Electronic structure engineering of PVA/ZnO/graphene oxide nanocomposites: a DFT study toward CO₂ and humidity detection

Due to their adjustable physicochemical properties and easy incorporation with functional nanomaterials, nanocomposites based on polyvinyl alcohol (PVA) have garnered significant interest for gas and humidity sensing applications. This study systematically examined the structural, electronic, adsorption, and sensing-related properties of PVA/ZnO/graphene oxide (GO) nanocomposites using density functional theory (DFT) at the B3LYP/LanL2DZ level. Strong interfacial interactions and hydrogen-bond-assisted stabilization within the nanocomposite structure were revealed by the calculated infrared spectra, molecular electrostatic potential (MESP), quantum theory of atoms in molecules (QTAIM), and non-covalent interaction (NCI) analyses. The electronic properties of PVA were significantly modified by the addition of ZnO and GO, as demonstrated by a reduction in the HOMO -LUMO energy gap from 7.334 eV to 1.075 eV and an increase in the total dipole moment from 7.147 to 12.243 Debye, which suggests that charge transfer and electronic polarization have been enhanced. Adsorption studies on H₂O and CO₂ molecules revealed that interactions are thermodynamically favorable, with adsorption energies of -0.306 eV and - 0.381 eV, respectively. PVA/OZn/GO-CO₂ showed the smallest energy gap (0.539 eV) and the largest dipole moment (14.264 Debye) among all configurations examined, indicating a marked electronic responsiveness and potential applicability in gas sensing. The analysis of the density of states further substantiated the emergence of electronic states that promote charge transport and enhance conductivity upon adsorption. The incorporation of ZnO/GO is offers an effective strategy for designing potential PVA-based nanocomposites for CO₂ gas and humidity sensing applications, as evidenced by the combined electronic modulation, strong adsorption affinity, and favorable charge redistribution.