Computational Investigation of Hafnium Carbide MXenes (Hf ₃ C ₂ T <i> _x </i> ) for Ultra-Sensitive Detection of Targeted Volatile Organic Compounds

Early detection of gastric cancer (GC) is critical for improving patient survival rates, yet the current diagnostic techniques are invasive and costly. Efficient detection of the targeted volatile organic compounds (VOCs) in patients' exhaled breath could be a promising method for timely GC diagnosis. In this study, we employ first-principles density functional theory (DFT) calculations to investigate the sensing potential of hafnium carbide MXenes (Hf₃C₂T_<i>x</i>; T_<i>x</i> = O, S, F) toward GC-related VOCs. van der Waals corrected simulations reveal relatively weak and unsuitable adsorption energies (<i>E</i>_ads) of -0.56, -0.47, -0.62, and -0.60 eV for the targeted VOCs, cyclohexanone, furaldehyde, pentanone, and phenol, respectively. However, a small doping of selected transition metals (Fe, Ni, and Zn) in Hf₃C₂O₂ improves the adsorption mechanism enormously. Among the studied systems, Fe-decorated Hf₃C₂O₂ (Fe-Hf₃C₂O₂) improves <i>E</i>_ads values to -1.97, -0.91, -1.34, and -1.84 eV for cyclohexanone, furaldehyde, pentanone, and phenol, respectively, which are perfect for sensing under ambient conditions. Apart from adsorption properties, charge transfer mechanism, electronic properties, work function, sensing response, recovery time, and electrostatic potential calculations further authenticated the potential of metal-decorated Hf₃C₂O₂ as ideal nanosensing materials toward the targeted VOCs. Finally, thermodynamic analysis based on the Langmuir adsorption model reveals that metal-decorated Hf₃C₂O₂ could detect the mentioned VOCs at concentrations below parts-per-billion (ppb) levels. These findings could serve as a foundation for developing efficient nanosensors for detecting GC-related VOCs, thus helping early diagnosis to improve survival rates.