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 Sc 2 CO 2 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 Sc 2 CO 2 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 Sc 2 CO 2 . Meanwhile, the chemiresistive sensorial behavior has been examined, and it is revealed that Sc 2 CO 2 is highly sensitive to acetonitrile (50.20%). Both ethanol (1.03 × 10 –3 s) and 2-propanol (5.24 × 10 –3 s) have a fast recovery at room temperature. Alternatively, the change in work function of Sc 2 CO 2 nanosheets on adsorption of VOC biomarkers has been examined. The corresponding results have proved that the work function-based Sc 2 CO 2 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 Sc 2 CO 2 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.