Two-Dimensional, Few-Layer MnPS₃ for Selective\nNO₂ Gas Sensing under Ambient Conditions

Abstract

In this study, two-dimensional\nfew-layer MnPS₃ is introduced\nas a selective and reversible NO₂ gas sensor in dry nitrogen\n(N₂) under ambient conditions. The solvent exfoliation\ntechnique is utilized to exfoliate bulk MnPS₃ into a few\nlayers, which are further assembled as thin films by the vacuum filtration\nmethod. The films are subsequently transferred onto a sensing device\nand used for NO₂ sensing. Exfoliated MnPS₃ shows\nexcellent sensitivity toward NO₂ gas with a low detection\nlimit of a few tens of ppb at 25 °C. A sensitivity of 9530% is\nobtained at 35 ppm concentration of NO₂ with the theoretical\nlimit of detection calculated to be ∼9.5 ppb. The sensor is\nhighly selective toward NO₂ gas (with respect to interferents\nNO, NH₃, H₂, CO, CO₂, C₂H₂, and O₂) and is fully reversible under ambient\nconditions. The time constant is determined to be in the range of\n30–160 s for adsorption and desorption processes. Raman spectroscopy\nreveals that the mechanism of sensing is based on charge transfer\ninteractions between the sensor and analyte. This study opens up ways\nto fabricate gas sensors using few-layer metal phosphochalcogenides\n(MPX₃).