Nickel-Doped Tin Selenide Nanosheets for Detection of NO₂ at pbb Levels with Fast Response and Recovery at Room Temperature

Monitoring of reactive nitrogen by the Internet of Things (IoT) is urgently needed for sustainable nitrogen management to debilitate ill-health and achieve climate-stable. However, the real-time detection of nitrogen dioxide (NO 2 ) at parts per billion (ppb) levels using a low-temperature chemiresistive gas sensor with high sensitivity and fast response and recovery remains a formidable challenge. In this study, we propose a facile one-step hydrothermal method for substituting nickel into tin selenide (SnSe) nanosheets, which effectively enhances the room temperature (RT) response/recovery speed and sensitivity of SnSe-based sensor toward NO 2 . The Ni-doped SnSe sensor with a vintage doping ratio exhibits an enhanced absolute response value of 20.06 times (58.99% vs 2.94%) toward 100 ppb NO 2, compared to the pristine SnSe sensor, while also demonstrating a remarkable reduction in response/recovery time (10.32 s and 11.88 s vs 112.43 and 111.14 s). Moreover, the Ni-doped SnSe sensor exhibits remarkable selectivity and exceptional response stability. Through density functional theory (DFT) analysis, we demonstrate that the introduction of Ni atoms into the SnSe lattice generates deep impurity energy levels in the band structures, creating more active sites that enhance the interaction between the NO 2 molecules and SnSe. Furthermore, these deep impurity energy levels contribute to the ultrafast response/recovery in detecting NO 2 using Ni-doped SnSe. Our study presents a straightforward and effective strategy for the development of pollutant gas sensors that exhibit high sensitivity, low power consumption, and fast response/recovery.