Phase Engineering of SnSeX (X = 1,2) Microstructures for High-Performance NO2 Chemiresistive Room-Temperature Sensor Systems: Toward Highly Reliable and Robust Detection Properties under Humidity and Interfering Gas Conditions.

Two-dimensional SnSeX (X = 1, 2) has emerged as a promising candidate for a NO2 chemiresistive sensor due to a remarkable affinity to NO2 gas adsorption. Although their gas sensing mechanism primarily relies on direct charge transfer, the underlying mechanisms of SnSe and SnSe2 remain unclear, despite various reported successes in phase engineering of SnSeX. Here, we investigate phase engineering of SnSeX in a hydrothermal route via 1-dodecanethiol (1-DDT), which served as a phase stabilizer, and comprehensively demonstrate phase-dependent NO2 detection properties. As the 1-DDT concentration increases, we directly confirm that the SnSe structure was gradually transformed to the SnSe2 one. This transformation correlates with a gradual increase in NO2 gas responses from 45 to 1430%, the highest value reported among SnSeX-based NO2 gas sensors. The obtained SnSe2-based sensors also exhibit a good NO2 discrimination without configuration of sensor arrays, under an interfering gas atmosphere in humidity conditions. Our computational calculation also unveils that these outstanding detection performances are attributed to well-constructed SnSe2 coupled with a single Se vacancy to enhance a stronger NO2 adsorption than SnSe. Finally, we demonstrate a sensor module system based on SnSe2, enabling real-time monitoring of NO2 gas.