Modified and enhancement polyvinyl alcohol/chitosan (PVA/Cs) films incorporated by hybrid silver tungstate (Ag2WO4) nanoparticles

Abstract

This study aims to synthesize silver tungstate (Ag₂WO₄) nanoparticles and incorporate them into a polyvinyl alcohol/chitosan (PVA/Cs) blend using a casting technique. X-ray diffraction (XRD) analysis confirms the presence of peaks corresponding to silver and tungsten, indicating the presence of these elements in the analyzed samples and providing conclusive evidence of their existence. The XRD profiles also revealed characteristic peaks corresponding to the monoclinic unit cell of PVA and an allomorphic transition within the chitosan structure. After adding Ag₂WO₄ nanoparticles, XRD analysis exhibited peaks for silver and tungsten with a crystallite size of 42.2 ± 3 nm. The UV–visible measurements indicate that incorporating Ag₂WO₄ causes a decrease in band gap energy values from 4.71 to 2.38 eV and from 5.8 to 3.73 eV for the direct allowed and direct forbidden transitions, respectively. Furthermore, the optical constants, including the extinction coefficient (k), real (${\epsilon }^{\prime }$), and imaginary (${\epsilon }^{″}$) parts, as well as the optical dielectric conductivity, were thoroughly discussed. Photoluminescence (PL) analysis revealed the emergence of a broad band centered at 434 nm with increasing Ag₂WO₄ concentration, indicating changes in the emission properties of the nanocomposites. The dielectric properties and the electrical modulus (Mʹ) values increased at higher frequencies, indicating charge carrier transfer through short-range mobility. The imaginary part (Mʹʹ) exhibited a peak attributed to dipolar polarization at the interfaces between grains, which experienced a frequency shift towards higher values. This shift indicates alterations in the distribution of Ag₂WO₄ within the PVA/Cs blend. These nanocomposites show potential in energy storage devices.