Biosynthesis and characterization of silver nanoparticles using Bacillus subtilis, Escherichia coli, and leaf extracts of Jatropha and Ocimum species

Abstract

Silver nanoparticles (AgNPs) are used in many fields for various purposes, and the biosynthesis of AgNPs through biological routes has recently gained attention. In this study, Bacillus subtilis and Escherichia coli isolated from soil within the premises of an abattoir in Minna, Niger State, Nigeria and plant extracts of Tulsi leaves (Ocimum tenuiflorum) and Jatropha leaves (Jatropha curcas) were evaluated for their ability to synthesize AgNPs. Through visual confirmation and ultraviolet and visible (UV–Vis) spectrum analysis, it was discovered that Bacillus subtilis and Escherichia coli had absorption peak at 425 and 318 nm, respectively, while Jatropha curcas and Ocimum tenuiflorum had absorption peaks at 416 and 400 nm, respectively. X-ray diffraction (XRD) analysis revealed that silver nanoparticles synthesized from B. subtilis and E. coli had a strong peak around 31.66°, which was absent in nanoparticles synthesized with O. tenuiflorum and J. curcas. Highresolution transmission electron microscopy (HRTEM) revealed that the obtained AgNPs had spherical shape and sizes for silver nanoparticles synthesized using B. subtilis and E. coli with an average size of 11.10 ± 0.21 and 38.89 ± 0.42, but the spherical shape of silver nanoparticles in E. coli was evenly distributed compared to the spherical shape in B. subtilis. Nanobars, nanopyramids, nanorods and hexagonal silver nanoparticles were observed in the HRTEM analysis of J. curcas with average size of 12.28 ± 0.37, and nanoflowers were observed in the AgNPs synthesized by O. tenuiflorum with an average size of 12.99 ± 0.15. These results of the study showed that Bacillus subtilis and Escherichia coli as well as plant extracts of Jatropha and Tulsi could be used to produce silver nanoparticles for application in various fields