Green synthesis of silver nanoparticles using leaves of <i>Lantana camara</i>: Impact of extract quantity, reaction time on shape, size and antibacterial activity

Types of plant extract, concentration of precursor solution and the incubation time play a significant role in the kinetics of nanoparticle formation during green synthesis. The present study focused on the effect of these factors on the size, uniformity and antibacterial activity of synthesized silver nanoparticles (AgNPs). Lantana camara leaf extract was used as a reducing and stabilizing agent for the biosynthesis of AgNPs. The synthesis process involved the careful preparation of leaf extract (10%), followed by the reaction of different volumes 10, 5, 2 and 1ml of extract with 50ml of 1.0mM silver nitrate solution under controlled conditions with reaction time of 10, 30, 45 and 1hrrespectively-vis spectrum indicated a characteristic single peak at 423nm, 429nm, 435nm and 443nm for samples following increasing quantity of leaf extract. Transmission electron microscopy (TEM) revealed a decrease in the size of nanoparticles and an increase in incubation time. The size of the particles was 12 nm, 15nm, 17nm and 23nm, respectively, during the incubation time of 10, 30, 45 and 1hr. The antibacterial efficacy of the AgNPs was evaluated against Escherichia coli O157:H7, and a significant increase in antibacterial activity was demonstrated with a decrease in size. FTIR revealed the involvement of hydroxyl, carbonyl and amide groups in reducing and stabilizing agents present in leaf extract for the synthesis of nanoparticles. This study authenticates the advantages of using L. camara for green synthesis of silver nanoparticles; more prolonged incubation with lower concentrations of precursor solution resulted in smaller nanoparticles with higher antibacterial activity.