Synthesis of silver nanoparticles using fresh bark of Pongamia pinnata and characterization of its antibacterial activity against gram positive and gram negative pathogens

The recent advancements in techniques for synthesis of zerovalent nanoparticles using green method show a clean, simple, less toxic and environmentally benign process. In this communication, silver nanoparticles were synthesized and characterized using the fresh bark extract of Pongamia pinnata. The bark extract was exposed to silver ions and the resultant biosynthesized silver nanoparticles characterized by UV–vis spectrophotometry shows the surface plasmon resonance band at 420 nm. X-ray diffraction spectrum shows crystalline structure while scanning electron microscope and transmission electron microscope analyses revealed the polydisperse distribution and particle size of 5–55 nm. The elemental analysis shows strong signal at 3 keV that corresponds to silver ions and confirms the presence of metallic silver. The antibacterial activity of silver nanoparticles was determined by agar well diffusion method against gram positive and gram negative bacteria. Maximum and minimum zones of inhibition were noted against Klebsiella planticola (15 mm) and Staphylococcus aureus (13 mm), respectively. This study reveals that silver nanoparticles possess good antibacterial activity at 100 µg/ml concentration.