Surfactant free microwave assisted synthesis of ZnO microspheres: Study of their antibacterial activity

A well-organized zinc oxide microspheres (ZnO-MS) structure has been synthesized with the aid of microwave process simply by tuning the reaction time and microwave power. Scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) measurements, X-ray diffractometer (XRD), UV–vis spectroscopy, FT-Raman spectrometer and X-ray photoelectron spectrometer (XPS) are employed to characterize and analyze the ZnO-MS powder annealed at 400 °C for 1 h. The SEM images demonstrate the formation of dense microspheres with lateral size around 1.5 μm which consists of ultrathin nanoplates with a typical thickness of ∼20 nm, and indicates a high lateral aspect ratio. The XRD spectra indicate the polycrystalline nature having hexagonal crystal structure. The surface elemental composition of ZnO-MS was analyzed by XPS studies. Antibacterial activity of ZnO-MS was evaluated against Staphylococcus aureus (S. aureus) Gram-positive and Escherichia coli (E. coli) Gram-negative microorganisms.