Radiation-Induced Synthesis and Superparamagnetic Properties of Ferrite FeO Nanoparticles.

Ultra-small magnetic FeO nanoparticles are successfully synthesized in basic solutions by using the radiolytic method of the partial reduction in Fe in the presence of poly-acrylate (PA), or by using the coprecipitation method of Fe and Fe salts in the presence of PA. The optical, structural, and magnetic properties of the nanoparticles were examined using UV-Vis absorption spectroscopy, high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and SQUID magnetization measurements. The HRTEM and XRD analysis confirmed the formation of ultra-small magnetite nanoparticles in a spinel structure, with a smaller size for radiation-induced particles coated by PA (5.2 nm) than for coprecipitated PA-coated nanoparticles (11 nm). From magnetization measurements, it is shown that the nanoparticles are superparamagnetic at room temperature. The magnetization saturation value = 50.1 A m kg of radiation-induced nanoparticles at 60 kGy is higher than = 18.2 A m kg for coprecipitated nanoparticles. Both values are compared with nanoparticles coated with other stabilizers in the literature.