Department of Chemistry and Macromolecules Innovation Institute, Virginia Tech, Blacksburg, Virginia 24061, United States.
J Phys Chem B. 2021 Dec 23;125(50):13767-13777. doi: 10.1021/acs.jpcb.1c06810. Epub 2021 Dec 13.
We present an investigation of the dynamics of water confined among rigid carbon rods and between parallel graphene sheets with molecular dynamics simulations. Diffusion coefficients, activation energy of diffusion, and residence-time correlation functions as a function of confinement geometry reveal a retardation of water dynamics under hydrophobic confinement compared to bulk water. In fact, water under various confinements possesses longer associations with its neighbors and exhibits diffusion dynamics characteristic of a lower temperature. Analysis of the residence-time correlation functions reveals long and short residence times, which we relate to the diffusion coefficient and activation energy of diffusion, respectively. Additional investigations reveal how the level of confining surface hydrophobicity affects water dynamics, further broadening our understanding of water diffusion inside diverse media. Overall, this study sheds light on the physical origin of retarded water dynamics under hydrophobic confinement and the close relationship between residence times and diffusion behavior.
我们通过分子动力学模拟研究了水在刚性碳棒之间和平行石墨烯片之间受限时的动力学。扩散系数、扩散的激活能以及作为约束几何形状函数的停留时间相关函数表明，与体相水相比，疏水约束下水的动力学被延迟。事实上，在各种约束下的水与相邻分子的缔合时间更长，并且表现出与较低温度相关的扩散动力学特征。停留时间相关函数的分析揭示了长停留时间和短停留时间，我们分别将其与扩散系数和扩散的激活能相关联。进一步的研究揭示了约束表面疏水性的程度如何影响水的动力学，从而进一步拓宽了我们对不同介质中水分子扩散的理解。总的来说，这项研究揭示了疏水约束下水动力学延迟的物理起源以及停留时间和扩散行为之间的密切关系。
