Controlled growth of iron oxide nanoparticles in the aqueous microdroplets.
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.
Jeon
Bong-sik
BS
Department of Chemical and Biomolecular Engineering, Center for Ultramicrochemical Process Systems, Korea Advanced Institute of Science and Technology, Daejeon, 305-701, Republic of Korea.
Lee
Seung-Jun
SJ
Kim
Jong-Duk
JD
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
D005290:Ferric Compounds; D008670:Metals; D014867:Water; C000499:ferric oxide; D007501:Iron; D052203:Ferrosoferric Oxide