Binary mixtures of larger and smaller colloids having charges of equal sign display unusual response to low frequency electric fields E. We previously reported the anomalous orientation - perpendicular to the electric field - of highly diluted rod-like particles when immersed in a sea of smaller spherical particles charged with same sign [1]. A correlated but more general phenomenon is observed in mixtures of large (dilute) and small (semi-dilute) spherical particles, whose total scattering cross section for light decreases as a low frequency electric field is applied to the dispersion [2]. Such field-induced clearing is general for mixtures and appears to be due to the build up of an anisotropic E2-dependent distribution of small spheres around the large ones. Having ruled out other mechanisms, we interpret this behavior as resulting from O(E2) electro-osmotic flows whose magnitude is greatly enhanced by the presence of the small particles. Various evidences suggest that this structuring, unaccountable on the only basis of dipole-dipole electric interaction, is at the origin of the anomalous torque in mixtures of rods and spheres. Overall, this work strengthens the notion that non-linear electrokinetic response is an essential part in the description of the electro-optic behavior of complex colloidal dispersions. 1 - F. Mantegazza, M. Caggioni, M.L. Jimenez and T. Bellini, Anomalous field-induced particle orientation in dilute mixtures of charged rod-like and spherical colloids, Nature Physics, 1, 103 (2005) 2 - L. Fornasari, F. Mantegazza, M. L. Jimenez, M. Buscaglia, and T. Bellini, Field-induced clearing in sphere-sphere and rod-sphere binary mixtures of charged colloidal particles, Physical Review E 79, 060401R (2009)
Field-induced clearing in sphere-sphere and rod-sphere binary mixtures of charged colloidal particles / L. Fornasari, M.L. Jimenez, M. Buscaglia, F. Mantegazza, T. Bellini. ((Intervento presentato al convegno Elopto 2010 tenutosi a Mainz nel 2010.
Field-induced clearing in sphere-sphere and rod-sphere binary mixtures of charged colloidal particles
L. FornasariPrimo
;M. Buscaglia;T. BelliniUltimo
2010
Abstract
Binary mixtures of larger and smaller colloids having charges of equal sign display unusual response to low frequency electric fields E. We previously reported the anomalous orientation - perpendicular to the electric field - of highly diluted rod-like particles when immersed in a sea of smaller spherical particles charged with same sign [1]. A correlated but more general phenomenon is observed in mixtures of large (dilute) and small (semi-dilute) spherical particles, whose total scattering cross section for light decreases as a low frequency electric field is applied to the dispersion [2]. Such field-induced clearing is general for mixtures and appears to be due to the build up of an anisotropic E2-dependent distribution of small spheres around the large ones. Having ruled out other mechanisms, we interpret this behavior as resulting from O(E2) electro-osmotic flows whose magnitude is greatly enhanced by the presence of the small particles. Various evidences suggest that this structuring, unaccountable on the only basis of dipole-dipole electric interaction, is at the origin of the anomalous torque in mixtures of rods and spheres. Overall, this work strengthens the notion that non-linear electrokinetic response is an essential part in the description of the electro-optic behavior of complex colloidal dispersions. 1 - F. Mantegazza, M. Caggioni, M.L. Jimenez and T. Bellini, Anomalous field-induced particle orientation in dilute mixtures of charged rod-like and spherical colloids, Nature Physics, 1, 103 (2005) 2 - L. Fornasari, F. Mantegazza, M. L. Jimenez, M. Buscaglia, and T. Bellini, Field-induced clearing in sphere-sphere and rod-sphere binary mixtures of charged colloidal particles, Physical Review E 79, 060401R (2009)Pubblicazioni consigliate
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