Ion Specificity of Confined Ion–Water Structuring and Nanoscale Surface Forces in Clays
Ion Specificity of Confined Ion–Water Structuring and Nanoscale Surface Forces in Clays
复制标题
约束离子的离子特异性——粘土中的水结构和纳米级表面力
DOI：
10.1021/acs.jpcb.2c01738
复制
发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Del Gado, Emanuela
中科院分区：
文献类型：
--
作者：
Dragulet, Francis;Goyal, Abhay;Ioannidou, Katerina;Pellenq, Roland J.-M.;Del Gado, Emanuela
离子特异性和相关的霍夫迈斯特效应，这是普遍存在于含水系统中，可以有壮观的后果，在水合粘土，离子特异性纳米表面力可以确定大规模的粘性膨胀和土壤和沉积物的收缩行为。我们已经使用了semiatomistic的计算方法和检查钠，钙，铝抗衡离子与水之间的粘土材料的带电表面的代表显示，离子-水结构在纳米级的限制是在粘土颗粒之间的表面力的起源本质上是离子特定的。当带电表面强烈约束离子和水时，净压力的振幅和振荡自然地从静电和空间效应的相互作用中出现，这不能被现有的理论所捕获。增加限制和表面电荷密度促进离子-水结构，其越来越偏离离子的本体水合壳，是强烈的各向异性、持久性和自组织成优化的、几乎固体状的组件，其中几乎没有任何游离水留下。在这些条件下，由于水的介电屏蔽和高度组织化的水离子结构的显著降低，带电表面之间可以存在强烈的吸引相互作用。通过解开这些纳米级相互作用的离子特异性的性质，我们提供的证据表明，离子特定的溶剂化结构确定的限制是在粘土中的离子特异性的起源，并可能在更广泛的范围内的封闭的含水系统。
Ion specificity and related Hofmeister effects, which are ubiquitous in aqueous systems, can have spectacular consequences in hydrated clays, where ion-specific nanoscale surface forces can determine large-scale cohesive swelling and shrinkage behaviors of soil and sediments. We have used a semiatomistic computational approach and examined sodium, calcium, and aluminum counterions confined with water between charged surfaces representative of clay materials to show that ion–water structuring in nanoscale confinement is at the origin of surface forces between clay particles which are intrinsically ion-specific. When charged surfaces strongly confine ions and water, the amplitude and oscillations of the net pressure naturally emerge from the interplay of electrostatics and steric effects, which cannot be captured by existing theories. Increasing confinement and surface charge densities promote ion–water structures that increasingly deviate from the ions’ bulk hydration shells, being strongly anisotropic, persistent, and self-organizing into optimized, nearly solid-like assemblies where hardly any free water is left. Under these conditions, strongly attractive interactions can prevail between charged surfaces because of the dramatically reduced dielectric screening of water and the highly organized water–ion structures. By unravelling the ion-specific nature of these nanoscale interactions, we provide evidence that ion-specific solvation structures determined by confinement are at the origin of ion specificity in clays and potentially a broader range of confined aqueous systems.