Optical and color modification in PVA/CMC/CeO2 nanocomposite films due to gamma irradiation

Polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC) and cerium oxide (CeO2) nanoparticles (NPs) were used to prepare PVA/CMC/CeO2 nanocomposite (NC) films. The morphology of the prepared CeO2 NPs was explored by means of a high resolution transmission electron microscopy (TEM); results indicated that the average particle size of the CeO2 was 22.6 nm. Also, the average crystallite size of the prepared CeO2 was 19.85 nm, as indicated by X-ray diffraction. Samples from the prepared PVA/CMC/CeO2 NC films were exposed to gamma radiation with different doses ranged from 10 to 50 kGy. The UV-vis spectroscopy and the International Commission on Illumination (CIE) color change methodology were used to explore the impact of the gamma irradiation on the optical and color properties of the prepared NC films. The impacts of gamma irradiation on the absorbance, extinction coefficient, Urbach Energy, refractive index and optical conductivity of the NC films were investigated. Both the direct and indirect optical bandgaps (Eg) decreased upon increasing the gamma dose up to 50 kGy. This could be attributed to the dominance of the chain crosslinking that damaged the ordered structure and so increased the amorphous regions. Additionally, the optical dielectric loss function (epsilon '') was used to recognize the kind of microelectronic transition for the PVA/CMC/CeO2 NC films, which was found to be a direct allowed transition. Moreover, the transmission records (370-780 nm) were used to estimate any color changes between the pristine and irradiated films. The irradiated PVA/CMC/CeO2 NC film exhibited significant color differences compared with the pristine film.