Si doped highly crystalline mesoporous In2O3 nanowires: synthesis, characterization and ultra-high response to NOx at room temperature

Abstract

1D highly crystalline mesoporous In₂O₃ nanowires (INWs) coated by an amorphous silica (HCMIAS) ultrathin surface layer were successfully fabricated using SBA-16 as a hard template. Various techniques, including XRD, SEM, TEM and X-ray photoelectron spectroscopy (XPS), were employed for material characterization. All the results demonstrated that the obtained INW-2 sample, which contained 15 at% SiO₂ and 85 at% In₂O₃ in 0.2 M In(NO₃)₃ solution, displayed high crystallinity with a rough surface coating layer of SiO₂ in the atomic scale. The domain diameter of INW-2 was approximately 4–8 nm with the pore size of 3–5 nm. The NO_x sensing properties of the INW-2 sensor exhibited an ultra-high response and selectivity with the low detection limit of 0.97 ppm and high response of 115.6 to 97.0 ppm NO_x at RT. The excellent gas sensing property of the 1D morphology with amorphous silica was associated with its higher surface area and space-charge layer, which induced highly effective surface interactions between the target gas molecules and the surface active sites. Moreover, the synergetic and electronic effect on INW-2 favored the effective adsorption of NO_x on the surface. All the factors considered had evident beneficial effects on enhancing the gas sensing performance of the sensor.