Noh Yechan, Aluru Narayana R
Department of Mechanical Science and Engineering, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States.
ACS Nano. 2020 Aug 25;14(8):10518-10526. doi: 10.1021/acsnano.0c04453. Epub 2020 Aug 10.
Ionic transport through a charged nanopore at low ion concentration is governed by the surface conductance. Several experiments have reported various power-law relations between the surface conductance and ion concentration, , ∝ . However, the physical origin of the varying exponent, α, is not yet clearly understood. By performing extensive coarse-grained Molecular Dynamics simulations for various pore diameters, lengths, and surface charge densities, we observe varying power-law exponents even with a constant surface charge and show that α depends on how electrically "perfect" the nanopore is. Specifically, when the net charge of the solution in the pore is insufficient to ensure electroneutrality, the pore is electrically "imperfect" and such nanopores can exhibit varying α depending on the degree of "imperfectness". We present an ionic conductance theory for electrically "imperfect" nanopores that not only explains the various power-law relationships but also describes most of the experimental data available in the literature.
在低离子浓度下，离子通过带电纳米孔的传输受表面电导支配。一些实验报道了表面电导与离子浓度之间存在各种幂律关系，即 ∝ 。然而，变化指数α的物理起源尚未完全清楚。通过对各种孔径、长度和表面电荷密度进行广泛的粗粒度分子动力学模拟，我们发现即使表面电荷恒定，幂律指数也会变化，并且表明α取决于纳米孔在电学上的“完美”程度。具体而言，当孔内溶液的净电荷不足以确保电中性时，该孔在电学上是“不完美的”，这种纳米孔可能会根据“不完美”程度表现出不同的α。我们提出了一种针对电学上“不完美”纳米孔的离子电导理论，该理论不仅解释了各种幂律关系，还描述了文献中现有的大部分实验数据。
