Tunable electrical properties of polysaccharide films from grafted-pectin nanocomposites

Abstract

Thin films of grafted pectin were prepared by incorporating thiourea into its structure, using epichlorohydrin as a cross-linker agent. In addition, silver nanoparticles were embedded in the polymer matrix. The changes in the chemical and structural properties of modified pectin were evidenced by FT-IR spectroscopy, XRD, and X-ray Photoelectron Spectroscopy (XPS), while its morphological properties of silver nanoparticles were evaluated by STEM and DLS. Such structural and morphological characterization, along with the optical properties determined by UV–Vis spectroscopy, confirmed the incorporation of silver nanoparticles in the pectin films. The XRD study indicates that the grafting of thiourea onto pectin reinforces its structure, which is reflected in the alteration of the resulting polymer’s amorphousness by hindering the relaxation of its structure; this change is responsible for the decrease in conductivity observed by EIS. The ionic conductivity and band gap energy were estimated by Tauc plot using the UV–Vis Diffuse Reflectance measurements. The remarkably different electrical behavior, diffuse reflectance, and electrochemical impedance (EIS) exhibited by the nanocomposite compared to pristine pectin are consistent with the observed structural changes. Due to a potential conductive network that facilitates ion movement, adding silver nanoparticles (AgNPs) to the pectin matrix improves ionic conductivity and influences the optical band gap.