Finite-Thickness-Enhanced Attractions for Oppositely Charged Membranes and Colloidal Platelets

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• 作者：Aldemar Torres ; Ren&eacute ; van Roij
• 刊名：Langmuir
• 出版年：2008
• 出版时间：February 19, 2008
• 年：2008
• 卷：24
• 期：4
• 页码：1110 - 1119
• 全文大小：263K
• 年卷期：v.24,no.4(February 19, 2008)
• ISSN：1520-5827

文摘

Within linearized Poisson-Boltzmann theory, we study the disjoining pressure of two oppositely charged parallelobjects (membranes and colloidal platelets) in a 1:1 electrolyte, with a focus on the effects of their finite thickness.This extension of the standard Gouy-Chapman model from an interacting pair of double layers to a quartet (one oneach side of the two interacting objects) is shown to enhance the regime of attractive interactions significantly, inparticular, when the separation and the thickness are on the order of the Debye length of the solvent, provided thedielectric mismatch between objects and solvent is not too extreme. The enhancement of attractions occurs for objectswith fixed charge as well as for those that exhibit charge regulation but not for those with a constant surface potential.The underlying mechanism for this enhancement for thin objects is the transfer of net ionic charge from the electrolytein between to the other sides. For biological membranes in water, this effect is small; however, it is due to strongimage charge effects.