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Hierarchical multiscale computations of ion transport in synthetic nanopores

机译：合成纳米孔中离子迁移的分层多尺度计算

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There is a growing interest in investigating transport and electrochemical phenomena in synthetic membrane nanopores because of the possibility of mimicking selective ion transport found in protein channels in cell membranes of living systems and also towards development of single molecule detection systems. Several experimental (Gu et al., 2001; Jirage et al., 1997; Kuo et al., 2001) approaches such as the track etch method and the ion beam method have been used with increasing success in recent years to characterize the ionic transport through nanopores of varying diameters. We first performed two level multiscale simulations combining the continuum Poisson Nernst Planck theory and the molecular dynamics simulations to obtain current-voltage characteristics of nanopores in a silicon dioxide membrane and to investigate the effects of the complex phenomena of conductivity and self diffusion of ions due to the confinement in nanopores. Statistical analysis from molecular dynamics simulations were used to obtain mobility and diffusion coefficient in SiO/sub 2/ nanopores 5nm in length and diameters of 3 nm, 2nm and 1.2nm in 1M KCl and NaCl solutions. The data from these simulations showed that the mobility and diffusion coefficient decreases with decrease in diameter and is significantly different from the bulk especially for diameters less than 2 nm. The transport coefficients obtained were used in a continuum based Poisson-Nernst-Planck solver in a multiscale framework to obtain the I-V curves. The partial charges were obtained using DFT and semiempirical AMI, which closely matches the data for silica clusters in literature. Preliminary results indicate that the presence of partial charges on the pore walls alter the transport coefficient because the counter ions stick to the walls for pores of small diameters.
机译：人们对研究合成膜纳米孔中的转运和电化学现象越来越感兴趣，因为它有可能模仿在活系统细胞膜的蛋白质通道中发现的选择性离子转运，并可能发展为单分子检测系统。近年来，已经使用了一些实验方法（Gu等人，2001; Jirage等人，1997; Kuo等人，2001），例如轨道蚀刻方法和离子束方法，这些方法越来越成功地描述了离子迁移的特征。通过直径不同的纳米孔。我们首先结合连续泊松Nernst Planck理论和分子动力学模拟进行了两级多尺度模拟，以获得二氧化硅膜中纳米孔的电流-电压特性，并研究了电导率和离子自扩散引起的复杂现象的影响。限制在纳米孔中。使用分子动力学模拟的统计分析来获得在1M KCl和NaCl溶液中长度为5nm，直径为3nm，2nm和1.2nm的SiO / sub 2 /纳米孔中的迁移率和扩散系数。这些模拟的数据表明，迁移率和扩散系数随直径的减小而减小，并且与体积显着不同，特别是对于直径小于2 nm的体积。所获得的传输系数在多尺度框架中的基于连续体的Poisson-Nernst-Planck求解器中使用，以获得I-V曲线。使用DFT和半经验AMI获得了部分电荷，这与文献中二氧化硅簇的数据非常匹配。初步结果表明，孔壁上存在部分电荷会改变传输系数，因为对于小直径的孔，抗衡离子会粘附在壁上。

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