Linear and nonlinear optical properties of hybrid Polyaniline/CoFe2O4 nanocomposites: Electrochemical synthesis, characterization, and analysis

Abstract

This study presents a focused investigation and comprehensive analysis of the synthesis of hybrid Polyaniline/Cobalt ferrite (PANI/CoFe2O4) nanocomposites using an optimized electrochemical polymerization method. CoFe2O4 nanoparticles (NPs) were incorporated into the PANI matrix at varying concentrations (3, 6, and 12 wt%). The research examined the newly synthesized hybrid nanocomposites in terms of their structure, dielectric properties, and both linear and nonlinear optical properties. As a result of the Williamson-Hall method, the average crystallite size varied between 45 and 99 nm. Initially, adding a small quantity of NPs decreased the nanocomposite size, but further additions increased it due to aggregation. The Tauc plot showed a gradual increase in the energy band gap of the films as the concentration of CoFe2O4 NPs increased up to 12 wt%. This trend showed stronger absorption bands and higher coefficients, indicating improved light absorption compared to pure PANI films. Dielectric properties, including dielectric constants (ɛr, ɛi) and dielectric loss (tan δ), were examined as a function of frequency. The experimental results indicated that PANI/CoFe2O4 exhibited lower dielectric constants than bare PANI. Concentration-dependent optical properties, such as electronic transition excitation energies, dispersion energies, and optical conductivity, were also investigated. These properties were modeled using a single oscillator based on the Wemple-DiDomenico (WDD) approach. The study revealed a reduction in key optical parameters—linear susceptibility, nonlinear third-order susceptibility, and nonlinear refractive index—as nanoparticle content increased. Conversely, increasing concentrations of CoFe2O4 NPs led to a significant increase in the ratio of free carriers to effective mass (N/m٭), from 3.89 × 10³⁶ to 4.04 × 10³⁶ m⁻³ kg⁻1. Additionally, the electrical conductivity of both PANI and PANI/CoFe2O4 nanocomposites exhibited temperature-dependent improvement, reaching maximum values. The observed findings indicate that hybrid PANI-CoFe2O4 nanocomposites possess enhanced properties, highlighting their promising potential as active materials for a broad range of optoelectronic applications.