needs of atmospheric pollutants,respectively.The details of the study are as follows:（1）The shape-controlled 3D nanosheet-like ZnO sensing material was prepared by the water bath method,and the sensor was developed with this sensitive material.The gas-sensitive test results show that the sensor exhibits the best gas-sensitive characteristics at 125℃,with a response value of 125 for 1 ppm NO₂,a lower detection limit of 100 ppb,and a fast response recovery for NO₂ in the range of 0.1-5 ppm.The sensor also has excellent selectivity and good long-term stability.（2）The ZnO/SnO₂ heterostructure was prepared in one step on a planar device by CVD technology,and the NO₂ sensor was constructed in this way.Gas sensitivity test results show that Z1（the best performing ZnO/SnO₂ heterojunction sensor）at 300°C,with a response value（270%）7 times higher than that of the pure SnO₂ sensor for 50 ppm NO₂,and a wide detection range of 0.05-1000 ppm and a low lower detection limit of 50ppb.The Z1 sensor also has excellent selectivity and good long-term stability.