title: Particle size and magnetic properties dependence on growth temperature for rapid mixed co-precipitated magnetite nanoparticles.
abstract: Magnetite nanoparticles have been prepared by co-precipitation using a custom-designed jet mixer to achieve rapid mixing (RM) of reactants in a timescale of milliseconds. The quick and stable nucleation obtained allows control of the particle size and size distribution via a more defined growth process. Nanoparticles of different sizes were prepared by controlling the processing temperature in the first few seconds post-mixing. The average size of the nanoparticles investigated using a Tecnai transmission electron microscope is found to increase with the temperature from 3.8 nm at 1 ± 1 °C to 10.9 nm for particles grown at 95 ± 1 °C. The temperature dependence of the size distribution follows the same trend and is explained in terms of Ostwald ripening of the magnetite nanoparticles during the co-precipitation of Fe(2+) and Fe(3+). The magnetic properties were studied by monitoring the blocking temperature via both DC and AC techniques. Strikingly, the obtained RM particles maintain the high magnetization (as high as ∼88 A m(2) kg(-1) at 500 kA m(-1)) while the coercivity is as low as ∼12 A m(-1) with the expected temperature dependence. Besides, by adding a drop of tetramethylammonium hydroxide, aqueous ferrofluids with long term stability are obtained, suggesting their suitability for applications in ferrofluid technology and biomedicine.
authors.affiliation: Department of Materials Science and Engineering, KTH-Royal Institute of Technology, Stockholm SE 10044, Sweden.
authors.forename: Mei
authors.initials: M
authors.lastname: Fang
authors.forename: Valter
authors.initials: V
authors.lastname: Ström
authors.forename: Richard T
authors.initials: RT
authors.lastname: Olsson
authors.forename: Lyubov
authors.initials: L
authors.lastname: Belova
authors.forename: K V
authors.initials: KV
authors.lastname: Rao
mesh_terms: D003460:Crystallization; D005290:Ferric Compounds / Q000737:chemistry; D005296:Ferrous Compounds / Q000737:chemistry; D006979:Hyperthermia, Induced; D058185:Magnetite Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D046529:Microscopy, Electron, Transmission; D036103:Nanotechnology / Q000379:methods; D010316:Particle Size; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D013696:Temperature; D014867:Water / Q000737:chemistry; D014961:X-Ray Diffraction
chemical_list: D005290:Ferric Compounds; D005296:Ferrous Compounds; D058185:Magnetite Nanoparticles; D000644:Quaternary Ammonium Compounds; D014867:Water; C027917:tetramethylammonium