Effect of Zn Concentration in Zinc-Doped 2D Layered Indium Oxides for Room-Temperature Optoelectronic Sensing of NO₂

The growing imperative for real-time monitoring of nitrogen dioxide (NO2)─a criterion air pollutant with chronic health impacts─necessitates the development of room-temperature, high-performance gas sensors. Two-dimensional (2D) metal oxides have emerged as a promising material group for high-performance and energy-efficient gas sensing. The transition metal doping strategy is deemed an effective method to enhance their gas interaction properties, especially at room temperature. 2D indium oxide nanostructures (In2O3) have garnered significant research interest due to their remarkable gas-sensing properties. Building on this interest, we present the gas sensing properties of zinc (Zn)-doped ultrathin 2D In2O3 nanocrystals. To this end, a range of mass concentrations of Zn-doped 2D In2O3, with a uniform thickness of approximately 4.0 ± 0.2 nm, was achieved by transferring the surface oxide layer from liquid In–Zn alloys under controlled conditions. The room-temperature optoelectronic NO2 sensing behavior and underlying mechanisms of Zn-doped 2D In2O3 were systematically investigated through combined experimental and theoretical approaches. The 2% Zn doping concentration sample demonstrated optimal NO2 sensing performance, with a response value of 6.16 and response/recovery times of 46.17 min/36.52 min, exhibiting good moisture resistance and selectivity. This work provides a viable approach for the preparation of 2D metal-doped oxides and demonstrates the effect of doping on gas sensitivity.