Green Fabrication, Characterization, and Photocatalytic Study of Ag-Au Bimetallic Nanocomposite

Green plant materials in the form of extract support the bio-reduction reaction as reducing and capping agents. The present work reports the synthesis of Ag-Au bimetallic nanoparticles (BMNPs) using Bacopa monnieri leaf extract as a precursor, with AgNO ₃ and AuCl ₂ as source metals. Specifically, silver and gold bimetallic nanoparticles (Ag-Au BMNPs) are synthesised by bio-reduction method using Bacopa monnieri leaf extract. The extract serves as a reducing, stabilizing, and capping agent for the effective green synthesis of said nanoparticle. The synthesized Ag-Au BMNPs was characterized by various analytical tools for its phase formation. FT-IR spectral analysis confirms the bio-derived Ag-Au BMNPs with absorption below 1000 cm⁻¹. The UV-Visible spectra show a strong absorption peak at 650 nm, which is the characteristic absorption of green-synthesized Ag-Au BMNPs. The XRD study confirms the validation of standard characteristics by crystalline phase formation. Scanning electron microscopic (SEM) and energy dispersive X-ray microanalysis (EDX) confirm the spherical morphology with some agglomeration and the presence of Ag and Au elements. Dynamic light scattering (DLS) indicates average particle sizes of 51 nm and 668 nm with a polydispersity index (PDI) of 5.1 and 94.9, suggesting moderate polydispersity. Raman and fluorescence studies further validate the structure and photonic potential. The photocatalytic activity was evaluated for methylene blue (MB) dye degradation, showing significant reduction over 60 minutes under light exposure. Results indicate excellent photocatalytic performance, highlighting potential for environmental remediation. This green approach emphasizes sustainability, biocompatibility, and cost-effectiveness.