Instituto de Ciencia de Materiales de Madrid, CSIC, c/ Sor Juana Ines de la Cruz 3, 28049 Madrid, Spain.
Department Física Teórica de la Materia Condensada, IFIMAC Condensed Matter Physics Center, UAM, 28049 Madrid, Spain.
Nat Commun. 2016 Jul 15;7:12164. doi: 10.1038/ncomms12164.
Interfacial liquid layers play a central role in a variety of phenomena ranging from friction to molecular recognition. Liquids near a solid surface form an interfacial layer where the molecular structure is different from that of the bulk. Here we report atomic resolution three-dimensional images of electrolyte solutions near a mica surface that demonstrate the existence of three types of interfacial structures. At low concentrations (0.01-1 M), cations are adsorbed onto the mica. The cation layer is topped by a few hydration layers. At higher concentrations, the interfacial layer extends several nanometres into the liquid. It involves the alternation of cation and anion planes. Fluid Density Functional calculations show that water molecules are a critical factor for stabilizing the structure of the interfacial layer. The interfacial layer stabilizes a crystal-like structure compatible with liquid-like ion and solvent mobilities. At saturation, some ions precipitate and small crystals are formed on the mica.
界面液层在各种现象中起着核心作用，从摩擦到分子识别等现象都涉及界面液层。在固体表面附近的液体形成界面层，其分子结构与本体不同。在这里，我们报告了云母表面附近电解质溶液的原子分辨率三维图像，证明了三种界面结构的存在。在低浓度（0.01-1 M）下，阳离子被吸附到云母上。阳离子层的顶部是几个水合层。在较高浓度下，界面层向液体中延伸数纳米。它涉及阳离子和阴离子平面的交替。流体密度泛函计算表明，水分子是稳定界面层结构的关键因素。界面层稳定了一种类似于晶体的结构，同时保持了液态离子和溶剂的迁移率。在饱和时，一些离子沉淀，在云母上形成小晶体。
