Effect of reaction and post-treatment conditions on physico-chemical properties of magnetic iron oxide nano-particles

Poor stability and dispersibility, as well as aggregation are considered as major challenges in clinical application of iron oxide nanoparticles (IONPs). Several studies have shown that the synthesis parameters and post-synthesis treatments e.g., drying methods, have the capability to improve the particles' characteristics. Herein, we investigate the combined effect of synthesis and post-treatment parameters on the particle size, stability and magnetism of IONPs. Magnetite (Fe3O4) NPs were prepared via co-precipitation and post-treated using different methods, i.e. (i) freeze dried at –53 °C, 0.133 mbar for 48 h (liquid nitrogen frozen (LFD) and freezer frozen (FFD)), (ii) vacuum oven dried (VOD) at 60 °C for 24 h, and (iii) kept wet colloidal (WET), dispersed in deionized water. The Fe3O4 NPs’ chemical functional groups, size, shape, crystallinity, stability, aggregation, porosity, and magnetic properties were further analysed using different characterisation techniques. Analytical results showed that, while the WET sample had the best stability and significantly less aggregation at different temperatures, amongst post-treated Fe3O4 NPs, LFD sample exhibited the best stability (up to 37 °C), dispersion and smallest polydispersity index. Furthermore, all dried NPs had superparamagnetic characteristics, while, LFD Fe3O4 NPs had better magnetic properties and stability than other drying methods.