Division of Quantum Phases and Devices, Department of Physics, Konkuk University, Seoul 143-701, Republic of Korea.
Sci Rep. 2013;3:2309. doi: 10.1038/srep02309.
The structure of water confined in nanometer-sized cavities is important because, at this scale, a large fraction of hydrogen bonds can be perturbed by interaction with the confining walls. Unusual fluidity properties can thus be expected in the narrow pores, leading to new phenomena like the enhanced fluidity reported in carbon nanotubes. Crystalline mica and amorphous silicon dioxide are hydrophilic substrates that strongly adsorb water. Graphene, on the other hand, interacts weakly with water. This presents the question as to what determines the structure and diffusivity of water when intercalated between hydrophilic substrates and hydrophobic graphene. Using atomic force microscopy, we have found that while the hydrophilic substrates determine the structure of water near its surface, graphene guides its diffusion, favouring growth of intercalated water domains along the C-C bond zigzag direction. Molecular dynamics and density functional calculations are provided to help understand the highly anisotropic water stripe patterns observed.
水在纳米级空腔中的结构很重要，因为在这个尺度上，大量的氢键可以通过与约束壁的相互作用而受到干扰。因此，在狭窄的孔隙中可以预期到异常的流动性特性，导致像在碳纳米管中报道的增强流动性等新现象。结晶云母和无定形二氧化硅是亲水的基底，它们强烈吸附水。另一方面，石墨烯与水的相互作用很弱。这就提出了一个问题，即在亲水基底和疏水石墨烯之间夹层时，是什么决定了水的结构和扩散性。使用原子力显微镜，我们发现，虽然亲水基底决定了水在其表面附近的结构，但石墨烯引导其扩散，有利于夹层水沿 C-C 键之字形方向的生长。提供分子动力学和密度泛函计算以帮助理解观察到的高度各向异性的水条纹图案。
