Fabrication of transparent, dopant-free OPVA–GO nanocomposites with tunable proton conductivity and optical transparency for photonic and energy applications

Polyvinyl alcohol (PVA) is valued for its transparency and film-forming ability, but its limited chemical reactivity and weak nanofiller interactions restrict functional tunability. Partially oxidized PVA (OPVA), enriched with ketone and hydroxyl groups, provides a versatile scaffold for nanocomposite design. Transparent OPVA–graphene oxide (GO) films were fabricated via dopant-free aqueous casting with low GO loadings (0.5–1.5 wt%). FTIR and XRD analyses confirmed hydrogen bonding interactions and disruption of lamellar crystallinity, enabling nanoscale dispersion. UV–Vis–NIR spectroscopy revealed high transmittance (> 90%) and suppressed reflectance (~ 12%), while Tauc plots indicated a tunable bandgap (~ 2.0 eV) through GO-induced electronic coupling. Electrochemical impedance spectroscopy demonstrated humidity-responsive proton conductivity up to 6.0 × 10 − 3 S/cm at 90 °C under 100% relative humidity, achieved without sulfonation or external doping. Mechanical testing showed enhanced tensile strength and stiffness at 1.0 wt% GO, identified as the optimal loading, with incipient aggregation effects at higher concentrations. These synergistic trends establish a clear structure–property–performance relationship, positioning OPVA–GO nanocomposites as sustainable platforms for transparent photonic films, flexible optoelectronic devices, and renewable energy interfaces.