Evanescent-wave dynamic light scattering at an oil-water interface: Diffusion of interface-adsorbed colloids

Antonio Stocco, Tahereh Mokhtari, Günter Haseloff, Andreas Erbe, and Reinhard Sigel
Phys. Rev. E 83, 011601 – Published 13 January 2011

Abstract

A light-scattering goniometer for evanescent-wave dynamic light scattering (EWDLS) measurements at a liquid-fluid interface is introduced, and used for measurements on two charge-stabilized polystyrene colloid systems adsorbed to alkane-water interfaces. The goniometer allows an independent variation of the penetration depth and the scattering vector components parallel and perpendicular to a liquid-fluid interface. The possible illumination geometries are compared. Ellipsometry at the liquid-fluid interface is implemented as a complementary tool. In EWDLS measurements, the absence of diffusive motion perpendicular to the interface is demonstrated, which confirms the adsorption of the particles. The two-step decay of the autocorrelation function is interpreted in terms of diffusion within a two-dimensional interface lattice of colloidal particles, stabilized by repulsive electrostatic interactions, and a desorption process. A significant slowing down of the in-plane diffusion of the colloids as compared to the bulk diffusion is observed.

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  • Received 29 July 2009

DOI:https://doi.org/10.1103/PhysRevE.83.011601

© 2011 American Physical Society

Authors & Affiliations

Antonio Stocco1, Tahereh Mokhtari2, Günter Haseloff1, Andreas Erbe1,*, and Reinhard Sigel2,†

  • 1Max Planck Institute of Colloids and Interfaces, D-14476 Golm, Germany
  • 2Adolphe Merkle Institute, CH-1700 Fribourg, Switzerland

  • *Present address: Max-Planck-Institut für Eisenforschung, D-40237 Düsseldorf, Germany.
  • Author to whom correspondence should be addressed. reinhard.sigel@unifr.ch

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Vol. 83, Iss. 1 — January 2011

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