ZnFe2O4 nanoparticle-modified biopolymer composites for next-generation energy and electronic applications

Zinc ferrite (ZnFe 2 O 4 ) nanoparticles were synthesized by the co-precipitation method, producing a spinel phase with an average crystallite size of ∼34 nm. These nanoparticles were then incorporated into a polyvinylpyrrolidone (PVP) and sodium alginate (NaAlg) blend matrix using the solution casting technique to fabricate nanocomposites. Structural characterization confirmed the successful dispersion of ZnFe 2 O 4 within the polymer matrix and revealed a decrease in crystallinity upon nanoparticle addition. FTIR spectra indicated strong interactions between Zn/Fe ions and polymer functional groups, leading to partial amorphization. UV-Vis spectroscopy revealed that as the nanofiller concentration increased, the material's ability to absorb light was enhanced, leading to a decrease in its transparency. This effect was directly correlated with a progressive narrowing of both the direct and indirect band gaps, which were reduced to 4.16 eV and 2.53 eV, respectively, from their initial values of 5.03 eV and 4.57 eV. Dielectric measurements demonstrated enhanced permittivity at low frequencies due to interfacial polarization and a consistent improvement in AC conductivity with nanoparticle loading. The dielectric constant increased from 10 to 60 after adding 2.4 wt.% of the nanofiller. The Modulus and Argand plot analyses provided evidence of a non-Debye-type relaxation mechanism, suggesting an enhancement in charge transport properties. Overall, the tailored optical and dielectric behaviors suggest that PVP/NaAlg–ZnFe 2 O 4 nanocomposites hold significant promise for optoelectronic, dielectric, and energy-related applications. • ZnFe 2 O 4 nanoparticles with a spinel structure (∼34 nm) were synthesized via the co-precipitation method and uniformly dispersed within the PVP/NaAlg matrix. • Incorporation of ZnFe 2 O 4 induced strong polymer–filler interactions and reduced crystallinity, confirming partial amorphization of the blend. • The optical band gaps decreased from 5.03→4.16 eV (direct) and 4.57→2.53 eV (indirect), indicating improved light absorption and semiconducting behavior. • The dielectric constant significantly increased from 10 to 60 at 2.4 wt.% filler loading, accompanied by enhanced AC conductivity and non-Debye relaxation behavior.