Z-Scan Characterization of Hybrid Alq₃–Gold Nanostructures for Enhanced Nonlinear Optics

Abstract

In this study, the linear and nonlinear optical properties of gold nanoparticles (AuNPs) and their nanocomposites with tris(8-hydroxyquinoline)aluminum (Alq₃) were examined . The AuNPs were synthesized using pulsed laser ablation in chloroform. XRD results confirmed that the nanoparticles had a face-centered cubic structure, with an average particle size around 7 nm. The UV–Vis spectrum showed a clear peak at 340 nm, indicating the surface plasmon resonance of AuNPs, with a blue shift observed upon the addition of Alq₃, indicating strong interaction within the nanocomposite. Alq₃:AuNPs nanocomposites were prepared in three volume ratios: 2:1, 2:2, and 1:2. Nonlinear optical measurements were performed using the Z-scan technique, which showed that the samples had negative nonlinear refractive indices around 10⁻¹¹ m²/W, consistent with self-defocusing effects. Among the tested samples, pure Alq₃ showed the highest third-order nonlinear behavior. However, the Alq₃:AuNPs (2:1) nanocomposite exhibited a clear improvement when compared to the response of pure AuNPs, suggesting that adding Alq₃ enhances the nonlinear behavior of AuNPs through a synergistic effect.