Hydrothermal synthesis of cubic-rhombohedral-In2O3 microspheres with superior acetone sensing performance

Efficient and reliable acetone gas sensors are of great significance to human health and safety. The acetone sensing properties of In2O3 materials can be further improved by morphology control and heterostructure engineering. Herein, rough microspheres of pure cubic-In2O3 nanoparticles, bumpy microspheres of cubic-rhombohedral-In2O3 nanoparticles, and porous aggregates of cubic-rhombohedral-In2O3 nanocubes and nanoparticles were prepared by setting the hydrothermal temperatures as 120℃, 160℃, and 200℃, respectively. At the lowest optimal working temperature of 190℃, the sensor based on the cubic-rhombohedral-In2O3 microspheres exhibited the highest gas response value of 16.9 to 100 ppm acetone, a shorter response/recovery time of 4.7/6.0 s, and the highest selectivity against N,N-dimethylformamide (DMF), ethanol, ethylene glycol (EG), and methanol. The superior acetone sensing performance of the cubic-rhombohedral-In2O3 microspheres is attributed to its maximum BET specific surface area (45.5 m2/g), largest relative contents of surface In+ (62.39 %) and OV (28.19 %), and efficient heterojunction between cubic-In2O3 and rhombohedral-In2O3 nanocrystals, which in combination enhance the regulation of acetone molecules on the carrier concentration and conduction within the microspheres.