Influence of polyethylene glycol on the physical properties of Co0.2Fe2.8O4 nanoparticles used as MRI contrast agent; synchrotron radiation Fe K-edge XAFS

Abstract We have synthesized and characterized the surface-modified nanoparticles (NPs) of Co0.2Fe2.8O4/x polyethylene glycol (PEG) (x = 0, 10, 20, 30, and 40%). The magnetic behavior was correlated with the electronic and structural properties by combining different techniques such as X-ray Diffraction (XRD), Fourier Transform Infrared (FTIR), High Resolution Transmission Electron Microscope (HRTEM), X-ray Absorption Fine structure (XAFS) (X-ray Absorption Near Edge Structure (XANES) & Extended X-ray Absorption Fine structure (EXAFS)), and Vibrating Sample Magnetometer (VSM). We have studied the effect of PEG capping with different percent on the structural, electronic, magnetic properties, and relaxivity r2 of the Co0.2Fe2.8O4 NPs. The value of r2 indicates the efficacy of the system as a Magnetic Resonance Imaging (MRI) contrast agent in vitro. XRD showed that the Co0.2Fe2.8O4 is a monophasic spinel structure. XAFS at Fe K-edge gave information about the oxidation state of Fe cations, their fractions, and site distribution, as well as the first and second neighbors' bond lengths. No pronounced changes appeared in XANES and EXAFS results as the main type, ratio, valence, and occupancy of metal ions were similar for all samples. The relationship between the chemical environment of Fe and Co cations and their influence on the physicochemical features of the target NPs, including magnetic performance and surface morphology, was investigated towards selecting the optimum samples for MRI contrast agent application. Although no significant changes in the magnetic properties or the average, morphological, and local/electronic structures, the compositions of 30% and 40% of PEG show promising results for MRI purposes reflecting the role of PEG as a capping agent.