Surface and edge functionalization of carbon nanotubes with iron oxide for enhanced gas sensing: A theoretical investigation

Carbon nanotubes (CNTs) functionalized with metal oxides exhibit enhanced properties due to synergistic effects, making them attractive for electrochemical sensors, energy storage, and catalytic applications. This study investigates the surface and edge functionalization of CNTs with iron oxide (Fe₃O₄) for gas sensing using quantum-chemical methods. We examine the interaction of Fe₃O₄ with both zigzag and armchair CNTs through density functional theory (DFT) calculations, analyzing surface and edge modification mechanisms. The results demonstrate stable adsorption complexes, with edge-functionalized CNTs exhibiting higher adsorption energies than surface-modified counterparts. Key parameters such as adsorption distances, electronic structure, density of states (DOS), and energy gap variations are systematically evaluated, revealing dependence on CNT geometry, adsorption site, and functionalization type. Furthermore, the interaction of CNT-Fe₃O₄ composites with methane (CH₄) and carbon dioxide (CO₂) is modeled, showing physisorption accompanied by measurable changes in electronic properties and charge distribution. The energy gap modulation and charge transfer mechanisms suggest tunable sensitivity, enabling tailored nanocomposite design for specific applications. Notably, edge-modified CNT (6,0) exhibits unique charge redistribution, with electron transfer from Fe to C atoms and additional C→O transfer due to oxide restructuring. These findings highlight CNT-Fe₃O₄ composites as promising candidates for high-performance gas sensors, with potential applications in environmental monitoring and medical diagnostics. The theoretical framework provides insights into structure-property relationships, guiding the development of advanced sensing materials with enhanced selectivity and sensitivity for detecting trace gases, metals, and organic molecules. This work paves the way for next-generation sensor devices with optimized performance through controlled nanomaterial functionalization. • The possibility of boundary modification of a carbon nanotube with an iron oxide has been theoretically proved. • The possibility of adsorption of iron oxide on the surface of carbon nanotubes studied. • CNT modified with iron oxide for sensing of carbon dioxide and methane has been examined. • Sensing gas molecules by changing the conductive characteristics of the system has been studied.