First-Principles Investigation of Gas-Sensing Performance of Ti/Sn Dual-Functionalized Carbon Nano-Onions for Atmospheric Gases: A DFT Study

This study explores the gas-sensing capabilities of Ti/Sn dual-functionalized carbon nano-onion (TiSn@CNO) nanostructured systems by density functional theory (DFT) at the B3LYP-D3/Def2-SVP computational approach. The electronic analysis of the pristine and functionalized derivatives reveals a systematic decrease in the HOMO-LUMO energy gap (ΔE) of 1.918 eV (pristine CNO) to 1.714 eV (Sn@CNO), 1.400 eV (Ti@CNO), and 1.389 eV (TiSn@CNO), indicating an increase in electronic responsiveness with metal addition. When gas is adsorbed on TiSn@CNO, the energy gaps of TiSnCNO are further reduced to the range of 1.277 eV. Based on the interacting gas, the CO-TiSnCNO system had the most significant ΔE decrease (1.277 eV) while the NO2-TiSn@CNO system had the most significant increase (1.603 eV), depicting that these gases respond to the device differently. The results of the adsorption energy show that all surface interactions are thermodynamically favourable, with a range of -0.020243 to -0.107616 a.u. Weak adsorption is observed with CH4-, and CO2-, while strong adsorption is obtained with H2O-, H2S-, and NH3-TiSn@CNO system. In general, the results from the energy gap alongside the negative adsorption energies confirm that the systems are thermodynamically favourable as a possible material in atmospheric gas sensor applications.