Tan Haojing, He Zhi, Zhou Ruhong, Feng Jiandong
Laboratory of Experimental Physical Biology, Department of Chemistry, Zhejiang University, Hangzhou 310058, China.
Institute of Quantitative Biology, College of Life Sciences, Zhejiang University, Hangzhou 310058, China.
J Chem Phys. 2024 Oct 21;161(15). doi: 10.1063/5.0227305.
The mass transport behavior through nanoscale channels, greatly influenced by the structures and dynamics of nanoconfined water, plays an essential role in many biophysical processes. However, the dynamics of nanoconfined water under an external field and its effects are still not fully understood. Here, on the basis of molecular dynamics simulations, we theoretically show that the ionic current of [Bmim][PF6] through narrow pores in graphene membrane exhibits an ionic negative differential resistance effect-the ionic current decreases as the voltage increases over a certain threshold. This effect arises from the violation of traditional fluid dynamics as the assumption of continuity and homogeneity of fluids is no longer effective in ultrathin nanopores. The gradient of electric field around the atomic-thin layer produces a strong gradient force on the polarized water inside the nanopore. This dielectrophoretically compressed water leads to a hydrostatic force that repels ions from entering the nanopore. Our findings may advance the understanding of hydrostatic mechanism, which governs ion transport through nanopores.
通过纳米级通道的质量传输行为在许多生物物理过程中起着至关重要的作用，它受到纳米限域水的结构和动力学的极大影响。然而，外部场作用下纳米限域水的动力学及其影响仍未被完全理解。在此，基于分子动力学模拟，我们从理论上表明，[Bmim][PF6] 通过石墨烯膜中窄孔的离子电流呈现出离子负微分电阻效应——在一定阈值以上，随着电压升高，离子电流减小。这种效应源于传统流体动力学的失效，因为流体的连续性和均匀性假设在超薄纳米孔中不再有效。原子薄层周围的电场梯度在纳米孔内的极化水上产生强大的梯度力。这种介电泳压缩水产生一种静水力，排斥离子进入纳米孔。我们的发现可能会推动对控制离子通过纳米孔传输的静水压机制的理解。
