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arXiv 1708.04409cond-mat.softcond-mat.mtrl-scicond-mat.stat-mechphysics.chem-ph
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混合水溶液中由拮抗盐组成的双电层:局部电荷分离和表面相变

Electric double layer composed of an antagonistic salt in an aqueous mixture: Local charge separation and surface phase transition

Shunsuke Yabunaka, Akira Onuki

摘要:

我们研究了双电层含有拮抗盐在水溶液中的混合物,其中阳离子是小的和亲水的,但阴离子是大的和疏水的。在这种情况下,在电荷密度和溶剂组成之间产生强耦合。结果,阴离子被捕获在疏水壁上的富油吸附层中。然后我们改变壁面上的表面电荷密度$σ$。对于$σ>0$,阴离子保持累积,但对于$σ<0$,阳离子随着$|σ|$的增加而被吸引到壁。此外,当溶剂相互作用参数$χ(T)$超过由本体中的组成和离子密度确定的临界值$χ_c$时,电势降$Ψ(σ)$是非单调的。这导致具有不同$σ$和相同$Ψ$的两种双电层之间的一级相变。在平衡中,这样的两层区域可以共存。由于有限的离子尺寸的空间效应是至关重要的,在这些现象。

英文摘要:

We examine an electric double layer containing an antagonistic salt in an aqueous mixture, where the cations are small and hydrophilic but the anions are large and hydrophobic. In this situation, a strong coupling arises between the charge density and the solvent composition. As a result, the anions are trapped in an oil-rich adsorption layer on a hydrophobic wall. % while the cations are expelled from it. We then vary the surface charge density $σ$ on the wall. For $σ>0$ the anions remain accumulated, but for $σ<0$ the cations are attracted to the wall with increasing $|σ|$. Furthermore, the electric potential drop $Ψ(σ)$ is nonmonotonic when the solvent interaction parameter $χ(T)$ exceeds a critical value $χ_c$ determined by the composition and the ion density in the bulk. This leads to a first order phase transition between two kinds of electric double layers with different $σ$ and common $Ψ$. In equilibrium such two layer regions can coexist. The steric effect due to finite ion sizes is crucial in these phenomena.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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