Green Synthesis, Characterization and Antibacterial Activity of Cobalt Nanoparticles from Parkia biglobosa Aqueous Stem Extract

Abstract

In this research article, Cobalt nanoparticles were green synthesized, Characterized and applied in antimicrobial study of some selected pathogens. The formation of cobalt nanoparticles was confirmed by first, its colour change from light brown to dark brown within 10 minutes. From the UV-Vis spectral analysis, it was observed that highest absorption peak appeared at 400nm reflecting the surface Plasmon resonance of Cobalt NPs from Parkia biglobosa stem which is characteristic of Cobalt Nanoparticles. From the FT-IR studies, the absorption peaks were seen at 3787.71 cm-1, 3660.31 cm-1, 3436.44 cm-1, 1638.75 cm-1, 1384.50 cm-1, 1090.80 cm-1and 798 cm-1. Investigation revealed a medium sharp peak absorption at 1090.80 cm-1which may be attributed to the stretching of aliphatic hydrocarbon (C–H). A peak at 1384.50 cm-1corresponds to C=C stretching while the absorption bands at 1638.75 cm-1and 3436.44 cm-1may be assigned to N-H and O-H stretching vibration modes respectively. Similarly, peaks were seen at 3787.71 cm-1 and 3660.31 cm-1 corresponding to O-H belonging to water and alcohol respectively. Furthermore, the very strong band at 798 cm-1emanates from C-O-C symmetric stretching and C-O-H bending vibrations of protein in the Cobalt nanoparticles. The surface morphology of the bio fabricated Cobalt nanoparticles, has revealed by SEM image, is spherical in shape having smooth surface and well dispersed with close compact arrangement. From the microbial study carried out, the surfaces of the cobalt nanoparticles might have interacted directly with the bacterial outer membrane, causing the membrane to rupture thereby killing the microbes. The antibacterial activity demonstrated by the cobalt nanoparticles in this study could be attributed to their small size and high surface to volume ratio, which therefore enables them to interact closely with bacterial membranes. From the minimum inhibitory concentration (MIC) study conducted, it showed clearly that the green synthesized cobalt nanoparticles inhibited the growth of the pathogens investigated.