Thermodiffusion of repulsive charged nanoparticles – the interplay between single-particle and thermoelectric contributions

Abstract : Thermodiffusion of different ferrite nanoparticles (NPs), ∼10 nm in diameter, is explored in tailor-made aqueous dispersions stabilized by electrostatic interparticle interactions. In the dispersions, electrosteric repulsion is the dominant force, which is tuned by an osmotic-stress technique, i.e. controlling of osmotic pressure Π, pH and ionic strength. It is then possible to map Π and the NPs’ osmotic compressibility χ in the dispersion with a Carnahan–Starling formalism of effective hard spheres (larger than the NPs’ core). The NPs are here dispersed with two different surface ionic species, either at pH ∼ 2 or 7, leading to a surface charge, either positive or negative. Their Ludwig–Soret $S_{T}$ coefficient together with their mass diffusion $D_{m}$ coefficient are determined experimentally by forced Rayleigh scattering. All probed NPs display a thermophilic behavior ($S_{T}$ < 0) regardless of the ionic species used to cover the surface. We determine the NPs’ Eastman entropy of transfer and the Seebeck (thermoelectric) contribution to the measured Ludwig–Soret coefficient in these ionic dispersions. The NPs’ Eastman entropy of transfer $Ŝ_{NP}$ is interpreted through the electrostatic and hydration contributions of the ionic shell surrounding the NPs.
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Article dans une revue
Physical Chemistry Chemical Physics, Royal Society of Chemistry, 2018, 20 (24), pp.16402 - 16413. 〈10.1039/c8cp02558d〉
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Soumis le : lundi 10 septembre 2018 - 16:39:36
Dernière modification le : mercredi 12 septembre 2018 - 01:12:59

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R. Cabreira Gomes, A. Ferreira da Silva, M. Kouyaté, G. Demouchy, G. Mériguet, et al.. Thermodiffusion of repulsive charged nanoparticles – the interplay between single-particle and thermoelectric contributions. Physical Chemistry Chemical Physics, Royal Society of Chemistry, 2018, 20 (24), pp.16402 - 16413. 〈10.1039/c8cp02558d〉. 〈hal-01871370〉

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