Fabrication of a ppb-level NO2 gas sensor by sensitizing nanobundles assembled by In2O3 nanotubes with TiO2 quantum dots

Oxygen deficiency in metal oxide semiconductors (MOS) is a significant factor in the performance of gas sensing. Quantum dots (QDs)-decorated MOS exhibit better gas sensing performance due to rich oxygen deficiencies induced by the QDs. Therefore, titanium oxide (TiO2) QDs-decorated indium oxide (In2O3) composite was synthesized for this study via electrospinning. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to observe the self-assembly of In2O3 nanotubes, and TiO2 QDs were uniformly dispersed on the In2O3 nanotube wall. Moreover, the result of X-ray photoelectron spectroscopy (XPS) reveals that TiO2 QDs can increase the proportion of oxygen deficiency. The sensor based on IT1 sample has a response toward 10 parts per million (ppm) NO2 (214.3) that is 7.76 times higher than that of the IT0. Furthermore, the sensor has fast response/recovery characteristics, low detection limit, and high moisture resistance. The enhanced sensing performance can be understood as electronic and geometrical effects. The method of QDs-induced oxygen deficiency to improve the sensing performance toward NO2 and in-depth study of the sensing mechanism can provide new perspectives for the construction of NO2 gas sensors.