Synthesis of Highly Stable Superparamagnetic Iron Oxide Nanoparticles Under Mild Alkaline Reagents and Anaerobic Condition

The present study reports a new idea for synthesis of highly stable superparamagnetic iron oxide nanoparticles (IONPs) in a mild alkaline anaerobic (N-2) environment and compare their crystalline structure, zeta potential, aggregation vulnerability, and magnetic characteristics with those of IONPs produced through common methods, using either strong alkaline reagent (NaOH) and/or aerobic environment. The IONPs were precipitated at 80 degrees C temperature from Ferric and ferrous precursors using ammonium hydroxide (NH4OH) or sodium hydroxide as mild and strong alkaline reagents, respectively. The obtained results indicated the crucial impact of the alkaline reagents on the zeta potential and particle morphology, while the synthesis atmosphere mainly governed the crystalline structure and magnetic properties. Although the IONPs precipitated with NaOH under anaerobic environment exhibited higher zeta potential and thus slightly less aggregation susceptibility, those synthesized using NH4OH in anaerobic environment provided smaller particle size with enhanced crystallinity and magnetic properties. Therefore, the anaerobic environment with NH4OH as the precipitating agent was suggested as the optimal synthesis condition, resulting in particles that possessed superior crystallinity with crystallite size of 14 nm and high stable superparamagnetic properties, with saturation magnetization of 59.62 emu.g(-1) and nearly zero coercivity.