Microbial and Plant Assisted Synthesis of Cobalt Oxide Nanoparticles and Their Antimicrobial Activities

Abstract

The development of sustainable, ecofriendly, and cost-effective methods for the synthesis of nanomaterials is an important aspect of nanotechnology these days. The present study was aimed at synthesizing cobalt oxide (Co3O4) nanoparticles by using plant extracts of Aerva javanica, bacterial isolates from rhizospheric soil of Potentilla atrosanguinea, Swertia petiolata, Senecio chrysanthemoides, and from fungus Fusarium oxysporum. X-ray diffraction spectroscopy (XRD) and scanning electron microscopy (SEM) techniques were used in the characterization of the synthesized nanoparticles. The bacterial strain, Bacillus subtilis, isolated from rhizosphere of Potentilla atrosanguinea (N1C1), Fusarium oxysporum, methanolic and aqueous extracts of Aerva javanica reduced the cobalt salts to cobalt oxide nanoparticles. The nanoparticles, synthesized from bacterial isolate N1C1 (Bacillus subtilis) and from Fusarium oxysporum had average particle size of 31.2 nm and 33.4 nm, respectively, whereas, the particle size of Aerva javanica was higher (39.2 nm) and all the nanoparticles were poly shaped. The nanoparticles synthesized from methanolic extract of Aerva javanica, bacterial strain (N1C1) and fungi Fusarium oxysporum showed better performance against Bacillus subtilis and P. aeruginosa, the bactericidal activity was higher against Gram-positive bacterial strains. Methanolic extracts of leaf and flower have shown a wide range of phytochemicals and higher antibacterial activity, and among all strains, Pseudomonas aeruginosa and Bacillus subtilis susceptibility was greater to extracts.