Forces between Carboxylic Acid Surfaces in Divalent Electrolyte Solutions

✍ Scribed by Thomas Ederth; Per M. Claesson

• Publisher: Elsevier Science
• Year: 2000
• Tongue: English
• Weight: 84 KB
• Volume: 229
• Category: Article
• ISSN: 0021-9797
• DOI: 10.1006/jcis.2000.6961

✦ Synopsis

The behavior of self-assembled monolayers of thiohexadecanoic acid adsorbed onto gold interacting in asymmetric 2:1 electrolytes has been studied with direct force measurements. The effects of two divalent cations (Mg(2+) and Ca(2+)) were studied at concentrations ranging from 1 µM to 10 mM. As compared to interactions in the presence of Na(+), the divalent ions adsorb strongly to the surfaces, with the effect of lowering the surface potential and decreasing the double-layer repulsion. At concentrations above 10 µM, the Ca(2+) ions were found to adsorb stronger than Mg(2+). Ca(2+) ions cause charge reversal at high concentrations, and the net interactions at 10 mM were attractive over the measurable range. Copyright 2000 Academic Press.