Green ZnO–methyl cellulose nanocomposites for optical and dielectric modulation

Green and sustainable polymer nanocomposite films are promising for optical and dielectric applications. In this study, methyl cellulose (MC) films incorporating green-synthesized zinc oxide (ZnO) nanoparticles prepared via a tea-mediated route and calcined at 500°C were fabricated by solution casting with ZnO contents of 0, 4, 8, and 12 wt%. Structural, morphological, and optical properties were investigated using Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), field-emission scanning electron microscopy/energy-dispersive X-ray spectroscopy, and UV–vis spectroscopy. FTIR analysis revealed shifts in O–H and C–O–C vibration bands, indicating hydrogen bonding and interfacial interactions between ZnO nanoparticles and MC chains. XRD confirmed phase-pure wurtzite ZnO, while broad polymer diffraction halos suggested nanoscale particle dispersion within the films. Optical analysis showed enhanced absorption and a redshift in the absorption edge with increasing ZnO concentration. Tauc and absorbance spectrum fitting methods demonstrated a gradual reduction in optical bandgap, while Urbach energy increased, indicating enhanced structural disorder. Wemple–DiDomenico analysis showed increased refractive index dispersion and polarizability. The results demonstrate that green-synthesized ZnO effectively tunes the optical and dielectric behavior of MC films for sustainable photonic and separator applications.