Zhang Shusong, Fu Li, Xie Yanbo
School of Physical Science and Technology, Northwestern Polytechnical University, Xi'an 710072, China.
Univ Lyon, Ecole Centrale de Lyon, CNRS, ENTPE, LTDS, UMR5513, 69130 Ecully, France.
J Phys Chem B. 2024 Sep 26;128(38):9206-9212. doi: 10.1021/acs.jpcb.4c03773. Epub 2024 Sep 11.
The Possion-Nernst-Planck theories fail to describe the ionic transport in Angstrom channels, where conduction deviates from Ohm's law, which is attributed to the dehydration/self-energy barrier and dissociation of Bjerrum ion pairs in previous work. Here, we find that the cations can be strongly bound to the surface charge, which blocks the ionic transport in a single-file water channel, causing nonlinear current-voltage curves. The presence of free ions significantly increases the probability of bound ions being released, resulting in an ionic current. We find that ionic conduction gradually becomes Ohmic as the surface charge density increases, but the conduction amplitude decreases due to the increased friction from the bound ions. We rationalize the ionic transport using 1D Kramers' escape theory framework, which describes nonlinear ionic current and the impact of surface charge density on the - curves. Our results show that the strong Coulomb interaction between the counterion and surface charge may cause ionic blockade in Angstrom channels.
泊松-能斯特-普朗克理论无法描述埃级通道中的离子传输，在该通道中传导偏离欧姆定律，在先前的工作中这归因于脱水/自能势垒和比耶鲁姆离子对的解离。在这里，我们发现阳离子可以与表面电荷强烈结合，这会在单排水分子通道中阻碍离子传输，导致电流-电压曲线呈非线性。自由离子的存在显著增加了结合离子被释放的概率，从而产生离子电流。我们发现随着表面电荷密度的增加，离子传导逐渐变为欧姆传导，但由于结合离子产生的摩擦力增加，传导幅度减小。我们使用一维克莱默斯逃逸理论框架对离子传输进行了合理的解释，该框架描述了非线性离子电流以及表面电荷密度对电流-电压曲线的影响。我们的结果表明，反离子与表面电荷之间的强库仑相互作用可能会导致埃级通道中的离子阻塞。
