Green versus Chemical Precipitation Methods of Preparing Zinc Oxide Nanoparticles and Investigation of Antimicrobial Properties

Comparison of green and chemical precipitation method syntheses of zinc oxide nanoparticles (ZnO NPs) was performed, and antimicrobial properties were investigated. Avocado, mango, and papaya fruit extracts were carried out for the green synthesising methods, while the chemical precipitation method was chosen from chemical synthesis methods. Zinc nitrate was used as a salt precursor, whereas leaf extract was served as a reducing agent for green synthesising methods. In addition, sodium hydroxide, polyvinyl alcohol, and potassium hydroxide were used as reducing agents in the case of chemical precipitation synthesis methods. ZnO NPs were characterised by characterizing techniques such as Fourier transform infrared (FT-IR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The antimicrobial activities of prepared nanoparticles were evaluated on Bacillus subtilis (B. subtilis), Staphylococcus aureus (S. aureus), and Salmonella typhimurium (S. typhimurium). The particle sizes of the prepared samples which were evaluated by the Scherrer equation were in the range of 11-21 nm for green synthesis, while 30-40 nm for chemical precipitation synthesis methods. Small agglomerations were observed from SEM results of prepared ZnO NPs from both methods. Prepared ZnO NPs were showed strong antimicrobial properties. From the result, the inhibition zone was in the range of 15-24 mm for the green route and 7–15 mm for chemical precipitation methods, where the standard drugs have 25 mm of the zone of inhibition. A green synthesised method of preparing ZnO NPs gives promising antimicrobial properties compared to chemical synthesis and is also eco-friendly and safe compared to the chemical synthesis.