Two-Dimensional, Few-Layer MnPS₃ for Selective NO₂ Gas Sensing under Ambient Conditions

In this study, two-dimensional few-layer MnPS₃ is introduced as a selective and reversible NO₂ gas sensor in dry nitrogen (N₂) under ambient conditions. The solvent exfoliation technique is utilized to exfoliate bulk MnPS₃ into a few layers, which are further assembled as thin films by the vacuum filtration method. The films are subsequently transferred onto a sensing device and used for NO₂ sensing. Exfoliated MnPS₃ shows excellent sensitivity toward NO₂ gas with a low detection limit of a few tens of ppb at 25 °C. A sensitivity of 9530% is obtained at 35 ppm concentration of NO₂ with the theoretical limit of detection calculated to be ∼9.5 ppb. The sensor is highly selective toward NO₂ gas (with respect to interferents NO, NH₃, H₂, CO, CO₂, C₂H₂, and O₂) and is fully reversible under ambient conditions. The time constant is determined to be in the range of 30-160 s for adsorption and desorption processes. Raman spectroscopy reveals that the mechanism of sensing is based on charge transfer interactions between the sensor and analyte. This study opens up ways to fabricate gas sensors using few-layer metal phosphochalcogenides (MPX₃).