Sensing of lung cancer biomarkers using titanium carbide (Ti₂C) MXenes

Recent studies have shown that titanium carbide MXenes are promising 2D materials for sensing volatile organic compounds (VOCs) in human breath. While pristine titanium carbide MXenes exhibit, in general, metallic characteristics, functionalization modifies their electronic properties. In this study, a Ti₂C monolayer functionalized with oxygen (O), a hydroxyl group (OH), sulfur (S), and fluorine (F) is investigated for its sensing characteristics for various VOCs, namely aniline (C₆H₇N), ethylbenzene (C₈H₁₀), 4-methyloctane (C₉H₂₀), and undecane (C₁₁H₂₄). The results based on van der Waals density functional theory indicate that most VOCs undergo chemisorption on the functionalized monolayers, except in the case of C₆H₇N and C₈H₁₀ on Ti₂CF₂. The calculations of electrostatic potential and Bader charge analysis affirm this; aniline acts as an electron donor, primarily attributed to the electron-donating nature of its N atom, whereas other molecules act as electron acceptors in the adsorbed complexes. The calculated current-voltage characteristics show the high sensitivity of aniline when interacting with the OH-functionalized Ti₂C monolayer, compared to other complexes. This may be due to the low work function of the OH-functionalized monolayer, together with the donor nature of aniline. The insights gained from this study are expected to contribute to the future development of biomarkers with targeted VOC selectivity through the appropriate functionalization of MXenes.