Comprehensive study of linear and nonlinear optical properties of polyaniline-Al2O3 nanocomposites for optoelectronic applications

This study explores the synthesis of polyaniline-aluminum oxide nanoparticle (PANI-Al2O3 NPs) hybrid nano-composites. An optimized electrochemical polymerization technique was employed to incorporate varying concentrations (5, 10, 15, and 20 wt.%) of Al2O3 NPs into the PANI matrix. Comprehensive characterization focused on structural, dielectric, and optical properties, both linear and nonlinear. Williamson-Hall (W-H) analysis revealed average crystallite sizes ranging from 57 nm for pure PANI to 119 nm for 20 wt.% Al2O3 nanocomposites. The initial incorporation of a small amount of Al2O3 NPs reduced crystallite size, indicating interactions with PANI chains. However, further addition of Al2O3 NPs reversed this trend, resulting in increased crystallite size due to NPs aggregation. The Urbach energy, which reflects the width of the tail of localized states in the band gap, increased from 446 meV for pure PANI to 528 meV for 20 wt.% Al2O3. Optical bandgap energies showed a slight decrease from 2.56 eV to 2.53 eV for E-g1 and from 3.70 eV to 3.85 eV for E-g2 as Al2O3 concentration increased. Furthermore, the plasma frequency resonance (omega(p)) of the materials decreased from 6.68x10(9) Hz for pure PANI to 3.69x10(9) Hz for 20 wt.% Al2O3, highlighting the impact of Al2O3 incorporation on electronic properties. Quantitative evaluation of optical properties revealed substantial improvements. The third-order nonlinear susceptibility (chi(3)) increased from 2.5 x 10(-11) to 7.7 x 10(-11) e.s.u. at 15 wt.% Al2O3, and the nonlinear refractive index (n(2)) increased from 5.8 x 10(-10) to 1.9 x 10(-9) e.s.u. These findings underscore the potential of Al2O3 NPs in enhancing the physical and optical properties of PANI, establishing these nanocomposites as promising candidates for advanced optoelectronic applications.