The Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka 567-0047, Japan.
Wuhan National Laboratory for Optoelectronics, School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, P. R. China.
J Phys Chem B. 2020 Aug 13;124(32):7086-7092. doi: 10.1021/acs.jpcb.0c04677. Epub 2020 Jul 30.
Fundamental understanding of ion transport in a fluidic channel is of critical importance for realizing iontronics. Here we report on asymmetric ion transport in a low thickness-to-diameter aspect ratio nanopore. Under uniform salt concentration conditions, the cross-pore ionic current showed ohmic characteristics with no bias polarity dependence. In stark contrast, despite the weak ion selectivity expected for the relatively large nanopores employed, we observed diode-like behavior when a salt gradient was imposed across the thin membrane. This unexpected result was attributed to the electroosmotic flow that served to modulate the access resistance through dragging the condensed ions into or out of the nanopore orifices. The simple mechanism was also revealed to be effective in fluidic channels of various size from micro- to nanoscale enabling rectification of the property engineering by the pore geometries. The present findings allow for novel designs of artificial ion channel building blocks.
对流体通道中离子传输的基本理解对于实现离子电子学至关重要。在这里，我们报告了在低纵横比纳米孔中不对称离子传输的情况。在均匀盐浓度条件下，跨孔离子电流呈现出欧姆特性，没有偏压极性依赖性。相比之下，尽管所采用的相对较大的纳米孔预计具有较弱的离子选择性，但当在薄膜上施加盐梯度时，我们观察到了类似二极管的行为。这种出乎意料的结果归因于电渗流，它通过将凝聚离子拖入或拖出纳米孔口来调节进入纳米孔的阻力。这种简单的机制也被证明在从微尺度到纳尺度的各种尺寸的流体通道中有效，从而通过孔几何形状实现了对特性工程的整流。本研究结果为人工离子通道构建模块的新型设计提供了依据。
