Zhang Xiaopeng, Tu Bin, Cao Zhouwen, Fang Munan, Zhang Guangjie, Yang Jinlei, Ying Yue, Sun Zhifei, Hou Junjun, Fang Qiaojun, Tang Zhiyong, Li Lianshan
CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Centre for Nanoscience and Technology, Beijing 100190, P. R. China.
University of Chinese Academy of Sciences, Beijing 100049, P. R. China.
J Am Chem Soc. 2023 Aug 16;145(32):17786-17794. doi: 10.1021/jacs.3c04655. Epub 2023 Aug 3.
Ion transport through nanoconfinement, driven by both electrical and mechanical forces, has drawn ever-increasing attention, due to its high similarity to stress-sensitive ion channels in biological systems. Previous studies have reported only pressure-induced enhancement in ion conductance in low-permeable systems such as nanotubes, nanoslits, or single nanopores. This enhancement is generally explained by the ion accumulation caused by the capacitive effect in low-permeable systems. Here, we fabricate a highly permeable COF monolayer membrane to investigate ion transport behavior driven by both electrical and mechanical forces. Our results show an anomalous conductance reduction activated by external mechanical force, which is contrary to the capacitive effect-dominated conductance enhancement observed in low-permeable nanopores or channels. Through simulations, we uncovered a distinct electrical-mechanical interplay mechanism that depends on the relative rate between the ion diffusion from the boundary layer to the membrane surface and the ion transport through the membrane. The high pore density of the COF monolayer membrane reduces the charge accumulation caused by the capacitive effect, resulting in fewer accumulated ions near the membrane surface. Additionally, the high membrane permeability greatly accelerates the dissipation of the accumulated ions under mechanical pressure, weakening the effect of the capacitive layer on the streaming current. As a result, the ions accumulated on the electrodes, rather than in the capacitive layer, dominating the streaming current and giving rise to a distinct electrical-mechanical interplay mechanism compared to that in low-permeable nanopores or channels. Our study provides new insights into the interplay between electrical and mechanical forces in ultra-permeable systems.
由电力和机械力驱动的通过纳米限域的离子传输，因其与生物系统中应力敏感离子通道的高度相似性而受到越来越多的关注。先前的研究仅报道了在低渗透系统（如纳米管、纳米狭缝或单个纳米孔）中压力诱导的离子电导增强。这种增强通常由低渗透系统中的电容效应引起的离子积累来解释。在这里，我们制备了一种高渗透性的共价有机框架（COF）单层膜，以研究由电力和机械力驱动的离子传输行为。我们的结果表明，外部机械力激活了异常的电导降低，这与在低渗透纳米孔或通道中观察到的以电容效应为主导的电导增强相反。通过模拟，我们发现了一种独特的电 - 机械相互作用机制，该机制取决于离子从边界层扩散到膜表面的速率与离子通过膜传输的速率之间的相对关系。COF单层膜的高孔隙密度降低了由电容效应引起的电荷积累，导致膜表面附近积累的离子减少。此外，高膜渗透性极大地加速了机械压力下积累离子的耗散，削弱了电容层对流动电流的影响。结果，电极上积累的离子而非电容层中的离子主导了流动电流，并与低渗透纳米孔或通道相比产生了独特的电 - 机械相互作用机制。我们的研究为超渗透系统中电力和机械力之间的相互作用提供了新的见解。
