Department of Mechanical Science and Engineering, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
J Chem Phys. 2014 Feb 28;140(8):084707. doi: 10.1063/1.4866643.
Graphene nanopore is a promising device for single molecule sensing, including DNA bases, as its single atom thickness provides high spatial resolution. To attain high sensitivity, the size of the molecule should be comparable to the pore diameter. However, when the pore diameter approaches the size of the molecule, ion properties and dynamics may deviate from the bulk values and continuum analysis may not be accurate. In this paper, we investigate the static and dynamic properties of ions with and without an external voltage drop in sub-5-nm graphene nanopores using molecular dynamics simulations. Ion concentration in graphene nanopores sharply drops from the bulk concentration when the pore radius is smaller than 0.9 nm. Ion mobility in the pore is also smaller than bulk ion mobility due to the layered liquid structure in the pore-axial direction. Our results show that a continuum analysis can be appropriate when the pore radius is larger than 0.9 nm if pore conductivity is properly defined. Since many applications of graphene nanopores, such as DNA and protein sensing, involve ion transport, the results presented here will be useful not only in understanding the behavior of ion transport but also in designing bio-molecular sensors.
石墨烯纳米孔是一种用于单分子传感的有前途的器件，包括 DNA 碱基，因为其单层原子厚度提供了高空间分辨率。为了获得高灵敏度，分子的大小应与孔径相当。然而，当孔径接近分子大小时，离子性质和动力学可能偏离体相值，连续分析可能不准确。在本文中，我们使用分子动力学模拟研究了在亚 5nm 石墨烯纳米孔中有和没有外加电压降时离子的静态和动态特性。当孔径小于 0.9nm 时，石墨烯纳米孔中的离子浓度从体相浓度急剧下降。由于孔中轴向方向的分层液体结构，离子在孔中的迁移率也小于体相离子迁移率。我们的结果表明，如果适当定义孔的电导率，连续分析在孔径大于 0.9nm 时是合适的。由于石墨烯纳米孔的许多应用，如 DNA 和蛋白质传感，都涉及离子传输，因此这里提出的结果不仅有助于理解离子传输的行为，还有助于设计生物分子传感器。
