Single-particle thermal diffusion of charged colloids: Double-layer theory in a temperature gradient

J.K.G. Dhont, Willem J. Briels

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The double-layer contribution to the single-particle thermal diffusion coefficient of charged, spherical colloids with arbitrary double-layer thickness is calculated and compared to experiments. The calculation is based on an extension of the Debye-Hückel theory for the double-layer structure that includes a small temperature gradient. There are three forces that constitute the total thermophoretic force on a charged colloidal sphere due to the presence of its double layer: i) the force F W that results from the temperature dependence of the internal electrostatic energy W of the double layer, ii) the electric force F el with which the temperature-induced non-spherically symmetric double-layer potential acts on the surface charges of the colloidal sphere and iii) the solvent-friction force F sol on the surface of the colloidal sphere due to the solvent flow that is induced in the double layer because of its asymmetry. The force F W will be shown to reproduce predictions based on irreversible-thermodynamics considerations. The other two forces F el and F sol depend on the details of the temperature-gradient-induced asymmetry of the double-layer structure which cannot be included in an irreversible-thermodynamics treatment. Explicit expressions for the thermal diffusion coefficient are derived for arbitrary double-layer thickness, which complement the irreversible-thermodynamics result through the inclusion of the thermophoretic velocity resulting from the electric- and solvent-friction force.
Original languageUndefined
Pages (from-to)61-76
Number of pages16
JournalEuropean physical journal E. Soft Matter
Issue number1
Publication statusPublished - 2008


  • METIS-247769
  • IR-60840

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