title: Controlled growth of iron oxide nanoparticles in the aqueous microdroplets.
abstract: Magnetite nanoparticles were synthesized by chemical coprecipitation of ferric and ferrous aqueous solutions via regulation of the microenvironment at ambient conditions. Nanocrystals having an average diameter of 6 to 12 nm were obtained by picoliter droplets, whereas only 9 nm diameter nanocrystals were prepared by microliter droplets. The size of the nanocrystals was controlled by a precise balance of reactions of hydroxide ions with positive ions at the surface layer and inner layers of the droplets. The crystal structure and average size were analyzed by X-ray diffraction pattern and transmission electron microscope images. The field dependence and temperature dependence on magnetization measured by a superconducting quantum interference device demonstrate that the as-synthesized particles are superparamagnetic at room temperature and have a size-dependent magnetic property. The anisotropy constant calculated by the blocking temperature and particle size was found to decrease with increasing particle size.
authors.affiliation: Department of Chemical and Biomolecular Engineering, Center for Ultramicrochemical Process Systems, Korea Advanced Institute of Science and Technology, Daejeon, 305-701, Republic of Korea.
authors.forename: Bong-sik
authors.initials: BS
authors.lastname: Jeon
authors.forename: Seung-Jun
authors.initials: SJ
authors.lastname: Lee
authors.forename: Jong-Duk
authors.initials: JD
authors.lastname: Kim
mesh_terms: D003460:Crystallization; D005290:Ferric Compounds / Q000737:chemistry*; D052203:Ferrosoferric Oxide / Q000737:chemistry; D007501:Iron / Q000737:chemistry; D053768:Metal Nanoparticles / Q000737:chemistry; D008670:Metals / Q000737:chemistry; D046529:Microscopy, Electron, Transmission; D008956:Models, Chemical; D008968:Molecular Conformation; D053758:Nanoparticles / Q000737:chemistry; D036103:Nanotechnology / Q000379:methods*; D014867:Water / Q000737:chemistry; D014961:X-Ray Diffraction; D014965:X-Rays
chemical_list: D005290:Ferric Compounds; D008670:Metals; D014867:Water; C000499:ferric oxide; D007501:Iron; D052203:Ferrosoferric Oxide