Nanotechnology is a growing field that has contributed to all areas of human life. The conventional synthesis of nanoparticles is complicated and suffers from serious problems such as high temperature, low yield, long reaction time, and the use of highly sensitive and toxic compounds. The green synthesis of nanoparticles has revealed better methods and approaches in the field of medicine. This article studies the synthesis of stable Fe3O4 nanoparticles by co-precipitation method using two stereoisomeric ionic imidazolium liquids as green solvents. The synthesized nanoparticles were characterized by UV-visible spectroscopy, Fourier transforms infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) analysis, Transmission Electron Microscopy (TEM), Energy-dispersive X-ray spectroscopy (EDX) analysis and magnetization measurements. The functional groups present in Fe3O4 nanoparticles were examined by FT-IR study. The formation of Fe3O4 nanoparticles has been confirmed through UV–visible spectroscopy by the change of colour owing to surface Plasmon resonance. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to characterize the size, crystalline nature and morphology of the synthesized Fe3O4 nanoparticles. The magnetic nature of the synthesized particles was found by magnetization measurements. Moreover, the synthesized nanoparticles (Fe3O4) were also screened for their antioxidant activities. From the experimental results, it has been examined that the size of the particles plays a vital role in Anti-Oxidant properties.