Fabrication, growth mechanism and antibacterial activity of ZnO micro-spheres prepared via solution process

This paper presents the high antibacterial activity of ZnO micro-spheres prepared via solution process using zinc nitrate hexahydrate, (+) l-cysteine, HMT and sodium hydroxide against four pathogenic bacteria Staphylococcus aureus, Escherichia coli, Salmonella typhimurium and Klebsiella pneumoniae. The antibacterial activity of ZnO micro-spheres was studied via nutrient broth medium at different concentrations (5 μg/ml–45 μg/ml) of ZnO micro-spheres. Our investigation reveals that the lowest concentration of micro-spheres solution inhibits the growth of microbial strain, which was found to be 5 μg/ml for S. aureus, S. typhimurium and K. pneumoniae whereas for E. coli, it was calculated to be 15 μg/ml. The diameter of each micro-sphere lie between 2 and 3 μm as observed from FESEM and Transmission electron microscopy. The composition of synthesized material was analyzed by FTIR spectroscopy and it shows the band of ZnO at 462 cm−1. Additionally, on the basis of morphological and chemical observations the growth mechanism of ZnO micro-spheres was also proposed.

► ZnO micro-sphere shows high antibacterial activity against pathogenic bacteria.
► The micro-spheres (5 μg/ml–45 μg/ml) inhibit the growth of four microbial strains.
► The micro-sphere lie between 2–3 μm composed with small (∼20 nm) nanoparticles.