Enhanced relaxation dynamics in silver-doped chitosan nanocomposites: Probing the charge carrier dynamics and terahertz dielectric response

This study investigates the influence of silver nanoparticle incorporation on the electro-optical properties of chitosan, a biocompatible and versatile polymer with promising applications in biomedicine, energy storage, and sensing technologies, to name a few. Silver nanoparticles were synthesized by nanosecond laser ablation of the silver target in the polymeric solution. Terahertz time-domain spectroscopy was used to determine the complex dielectric function of pure chitosan and chitosan-silver nanocomposite films over a broad frequency range. The experimental data were analyzed using theoretical models, based on the Drude-Smith and Havriliak-Negami equations, to elucidate the underlying charge carrier dynamics and dielectric relaxation processes. Additionally, complex impedance and complex dielectric modulus analyses were conducted, incorporating Cole-Cole plots. The findings reveal a significant enhancement in the relaxation dynamics of the nanocomposite compared to pure chitosan, evidenced by a shift towards higher frequencies in the imaginary part of the dielectric function and a characteristic quarter-circle arc in the Cole-Cole plot. This study provides valuable insights into the structure-property relationships governing the electro-optical behavior of chitosan-based nanocomposites, paving the way for their tailored design and optimization for advanced technological applications.