Highly Selective Ethyl Mercaptan Sensing Using a MoSe₂/SnO₂ Composite at Room Temperature

Volatile organic sulfur compounds (VOSCs) serve not only as biomarkers for dental diseases such as halitosis but also as a tracer for monitoring air quality. Room-temperature selective detection and superior sensitivity against VOSCs at a sub-ppm level has remained a challenging task. Here, we propose a heterostructure-based design using a MoSe₂/SnO₂ composite for achieving sensitive and selective detection of ethyl mercaptan at room temperature. The composite was synthesized via a facile two-step method. A composite-based device has shown detection down to 1 ppm of ethyl mercaptan over a wider range of relative humidity (40-90%). Notably, the composite has shown adsorption selectivity toward ethyl mercaptan compared to hydrogen sulfide and other reducing or oxidizing analytes. Moreover, a density functional theory (DFT) study has been performed to understand the adsorption selectivity, charge transfer, and modification in the electronic properties after molecule adsorption on the host surface. Simulations predicted the lowest negative adsorption energy for ethyl mercaptan, implying the chemisorption (-142.029 kJ mol^-1) process of adsorption. The device thus-obtained has also shown a stable response even at an extreme relative humidity level of 90%. The obtained results and superior signal-to-noise ratio indicate that a MoSe₂/SnO₂-based sensor may be a promising candidate for highly selective and sensitive detection of ethyl mercaptan even below 1 ppm.