Ion transport through a graphene nanopore.
Ion transport through a graphene nanopore.
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通过石墨烯纳米孔的离子传输
DOI：
10.1088/0957-4484/23/39/395501
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发表时间：
2012-10-05
期刊：
影响因子：
3.5
通讯作者：
Ghosal S
中科院分区：
文献类型：
--
作者：
Hu G;Mao M;Ghosal S
采用分子动力学模拟方法，研究了外加电场作用下，氯化钠溶液中离子在石墨烯纳米孔中的输运过程。结果表明，在石墨烯薄片附近形成了浓差极化层。如果电场足够强，足以克服粘度和热波动的影响，离子分布的不均匀就会产生电场，从而驱动流体中的涡流运动。研究了流体动力输运和热涨落在决定孔隙电导率中的相对重要性。观察到的第二个重要效应是水通过纳米孔的质量传输，平均速度与施加的电压成正比，与孔径无关。通量的产生是离子分布不对称的结果，离子分布的不对称可归因于钠离子和氯离子的不同迁移率以及水分子的极性。由于局部电场使水偶极子重新取向，液体分子在纳米孔附近聚集，导致液体密度局部增加。结果证实，在我们模拟的参数范围内，电导与纳米孔直径成正比。发现流体涡旋的出现导致了有效电导的增加。
Molecular dynamics simulation is utilized to investigate the ionic transport of NaCl in solution through a graphene nanopore under an applied electric field. Results show the formation of concentration polarization layers in the vicinity of the graphene sheet. The nonuniformity of the ion distribution gives rise to an electric pressure which drives vortical motions in the fluid if the electric field is sufficiently strong to overcome the influence of viscosity and thermal fluctuations. The relative importance of hydrodynamic transport and thermal fluctuations in determining the pore conductivity is investigated. A second important effect that is observed is the mass transport of water through the nanopore, with an average velocity proportional to the applied voltage and independent of the pore diameter. The flux arises as a consequence of the asymmetry in the ion distribution which can be attributed to differing mobilities of the sodium and chlorine ions and to the polarity of water molecules. The accumulation of liquid molecules in the vicinity of the nanopore due to re-orientation of the water dipoles by the local electric field is seen to result in a local increase in the liquid density. Results confirm that the electric conductance is proportional to the nanopore diameter for the parameter regimes that we simulated. The occurrence of fluid vortices is found to result in an increase in the effective electrical conductance.
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