UNIGE document Scientific Article
previous document  unige:114717  next document
add to browser collection
Title

Unexpectedly Large Decay Lengths of Double-Layer Forces in Solutions of Symmetric, Multivalent Electrolytes

Authors
Published in Journal of Physical Chemistry. B, Condensed Matter, Materials, Surfaces, Interfaces and Biophysical. 2019, vol. 123, no. 7, p. 1733-1740
Abstract Double layer forces acting between micron-sized silica particles are measured with the atomic force microscope (AFM) in solutions of symmetric, multivalent electrolytes. In particular, the following 2:2 electrolytes, CuSO4, MgSO4, and the 3:3 electrolyte LaFe(CN)6 were investigated. For the multivalent electrolytes, the measured decay lengths are substantially larger than the ones expected on the basis of simple Debye-Hückel (DH) theory. These deviations can be explained quantitatively by the formation of neutral ion pairs. The measured surface charge density decreases in magnitude with increasing valence. Both effects are caused by ion-ion correlations, which are not included in the classical DH theory. However, this theory remains applicable provided one considers the formation of ion pairs in solution and an effective surface charge density. This effective charge is substantially smaller in magnitude than the one of the bare surface. This reduction results from adsorption of counter-ions, which becomes stronger with increasing valence. These observations reveal that DH theory is applicable even in the presence of multivalent ions, provided the effective parameters are chosen appropriately.
Identifiers
Full text
Article (Author postprint) (648 Kb) - document accessible for UNIGE members only Limited access to UNIGE (until 2020-02-28)
Other version: http://pubs.acs.org/doi/10.1021/acs.jpcb.8b12246
Dataset: https://zenodo.org/record/2579641#.XHf4SYlKhhE
Structures
Citation
(ISO format)
SMITH, Alexander et al. Unexpectedly Large Decay Lengths of Double-Layer Forces in Solutions of Symmetric, Multivalent Electrolytes. In: Journal of Physical Chemistry. B, Condensed Matter, Materials, Surfaces, Interfaces and Biophysical, 2019, vol. 123, n° 7, p. 1733-1740. https://archive-ouverte.unige.ch/unige:114717

116 hits

0 download

Update

Deposited on : 2019-03-04

Export document
Format :
Citation style :