Green synthesis and enhanced antioxidant activity of ZnO nanoparticles: the role of Ag incorporation

Abstract The green synthesis of ZnO NPs, AgNPs, and Ag-ZnO NPs was conducted utilizing the aqueous extract of Nigella sativa. The bioactive molecules in the extract serve as reducing agents in facilitating the synthesis of nanoparticles. Various analytical techniques were utilized to characterize the nanoparticles. Fourier transform infrared spectroscopy (FTIR) was employed to determine the functional groups present in the extract, such as hydroxyl, carbonyl, and amino groups, which played a crucial role in nanoparticle formation and stabilization. The presence of specific Zn-O and Ag-O peaks confirmed the successful synthesis of ZnO NPs and AgNPs. UV-visible spectroscopy (UV-Vis) showed characteristic peaks for the nanoparticles, while X-ray diffraction (XRD) revealed the hexagonal wurtzite structure of ZnO NPs and the cubic structure of Ag NPs. Field emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectroscopy (EDX) confirmed the morphology and elemental composition of the nanoparticles, and zeta potential analysis indicated their stability. Transmission electron microscopy (TEM) confirmed the incorporation of Ag into the ZnO matrix. The antioxidant activity of the nanoparticles was assessed by the DPPH method. Calcination enhanced the crystallinity and stability of Ag-ZnO NPs, and AgNPs exhibited the strongest radical scavenging activity, demonstrating an IC50 value of 36.96 μg/mL, which was nearly equivalent to that of the positive control.