Synthesis of Highly Crystalline and Monodisperse Cobalt Ferrite Nanocrystals

Abstract

Highly crystalline and monodisperse cobalt ferrite nanocrystals were fabricated by the high-temperature aging of a metal-surfactant complex followed by mild oxidation. Particle sizes were varied from 4 to 9 nm by changing the experimental conditions. Transmission electron microscopic (TEM) images of the particles showed two- and three-dimensional assembly of the particles, demonstrating the uniformity of the nanocrystals. Electron diffraction, X-ray diffraction, and high-resolution transmission electron microscopic images of the nanocrystals confirmed the highly crystalline nature of the cobalt ferrite structure. The elemental analysis confirmed the stoichiometry of cobalt ferrite, despite some variations in the relative atomic composition of nanocrystals. The nanocrystals were found to have typical behaviors of magnetic nanocrystals and the narrow energy barrier distributions of magnetic anisotropy, implying that the nanocrystals obtained are very uniform. The development of uniform magnetic nanocrystals has been intensively pursued because of their applications in magnetic data storage, ferrofluids, medical imaging, drug targeting, and catalysis.1,2 Recently, several metallic magnetic nanocrystals of uniform particle size have been fabricated.3 Magnetic oxide nanocrystals having uniform particle size have been synthe-