Abstract
Recently, there advances the collaboration of magnetics and life science fields. We focused on iron storage protein ferritin, which has a cavity of 6∼8 nm in a diameter after the removal of iron oxide from inside of it. Magnetic ferritin can be expected when ultrafine cobalt ferrite particle could be included in the cavity of ferritin because balk CoFe2O4 have large magnetocrystalline magnetic anisotropy constant K1 and suitable high magnetization. In this research, the morphology and magnetic properties of ultrafine cobalt particles less than 12 nm in diameter prepared by the coprecipitation method have been investigated. The X-ray diffraction data and TEM observations indicate that cubic-structured spinel particles are formed in granular shape in the reaction condition of pH 9∼13 and the temperatures 60∼105°C. For example, 7.3 nm particles in diameter, which are as small as the diameter of the cavity of ferritin, have been obtained successfully at a pH of 10 at 60°C for 0.5 hour reaction. Saturation magnetization and coercivity of the particles 6∼8 nm are 20∼40 emu/g and are less than 30 Oe at 300 K, respectively. Furthermore, after the removal of iron oxides from ferritin, the inclusion of ultrafine cobalt ferrite particles have been attempted. The change of UV-vis spectrum after the reaction might indicate the inclusion of ultrafine cobalt particle in the cavity of ferritin.
