Optical signatures and functional insights of E-C-C-Ce bio-nanocomposite

In the present study, a novel and flexible eco-friendly E-C-C-Ce (ethyl cellulose-chitosan-carbon black-CeO 2 ) bio-nanocomposite film has been developed via a simple solution-casting route. The work focuses on understanding the influence of CB/CeO 2 nanofillers on the optical, dielectric, and nonlinear properties of the EC/CS polymer blend matrix. The results reveal a significant decrease in the optical bandgap (from 4.52 eV to 2.91 eV) along with an increase in refractive index (2.07 to 2.42), extinction coefficient and Urbach energy (0.67 eV to 3.67 eV), indicating the formation of localized defect states associated with Ce 3+ ions and oxygen vacancies. The nanocomposites exhibit enhanced optical conductivity, oscillator wavelength, dielectric polarization, and reduced skin depth due to improved interfacial interactions and charge carrier mobility. The Wemple–DiDomenico model analysis confirms strengthened interband transitions, increased oscillator strength (4.719 nm −2 to 11.375 nm −2 ) and dispersion energy (5.46 eV to 13.96 eV) with nanofiller loading. Furthermore, significant enhancement in nonlinear optical parameters, including third-order susceptibility and nonlinear refractive index, is observed. Thus, the combined effects of charge-transfer interactions, defect engineering, and polymer-nanofillers interfacial coupling establish this nanocomposite as a promising candidate for flexible optoelectronic, photonic, and EMI shielding applications.