title: Stable ferrofluids of magnetite nanoparticles in hydrophobic ionic liquids.
abstract: Ferrofluids (FFs) of metal oxide nanoparticles in ionic liquids (ILs) are a potentially useful class of magnetic materials for many applications because of their properties related to temperature/pressure stability, hydrophobicity, viscosity and recyclability. In this work, the screening of several designer surfactants for their stabilizing capabilities has resulted in the synthesis of stable FFs of superparamagnetic 7 ± 2 nm magnetite (Fe3O4) nanoparticles in the hydrophobic IL 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C(R)MIM][NTf2]). The designed and synthesized 1-butyl-3-(10-carboxydecyl)-1H-imidazol-3-ium bromide (ILC10-COOH) surfactant that combines the same imidazole moiety as the IL with a long alkyl chain ensured compatibility with the IL and increased the steric repulsion between the magnetite nanoparticles sufficiently such that stable dispersions of up to 50 wt% magnetite were obtained according to stability tests in the presence of a magnetic field (0.5-1 Tesla). Cryo-transmission electron microscopy (cryo-TEM) of the IL-based FFs allowed direct visualization of the surfactant-stabilized nanoparticles in the ILs and the native, hardly aggregated state of their dispersion.
authors.affiliation: Laboratory of Materials and Interface Chemistry and Soft Matter CryoTEM Research Unit, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven, The Netherlands. Ioniqa Technologies B.V., De Lismortel 31, 5612 AR Eindhoven, The Netherlands.
authors.forename: Luuk
authors.initials: L
authors.lastname: Mestrom
authors.forename: Jos J M
authors.initials: JJ
authors.lastname: Lenders
authors.forename: Rick
authors.initials: R
authors.lastname: de Groot
authors.forename: Tonnis
authors.initials: T
authors.lastname: Hooghoudt
authors.forename: Nico A J M
authors.initials: NA
authors.lastname: Sommerdijk
authors.forename: Marcel Vilaplana
authors.initials: MV
authors.lastname: Artigas