Eur. Phys. J. E 27, 425-434 (2008)
DOI: 10.1140/epje/i2008-10410-8

Thermoelectric effect on charged colloids in the Hückel limit

J. Morthomas and A. Würger

CPMOH, Université Bordeaux 1 & CNRS, 351 cours de la Libération, 33405, Talence, France

a.wuerger@cpmoh.u-bordeaux1.fr

Received 1 August 2008 / Published online 23 December 2008

Abstract

We study the thermophoretic coefficient D_T of a charged colloid. The non-uniform electrolyte is characterized in terms of densities and diffusion currents of mobile ions. The hydrodynamic treatment in the vicinity of a solute particle relies on the Hückel approximation, which is valid for particles smaller than the Debye length, a ≪ . To leading order in the parameter a/ , we find that the coefficient D_T consists of two contributions, a dielectrophoretic term proportional to the permittivity derivative d /dT , and a Seebeck term, i.e., the macroscopic electric field induced by the thermal gradient in the electrolyte solution. Depending on the particle valency, these terms may take opposite signs, and their temperature dependence may result in a change of sign of thermophoresis, as observed in several recent experiments.

PACS
66.10.C- - Diffusion and thermal diffusion.
82.70.-y - Disperse systems; complex fluids.
47.57.J- - Colloidal systems.

© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2008

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