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Issue 12, 2016
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Nanometer-ranged attraction induced by multivalent ions between similar and dissimilar surfaces probed using an atomic force microscope (AFM)

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Abstract

Direct force measurements between positively charged amidine latex (AL) and negatively charged sulfate latex (SL) particles are carried out using an atomic force microscope (AFM). Forces between three different pairs, namely AL–AL, AL–SL, and SL–SL, are measured in solutions containing multivalent cationic aliphatic hexamines (N6) and in simple monovalent KCl solutions. The classical theory of Derjaguin, Landau, Verwey, and Overbeek (DLVO) can rationalize the observed force profiles very well, provided the PB equation is solved for the appropriate asymmetric electrolyte and charge regulation effects are included in the analysis. However, the DLVO description is typically valid only at distances beyond several nanometers. At shorter distances, a short-ranged non-DLVO attraction is present, which can be modeled with an exponential force profile. In KCl solutions, the range of this attraction is around 0.3 nm. In N6 solutions, the range of this attraction is about 1.0 nm in the SL–SL system, 0.6 nm in the AL–SL system, and 0.3 nm in the AL–AL system.

Graphical abstract: Nanometer-ranged attraction induced by multivalent ions between similar and dissimilar surfaces probed using an atomic force microscope (AFM)

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Publication details

The article was received on 18 Dec 2015, accepted on 23 Feb 2016 and first published on 24 Feb 2016


Article type: Paper
DOI: 10.1039/C5CP07830J
Citation: Phys. Chem. Chem. Phys., 2016,18, 8739-8751
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    Nanometer-ranged attraction induced by multivalent ions between similar and dissimilar surfaces probed using an atomic force microscope (AFM)

    M. Moazzami-Gudarzi, G. Trefalt, I. Szilagyi, P. Maroni and M. Borkovec, Phys. Chem. Chem. Phys., 2016, 18, 8739
    DOI: 10.1039/C5CP07830J

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