Synthesis And Gas Sensing Properties Of Indium Oxide Templating From Rape Pollen

The global environmental pollution and all kinds of noxious, inflammable and explosive gases have seriously jeopardized social progress and humans'health and safety. It is urgently necessary to develop new enhanced gas sensing materials to realize gas monitoring and security of life and property. As a matter of fact, the gas sensing effect can be ascribed to physical-chemical reaction of surface, which not only depends on the composition, but also lies on their structure hierarchy, like porosity, grain size, specific surface area, etc. Therefore, some unique porous hierarchical nanocomposites with peculiar channel structure and high specific surface area, has the potential to improve gas sensing property for its promotion of gas diffusion. However, it is nearly inaccessible to obtain subtle and complex framework through current traditional nanoprocessing technology.Biological tissue exhibits well-ordered fine structure from macroscopy to microscopy and excellent biological function to adapt the complicated environment. Inspired by the nature and combining biotechnology and nanotechnology, porous hierarchical indium oxide was prepared by duplicating the template of pollen grain in this work and further studied on its gas sensing property.Rape pollen was selected as the template and indium oxide was synthesized through washing and liquid impregnation process followed by calcination. A series of indium oxide composites were obtained by varying the indium compounds, precursor solution, impregnation methods, purge methods, calcination temperature and atmosphere. Based on the characterization, the product calcinated in air, 600℃removed the template completely and achieved indium oxide containing single component. For the composites of carbon and indium oxide calcinated in N2, 500℃and air, 400, 450, 500℃, the carbon content of the product calcinated in N2 atmosphere was the highest, and further decreased with calcination temperature rose in the air atmosphere. All the products finely reserved the morphology of rape pollen, and generated ridges on the surface as well. The BET surface area, average pore diameter and pore volume of indium oxide were calculated to be 127 m~2/g, 6.32 nm and 0.21 cm3/g, respectively by N2 adsorption-desorption method.Moreover, the interactions in the whole process were illustrated. It is believed that under the direction of reactive biotemplate, the layer by layer liquid impregnation make it feasible to duplicate the morphology of pollen grain. Besides, indium coated on the surface of pollen finally transformed to indium oxide and sporopollenin was carbonized or oxidized to be removed after calcination.In the research of gas sensing, as prepared indium oxide could respond to different gases such as ethanol, acetone and the signal of gas sensing was strengthened with the increasing concentration. According to gas sensing mechanism of metal oxide semiconductor, ordered porous hierarchical architecture derived from pollen grain could greatly promote gas flow to enhance gas sensing property due to its large specific surface area and considerable reactive sites.