First-Principles Density Functional Theory Calculations on the Potential of Sc2CO2 MXene Nanosheets as a Dual-Mode Sensor for Detection of Volatile Organic Compounds in Exhaled Human Breath

Volatile organic compounds (VOCs), namely, acetone, ethanol, acetonitrile, 2-propanol, isoprene, and toluene exhaled in human breath act as potential biomarkers for the identification of certain physiological disorders. This work investigates the sensing capability of two-dimensional Sc2CO2 MXene nanosheets toward these VOCs using first-principles density functional theory calculations. Since carbon dioxide and water vapor persist in the exhaled breath, their interaction with Sc2CO2 as interferent species is examined too. It is found that 2-propanol (-0.63 eV), ethanol (-0.59 eV), and acetonitrile (-0.51 eV) show higher interaction with the Sc2CO2. Meanwhile, the chemiresistive sensorial behavior has been examined, and it is revealed that Sc2CO2 is highly sensitive to acetonitrile (50.20%). Both ethanol (1.03 x 10-3 s) and 2-propanol (5.24 x 10-3 s) have a fast recovery at room temperature. Alternatively, the change in work function of Sc2CO2 nanosheets on adsorption of VOC biomarkers has been examined. The corresponding results have proved that the work function-based Sc2CO2 sensor is sensitive to physisorbed species like toluene (47.62%) and isoprene (37.83%) that are not quantifiable using the chemiresistive sensing mechanism. Overall, our research predicts that the Sc2CO2 MXene nanosheet can be utilized as a dual-mode sensor to detect potential VOC biomarkers in the exhaled breath. Also, our results will assist the experimentalists in designing MXene nanosheet-based room-temperature sensors as point-of-care breathalyzers for disease diagnosis.