Studies of the Structural, Optical, Thermal, Electrical and Dielectric Properties of a Polyvinyl Alcohol‏/Sodium Alginate Blend Doped with Cu Nanoparticles and ZnO Nanorods as Hybrid Nanofillers for Use in Energy Storage Devices

In this work, polyvinyl alcohol‏/sodium alginate (PVA/SA) blend was used as a polymeric material for fabricating nanocomposites reinforced with copper nanoparticles (Cu NPs) and zinc oxide nanorods (ZnO NRs) as hybrid nanofillers in different concentrations. The TEM micrographs show that the shape of Cu NPs is perfectly round spheres and the shape of ZnO NRs are rods. Both pure PVA/SA blend and nanocomposite samples were characterized using X-ray diffraction (XRD) and Fourier transform infrared (FTIR) analyses, which revealed presence of coordinated hydrogen bonds and highly amorphous PVA/SA blend structure. Moreover, as evidenced by the UV–Vis spectra, the presence of the hybrid nanofillers in the blend considerably enhanced its optical properties, as absorption was increased while the indirect energy gap was reduced from 4.82 eV for the pure blend to 1.93 eV for the sample with highest concentration. The inclusion of Cu NPs and ZnO NRs also enhanced the thermal stability at higher temperatures, as confirmed by the thermogravimetric (TGA) curves. In addition, the impedance spectroscopic study findings confirmed that the alternating current (AC) conductivity was enhanced by adding the nanofillers to the polymeric matrix. The DC conductivity value (σ_dc) of PVA/SA blend doped with 1.2 wt% of nanofiller was 3.16 × 10^–9 S.cm⁻¹, which increased by approximately three orders of magnitude due to the increase of charges carriers and the creation of 3-D channels that lead to an increase in the movement of charges carriers within the blend matrix. As the dielectric parameters, such as dielectric permittivity and electrical modulus, can be tuned by varying the nanofiller content, these nanocomposites can be utilized in the development of solid polymeric electrolytes for use in advanced high-density energy storage applications and flexible-microelectronic devices.