Monodisperse silver (Ag) nanoparticles were synthesized by using Parthenium hystrophorus L leaf extract in aqueous media. The synthesized nanoparticles were characterized by using UV-vis spectrophotometer, X-ray diffracto-meter (XRD), transmission electron microscope (TEM), and dynamics light scattering (DLS). Size-dependent antibacterial activities of Ag nanoparticles were tested against Gram negative Pseudomonas aeruginosa and Gram positive Staphylococcus aureus. Ag nanoparticles having 20 ± 2 nm size in diameter show maximum zone of inhibition (23 ± 2.2 mm) in comparison to 40 nm and 70 nm diameter nanoparticles for Pseudomonas aeruginosa. The zone of inhibition against Staphylococcus aureus were 19 ± 1.8 mm, 15 ± 1.5 mm and 11 ± 1 mm for 20 nm, 40 nm, and 70 nm, respectively. In addition, affect of concentration of 20 nm size Ag nanoparticles on Bacillus cereus, Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus species were also reported and results were compared with 10 µg/ml dose of Gentamicin sulphate. The Parthenium hystrophorus L leaf extract capped 20 ± 2 nm Ag nanoparticles (7.5 µg/ml) shows statistically significant antibacterial activity than Gentamicin sulphate (10 µg/ml) against Staphylococcus aureus.
Keywords: Antibacterial activity; Parthenium leaf; Pseudomonas aeruginosa; Staphylococcus aureus; green synthesis; silver nanoparticles.