Application of Cs/GO/TiO₂ as gas sensor

Chitosan (Cs), a biodegradable, and low-cost polymer is a good choice for gas sensor applications. In this study, Cs was modified with graphene oxide (GO) and titanium dioxide (TiO₂), and its electronic properties were calculated using density functional theory (DFT) at B3LYP/LANL2DZ level. The calculated physical parameters include total dipole moment (TDM), HOMO/LUMO energy gap (ΔE), global reactivity descriptors and density of states (DOS) and mapping the electrostatic potential (MESP). Results indicated Cs had significant modification such as enhanced ΔE from 6.908 to 2.197 eV and TDM from 5.884 to 14.432 Debye, global reactivity revealed enhanced reactivity with increased absolute softness and high electrophilicity index. DOS show more available states and more localized HOMO/LUMO orbitals all enhance charge transfer. MESP shows reactivity and active sites for the interaction with its surroundings. The nanocomposite Cs/GO/TiO₂ is supposed to interact with three different gases: H₂O, CO₂, and CH₄. The results exhibited changes in the ΔE and TDM, with Cs/GO/TiO₂/CO₂ have the most pronounced changes. Partial density of states PDOS plots exhibited Ti atoms contribution in HOMO orbitals and LUMO with Cs/GO/TiO₂/CO₂ having the most changes in its energy states. Adsorption energy (E_a) and Gibbs free energy (ΔG) calculations revealed that CH₄ (E_a = 4.396 eV, ΔG = - 3.684 eV) and H₂O (E_a = 4.000 eV, ΔG = - 3.263 eV) exhibited stronger and more favorable adsorption than CO₂ (E_a a = - 0.104 eV, ΔG = + 0.801 eV). Non-covalent interaction (NCI) and Quantum theory of atoms in molecules (QTAIM) confirmed the weak interaction with gases molecules and enhanced stability via hydrogen and vdWs bonding. The Cs/GO/TiO₂ nanocomposite was synthesized, and FTIR spectroscopy was conducted and compared with calculated IR to verify the models.