The Fabrication And Gas Sensing Performance Of Porous Tinoxide Produced Using Biological Template

In recent years,gas sensors have played an outstanding role in the fields of environmental protection,industrial production and safety inspection.As one of the most widely applied semiconductor gas sensors,tin oxide gas sensors have always been focused and studied in the field of gas sensors.Due to SnO2 gas sensors belong to the surface-resistance-control type,increasing the specific surface area can improve the gas sensing property of SnO2 effectively.Therefore,bio-temlate method can be utilized to fabricate porous SnO2 materials in order to enhance the gas sensing performance.In this work,we pay close attention to ethanol and n-butanol as two target gases,tin oxide materials as the main research object,using biological template method as the main preparation method,and mainly focused on the gas sensing properties of tin oxide materials for a series of exploratory.Based on the above researches,different metal ions were used for SnO2 doping modification,and the gas sensing properties of the as-prepared porous SnO2 were investigated.The obetained resluts are as follows:1.Firstly,by using SnCl4·5H2O as a source of tin,a variety of morphologies of tin oxide were prepared using different bio-template materials.Yeast cell bio-template was used to synthesize SnO2 core-shell microspheres with a size of about 2-3μm,and the average crystallite size was about 6± 0.5 nm.The as-prepared SnO2 presented a high specific surface area of 85.7 m2/g and the pore size distribution of the as-prepared SnO2 concentrated on 38.8nm;combined with hydrothermal method,Stahlianthus involucratus leaves were used as the biological template to prepare mesoporous SnO2 materials with a specific surface area as high as 95.4 m2/g,and the pore size distribution concentrated on 9.6nm;the grapefruit peel bio-template was pre-treated by caustic washing to obtain a hierarchical pore structure SnO2 with the improved morphology integrity.The as-prepared SnO2 presented a high specific surface area of 42.98 m2/g and the pore size distribution of the as-prepared SnO2 concentrated on 9.46nm;hollow SnO2 fibers were prepared by caustic washing of bio-templates and titration combined with the hydrothermal method using the chorionic villi of metaplexis fruit as the bio-template.The specific surface area of the products calcined at 600℃ was about 73.665 m2/g and the pore size distribution concentrated on 7.821nm.It was found that the caustic washing pre-treated method and the titration process are conducive to the replication of the structure of the bio-template material by comparing the morphology of the SnO2 material prepared by different methods.2.On this basis,the gas sensing properties of SnO2 gas sensors with different morphologies were investigated.At the optimal operating temperature of 250℃,SnO2 microspheres produced using yeast cell as the bio-template had a good response and selectivity to ethanol,and the sensitivity to 500ppm ethanol was as high as 165;mesoporous SnO2 materials produced using Stahlianthus involucratus leaves as the bio-template showed the best response and selectivity to n-butanol.The sensitivity to 300ppm n-butanol at was as high as 207.8 at the optimal operating temperature of 3000C;hierarchical pore structure SnO2 produced using grapefruit peel as the bio-template showed the best response to n-butanol at an optimal operating temperature of 200℃;hollow SnO2 fibers prepared using the chorionic villi of metaplexis fruit as the bio-template showed the best response and selectivity to n-butanol.Due to the response/recovery time was too long at 150℃,200℃ was selected as the best operating temperature,and the sensitivity of gas sensors is 415.3 to 300 ppm n-butanol at 200℃(The sensitivity is 556.5 to 300ppm n-butanol at 150℃).Compare with other Sn02 gas sensors produced by different biological template in this work,Sn02 gas sensors prepared using the chorionic villi of metaplexis fruit as the bio-template showed the higher response to n-butanol and had a lower optimal operating temperature.3.Based on the structure investigation,by doping with CeO2,ZnO and NiO,we explored the influence on the gas sensing properties of SnO2 materials.The results showed that NiO can significantly improve the selectivity to ethanol gas in the aspect of improving the gas sensing performance of ethanol or n-butanol.