First-principles investigation of the 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) using 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) from 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 a gas is adsorbed on TiSn@CNO, the energy gaps of TiSn@CNO are further reduced to around 1.277 eV. Based on the interacting gas, the CO-TiSn@CNO system exhibited the most significant ΔE decrease (1.277 eV), while the NO2-TiSn@CNO system exhibited the most significant increase (1.603 eV), depicting that the device responds to these gases 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 for the H2O-, H2S-, and NH3-TiSn@CNO systems. In general, the energy gap results, together with the negative adsorption energies, confirm that these systems are thermodynamically favourable for potential application in atmospheric gas sensors.