Characterization and Comparative Antibacterial Activities of Gold Nanoparticles Synthesized by Tagetes patula L. (Asteraceae) Flower Extract

In this study, gold nanoparticles (AuNPs) were successfully synthesized through a green approach using Tagetes patula L. flower extract. The phytochemical composition of the extract was analyzed by GC–MS. The characterization of AuNPs was performed by Fourier transform infrared spectroscopy (FTIR), x-ray powder diffraction, UV–visible spectroscopy, and scanning electron microscopy (SEM) in combination with energy dispersive x-ray analysis (EDX). The UV absorption peak at 550 nm was identified as characteristic of gold nanoparticles, and the XRD results confirmed their crystalline nature, with the crystallite size estimated to be around 40 ± 5 nm based on the x-ray peak widening. FTIR, SEM, and EDX analyses confirmed the successful synthesis of AuNPs. The antimicrobial properties of AuNPs were investigated against both plant and human pathogens, demonstrating larger inhibition zones compared to conventional antibiotics. Significant zones of inhibition were observed, including Pseudomonas aeruginosa (26.65 mm), Escherichia coli (23.15 mm), Klebsiella pneumoniae (20.85 mm), and Staphylococcus aureus (12.25 mm). For plant pathogens, inhibition zones included Xanthomonas campestris (31.08 mm), Ralstonia solanacearum (28.95 mm), and Erwinia amylovora (25.4 mm). The AuNPs, produced through an environmentally friendly method, exhibited strong antibacterial activity, indicating their potential as an effective alternative for agricultural pest management. This research provides scientific support for the promising applications of AuNPs as valuable medications in the future.