Highly efficient in vitro biosynthesis of silver nanoparticles using Lysinibacillus sphaericus MR-1 and their characterization

Silver nanoparticles (AgNPs) have been widely used in diverse fields due to their superior properties. Currently the biosynthesis of AgNPs is in the limelight of modern nanotechnology because of its green properties. However, relatively low yield and inefficiency diminish the prospect of applying these biosynthesized AgNPs. In this work, a rapid mass AgNP biosynthesis method using the cell-free extract of a novel bacterial strain, Lysinibacillus sphaericus MR-1, which has been isolated from a chemical fertilizer plant, is reported. In addition, the optimum synthesis conditions of AgNPs were investigated. The optimum pH, temperature, dosage, and reaction time were 12, 70 °C, 20 mM AgNO₃, and 75 min, respectively. Finally, AgNPs were characterized by optical absorption spectroscopy, zeta potential and size distribution analysis, x-ray diffraction, electron microscopy, and energy-dispersive x-ray spectroscopy. The results revealed that these biosynthesized AgNPs were bimolecular covered, stable, well-dispersed face centered cubic (fcc) spherical crystalline particles with diameters in the range 5–20 nm. The advantages of this approach are its simplicity, high efficiency, and eco-friendly and cost-effective features. (paper)