How Co-Precipitation Reaction Parameters Control the Characteristics and Features of Iron Oxide Nanoparticles

The main purpose of this study was to find a simple reaction condition for reproducible synthesis of water-soluble superparamagnetic iron oxide nanoparticles (SPIONs) through the co-precipitation method. For this purpose, the effect of alkali solution, working atmosphere and final reaction temperature on type, size and magnetic properties of synthesized particles were examined. The characterization of chemical composition, structural and magnetic properties of the particles obtained was carried out by investigating suspension appearance, dynamic light scattering (DLS), scanning electron microscopy (SEM), UV-Vis spectrum, vibrating sample magnetization (VSM) and X-ray diffraction (XRD) results. The results reveal that from two different tested alkali precipitants including ammonia and 1 M NaOH, samples synthesized using ammonia demonstrate proper magnetic properties, while the latter agent leads to production of nonmagnetic brown suspensions in all reaction conditions. UV-Vis absorption spectrum and XRD peaks showed the typical magnetite pattern for samples synthesized by using ammonia as the alkali precipitant. In addition, the results show that higher reaction temperatures lead to the production of smaller size black particles with lower oxidation level, better crystallization, and higher saturation magnetization. The optimal results were obtained when the ammonia was used as an alkali precipitant and the reaction temperature was set to 80 ˚C under N2 atmosphere. Furthermore, particles made under the air condition at 80 ˚C using 25% ammonia showed satisfactory dimensional and magnetic properties. The simple reaction condition used in this study could be applicable for large scale synthesis of stable SPIONs.