Synthesis of nickel ferrite nanoparticles and fabrication of PVA/CS-NiFe2O4 nanocomposite films for optoelectronic applications and electromagnetic interference shielding
摘要
In this study, NiFe₂O₄ nanoparticles were synthesized using a sol–gel auto-combustion technique and incorporated into a biopolymer matrix composed of PVA and chitosan to produce flexible nanocomposite films aimed at EMI shielding applications. The structural analysis confirmed a clear an increase in crystallite size and crystallinity of the NiFe₂O₄ nanophase, while inducing partial amorphization in the polymer matrix due to strong interfacial interactions. FTIR results confirmed strong interactions between Ni2⁺/Fe3⁺ ions and the polymer functional groups, leading to partial amorphization of the matrix. The incorporation of these nanofillers significantly enhanced the dielectric properties, electrical conductivity, and nonlinear optical performance of the nanocomposites. This study examined the optical, structural, morphological, and electromagnetic interference (EMI) properties of (PVA–Cs/NiFe2O4) nanocomposites. The optical microscope images illustrate a uniform distribution of blended nanoparticles, forming a cohesive network within the polymer matrix. The findings regarding the optical characteristics show that absorbance, absorption coefficient, refractive index, dielectric constant (both real and imaginary), and optical conductivity rise with increased concentrations of (NiFe2O4) nanoparticles. Simultaneously, the transmittance of the nanocomposites diminishes with an increase in nanoparticle concentration. The band gaps of (PVA–Cs/NiFe2O4) polymer nanocomposites diminish from 4.56 to 3.63 eV for permitted transitions and from 4.21 to 3.26 eV for forbidden transitions when the concentration of (NiFe2O4) nanoparticles increases the results indicate that the dispersion energy (Ed), average oscillator strength (So), and single oscillator energy (Eo) decrease progressively with increasing nanoparticle content. Conversely, the Urbach energy (Eu), linear optical susceptibility (χ1), third-order nonlinear susceptibility (χ3), nonlinear refractive index (n₂), oscillator wavelength parameter (λo), static dielectric constant (εo), and zero-frequency refractive index (no) show a consistent upward trend with higher nanofiller concentrations. From an electrical standpoint, the dielectric constant (ε′), dielectric loss (ε″), and electrical conductivity also increase as the nanoparticle loading rises, indicating enhanced polarization effects and improved charge carrier mobility within the nanocomposite matrix. The nanocomposite containing NiFe₂O₄ exhibited a total shielding effectiveness approaching ~ 65 dB, highlighting its capability to suppress electromagnetic pollution through absorption-dominated mechanisms. These results demonstrate that combining magnetic ferrite nanocrystals with a biodegradable polymer system offers a strategic route for fabricating efficient, lightweight, and flexible EMI shielding materials suitable for advanced electronic, stealth, and communication technologies.