Integration of ZnO and Fe₂O₃ into Cellulose/PVP/Graphene Oxide Nanocomposite for Enhanced Optical Absorption, Dielectric Stability, and Antimicrobial Activity

Cellulose/Polyvinylpyrrolidone/graphene oxide (cell/PVP/GO) nanocomposite films doped with ZnO and varying Fe₂O₃ contents were fabricated and investigated for optical, dielectric, and antimicrobial applications. Diffuse reflectance and absorbance analysis revealed a progressive reduction in the indirect optical band gap from the GO-based composite to Fe₂O₃-loaded films, accompanied by enhanced UV shielding and extended absorption into the visible–NIR region. The incorporation of ZnO and Fe₂O₃ increased light absorption and modified the optical response due to additional electronic states and interfacial interactions. Dielectric measurements performed over a frequency range of 4 Hz–8 MHz and temperature range of 30–190 °C showed high dielectric permittivity at low frequencies due to Maxwell–Wagner interfacial polarization, followed by stable behavior at high frequencies. The dielectric stability improved with Fe₂O₃ loading, where samples remained thermally stable up to 100 °C, 120 °C, 140 °C, and 160 °C for C0–C4, respectively. The loss tangent spectra exhibited thermally activated relaxation peaks shifting toward higher frequencies with increasing temperature, indicating improved dielectric reliability. The CNC/PVP/GO films reinforced with ZnO/Fe₂O₃ nanoparticles exhibited strong antimicrobial activity against Escherichia coli, Micrococcus luteus, Staphylococcus aureus, and Candida albicans. The inhibition zones reached 38 mm, 41 mm, 38 mm, and 30 mm, respectively, for sample C4, exceeding the gentamicin reference (20–22 mm). The enhanced performance is attributed to the synergistic effects of GO-induced membrane disruption and reactive oxygen species generated by ZnO and Fe₂O₃ nanoparticles. These results demonstrate that the developed nanocomposites exhibit tunable optical properties, thermally stable dielectric behavior, and strong, broad-spectrum antimicrobial activity, promising for optoelectronics, UV-shielding coatings, and antimicrobial applications.