Synthesis and Evaluation of <i>Helianthus annuus</i> Silver Nanoparticles

The increasing prevalence of antibiotic-resistant bacteria necessitates the exploration of novel antimicrobial agents. Silver nanoparticles (AgNPs) have emerged as promising candidates due to their broad-spectrum antimicrobial properties. This study aimed to synthesize and characterize silver nanoparticles using a green synthesis approach employing <i>Helianthus annuus</i> (sunflower) extract and to evaluate their antibacterial activity against selected bacterial strains. The formation of AgNPs was initially indicated by a visible color change from light yellow to brown in the reaction medium. The nanoparticles obtained were evaluated using UV, FTIR, Zeta Sizer and SEM analysis. The UV-Vis spectrum of reaction medium for all concentrations displayed an emission peak at 347.5 nm, which corresponded to the absorbance of silver nanoparticles (300 to 500 nm) and showed well dispersed nanoparticles in the aqueous solution without aggregation in UV-Vis absorption spectrum. The zeta sizer showed a particle size of 70.37 nm with a polydispersity index of 0.382. The greatest antibacterial activity of Synthesized Silver nanoparticles was observed against the <i>Pseudomonas aeruginosa</i> with an inhibition zone diameter (IZD) of 20 ± 0.12 mm followed by <i>Escherichia coli</i> (IZD of 19 ± 0.12 mm), <i>Bacillus subtillis</i> (IZD of 14 ± 0.06 mm and lastly <i>Staphylococcus</i> <i>aureus</i> with inhibition zone diameter of 12 ± 0.06 mm. The results of the antimicrobial studies conducted on the synthesized <i>H. annuus</i> nanoparticle showed promising activity against both gram-positive and gram-negative bacteria, suggesting their potential application in the biomedical field as an antimicrobial agent.