Effect of synthetic conditions on the structure and magnetic properties of iron oxide nanoparticles in diethylene glycol medium

Abstract This paper presents a study on the influence of synthetic conditions on the structure and properties of hydrophilic iron oxide nanoparticles obtained by thermal decomposition in diethylene glycol. The phase composition of the nanoparticles was studied using X-ray diffraction analysis and Mössbauer spectroscopy. The mass content of the magnetic phase was determined by thermogravimetric analysis. Transmission electron microscopy was used to determine the sizes of the nanoparticles. The magnetic properties were measured using a vibration magnetometry and magnetic resonance imaging. X-ray diffraction revealed that all the obtained samples are of spinel structure (Fd-3m), specific to both magnetite and maghemite. Sample 60-2h is maghemite in terms of isomer shift (Is=0.353 ± 0.001 mm/s). With an increase in the synthesis time and concentration of iron (III) acetylacetonate, crystallite size changed from 1.8 ± 0.2 to 5.2 ± 0.5 nm, the mass fraction of non-volatile residue increased from 67.6 ± 0.1% to 85.9 ± 0.1%, the average size according to transmission electronic microscopy changed from 3.3 ± 0.8 to 3.8 ± 0.4 nm, and the saturation magnetization from 13.9 ± 0.3 to 83.3 ± 1.7 A•m²/kg. It was shown that the samples obtained using this synthesis method have high values of r₂-relaxivity, up to 235 mM⁻ ¹•s⁻ ¹, which is usually uncharacteristic for iron oxide nanoparticles of this size range. The studied method for the synthesis of iron oxide nanoparticles is promising for use in creating T₂ contrast agents for MRI.