Cain DaVante, Cao Ethan, Vlassiouk Ivan, Schäffer Tilman E, Siwy Zuzanna S
Department of Physics and Astronomy, University of California, Irvine, 92697, California, USA.
Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, 37831, TN, USA.
Faraday Discuss. 2025 Feb 17;257(0):344-359. doi: 10.1039/d4fd00148f.
There has been a great amount of interest in nanopores as the basis for sensors and templates for preparation of biomimetic channels as well as model systems to understand transport properties at the nanoscale. The presence of surface charges on the pore walls has been shown to induce ion selectivity as well as enhance ionic conductance compared to uncharged pores. Here, using three-dimensional continuum modeling, we examine the role of the length of charged nanopores as well as applied voltage for controlling ion selectivity and ionic conductance of single nanopores and small nanopore arrays. First, we present conditions where the ion current and ion selectivity of nanopores with homogeneous surface charges remain unchanged, even if the pore length decreases by a factor of 6. This length-independent conductance is explained through the effect of ion concentration polarization (ICP), which modifies local ionic concentrations, not only at the pore entrances but also in the pore in a voltage-dependent manner. We describe how voltage controls the ion selectivity of nanopores with different lengths and present the conditions when charged nanopores conduct less current than uncharged pores of the same geometrical characteristics. The manuscript provides different measures of the extent of the depletion zone induced by ICP in single pores and nanopore arrays, including systems with ionic diodes. The modeling shown here will help design selective nanopores for a variety of applications where single nanopores and nanopore arrays are used.
作为传感器的基础、仿生通道制备的模板以及理解纳米尺度传输特性的模型系统，纳米孔已引发了大量关注。与不带电的孔相比，孔壁上表面电荷的存在已被证明会诱导离子选择性并增强离子电导。在此，我们使用三维连续介质建模来研究带电纳米孔的长度以及施加电压在控制单个纳米孔和小纳米孔阵列的离子选择性和离子电导方面所起的作用。首先，我们给出了具有均匀表面电荷的纳米孔的离子电流和离子选择性保持不变的条件，即便孔长度减小了6倍。这种与长度无关的电导可通过离子浓度极化（ICP）效应来解释，ICP不仅会以电压依赖的方式改变孔入口处的局部离子浓度，还会改变孔内的局部离子浓度。我们描述了电压如何控制不同长度纳米孔的离子选择性，并给出了带电纳米孔比具有相同几何特征的不带电孔传导电流更少的条件。本文提供了在单个孔和纳米孔阵列（包括带有离子二极管的系统）中由ICP诱导的耗尽区范围的不同度量。此处展示的建模将有助于为使用单个纳米孔和纳米孔阵列的各种应用设计选择性纳米孔。
