Green synthesis of silver nanoparticles (AgNPs) is of particular interest due to their catalytic and antibacterial properties. In this study, the extract of Crocus Haussknechtii Bois was used to synthesize small-sized AgNPs and the effective parameters were investigated. The experimental optimization of temperature and pH reveals that spherical nanoparticles with a size of about 10–25 nm could be obtained using 0.5 mL of AgNO3 (20 mM) and 0.5 mL of the plant extract with total volume of 20 mL at pH = 7 and temperature of 75 °C within 120 min. The catalytic activity of synthesized nanoparticles was evaluated in the degradation of a Congo Red dye in the presence of sodium borohydride. The results indicate that 16.67 μM Congo Red dye could be degraded in only 220 s (frst-order kinetic model constant of Kapp = 0.011 s−1 for only 5.39 μg of synthesized AgNPs). The rate of degradation is one of the highest values reported for catalytic reduction of Congo Red dye. In addition, the synthesized AgNPs showed a signifcant inhibitory effect against both gram-positive and gram-negative bacteria, where the minimum inhibitory concentration (MIC) values of 26.9 and 20.2 μg/mL were obtained for synthesized AgNPs against S. aureus and P. aeruginosa, respectively
