Research On Surface Modification And Selectivities Of Gas Sensors Based On Stannic Oxide

As a basic material of emerging technologies,the metal oxide materials are widely used in optics,electronics,optoelectronics and biology field.In these applications,the response and performance of the devices are mostly depend on the size,shape,and surface activity of the metal oxide materials.Among all of them,as a metal oxide semiconductor material,great emphasis is being given to SnO2 because of the good electric,optics and electrochemical performance.In rhis paper,the sensitive performances of the SnO₂ gas sensors are studied.Then,use the different materials as the modified layers to the SnO₂ gas sensors.The sensitivities of the different gas sensors were studied.The mesoporous SnO₂ powders were prepared in sol-gel method by using the Na₂SnO₃·4H₂O as the Sn source and n-cetylpyridinium chlotird(C₁₆PyCl)as the template.The fabricated powders were characterized via X-ray diffraction analysis（XRD）,scanning electron microscope（SEM）,transmission electrom microscope（TEM）and N₂ adsorption isotherm（BET）.It is confirmed that the powders have the ordered mesoporous structure with low crystallinity.And the mesoporous SnO₂powders show the large SSA of 262.30 m²/g.In this paper,the thick gas sensors were prepared by screen printing method.By using the commercial SnO₂ powders with the frit of 2%,the SnO₂ gas sensors were fabricated.Then,the mesoporous SnO₂ were printed at the surface of the SnO₂ gas sensors as the modified layers for one layer,two layers,and three layers,respectively.By testing the sensitive performances,it showed that the performances of the SnO₂gas sensors with the mesoporous SnO₂ modified layers were highly improved.Especially,the gas sensor with two modified layers exhibited the largest response（response=22.2）.In addition,in this paper,the gas sensors employed the commercial SnO₂powders with the frit of 2%were also prepared by transfer printing method.And modified layers of the mesoporous SnO₂ were transferred on the surface of the SnO₂gas sensors for one layer,two layers,and three layers.It showed that the performances of the SnO2 gas sensors with the mesoporous SnO2 modified layers were also improved,but not as well as the screen printing method in this paper.The m-SiO2 was also considered as the surface modification of the SnO2 gas sensor.M-SiO2 was prepared by sol-gel method,and the SnO2 gas sensor with 1,2 and3 m-SiO₂ modified layer were printed by screen printing.Based on its gas sensitive performance test,the result proves that the response with the m-SiO₂ modified layer of the SnO₂ gas sensor to 10 ppm ethanol increase to a certain extent.To 10 ppm acetone and benzene the gas sensors exhibited little improves.To 1000 ppm hydrogen the gas sensors exhibited even no improves.For some improved gas sensors,the performance of the SnO₂ gas sensor with three m-SiO₂ modified layers proved to be better than the other two.