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Aqueous Superparamagnetic Magnetite Dispersions with Ultrahigh Initial Magnetic Susceptibilities.
- Source :
-
Langmuir : the ACS journal of surfaces and colloids [Langmuir] 2018 Jan 16; Vol. 34 (2), pp. 622-629. Date of Electronic Publication: 2017 Dec 29. - Publication Year :
- 2018
-
Abstract
- Superparamagnetic nanoparticles with a high initial magnetic susceptibility χ <subscript>o</subscript> are of great interest in a wide variety of chemical, biomedical, electronic, and subsurface energy applications. In order to achieve the theoretically predicted increase in χ <subscript>o</subscript> with the cube of the magnetic diameter, new synthetic techniques are needed to control the crystal structure, particularly for magnetite nanoparticles larger than 10 nm. Aqueous magnetite dispersions (Fe <subscript>3</subscript> O <subscript>4</subscript> ) with a χ <subscript>o</subscript> of 3.3 (dimensionless SI units) at 1.9 vol %, over 3- to 5-fold greater than those reported previously, were produced in a one-pot synthesis at 210 °C and ambient pressure via thermal decomposition of Fe(II) acetate in triethylene glycol (TEG). The rapid nucleation and focused growth with an unusually high precursor-to-solvent molar ratio of 1:12 led to primary particles with a volume average diameter of 16 nm and low polydispersity according to TEM. The morphology was a mixture of stoichiometric and substoichiometric magnetite according to X-ray diffraction (XRD) and Mössbauer spectroscopy. The increase in χ <subscript>o</subscript> with the cube of magnetic diameter as well as a saturation magnetization approaching the theoretical limit may be attributed to the highly crystalline structure and very small nonmagnetic layer (∼1 nm) with disordered spin orientation on the surface.
Details
- Language :
- English
- ISSN :
- 1520-5827
- Volume :
- 34
- Issue :
- 2
- Database :
- MEDLINE
- Journal :
- Langmuir : the ACS journal of surfaces and colloids
- Publication Type :
- Academic Journal
- Accession number :
- 29262258
- Full Text :
- https://doi.org/10.1021/acs.langmuir.7b03702