Green synthesis of zinc oxide nanoparticles using Cinnamomum camphora (L.) Presl leaf extracts and its antifungal activity

In this study, zinc oxide nanoparticles (ZnO NPs) were synthesized using leaf extract of Cinnamomum camphora (L.) Presl and zinc acetate. Its antifungal activity was evaluated against Alternaria alternata which caused early blight disease in Solanum lycopersicum. The results showed that the size of the synthesized ZnO NPs obviously depended on the pH during the reaction. The peak of the UV-Vis spectra was at 368-374 nm, which confirmed the synthesis of ZnO NPs. SEM showed that the synthesized ZnO NPs agglomerated into spherical particles. TEM reveled that the average particle sizes of ZnO NPs synthesized at pH 7, pH 8 and pH 9 were about 13.92, 15.19 and 21.13 nm, respectively. Furthermore, ZnO NPs treatments at 20-160 mg/L could significantly inhibit the mycelia growth of A. alternata, and ZnO NPs synthesized at pH 7 showed the best antifungal effect with MIC value recorded as 20 mg/L. Moreover, 20 mg/L ZnO NPs synthesized at pH 7 significantly limited spore germination and germ tube elongation of A. alternata. In addition, ZnO NPs induced excessive accumulation of MDA in A. alternata and caused the damage of cell membrane, leading to the leakage of protein and nucleic acid. Therefore, green synthesized ZnO NPs, as a promising biocontrol agent, could be used to control fungal diseases.