Modification Of Low Dimensional SnO₂ Nanostructures And Their Gas Sensing Properties

With the rapid development of industrial technology,air quality problems have become increasingly prominent.These polluting gases will not only cause damage to the ecological environment,but also harm human health.Therefore,it is very necessary to carry out efficient detection and monitoring of polluted gases.The advantages of simple operation,portability,and low price make metal oxide semiconductor gas sensors play an important role in gas detection.Among them,Sn O₂,as a typical n-type semiconductor,is the most studied metal oxide due to its advantages of low cost,high thermal and chemical stability,and environmental protection.However,Sn O₂still has some shortcomings,such as poor selectivity and high operating temperature,which limit its practical application to a certain extent.In order to better meet the needs of current gas detection,methods such as adjusting the morphology of gas-sensing materials and adding dopants have been used to improve the gas-sensing performance.Therefore,this thesis takes Sn O₂as the research object,and improves the gas sensing performance of Sn O₂by means of morphology control and doping modification of transition metal elements.In general,this paper mainly studies the synthesis of low-dimensional Sn O₂nanostructured gas-sensing materials and the mechanism of gas-sensing performance improvement after doping with transition metal elements.The work of this paper is divided into the following three parts:（1）Sn O₂nanorods with different Ni doping amounts were prepared by a one-step template-free hydrothermal method.XRD,SEM,TEM,XPS,BET and other characterization methods and gas sensing performance tests show that Ni doping can significantly improve the gas sensing performance of Sn O₂,which is mainly due to the increase of oxygen vacancies and specific surface area caused by Ni doping.Among them,Ni_1.5-Sn O₂has the best isopropanol gas sensing performance at 225℃,its detection limit for isopropanol is as low as 10 ppb,and the response value reaches 250,which is 8.3 times that of undoped Sn O₂.It also has the advantages of high selectivity,repeatability,and good stability,which further proves that Ni-Sn O₂nanorod is a promising sensing material for the detection of isopropanol gas.（2）The synthesis of Cu-doped Sn O₂leaf-like nanostructured gas-sensing materials is mainly carried out in two steps,the first is the hydrothermal process,and the second is the calcination process.The materials were characterized by XRD,SEM,XPS and gas sensing performance.The experimental results show that the sensor based on Cu_2.0-Sn O₂has high sensitivity（139.65）to ethanol at 250℃,extremely fast response time（2 s）,The high selectivity,in addition,the improvement of the ethanol gas sensing performance is mainly due to the oxygen vacancies generated after Cu doping,the existence of which accelerates the adsorption of oxygen on the surface of the sensing material..（3）The Cr-doped Sn O₂porous nanosheets were also synthesized by hydrothermal method and calcination process.Through XRD,SEM,XPS and other characterization tests and gas sensing performance tests,it is found that the porous material based on Cr_1.0-Sn O₂has high sensitivity（125.65）,low detection limit（200 ppb）,and high sensitivity to n-butanol at 225℃.Good selectivity,the porous structure of this material provides favorable conditions for gas diffusion and adsorption,while Cr doping provides more oxygen vacancies.