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Attractive non-DLVO forces induced by adsorption of monovalent organic ions

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Abstract

Direct force measurements between negatively charged colloidal particles were carried out using an atomic force microscope (AFM) in aqueous solutions containing monovalent organic cations, namely tetraphenylarsonium (Ph4As+), 1-hexyl-3-methylimidazolium (HMIM+), and 1-octyl-3-methylimidazolium (OMIM+). These ions adsorb to the particle surface, and induce a charge reversal. The forces become attractive at the charge neutralization point, but they are stronger than van der Waals forces. This additional and unexpected attraction decays exponentially with a decay length of a few nanometers, and is strikingly similar to the one previously observed in the presence of multivalent ions. This attractive force probably originates from coupled spontaneous charge fluctuations on the respective surfaces as initially suggested by Kirkwood and Shumaker.

Graphical abstract: Attractive non-DLVO forces induced by adsorption of monovalent organic ions

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Publication details

The article was received on 18 Sep 2017, accepted on 30 Nov 2017 and first published on 30 Nov 2017


Article type: Paper
DOI: 10.1039/C7CP06383K
Citation: Phys. Chem. Chem. Phys., 2018, Advance Article
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    Attractive non-DLVO forces induced by adsorption of monovalent organic ions

    A. M. Smith, P. Maroni and M. Borkovec, Phys. Chem. Chem. Phys., 2018, Advance Article , DOI: 10.1039/C7CP06383K

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