Impact of NaI/KI blending on structural, optical, and impedance properties of sodium carboxymethyl cellulose biopolymer films

Abstract: The study investigates the structural, optical, and electrical characteristics of Na-CMC + PEG 600 polymer composite films doped with KI and NaI salts. UV–visible absorption spectroscopy revealed a redshift in the absorption peak (from 250 to 255 nm), indicating that the dopants altered the electronic transitions within the films. The absorption and extinction coefficients at 600 nm highlighted strong absorption by the KI and NaI blends. The blended films exhibited lower refractive indices in the violet region, suggesting good miscibility and enhanced scattering effects. An observed decrease in the dielectric constant with increasing KI doping demonstrated the impact of salt concentration on material properties, with the highest dielectric constant recorded for the Na-CMC + PEG blend. Impedance spectroscopy further indicated bulk ionic conduction, with resistance decreasing as salt concentration increased, confirming the enhanced ionic conductivity of KI-doped films over NaI. The study also reveals that the inclusion of NaI and KI salts influences both the direct and indirect bandgaps of the materials. This work highlights the potential of biodegradable polymer electrolytes for sustainable applications in energy storage, flexible electronics, and environmental sensors, offering an eco-friendly alternative to non-biodegradable materials in electronic technologies due to their natural degradation properties.