Preparation and characterization of calcium oxide/carboxymethyl cellulose nanocomposites with enhanced dielectric and optical properties.

Carboxymethyl cellulose (CMC)-based organic-inorganic nanocomposites with tailored functional properties are of increasing interest for sustainable electronic and optoelectronic applications. In this work, calcium oxide/carboxymethyl cellulose (CaO/CMC) nanocomposite films were successfully fabricated via a facile solution-casting approach, enabling controlled incorporation of calcium oxide within the polymer matrix. Structural and spectroscopic analyses using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) confirmed the formation of uniformly dispersed nanocrystalline CaO (~27-28 nm) and strong interfacial interactions with CMC functional groups. Dielectric investigations revealed enhanced permittivity, increased AC conductivity, and non-Debye relaxation behavior governed by interfacial polarization and charge-hopping mechanisms. Optical measurements demonstrated a clear transition from indirect to direct bandgap behavior accompanied by systematic bandgap narrowing with increasing CaO content. These experimental observations were strongly supported by density functional theory (DFT) calculations, which showed pronounced CaO-CMC interactions and a significant reduction of the HOMO-LUMO energy gap to 2.363 eV, facilitating charge transport along the polymer backbone. The close agreement between experimental and computational results highlights the robustness of the established structure-property relationship and positions CaO/CMC nanocomposites as promising low-cost materials for dielectric layers, optoelectronic coatings, and flexible electronic devices.