title: Preparation of superparamagnetic magnetite nanoparticles by reverse precipitation method: contribution of sonochemically generated oxidants.
abstract: Magnetic iron oxide nanoparticles were successfully prepared by a novel reverse precipitation method with the irradiation of ultrasound. TEM, XRD and SQUID analyses showed that the formed particles were magnetite (Fe(3)O(4)) with about 10nm in their diameter. The magnetite nanoparticles exhibited superparamagnetism above 200K, and the saturation magnetization was 32.8 emu/g at 300 K. The sizes and size distributions could be controlled by the feeding conditions of FeSO(4).7H(2)O aqueous solution, and slower feeding rate and lower concentration lead to smaller and more uniform magnetite nanoparticles. The mechanisms of sonochemical oxidation were also discussed. The analyses of sonochemically produced oxidants in the presence of various gases suggested that besides sonochemically formed hydrogen peroxide, nitrite and nitrate ions contributed to Fe(II) ion oxidation.
authors.affiliation: Osaka Center for Industrial Materials Research, Institute for Materials Research, Tohoku University, 1-2 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531, Japan. mizukosi@imr.tohoku.ac.jp
authors.forename: Yoshiteru
authors.initials: Y
authors.lastname: Mizukoshi
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Shuto
authors.forename: Naoya
authors.initials: N
authors.lastname: Masahashi
authors.forename: Shuji
authors.initials: S
authors.lastname: Tanabe
mesh_terms: D011232:Chemical Precipitation; D052203:Ferrosoferric Oxide / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D046529:Microscopy, Electron, Transmission; D016877:Oxidants / Q000138:chemical synthesis* / Q000737:chemistry; D010316:Particle Size; D014465:Ultrasonics; D014867:Water / Q000737:chemistry; D014961:X-Ray Diffraction
chemical_list: D016877:Oxidants; D014867:Water; D052203:Ferrosoferric Oxide