Architecture of designed hollow indium oxide microspheres assembled by porous nanosheets with high gas sensing capacity

Gas sensing properties could be remarkably enhanced by self-assembly of zero, one or two dimensional nano-size units into three dimensional (3D) complicated superstructures. In this work, the 3D hollow indium oxide (In2O3) microspheres (HIOMs) assembled with porous 2D sheets were successfully synthesized by solvothermal method in Oleic acid (OA) and trioctylamine (TOA) system with the help of glycerine (Gl) combined with subsequent heat treatment. The density of self-assemble porous 2D nanosheet could be regulated by changing the calcination temperature from 400 °C to 600 °C. The gas-sensing performance of the as-prepared HIOMs had been measured towards unstable organic compounds containing methanol, acetone, ethanol, dichloromethane (DCM) and tetrahydrofuran (THF). Experimental results revealed that HIOMs-400 showed the highest response and selectivity to ethanol, followed by HIOMs-500 and HIOMs-600. At an ethanol concentration of 600 ppm, the HIOMs-400 sensor had a sensitivity of up to 15.6, while the sensitivity was about 11.9 for HIOMs-500 and 6.7 for HIOMs-600. HIOMs-400 also presented long term stability and repeatability even after five months. Such outstanding gas sensing properties of HIOMs-400 benefited from the larger BET surface area, denser pore structure and excellent capabilities of surface adsorbed oxygen.