Kyakuno Haruka, Matsuda Kazuyuki, Nakai Yusuke, Ichimura Ryota, Saito Takeshi, Miyata Yasumitsu, Hata Kenji, Maniwa Yutaka
Department of Physics, Graduate School of Science and Engineering, Tokyo Metropolitan University, Hachioji, 192-0397, Japan.
Institute of Physics, Faculty of Engineering, Kanagawa University, Yokohama, 221-8686, Japan.
Sci Rep. 2017 Nov 1;7(1):14834. doi: 10.1038/s41598-017-13704-6.
Water in a nanoconfined geometry has attracted great interest from the viewpoint of not only basic science but also nanofluidic applications. Here, the rotational dynamics of water inside single-walled carbon nanotubes (SWCNTs) with mean diameters larger than ca. 1.4 nm were investigated systematically using H nuclear magnetic resonance spectroscopy with high-purity SWCNTs and molecular dynamics calculations. The results were compared with those for hydrophilic pores. It was found that faster water dynamics could be achieved by increasing the hydrophobicity of the pore walls and decreasing the pore diameters. These results suggest a strategy that paves the way for emerging high-performance filtration/separation devices. Upon cooling below 220 K, it was found that water undergoes a transition from fast to slow dynamics states. These results strongly suggest that the observed transition is linked to a liquid-liquid crossover or transition proposed in a two-liquid states scenario for bulk water.
从基础科学以及纳米流体应用的角度来看，处于纳米受限几何结构中的水引起了人们极大的兴趣。在此，使用高纯度单壁碳纳米管和分子动力学计算，系统地研究了平均直径大于约1.4纳米的单壁碳纳米管（SWCNTs）内部水的旋转动力学。将结果与亲水性孔隙的结果进行了比较。发现通过增加孔壁的疏水性和减小孔径，可以实现更快的水动力学。这些结果提出了一种为新兴的高性能过滤/分离装置铺平道路的策略。当冷却至220 K以下时，发现水经历了从快速动力学状态到缓慢动力学状态的转变。这些结果有力地表明，观察到的转变与在大块水的双液体状态情景中提出的液-液交叉或转变有关。
