Preparation Of SnO₂ Nanospheres And Micron-sized Hollow Hexagonal Prisms And Investigation Of Their Gas Sensing Properties

Although modern industrial society provides people with a rich material life,it is followed by the destruction of the living environment.For example,the haze weather caused by the massive emission of various toxic and harmful gases has a direct impact on people’s normal production and daily life.At the same time,all kinds of secondary aerosol particles generated by gas reaction are easy to attach harmful substances on the surface,resulting in various respiratory diseases and cancer.Therefore,environmental protection has been paid great attention to,at the same time,it also promotes the development of all kinds of gas detection technology.According to the different detection technology,the current developed gas sensor has resistance gas sensor,optical gas sensor,electrochemical gas sensor,surface acoustic gas sensor,micro cantilever gas sensor,surface plasmon resonance gas sensor and other gas sensors.Among these many types of gas detection technology,resistance gas sensor has the advantages of small volume,low power consumption,fast response and easy operation,and occupies a large market in the field of gas detection.It has been successfully applied to the real-time monitoring of air quality,medical and food safety fields.As an important n-type semiconductor material,SnO₂ is a wide band gap semiconductor material,with a band gap of about 3.6 eV.However,due to its good chemical stability and excellent electrical properties,it has become a potential gas sensing metal oxide.In the work reported in this paper,we used solvothermal synthesis technology combined with calcination to prepare SnO₂ materials with different morphologies.Through various characterization technologies,we studied the gas sensitive characteristics and influencing factors of the materials in detail.The detailed work is as follows:1.Tin glycerate nanospheres were synthesized as template by solvothermal method,and SnO₂ nanospheres were successfully prepared by calcination.The structure,morphology and gas sensitive properties of prepared nanomaterials were characterized by XRD,SEM,TEM,XPS,FTIR,TGA and gas sensing test system.The results of gas sensing test show that the gas sensing performance of the sample is the best when the annealing temperature reaches 450℃,and the response value of the sample to 10 ppm formaldehyde at 100℃is as high as 1419,and the response/recovery time is 19 s and 49s respectively.Finally,the gas sensing mechanism of SnO₂ gas sensor is analyzed in detail.2.Solvothermal method was used to synthesize metal organic framework material Sn-MOF,and the micron-scale SnO₂ hollow hexagonal prism was successfully prepared by calcination technology.The structure,morphology and gas sensitive properties of the products were studied by XPS,XRD,SEM,BET,TEM,Raman,FTIR and gas sensing test system.The results show that the sensor based on SnO₂ hexaprism has a very high gas sensitivity（response value 882,response time 19 s）to 2 ppm formaldehyde at120℃,which may be attributed to the large specific surface area（46.42 m²/g）providing a large number of reactive sites.