Antibacterial activity of yellow zinc oxide prepared by high-energy ball milling technique

Size reduction in nanoscale of commercial zinc oxide (ZnO) powder is required to enhance its promising properties. Therefore, milling technique is one of an effective method to produce ultrafine ZnO powder. Milling speed is the important parameter that affected on size reduction of the particles. In this work, commercial ZnO powder was milled at 0, 200, 400 and 600 rpm by high energy ball milling process during 10 min. Surface morphology of milled ZnO powder was monitored by scanning electron microscopy (SEM). Meanwhile, crystalline structure of all samples was investigated by X-ray diffractometer (XRD). Moreover, the defect in the samples after milling process at different speed was analyzed by photoluminescence emission spectra (PL). XRD result showed that ZnO diffracted patterns was identically in hexagonal crystalline phase at different milling speed. ZnO particle size was distinctly decreased approximately 200 nm according to the increase of milling speed as affirmed by SEM images. However, yellow ZnO powder was obviously occurred at the highest milling speed (600 rpm). This phenomenon is originated from the deep defect levels of oxygen vacancies as identified and interpreted by PL spectra at green emission. Additionally, ZnO powders in white and yellow status at different milling speed were monitored by antibacterial application compared with commercial grade. The efficiency of yellow ZnO powder after milling at 600 rpm in antibacterial property still showed its excellent properties as considering in the largest clear zone in the experiment.