A study on the optical and dielectric behavior of Au-PVA nanocomposite films

In the current work, gold nanoparticles (AuNPs) embedded poly(vinyl alcohol) (PVA) composites were fabricated via solution casting technique. The AuNPs were synthesised in situ by the reduction of the metal precursor in the PVA matrix, acts as reducing and stabilising agent. The Plasmon resonance bands registered around 562–564 nm wavelength range of UV–Visible (UV–Vis) absorption spectra evidenced AuNPs’ generation in PVA. X-ray diffraction (XRD) studies revealed the FCC crystalline structure of the formed AuNPs. The generation of AuNPs in PVA has significantly reduced the optical energy gap for both direct and indirect transitions. Dielectric properties of the nanocomposites were investigated in the frequency range of 50 Hz-50 MHz revealed that dielectric constant and dielectric loss are enhanced in nanocomposites. Cole-Cole plot shows semi-circular arc originating from single point implying broad relaxation exists in nanocomposites. DC conductivity was enhanced with increase in gold salt concentration in Au-PVA nanocomposite, which is two orders of magnitude higher than the pristine PVA films.