One-Pot Synthesis of Au Nanoparticles/Polypyrrole Nanocomposites for Optoelectronic and Bioelectronic Devices

We report the optimized one-pot synthesis of gold nanoparticle/polypyrrole (AuNPs/PPy) nanocomposites via a 23 factorial design, enabling control of key optical and electrochemical properties. The nanocomposite formulation with the highest performance exhibited a maximum fluorescence intensity of (3.55 ± 0.063) × 106 CPS upon excitation at 350 nm. Nonlinear optical characterization by the Z-scan technique revealed self-defocusing behavior with a negative nonlinear refractive index of −9.6 × 10–8 cm2/W. Electrochemical impedance spectroscopy confirmed the hybrid’s capacitive and conductive characteristics, with a charge transfer resistance of approximately 81 Ω and a distinct capacitive response in the Bode phase angle. STEM analysis revealed a core–shell nanostructure with an average particle size of 66.4 ± 12.0 nm, consistent with direct measurement. Thermogravimetric analysis confirmed thermal stability, while cytotoxicity assays in four mammalian cell lines revealed no significant toxic effects up to 500 μg/mL, supporting the material’s biocompatibility. These combined features position the AuNPs/PPy nanocomposite as a promising multifunctional platform for integrated optical, electrochemical, and biosensing technologies.