Structural, Optical, and Dielectric Characterization of NiO Nanoparticles and Their Integration into PVA/SA Blends for Enhanced Nanocomposite Properties

This study investigates the optical, structural, and dielectric properties of NiO nanoparticles (NPs) incorporated into a poly(vinyl alcohol)/sodium alginate (PVA/SA) polymer blend. The x-ray diffraction (XRD) pattern confirmed the formation of face-centered cubic NiO NPs with a crystallite size of around 9.9 nm and lattice strain of 5.6 × 10⁻³, as determined by the Williamson–Hall method. High-resolution transmission electron microscopy (HRTEM) revealed spherical NiO NPs with sizes ranging from 5 nm to 12 nm. The embedding of NiO NPs into the matrix structure of PVA/SA was confirmed by peak shifting and new peaks from the XRD patterns, and the appearance of spherical nanoparticles with size ranging between 5 nm and 12 nm from HRTEM images. Significant shifting was observed in the Fourier transform infrared (FTIR) spectral bands, indicating strong interaction between the blend components and NiO. Optical studies showed that doping of PVA/SA with NiO NPs enhanced the material’s absorption, with a consequent effect on the optical energy band gap, demonstrated by a red shift in the absorption edge with a decrease from 5.0 eV for pristine PVA/SA to 0.09 eV for the 8 wt.% NiO-doped film. In addition, dielectric studies showed an increase in conductivity with the addition of NiO NPs, suggesting their suitability for solid polymer electrolyte applications. Graphical Abstract: (Figure presented.)