Tailoring the Optical Properties of Gamma Ray Irradiated Polyvinyl Alcohol/Carboxymethyl Cellulose/Sodium Lignosulfonate Blend Films for their Application in Optoelectronic Devices

Polyvinyl alcohol, carboxymethyl cellulose and sodium lignosulfonate (PVA/CMC/LS) blends were fabricated using a casting technique. Samples from the prepared PVA/CMC/LS films were irradiated with gamma ray doses ranging from 5 to 110 kGy. To explore the resulting effects of the gamma ray irradiation on the optical properties of the prepared films UV-vis spectroscopy was used. The effects of the gamma ray irradiation on the light absorbance, transmission, extinction coefficient, refractive index, dielectric loss and optical conductivity of the PVA/CMC/LS films were investigated. The absorbance of the blend films increased as it was irradiated with the gamma ray doses up to 110 kGy, the maximum dose used. The increase in absorbance was associated with a decrease in the direct bandgap from 5.60 to 4.55 eV, and an increase of Urbach energy from 0.31 to 0.84 eV. We attribute this behavior to the domination of crosslinking that destroyed the ordered structure and thus increased the amorphous regions. Additionally, we used the optical dielectric loss (epsilon") to detect the type of microelectronic transition for the PVA/CMC/LS films, which was found to be a direct allowed transition. Moreover, the optical color changes between the pristine and the irradiated films were evaluated using the International Commission on Illumination (CIE) color differences technique. The pristine PVA/CMC/LS film was uncolored. It showed significant color changes when irradiated with gamma radiation up to 110 kGy. The changes in the optical properties of PVA/CMC/LS film suggested its usage as a promising candidate for future optoelectronics characterization techniques.