Direct Observation of Critical Adsorption on Colloidal Particles

Published

August 25, 2015

Author(s)

Christopher E Bertrand, P. D. Godfrin, Yun Liu

Abstract

Despite the fundamental role adsorbed solvent layers play in generating critical Casimir forces between colloidal particles, the structure of these layers has yet to be directly determined. Using small-angle neutron scattering ,we have measured critical adsorption on the surface of small spherical silica particles suspended in a binary mixture of lutidine and water. The surface concentration profile and excess adsorption Γ were studied as functions of temperature at the critical concentration and three off-critical concentrations. We are able to differentiate three distinct contributions to the excess adsorption including the intrinsic shape of the concentration profile. The adsorption associated with the profile shape is found to increase monotonically with increasing 2,6-lutidine concentration and to decrease with increasing temperature, this later observation is consistent with expectations for curvature induced corrections to planar adsorption and leads to Γ t^0.52. this scaling relation corresponds to a stronger divergence than found in the planar case, but a substantially weaker divergence than found previously.

Citation

Journal of Chemical Physics

Volume

143

Issue

8

Pub Type

Journals

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Keywords

critical adsorption, critical Casimir force, small angle neutron scattering

Citation

Bertrand, C. , Godfrin, P. and Liu, Y. (2015), Direct Observation of Critical Adsorption on Colloidal Particles, Journal of Chemical Physics, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=918811 (Accessed December 9, 2024)