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Colloids Interfaces 2018, 2(4), 65; https://doi.org/10.3390/colloids2040065

Measuring Inner Layer Capacitance with the Colloidal Probe Technique

Department of Inorganic and Analytical Chemistry, University of Geneva, Sciences II, 30 Quai Ernest-Ansermet, 1205 Geneva, Switzerland
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Received: 26 October 2018 / Revised: 21 November 2018 / Accepted: 22 November 2018 / Published: 27 November 2018
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Abstract

The colloidal probe technique was used to measure the inner layer capacitance of an electrical double layer. In particular, the forces were measured between silica surfaces and sulfate latex surfaces in solutions of monovalent salts of different alkali metals. The force profiles were interpreted with Poisson-Boltzmann theory with charge regulation, whereby the diffuse layer potential and the regulation properties of the interface were obtained. While the diffuse layer potential was measured in this fashion in the past, we are able to extract the regulation properties of the inner layer, in particular, its capacitance. We find systematic trends with the type of alkali metal ion and the salt concentration. The observed trends could be caused by difference in ion hydration, variation of the binding capacitance, and changes of the effective dielectric constant within the Stern layer. Our results are in agreement with recent experiments involving the water-silica interface based on a completely independent method using X-ray photoelectron spectroscopy in a liquid microjet. This agreement confirms the validity of our approach, which further provides a means to probe other types of interfaces than silica. View Full-Text
Keywords: surface forces; DLVO; charge regulation; inner layer capacitance surface forces; DLVO; charge regulation; inner layer capacitance
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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MDPI and ACS Style

Smith, A.M.; Maroni, P.; Borkovec, M.; Trefalt, G. Measuring Inner Layer Capacitance with the Colloidal Probe Technique. Colloids Interfaces 2018, 2, 65.

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