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n this study, we study the physical property and antibacterial bioactivity of ZnO nanopowder towards Staphylococcus Aureus. Transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), FTIR, Raman spectroscopy and UV-Vis were used to characterize the ZnO nanopowder. The major morphology consists of nanorods which have length 70-200 nm and width 30-120 nm. FTIR spectra performed a well-synthesis of ZnO that has Zn-O stretching bond (482 cm-1). UV-Vis absorption spectra showed an intense UV absorption at 387 nm, corresponding to optical bandgap 3.24 eV. Raman spectroscopy exhibited a prominent peak in E2high mode located at 435 cm-1. The antibacterial response of ZnO was performed toward Staphylococcus aureus. Higher concentration of ZnO had caused higher inhibition of the bacteria. Besides, the increment of capability of ZnO towards the bacteria was observed under UV radiation. It was believed that the irradiation had induced oxygen to be released from the surface of the ZnO and caused the increasing of reactive oxygen species, which enhance the bacteria inhibition.

We investigated the structural, optoelectronic and antibacterial properties of two commercial ZnO powder namely White (rubber grade) and Pharma (pharmaceutical grade) in order to study the correlation between the structural-optical property and the antibacterial efficacy. Transmission electron microscopy (TEM) micrographs showed rod-like morphology for the Pharma specimen and grainular shape for the White sample. X-ray diffractometry (XRD) results confirmed the superior crystallinity of the Pharma powder and photoluminescence (PL) data also showed higher UV photocatalysis of the Pharma powder if compared to that of White powder. Using the broth macrodilution method to determine the antibacterial activity of ZnO specimens, we discovered the Pharma grade exhibited stronger inhibition (80-98%) on the growth of Escherichia Coli (E. coli) especially for the ZnO suspension concentration of 10-20 mM. We believe that the superior crystallinity and stronger photocatalysis of the rod-like Pharma powder could have generated much more reactive oxygen species (OH-, H2O2 and O22-) than that of White sample resulting in the higher growth inhibition of E.coli. This work also highlights the impact of rod-like primary particles of Pharma powder in exhibiting good antibacterial efficacy if compared to the grainular particles of White powder and this observation justifies the usage of ZnO Pharma powder in pharmaceutical and healthcare products.

Nanomaterials have attracted much attention for their unique properties and promising performance compared to macroscopic materials. Nanotechnology refer to the cutting-edge approach of synthesis and modification of nanomaterials whose structures exhibit novel and improved physical, chemical, biological properties and functionality due to their nanoscaled size [1-2]. The ongoing revolution of the technology has imposed significant impact into several areas of biomedical research and engineering applications. Among the biomedical application include nanoparticle drug delivery, cell imaging, and cancer therapy.