Optical and Color Properties of Gamma Irradiated Polyvinyl Alcohol-Sodium lignosulfonate-Cadmium sulfide Nanocomposite Films

We prepared a nanocomposite (NC) film containing sodium lignosulfonate (LS), polyvinyl alcohol (PVA) and nano-sized cadmium sulfide (CdS) using the thermolysis and ex-situ casting procedures. Samples from the prepared PVA-LS/CdS NC film were exposed to gamma radiation doses (2 - 20 kGy). To study the resultant outcome of the gamma ray irradiation on the optical and color properties of the synthesized NCs, we used UV-vis spectroscopy and the International Commission on Illumination (CIE) color changes technique. When the gamma dose was increased to 20 kGy, the refractive index increased along with a decrease in the direct optical bandgap from 4.41 to 3.90 eV. We attribute this to the dominance of crosslinking that damaged the ordered configuration and thus increased the amorphous phase. This suggests that the gamma radiation can facilitate the spreading of CdS within the composite matrix suggesting an extra compacted structure of the PVA-LS/CdS NC samples. Moreover, the values of E-g, obtained from epsilon '' vs. energy plots were close to those values obtained by means of Tauc's relation, indicating that the NC films exhibited a direct allowed transition. Finally, the color changes between the pristine and irradiated samples were characterized. The pristine PVA-LS/CdS NC film exhibited substantial color differences.