Two-dimensional SnS2 single crystal for sensitive NO2 detection at room temperature

Two-dimensional (2D) materials are intensively studied as promising materials for gas sensors owing to their large surface area and low working temperature. In this work, we report the synthesis of a layered SnS₂ single crystal by a chemical vapor deposition (CVD) approach for NO₂ sensing. By tuning the growth temperature, high-quality crystals with a lateral size over 3 mm are obtained in 30 min. The 2D SnS₂ sensor with optimized thickness (~15 nm) shows a low detection limit (2 ppb), a fast recovery time (66 s/1 ppm), and a high response (~4702% @ 1 ppm NO₂) at room temperature (RT) under UV illumination. An in-situ Kelvin probe force microscope is employed to reveal the high selectivity of SnS₂ through qualitative and semi-quantitative analysis of charge transfer behavior, including the directions and amount of charge transfer, upon exposure to different gases. In-situ Raman and first-principles density functional theory calculations further confirm the sensing mechanism toward NO₂. Both experimental and theoretical results suggest that 2D SnS₂ holds promising potential as an RT NO₂ sensing material.