Lao Junchao, Zhou Ke, Pan Shangfa, Luo Jiayan, Gao Jun, Dong Anping, Jiang Lei
Shanghai Key Lab of Advanced High-temperature Materials and Precision Forming and State Key Lab of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
Qingdao Institute of Bioenergy and Bioprocess Technology Chinese Academy of Sciences, Qingdao 266101, China.
ACS Nano. 2022 Jun 28;16(6):9142-9149. doi: 10.1021/acsnano.2c01304. Epub 2022 May 23.
Biological ion pumps selectively transport target ions against the concentration gradient, a process that is crucial to maintaining the out-of-equilibrium states of cells. Building an ion pump with ion selectivity has been challenging. Here we show that a TiCT MXene film suspended in air with a trapezoidal shape spontaneously pumps K ions from the base end to the tip end and exhibits a K/Na selectivity of 4. Such a phenomenon is attributed to a range of properties of MXene. Thanks to the high stability of MXene in water and the dynamic equilibrium between evaporation and swelling, the film keeps a narrow interlayer spacing of ∼0.3 nm when its two ends are connected to reservoirs. Because of the polar electrical structure and hydrophilicity of the MXene nanosheet, K ions experience a low energy barrier of ∼4.6 when entering these narrow interlayer spacings. Through quantitative simulations and consistent experimental results, we further show that the narrow spacings exhibit a higher energy barrier to Na, resulting in K/Na selectivity. Finally, we show that the spontaneous ion transport is driven by the asymmetric evaporation of the interlayer water across the film, a mechanism that is similar to pressure driven streaming current. This work shows how ion transport properties can be facilely manipulated by tuning the macroscopic shape of nanofluidic materials, which may attract interest in the interface of kirigami technologies and nanofluidics and show potential in energy and separation applications.
生物离子泵能选择性地逆浓度梯度运输目标离子，这一过程对于维持细胞的非平衡状态至关重要。构建具有离子选择性的离子泵一直具有挑战性。在此，我们展示了一种悬浮在空气中的梯形TiCT MXene薄膜能自发地将钾离子从底端泵送到顶端，并表现出4的K/Na选择性。这种现象归因于MXene的一系列特性。由于MXene在水中的高稳定性以及蒸发与膨胀之间的动态平衡，当薄膜两端与储液器相连时，其层间距保持在约0.3nm的狭窄状态。由于MXene纳米片的极性电结构和亲水性，钾离子进入这些狭窄层间距时的能量势垒较低，约为4.6 。通过定量模拟和一致的实验结果，我们进一步表明狭窄间距对钠离子表现出更高的能量势垒，从而产生K/Na选择性。最后，我们表明自发离子运输是由薄膜层间水的不对称蒸发驱动的，这一机制类似于压力驱动的流动电流。这项工作展示了如何通过调整纳米流体材料的宏观形状来轻松操控离子传输特性，这可能会引起对剪纸技术与纳米流体学界面的关注，并在能量和分离应用中展现出潜力。
