Abstract:Novel hierarchical flower- and nanorod-shaped ZnO nanoparticles with uniform morphological features were successfully synthesized through controlled precipitation method in aqueous media without using any surfactant or template. To elucidate the growth mechanism of the synthesized nanoparticles, the effects of pH, reaction time and temperature were studied systematically. Selected ZnO samples were then subjected to SEM, FT-IR and XRD analysis. XRD patterns confirmed well crystalline nature of the as-synthesized powders. Furthermore, synthesized nanoparticles (hierarchical flowers as ZnO-1 and nanorods as ZnO-2), as well as commercial ZnO (ZnO-Com), were then investigated for in-vitro evaluation of antibacterial activity against various bacterial strains of clinical importance. Results showed that ZnO-2 exhibited higher antibacterial activity to all tested strains than ZnO-1, while ZnO-Com showed no antibacterial response in the applied experimental conditions. In addition, ZnO concentration-dependent antibacterial study unfolded that size of inhibition zones increased significantly from ~30 to 33 mm against Streptococcus mutans and from ~28 to 30 mm against Escherichia coli with increasing ZnO-2 concentration from 0.25 to 0.75 μg/μL. The present study, therefore, suggests that the application of synthesized ZnO nanoparticles as the antibacterial agent may be effective for inhibiting certain pathogenic bacteria in biomedical sides.

Key words: ZnO; nanoparticles; bacterial strain; antibacterial activity