Steric repulsion as a way to achieve the required stability for the preparation of ionic liquid-based ferrofluids

Laura Rodríguez-Arco; Modesto T López-López; Fernando González-Caballero; Juan D G Durán

doi:10.1016/j.jcis.2011.01.083

Steric repulsion as a way to achieve the required stability for the preparation of ionic liquid-based ferrofluids

J Colloid Interface Sci. 2011 May 1;357(1):252-4. doi: 10.1016/j.jcis.2011.01.083. Epub 2011 Jan 31.

Authors

Laura Rodríguez-Arco¹, Modesto T López-López, Fernando González-Caballero, Juan D G Durán

Affiliation

¹ Department of Applied Physics, University of Granada, Avda. Fuentenueva s/n, 18071 Granada, Spain.

PMID: 21345446
DOI: 10.1016/j.jcis.2011.01.083

Abstract

With this work we would like to emphasize the necessity of steric repulsion to stabilize novel ionic liquid-based ferrofluids. For this purpose, we prepared a suspension of magnetite nanoparticles coated with a double layer of oleic acid, dispersed in 1-ethyl-3-methylimidazolium ethylsulphate ([EMIM][EtSO(4)]). For comparison, a suspension of bare magnetite nanoparticles in [EMIM][EtSO(4)] was also prepared. The stability of these suspensions was checked by magnetic sedimentation and centrifugation processes. Furthermore, their yield stress was measured as a function of the applied magnetic field, which gave additional information on their stability. The results of these experiments showed that the suspension of bare nanoparticles was rather unstable, whereas the suspension of double layer coated nanoparticles gave rise to a true (stable) ferrofluid.