Origin of ion selectivity at the air/water interface.
Origin of ion selectivity at the air/water interface.
复制标题
空气/水界面离子选择性的起源。
DOI：
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发表时间：
2015
期刊：
影响因子：
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通讯作者：
H. Ågren
中科院分区：
文献类型：
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作者：
Lu Sun;Xin Li;Yaoquan Tu;H. Ågren
在离子的许多特性中，它们在空气/水界面积聚的能力是一个特别的问题，一直是许多研究关注的主题。例如，卤化物阴离子（Cl(-)、Br(-)、I(-)）在水面的积累对于环境问题的多相反应非常重要。然而，驱动阴离子流向空气/水界面的实际机制仍不清楚。在这项工作中，我们使用极化模型进行了原子模拟，以模拟大气条件下的离子行为。我们发现水面上存在大量较大的阴离子，并且阳离子被反离子拉得更靠近表面。我们提出，当接近表面时，极化效应可以稳定具有大半径的阴离子。这种能量上更有利的情况是由于表面的极化阴离子越多，对水分子的吸引力就越强。相关的还有表面水分子的排序，其氢原子指向外侧，这会产生外部电场，从而导致阴离子和阳离子的不同表面行为。水-水相互作用因独特的水-离子吸引力而减弱，这一点与 F(-) 是亲液剂的命题相矛盾。因此，模拟结果使我们能够更全面地了解离子溶液和大气气溶胶的界面特性。
Among many characteristics of ions, their capability to accumulate at air/water interfaces is a particular issue that has been the subject of much research attention. For example, the accumulation of halide anions (Cl(-), Br(-), I(-)) at the water surface is of great importance to heterogeneous reactions that are of environmental concern. However, the actual mechanism that drives anions towards the air/water interface remains unclear. In this work, we have performed atomistic simulations using polarizable models to mimic ionic behavior under atmospheric conditions. We find that larger anions are abundant at the water surface and that the cations are pulled closer to the surface by the counterions. We propose that polarization effects stabilize the anions with large radii when approaching the surface. This energetically more favorable situation is caused by the fact that the more polarized anions at the surface attract water molecules more strongly. Of relevance is also the ordering of the surface water molecules with their hydrogen atoms pointing outwards which induce an external electronic field that leads to a different surface behavior of anions and cations. The water-water interaction is weakened by the distinct water-ion attraction, a point contradicting the proposition that F(-) is a kosmotrope. The simulation results thus allow us to obtain a more holistic understanding of the interfacial properties of ionic solutions and atmospheric aerosols.