DFT study on tunable electronic and adsorption properties of poly(vinyl alcohol)/copper oxide/graphene oxide hybrid...

The rapid development of nanoelectronics and environmental monitoring requires multifunctional polymeric materials with tailored electronic properties. In this work, Density Functional Theory (DFT) calculations at the B3LYP/LanL2DZ level are used to investigate the structural and electronic properties of poly(vinyl alcohol) (PVA) nanocomposites incorporating copper oxide (CuO) and graphene oxide (GO). The incorporation of CuO and GO significantly reduces the energy gap (ΔE) from 7.334 eV in pristine PVA to 1.415 eV for the Cu-mediated PVA-Cu/CuO/GO model and further to 0.819 eV for the oxygen-mediated PVA-O/CuO/GO configuration, indicating enhanced semiconducting behavior. Molecular electrostatic potential (MESP), density of states (DOS), and frontier orbital analyses reveal charge redistribution and the formation of interfacial states near the Fermi level. Non-covalent interaction (NCI), reduced density gradient (RDG), and QTAIM analyses confirm extensive hydrogen bonding and dispersive interactions across the interfaces. Gas adsorption studies show that H₂O and CO₂ adsorption increase the total dipole moment (TDM) and modulate ΔE, as seen in PVA-Cu/CuO/GO-2 H₂O (TDM = 10.447 Debye, ΔE = 1.112 eV) and PVA-O/CuO/GO-2CO₂ (TDM = 11.599 Debye, ΔE = 2.446 eV). The adsorption energy for CO₂ on PVA-Cu/CuO/GO is - 0.406 eV, indicating favorable and reversible physisorption with partial charge transfer. Overall, the calculations demonstrated that the combination of PVA, CuO, and GO effectively tunes the electronic structure and enhances interfacial interactions, leading to improved sensitivity and selectivity for gas and humidity sensing applications in future research.