Abstract

An interesting area of modern membrane science is the development of “smart” membranes, which can affect the transport properties of selected components via external tuning. When the target components are ions, such a tuning can be realized with the help of electric field created by the conductive pore surface. We have proposed in this work a mathematical model of ions transport in a cylindrical nanopore with the electronic charge at the conductive surface and the chemical charge, which is separated from the surface by the Stern layer. The model is based on one-dimensional equations for potential, ion concentrations, and pressure in the diffuse layer. It is applied for describing the membrane potential at zero current, which characterizes the type and strength of ionic selectivity. It is shown that the change of surface potential in the direction from negative to positive results in the continuous change of pore selectivity from cation to anion. The decrease in the Stern layer capacitance and increase in the pore radius lead to the decrease in ionic selectivity. The presence of positive (negative) chemical charge causes the shift of potential value, at which the selectivity is switched, in the direction of negative (positive) values. At this value of potential, the membrane becomes non-selective, the diffusive flux of ions reaches maximum, and the osmotic flow ceases. The suggested model provides a qualitative and quantitative description of experimental results on switchable selectivity of track-etched membranes modified by the gold coating.

中文翻译：

---

具有可切换离子选择性的导电纳米多孔膜的建模

摘要

现代膜科学的一个有趣领域是“智能”膜的开发，该膜可通过外部调节影响所选组分的传输性能。当目标成分是离子时，可以借助于由导电孔表面产生的电场来实现这种调节。我们在这项工作中提出了一个离子在圆柱状纳米孔中传输的数学模型，该导电模型中的电荷在导电表面，而化学电荷则通过斯特恩层与表面隔开。该模型基于一维方程式，用于扩散层中的电势，离子浓度和压力。它用于描述零电流下的膜电势，它表征了离子选择性的类型和强度。结果表明，在从负到正的方向上表面电势的变化导致孔选择性从阳离子到阴离子的连续变化。斯特恩层电容的减小和孔半径的增大导致离子选择性的减小。正（负）化学电荷的存在会导致电势值​​在负（正）值方向上发生位移，在该位置上切换选择性。在此电势值下，膜变为非选择性，离子的扩散通量达到最大值，并且渗透流停止。建议的模型提供了定性和定量的实验结果，描述了由金涂层改性的迹线蚀刻膜的可切换选择性的实验结果。