Enhanced optical and UV shielding performance of CoFe2O4@GONDs embedded PVA nanocomposites

Abstract

Herein, cobalt ferrite-graphene oxide nanodot heterojunctions (CoFe₂O₄@GONDs) were synthesized via a hydrothermal route and incorporated into a polyvinyl alcohol (PVA) matrix using solution casting to develop nanocomposites with filler contents ranging from 0.0wt% to 2.0 wt%. Comprehensive structural and morphological analyses were performed using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HR-TEM). These characterizations confirmed homogeneous dispersion of CoFe₂O₄@GONDs within the PVA polymer matrix and strong interfacial bonding, which facilitated structural stability. Optical characterization through UV–Visible spectroscopy demonstrated enhanced absorption in the UVB and UVC regions (240–315 nm), with an increase in absorption intensity as the filler loading was increased. The optical band gap narrowed to 3.79 eV, accompanied by a reduction in Urbach energy to 0.32 eV, indicating improved structural order and decreased defect density. Key linear optical constants, including refractive index, extinction coefficient, and optical conductivity, were extracted from absorption spectra, while dispersion analysis revealed a zero-frequency dielectric constant of 3.52. The calculated third-order nonlinear susceptibility (χ³) was 2.15 × 10⁻⁸ esu, indicating robust nonlinear optical activity. These findings underscore the suitability of PVA/CoFe₂O₄@GOND nanocomposites for next-generation photonic, optoelectronic, and UV-shielding applications.