Preparation Of Micro/Nanostructured In₂O₃ Semiconductor Material And Their Gas Sensing Properties

Gas sensing technology,chiefly involving discriminating and monitoring the concentration of gases in the industrial processes as well as everyday life,is receiving much attention.Until now,researchers have synthesized metal oxides with various morphologies and different dimensional nanostructures,among which,metal oxides with ultrathin nanoscale subunits have excellent gas sensing properties.However,in contrast to the ease of making layered compounds into ultrathin 2D nanomaterials,preparing such nanomaterials based on non-layered compounds still remains to be challenging.To resolve this problem,this paper respectively designs UV-assisted,template-free synthesis method and hydrothermal method to synthesize 3D and 2D In₂O₃ ultrathin nanomaterials.The experiment results show that this method can effectively avoid the nanosheets stacking,and this research systematically studies the growth process and formation mechanism.The major work in this thesis can be devided into the following aspects:（1）This paper employs a novel,UV-assisted,and template-free synthesis of hollow indium oxide microstructures semiconductor materials that are composed of ultrathin nanosheets.First of all,the UV induced photoactive solid indium alkoxide precursor to convert into hollow indium hydroxide microspheres consisting of ultrathin nanosheets,and then,the thermal treatment transformed the resulting hollow hydroxide microspheres into the hollow In₂O₃ material.We show that the as-obtained hollow nanomaterials exhibit excellent sensing performance,such as high response,good stability,and fast response speed,for detecting ppm-level gaseous formaldehyde.The mechanism of gas sensing improvement shows that efficient gas sensing performance of the hollow In₂O₃ material is closely related to their overall conducive structural features,including their hollow architecture and ultrathin nanoscale building subunits,which can offer a large amount of active sites on the surface as well as facilitate the diffusion and adsorption of the target gas,and thus enhance the material’s sensing performance.（2）This paper employs a template-free method for the synthesis of porous indium oxide 2D ultrathin nanosheets with a thickness of ³.7 nm,and the material exhibits an ultra-high response of 210 in ⁴ s when detecting 10 ppm NO_x under relatively low temperature（120 oC）.Furthermore,detection limit of the as-prepared gas sensor materials could be as low as 10 ppb.Compared with the reported metal oxides sensors for NO_x gas,the as-prepared porous indium oxide 2D ultrathin nanosheets materials well achieve the application demands,including high and fast response,low detection temperature and ultra-low detection limit.The mechanism of gas sensing shows that efficient gas sensing performance is closely related to the 2D ultrathin nanosheets and porous nanostructure.