Götte Lisa, Parry Krista M, Hua Wei, Verreault Dominique, Allen Heather C, Tobias Douglas J
Lehrstuhl für Theoretische Chemie, Ruhr-Universität , 44780 Bochum, Germany.
Department of Chemistry, University of California , Irvine, California 92679-2025, United States.
J Phys Chem A. 2017 Aug 31;121(34):6450-6459. doi: 10.1021/acs.jpca.7b05600. Epub 2017 Aug 16.
The ion distribution and ion pairing properties of Mg, SO, NO, and Cl in the interfacial region of MgSO, Mg(NO), and MgCl solutions were investigated using vibrational sum frequency generation (VSFG) spectroscopy and molecular dynamics (MD) simulations. An electric field reversal relative to Mg(NO) and MgCl solutions is observed at the interface of a MgSO solution. We show that, although magnesium cations are expected to have preference for bulk solvation, solvent-shared ion pairs (SIPs) exist in the interfacial region in which Mg cations are closer to the solution surface than sulfate anions. While interfacial SIPs are few, they dominate the electric field effect observed. Thus, SIPs play a significant role in determining the electric field direction and magnitude at the air-aqueous interface. In addition to impact on the fundamental understanding of aqueous surfaces and interfacial ion-ion interactions, these findings have implications for atmospheric aerosol chemistry and thundercloud electrification.
利用振动和频产生（VSFG）光谱和分子动力学（MD）模拟研究了MgSO₄、Mg(NO₃)₂和MgCl₂溶液界面区域中Mg²⁺、SO₄²⁻、NO₃⁻和Cl⁻的离子分布及离子配对性质。在MgSO₄溶液界面观察到相对于Mg(NO₃)₂和MgCl₂溶液的电场反转。我们表明，尽管镁阳离子预期更倾向于本体溶剂化，但在界面区域存在溶剂共享离子对（SIPs），其中Mg²⁺阳离子比硫酸根阴离子更靠近溶液表面。虽然界面SIPs数量很少，但它们主导了观察到的电场效应。因此，SIPs在确定气-水界面的电场方向和强度方面起着重要作用。除了对水表面和界面离子-离子相互作用的基本理解有影响外，这些发现对大气气溶胶化学和雷暴云起电也有意义。
