Synthesis And Gas Sensing Characteristics Of Micro-nano-structure Of Tin Dioxide Nanomaterials

SnO₂, an n-type semiconductor with a wide band-gap, has been widely used insolar cells, catalysis, and gas sensors. As we know, the sensitivity is mainly dependenton the structure of materials （surface area, pore structure, and grain size）. In this paper,different methods （hard-template, electrospining, hydrothermal） were used tosynthesize porous SnO₂materials.These materials were characterized by X-raydiffraction, scanning electron microscope, nitrogen adsorption-desorption, andtransmission electron microscope. The sensing properties of these SnO₂nanomaterialsto ethanol, methanol and acetone were detected in detail. And sensor mechanisms werediscussed as well.The main content is as follows:（1） Mesoporous SnO₂nanomaterials were synthesized by hard template method,using tin dichloride as tin source. The different structure of SnO₂-15, SnO₂-5, andSnO₂-6were obtained by replicated from SBA-15, KIT-5, and KIT-6, respectively.After removing the template, these mesoporous SnO₂nanomaterials show largespecific surface area (57-96m²g^-1), and ordered mesoporous structure. SnO₂-5（4-6nm）shows the smallest particle size, followed with SnO₂-6（5-7nm） and SnO₂-15（7-9nm）.Gas sensing tests show that mesoporous nanomaterial has the highest sensitivity toacetone. The sensitivity increased to28.2as the concentration of acetone was increasedto200ppm.（2） SnO₂nanotubes were synthesize by electrospinning, using tin dichloride as tinsource, DMF and ethanol as solvent, PVP as the viscous agent. After adding P123, thenanotubes transform to porous fibers. These materials are composed of small SnO₂nanoparticles （20-40nm）, which is benefit for the gas sensitivity. Gas sensing testsindicate that the lowest detection limit reaches200ppb. The sensitivity reaches25.5,31.0, and36.4at200ppm for methanol, ethanol, and acetone, respectively. The sensorexhibits the highest sensitivity to acetone than the others, implying a good selectivity toacetone. The sensor based SnO₂nanofibers exhibit six fold enhancements in sensitivitycompared to commercial SnO₂powder which shows the potential application in gas sensor.（3） Flower-like SnO₂nanomaterials were synthesized by hydrothermal methodwithout any surfactant, using Na2SnO3.4H2O as tin source. From the investigation, itcan be found that the use of sodium hydroxide can effectively regulate the morphologyof the sample. With0.35M NaOH solution increase to20ml, the SnO₂nanoflowerscan be observed and the SnO₂nanoflowers consist of nanorods about100nm in size.Gas sensing tests show that the sensitivity reaches13.4,16.4, and26.5at200ppm formethanol, ethanol, and acetone, respectively. The sensor exhibits the highest sensitivityto acetone than the others, implying a good selectivity to acetone.It can be concluded that the structure of the material plays the significant role inthe gas sensing performance. The large surface area and small particle size of materialscan improve their gas sensing performance significantly. Gas sensing tests show thatthese material has the highest sensitivity to acetone. These porous SnO₂nanomaterialsmay have potential application on catalysis, adsorption and batteries, ect.