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 (N-2) 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 degrees C. A sensitivity of 9530% is obtained at 35 ppm concentration of NO2 with the theoretical limit of detection calculated to be similar to 9.5 ppb. The sensor is highly selective toward NO2 gas (with respect to interferents NO, NH3, H-2, CO, CO2, C2H2, and O-2) 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).