Visible light activated Zinc-doped MIL-68(In)-derived indium oxide nanotubes for rapid and ultra-sensitive room-temperature NO2 detection

Highly-sensitive NO 2 gas sensors based on metal oxide semiconductors (MOS) are promising but often limited by poor sensing-recovery characteristics and high operating temperatures. Herein, we address these challenges by combining Zn doping modification with mild visible light activation, effectively tuning the electronic and chemical properties of MIL-68(In)-derived In 2 O 3 nanotubes (NTs), providing an advanced approach to realize rapid recovery towards sub-ppm NO 2 at room temperature (RT). The optimized 5 at% Zn-doped In 2 O 3 (Zn x In 2-x O 3 (x = 0.10)) NTs achieves an exceptional response of 15,257 toward 10 ppm NO 2 under dark condition and a rapid 4 s recovery under visible light irradiation at RT. Additionally, the sensor exhibits superior NO 2 selectivity, excellent reproducibility and long-term stability over 36 days. The enhanced sensing performance is driven by the mesoporous frameworks which enhance free electrons transfer in the modulated energy-level structure and introduce abundant photo-induced holes via visible light irradiation at the sensing-recovery stage. This work offers new insights into surface chemistry modulation in MOS nanomaterials, advancing the development of cost-effective and low-energy-consumption room-temperature NO 2 sensors.