Eur. Phys. J. E (2017) 40: 14
https://doi.org/10.1140/epje/i2017-11503-y

Regular Article

Non-equilibrium concentration fluctuations in superparamagnetic nanocolloids

¹ College of Charleston, Department of Physics and Astronomy, Charleston, SC, USA
² Erlangen Graduate School in Advanced Optical Technologies (SAOT), University of Erlangen-Nuremberg, Erlangen, Germany
³ Laboratoire des Fluides Complexes et leurs Réservoirs - UMR5150, Université de Pau et des Pays de l’Adour, Anglet, France
⁴ Centre Nationale d’Etudes Spatiales (CNES), Paris, France

^* e-mail: oprisana@cofc.edu

Received: 20 August 2016
Accepted: 11 January 2017
Published online: 10 February 2017

Abstract

We investigate non-equilibrium concentration fluctuations during the free diffusion of a colloidal suspension against pure water. We investigate Fe₂O₃ superparamagnetic nanocolloids with sizes between 1 and 10 nm by means of a shadowgraph apparatus to determine the mixture mass diffusion coefficient and kinematic viscosity. The experiments were performed in three distinct conditions: Experiment 1 is without any magnetic field; Experiment 2 with a vertical magnetic field; Experiment 3 after turning off the magnetic field. We found no correlation between the kinematic viscosity coefficient and the external magnetic field. Conversely, we found that the mass diffusion coefficient decreases in the presence of the external magnetic field and slowly rebounds after the magnetic field was turned off.