Improving the polyethylene oxide/carboxymethyl cellulose blend's optical and electrical/dielectric performance by incorporating gold quantum dots and copper nanoparticles: nanocomposites for energy storage applications

Herein, nanocomposite polymer electrolyte films were prepared from the blend of two polymers, polyethylene oxide (PEO) and carboxymethyl cellulose (CMC), stuffed with various contents of gold quantum dots (AuQDs) and copper nanoparticles (CuNPs) as hybrid nanofiller via the solution casting method. AuQDs were prepared using laser ablation in liquid (LAL). TEM images showed that the average size of AuQDs is nearly 6.21 nm with a spherical shape. The effects of AuQDs and the hybrid nano-filler (AuQDs and CuNPs) on the PEO/CMC blend structural, optical, and electrical/dielectric characteristics have been investigated and discussed. XRD results revealed that the crystallinity degree of the nanocomposite samples decreased with increasing AuQDs/CuNPs content. Also, UV–Vis spectroscopy analysis uncovered that the optical energy gap reduced as the hybrid nanofillers' content increased. At room temperature, the electrical impedance spectroscopy (EIS) measurements showed that the hybrid nanofiller loading increases the electrolyte films’ electrical conductivity. In the dielectric properties, space charges polarization revealed higher values, where the dielectric constant (ε′) increased at lower frequency regions. The Nyquist diagram showed a semicircular shape at the lower frequencies part with a linear shape at the higher frequencies part with decreasing radius; two equivalent circuit models could be the best fit. These results suggest that these nanocomposite electrolyte films could be candidates for capacitors and flexible energy storage devices.