Formation and antibacterial activity of heterogeneous zinc oxide nanoparticles greenly synthesized by the electrochemical method under microwave treatment

Abstract

In this study, heterogeneous zinc oxide nanoparticles (ZnO NPs) were greenly synthesized from zinc bars using the electrochemical method and then treated by microwave. Two purified zinc bars were immersed in bi-distilled water containing 0.02% of trisodium citrate and then synthesized using a direct current power. After 2 hrs of the synthesis, the solution was microwaved to investigate the influence of the microwave to the morphology, structure and physicochemical properties of heterogeneous ZnO NPs formed, as well as their antibacterial activity. The samples were characterized by ultraviolet-visible (UV–vis) spectroscopy, photoluminescence (PL) spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy and Zeta potential measurement. The antibacterial activity of heterogeneous ZnO NPs was studied using modified Kirby–Bauer disc diffusion and minimum inhibitory concentration (MIC). Results showed that heterogeneous ZnO NPs were formed in different sizes and shapes including hexagon, porous spherical, annular, and ring, depending on the time of microwave heating, the change in UV–vis absorption peaks of ZnO NPs solution was also observed from 354 to 372 nm. It also revealed that the lowest MICs were found at 14.2 and 20.8 µg/mL, corresponding to heterogeneous ZnO NPs microwaved for 5 min, against two pathogenic bacteria of methicillin-resistant Staphylococcus aureus (MRSA) and multidrug-resistant Pseudomonas aeruginosa (P. aeruginosa), respectively. This study introduced a cost-effective way to synthesize greenly heterogeneous ZnO NPs and high antibacterial activity against hospital-acquired infections.