Research On Nitrogen Dioxide Gas Sensor Based On Metal Oxide Semiconductor Nanomaterials

With the continuous progress of our economy and the rapid development of industrialization,the environmental problems have become increasingly serious.A large number of industrial waste gases and vehicle exhaust have been emitted into the atmosphere,which leads to the occurrence of smog in major regions.As a harmful gas,NO2 is one of the main members of smog.Excessive NO2 will not only lead to the formation of acid rain,but also cause damage to the human respiratory system.Gas sensors based on metal oxide semiconductors can quickly and efficiently detect NO2 gas,which has been a research hotspot for researchers.The gas sensing materials are the key of gas sensors,and the gas-sensitive properties of the material can be improved from the aspects of structure and composition.In this paper,indium oxide and tungsten oxide nanostructured materials with excellent properties were prepared by simple oil bath and hydrothermal method,respectively.Through the regulation of indium oxide internal structural defects,the correlation between the microstructure and gas-sensing properties of metal oxides semiconductor is established;The noble metal(such as Au)nanoparticles are modified on the tungsten oxide surface to improve gas response by utilizing the catalytic effect of Au nanoparticles.The main contents are as follows:(1)The In2O3 nanobricks had been prepared through a facile oil-bath precipitation method and their gas-sensing properties have been studied.From the material itself,microstructural and internal defects are controlled by changing the calcination temperature and the difference of gas responses was compared.Through the characterization of XRD,SEM,and BET,the changes of the microstructures are analyzed;XPS and PL characterization are used to analyze the changes of the internal structural defects and the surface oxygen adsorption;The Hall effect test is used to study the difference in electrical properties.Combined with the above characterizations,the correlation between microstructure and gas-sensing properties is established and the reason for the improvement of indium oxide gas property is explained.Moreover,the In2O3 sample annealed at 400? exhibited a high response(402)toward 500 ppb NO2,and the response and recovery time are 114 s and 49 s at rather low operating temperature of 50?.(2)Tungsten oxide nanomateriala with a thickness of 60 nm and a length of 200 nm are prepared by a simple hydrothermal method using sodium tungstate and hydrochloric acid as raw materials and citric acid as an assistant agent at 130?.Different amount of Au are loded on WO3 samples and the gas sensing properties to low concentration of NO2 are studied.The modification of Au nanoparticles can greatly reduce the operating temperature from 100 C to 30?.At 30?,the gas response of 0.5%Au-WO3 sample to 500 ppb NO2 is about 290,which is 8 times higher than pure WO3.