Improvement of the optical properties, dielectric behaviors and Cole-Cole plot of gamma-irradiated polyvinyl alcohol filled by nanostructured aluminum metal oxide

This research elucidates the possibility of modifying the optical, fluorescence and electrical characteristics of polymer nanocomposites (PNCs) composed of a polyvinyl alcohol (PVA) matrix with alumina (Al2O3) nanoparticles before and after gamma irradiation. Various techniques were used to investigate the optical and electrical properties of PVA, unirradiated, and irradiated PVA/Al2O3 films. The UV/Vis spectra revealed that the absorption edges of unirradiated and irradiated PVA/Al2O3 films were shifted toward lower photon energy, reflecting the decrease of optical energy gap and consequently the increase of electrical conductivity where the direct band gap energy reduced from 5.15 eV at the unirradiated PVA/Al2O3 to 4.7 eV at the highest dose, while indirect band energy gap is reduced from 4.9 eV at the unirradiated PVA/Al2O3 to 4.5 eV at the highest dose. Additionally, refractive index was increased to ∼1.6386 at the highest dose of PVA/Al2O3 compared with pure PVA, which was estimated to be ∼1.4567. Moreover, the transmittance of pure PVA decreased from 90% to 75% for unirradiated PVA/Al2O3 films to 33% for irradiated PVA/Al2O3 films. A change in the optical parameters of unirradiated and irradiated PVA/Al2O3 films was observed compared to pure PVA. The PVA/Al2O3 film showed a fluorescence response in the photoemission spectra, and considerable emission bands were produced after dispersion of Al2O3 nanoparticles in the host polymer. The increase in gamma dose led to an increase in the formation of fluorescence peaks due to the increased number of defects in the irradiated films. Moreover, the study revealed that the frequency dependence of dielectric constant, dielectric loss, and AC conductivity improved the dielectric properties. The results indicate that the PVA/Al2O3 nanocomposite films can be used as a layer in thin film transistors and optoelectronic devices due to the change in optical absorption and transmission, band gap energy with high refractive index, and high dielectric constant.