Hypothesis

The stability of colloidal dispersions in the presence of multivalent ions depends strongly on the electrostatic interactions between the suspended particles. Of particular interest are colloidal particles having dimensions in the nanometric range and with an anisotropic shape due to its high surface area per unit mass, for example clay, which has the key characteristic of a negatively charged surface, surrounded by an oppositely charged rim.

Experiments

In this study, we investigate the interactions in nanoplatelet dispersions for the model system of Laponite® clay with addition of mono- and multivalent salt. Molecular dynamics simulations with enhanced umbrella sampling have been utilised in combination with the experimental techniques of zeta-potential measurements, dynamic light scattering, and transmission electron microscopy.

Findings

It was observed that tactoid formation and tactoidal dissolution due to overcharging occur upon the addition of trivalent salt. The overcharging effect was captured from calculated potential of mean force and confirmed from the zeta-potential, which changed sign from negative to positive when increasing the stoichiometric charge-ratio between the positive salt ions and the clay. Consequently, the gained information could provide useful physical insight of nanoplatelet interactions in the presence of multivalent ions.

中文翻译：

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多价离子存在下的纳米血小板相互作用：过度充电和稳定性的影响。

假设

在多价离子存在下，胶态分散体的稳定性在很大程度上取决于悬浮颗粒之间的静电相互作用。特别令人关注的是胶体颗粒，其尺寸在纳米范围内并且由于其每单位质量的高表面积而具有各向异性的形状，例如粘土，其具有带负电荷的表面的关键特性，并被带相反电荷的边缘包围。

实验

在这项研究中，我们研究了添加单价盐和多价盐的Laponite®粘土模型系统在纳米血小板分散液中的相互作用。具有增强伞状采样的分子动力学模拟已与Zeta电位测量，动态光散射和透射电子显微镜等实验技术结合使用。

发现

观察到，在添加三价盐时，由于过度充电而产生触觉样物和触觉样物溶解。从计算出的平均力电势中捕获了过充电效应，并从zeta势中得到了证实，当增加正盐离子与粘土之间的化学计量电荷比时，其符号将从负变为正。因此，所获得的信息可以为多价离子存在下纳米血小板相互作用提供有用的物理见解。