Free radical scavenging activity of zinc oxide nanoparticles biosynthesised using Aspergillus carneus

Zinc oxide nanoparticles (ZnO NPs) were confirmed in this work as a good antioxidant source. They were biosynthesised by the preformed biomass of Aspergillus carneus when contacted with 1 mM zinc nitrate solution of pH 9 after 24 h at 150 rpm and 30°C. The biosynthesised NPs were moderately distributed, quasi-spherical in shape with clear edges and the average size of 8–12 nm. The NPs retained full stability at 4°C for at least six months. Their zeta potential was found to be 18.3 mV. Crystalline nature of the ZnO NPs was suggested from diffraction rings appeared as lighted spots on the selected area electron diffraction pattern and confirmed by the X-ray diffraction analysis. High radical scavenging activities (RSA) were found against peroxide (${\rm O}_2^{2 - } $O22−) and 2,2–diphenyl-1-picrylhydrazyl (DPPH). Good activities were also recorded against hydroxyl (OH−) and superoxide (${\rm O}_2^ - $O2−) radicals. This potential RSA can be rendered to the adsorbed biomolecules on the NPs surface especially the phenolic compounds detected by Fourier transform infrared analysis.