Heat capacity-driven inverse Soret effect of colloidal nanoparticlesAlois Würger
CPMOH, CNRS-Université Bordeaux 1 351 cours de la Libération, 33405 Talence, France
received 23 November 2005; accepted in final form 26 March 2006
published online 12 April 2006
We discuss the thermophoresis of colloidal suspensions and derive their Soret coefficient in terms of known thermodynamic functions. For solid nanoparticles, ST is determined by the ratio of the heat capacities of the solute and the solvent, and is in general much larger than the ideal gas value ST=1/T. For aqueous suspensions of most solid materials, we obtain a strong inverse Soret effect (ST<0), whereas a positive sign occurs for common organic solvents such as toluene and cyclohexane. These findings provide an explanation for recent experiments on ferrofluids.
66.10.Cb - Diffusion and thermal diffusion.
82.70.Dd - Colloids.
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