Improved ppb level SnO2@In2O3 sensor induced by In2O3 nanoparticles embedded on SnO2 nanoflower for superior NO2 sensing performance

The current study, accurately designed and created a two-dimensional (2D) structure of SnO2 nano-flowers and In2O3 nanoparticles using a simple hydrothermal technique and sol-gel method, respectively. On the outer surface of SnO2 nanoflowers the In2O3 nanoparticles were uniformly growing, clearly revealed by field emission scanning electron microscopic. Besides, crystal phase structure, surface area and elementals composition were characterized by XRD, BET, TEM, EDS, XPS and the gas sensing properties of In2O3@SnO2 NFs. The results exhibited that 2 wt% In2O3@SnO2 NFs sensor is highly sensitive to NO2, the response (Rg/Ra) to 30 ppm NO2 is 94.5, and at 50 ppb the response measured 0.61 at 150 °C, the response time is 32 and 51s, respectively, along with good moisture resistance. Besides along with excellent selectivity, long-term stability, and relative humidity (RH) in high-humidity environment, the 2 wt% In2O3@SnO2 NFs still maintain high response 91 at 30 ppm. More importantly, at room temperature the response was (Rg/Ra = 1.01) at detection limit 300 ppb towards NO2, which could use be for trace NO2 gas detection. The large specific surface areas of SnO2, the abundance of oxygen species adsorbed on the surface, the distinctive electron transformation between heterojunction materials, and high electron transmission channel of SnO2 and In2O3 transition layer were all considered to have a synergistic effect thatin2 contributed to excellent sensing properties of In2O3@SnO2 NFs.