Study Of The Controlled Synthesis Of Indium Oxide Nanomaterials And Their Application For Gas Sensing

Hollow or porous materials have recently attracted considerable attention due to their specific structure with low density, high specific surface in chemical sensor, drug delivery and photocatalysis. As a very important n-type wide-band gap (3.6eV) semiconductor, In2O3has been widely used in solar cells, flat panel displays, gas detectors, etc, owing to its high electric conductance, high transparency to visible light, and the strong interaction between certain poisonous gas molecules and In2O3surfaces. Because of the size and shape-dependent properties, controllable growth and mechanism studies of hollow or porous In2O3with different morphologies are important. In this work, different morphologies of porous indium-oxide (In2O3) nanomaterials, including hollow spheres and hollow nanorods, have been successfully prepared by hydrothermal process. The main works can be summarized as follows:First In2O3hollow microspheres were successfully synthesized by hydrothennal process in the system of saccharides and In(NO3)3mixtures in combination with heat-treatment. The effects of saccharides amount, temperatures and reaction times have been explored. It is found that the wall-thick of the hollow spheres increases at first, then decrease with the reaction temperatures increased from150℃,180℃to210℃, and the maximum wall-thick was150nm when the temperatures was180℃. Similarly, the gas sensing properties also present the same change trend with the amounts of saccharide changed from2g,4g to8g. The highest gas sending response to ethanol and formaldehyde was90and72, respectively, when the products obtained from the system of3mmol (In2O3) and4g saccharides.Next this work focuses on the design and synthesis of mesoporous In2O3nanotubes with hollow structures. So, a method for the preparation of mesoporous In2O3nanotubes(the three-step method)was developed. Firstly, ZnO nanorods were prepared which acting as hard templates to hollow In2O3structures; Then, In(OH)3nanoparticles grown on the surface of ZnO nanorods, and followed by the formation of mesoporous In2O3shell on ZnO nanorods by heat-treatment at600℃; Finally, acidic etching was adaped to remove the ZnO nanorods to form hollow structured In2O3nanotubes. The influence factors on the morphologies, gas sensing properties, and aspect ratios of In2O3hollow nanotubes, such as deposition times, concentration of acidic, were investigated. The results show that the optimum fabrication conditions are as follow:aspect ratios of ZnO nanorods8; deposition times8; acidic concentration pH=1. The In2O3nanotubes obtained under this condition show improved hollow morphologies. Furthermore, the as-obtained In2O3hollow rods exhibited good sensitivity and quick response to dilute ethanol, the gas sensing properties to4ppm ethanol is4, and the response reached92when the concentration of ethanol is350ppm, which better than In2O3hollow spheres.