Multivalent Surface Cations Enhance Heterogeneous Freezing of Water on Muscovite Mica
Multivalent Surface Cations Enhance Heterogeneous Freezing of Water on Muscovite Mica
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多价表面阳离子增强白云母上水的异质冻结
DOI：
10.1021/acs.jpclett.0c02121
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发表时间：
2020
期刊：
影响因子：
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通讯作者：
Cantrell, Will
中科院分区：
文献类型：
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作者：
Lata, Nurun Nahar;Zhou, Jiarun;Hamilton, Pearce;Larsen, Michael;Sarupria, Sapna;Cantrell, Will
非均相冰成核是基础科学和应用科学各个领域的重要现象。研究了表面阳离子对水在白云母上结冰的影响。云母的独特之处在于其表面暴露的离子可以很容易地交换，而不会影响表面粗糙度等其他特性。我们研究了天然（K+）云母和云母的冷冻，其中我们将K+交换为Al3+， Mg2+， Ca2+和Sr2+。我们发现，当液态水表面存在高价离子时，液态水会在更高的温度下结冰，从而暴露出更多的二氧化硅层。我们的数据还表明，离子的大小影响特征冻结温度。利用分子动力学模拟，我们研究了离子价和暴露的二氧化硅层对表面水行为的影响。结果表明，多价阳离子增加了形成大簇氢键水分子的可能性，这些水分子由阳离子的水合壳锚定。这些团簇也有很大一部分自由水，可以重新定向成冰状结构，这是由云母上缺乏离子的区域促进的。因此，这些团簇可以作为冰核的种子床。实验与模拟相结合的研究为研究表面离子对非均相冰成核的影响提供了新的思路。
Heterogeneous ice nucleation is a crucial phenomenon in various fields of fundamental and applied science. We investigate the effect of surface cations on freezing of water on muscovite mica. Mica is unique in that the exposed ion on its surface can be readily and easily exchanged without affecting other properties such as surface roughness. We investigate freezing on natural (K+) mica and mica in which we have exchanged K+for Al3+, Mg2+, Ca2+, and Sr2+. We find that liquid water freezes at higher temperatures when ions of higher valency are present on the surface, thus exposing more of the underlying silica layer. Our data also show that the size of the ion affects the characteristic freezing temperature. Using molecular dynamics simulations, we investigate the effects that the ion valency and exposed silica layer have on the behavior of water on the surface. The results indicate that multivalent cations enhance the probability of forming large clusters of hydrogen bonded water molecules that are anchored by the hydration shells of the cations. These clusters also have a large fraction of free water that can reorient to take ice-like configurations, which are promoted by the regions on mica devoid of the ions. Thus, these clusters could serve as seedbeds for ice nuclei. The combined experimental and simulation studies shed new light on the influence of surface ions on heterogeneous ice nucleation.