Chirality-Dependent Sensing of Lung-Cancer-Associated Volatile Organic Compounds on Ag-Functionalized Single-Walled Carbon Nanotubes: A DFT Investigation

Abstract

Theoretical investigation of volatile organic compounds (VOCs) using nanostructured sensing materials provides a useful approach for identifying materials with potentially distinguishable electronic responses. In this work, density functional theory calculations were employed to investigate the chirality-dependent interaction of benzene (C₆H₆) and styrene (C₈H₈) with Ag-functionalized single-walled carbon nanotubes (SWCNTs). Armchair and zigzag CNT configurations were examined before and after Ag functionalization and VOC adsorption. Structural, electronic, projected density-of-states, optical, sensing-response, and Arrhenius-estimated recovery-time properties were analyzed. The calculated adsorption energies show different interaction characteristics for the two CNT configurations, with benzene exhibiting a positive adsorption energy on the Ag-zigzag model (+ 0.71 eV), whereas styrene shows exothermic adsorption on both configurations, with the strongest interaction obtained for Ag-armchair (− 0.94 eV). VOC adsorption also modifies the calculated band gaps and electronic states near the Fermi level, indicating chirality-dependent electronic responses. Optical calculations reveal changes in the absorption coefficient and optical conductivity following Ag functionalization and VOC adsorption. The theoretical sensing response was evaluated over 300–500 K, while recovery times were estimated using an Arrhenius-type model. Overall, the results demonstrate that Ag functionalization and CNT chirality can modify the predicted response toward the investigated VOCs. These findings provide a theoretical basis for further experimental investigation of chirality-dependent CNT sensing platforms for lung-cancer-associated breath VOCs

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