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Accueil du site > Productions scientifiques > Séminaires à PHENIX > 2019 > Séminaire de Simone Wiegand (Forschungszentrum Jülich/Univ. Cologne) - 03/07/2019 à 15h

Séminaire de Simone Wiegand (Forschungszentrum Jülich/Univ. Cologne) - 03/07/2019 à 15h

par Pierre Illien - 21 juin

Séminaire de Simone Wiegand

(ICS-3 Soft Condensed Matter, Forschungszentrum Jülich GmbH, D-52428 Jülich, Germany & Chemistry Department – Physical Chemistry, University Cologne, D-50939 Cologne, Germany)

Movement of charged colloidal spheres and rods 
in thermal gradients

le mercredi 3 juillet 2019 à 15h, bibliothèque de PHENIX (32-42.219).

Résumé

Movement of charged colloidal spheres and rods 
in thermal gradients

Mass transport caused by a temperature gradient, influences many processes such as magmatic differentiation, biological transport and it has been used in characterization of polymers, colloids and protein interactions. In the last years especially its application potential in the analysis of protein-ligand binding and the understanding of the movement of biological active matter in temperature gradients gained a lot of interest. Due to a lack of a microscopic understanding we use colloidal model systems to perform systematic experiments and to compare with theoretical concepts. Conceptually two theoretical approaches are used to describe the motion of charged colloidal particles in a temperature gradient : One contribution is stemming from the double layer around the particle [1] and another contribution is caused by an electric field created by added salt ions, which form an ion concentration gradient in the temperature field [2]. We used the double-layer concept to describe the Soret coefficient of Ludox particles as a function of the Debye length [2] and found good agreement between experiment and theory using only one adjustable parameter (intercept at zero Debye length). Later the concept was extended to charged colloidal rods without and with a grafted polymer layer [3]. In the experiments we use rod-like fd-virus particles as a model system for charged rods. Here we used the surface charge density as an additional adjustable parameter. Applying the theoretical model to the experimental data we found a surface charge density, which compares well to the one determined by electrophoresis measurements taking into account the ion condensation. Finally, we discuss literature result using various salts [6] under which conditions the Seebeck contributions can be separated from chemical contributions in thermophoresis experiments.

REFERENCES

[1] J.K.G. Dhont and W.J. Briels, Eur. Phys. J. E 25 (2008)61.

[2] A. Würger, Rep. Prog. Phys. 73 (2010)126601.

[3] H. Ning et al., Langmuir, 24 (2008) 2426.

[4] Z. Wang et al., Soft Matter, 9 (2013) 8697.

[5] Z. Wang et al., Langmuir 35 (2019) 1000.

[6] D. Vigolo et al., Langmuir, 26 (2010) 7792 ; M. Reichl et al., Phys. Rev. Lett., 112 (2014) 198101 ; K. A. Eslahian et al., Soft Matter, 10 (2014) 1931 ; A. L. Sehnem et al., Phys. Rev. E, 98 (2018) 989.