Preparation Of Nano-heterostructure Of SnO₂/TiO₂ And The Research Of Gas Sensitivity Properties

With the improvement of people’s living standards,people pay more and more attention to the protection of the environment.Real-time monitoring the surrounding environment with portable devices has become an indispensable method in production and life.Gas sensor is a kind of equipment to monitor the ambient gas concentration.Metal oxide gas sensor has been widely used because of its low price,easy to carry and high accuracy.wide-bandgap semiconductor SnO₂ and TiO₂ have become the research hotspots of gas-sensing materials because of their stable chemical properties,excellent gas-sensing properties,wide sources and low cost.To improve the gas sensing properties,in this thesis,the SnO₂/TiO₂ heterostructure consisting of SnO₂ nanoparticles and TiO₂ nanofibers was prepared by electrospinning technology,and its gas sensitivity was studied in detail.And UV irradiation were further introduced to improve the gas sensing properties.First,SnO₂ nanoparticles and TiO₂ nanofibers were first prepared and their gas sensing properties were studied.SnO₂ nanoparticles were prepared by thermal synthesis,The SEM shows that the SnO₂ particles are completely random granular,and the particle size is about 100 to 300 nm.The sensitivity to ethanol at 240℃is 5.09.Secondly,TiO₂ nanofibers were prepared by electrospinning.The obtained TiO₂ is a rough and porous fiber with diameter of about 100 to 200 nm.It also has the best selectivity for ethanol gas,with a maximum response of 5.45 at 260℃.Sencondly,the SnO₂ nanoparticles and the TiO₂ nanofibers were then composited by electrospinning.It was proved that the SnO₂ nanoparticles in the prepared nanocomposite uniformly coated on the surface of the TiO₂ nanofibers.XRD showed that the prepared SnO₂/TiO₂ nanocomposites possess the diffraction peaks of tetragonal rutile phase SnO₂ and anatase TiO₂,respectively.And the gas sensitivity of SnO₂/TiO₂nanocomposites was significantly improved compared with pure SnO₂ nanoparticles and TiO₂ nanofibers.The optimum operating temperature of the SnO₂/TiO₂heterogeneous composite with a mass ratio of 1.5:1 is 240℃,and the maximum response for 100 ppm ethanol gas is 9.58.They are about 1.89 and 1.88 times higherthan pure TiO₂ nanofibers and SnO₂ nanoparticles,respectively.Finally,in order to increase the gas sensitivity,ultraviolet light irradiation is introduced on the basis of the composite.The SnO₂/TiO₂ heterogeneous composite with a mass ratio of 1.5:1 has a high response to HCHO under UV irradiation.Under UV irradiation,the response of ST-1.5 to 100 ppm HCHO reached 18.32,much higher than the sensitivity of 4.5 in dark conditions.In addition,the response and recovery time was reduced from 20 seconds to 13 seconds and from 16 seconds to 9 seconds by ultraviolet irradiation,respectively.Importantly,the response to HCHO in high humidity environments is also enhanced by UV irradiation.The research in this thesis provides a new way to improve the performance of gas sensor.