School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore, 637459, Singapore.
Institute of Nanotechnology, Gebze Technical University, Kocaeli, 41400, Turkey.
Small. 2020 Jun;16(25):e1907575. doi: 10.1002/smll.201907575. Epub 2020 May 20.
Carbon nanotubes (CNTs) with hydrophobic and atomically smooth inner channels are promising for building ultrahigh-flux nanofluidic platforms for energy harvesting, health monitoring, and water purification. Conventional wisdom is that nanoconfinement effects determine water transport in CNTs. Here, using full-atomistic molecular dynamics simulations, it is shown that water transport behavior in CNTs strongly correlates with the electronic properties of single-walled CNTs (metallic (met) vs semiconducting (s/c)), which is as dominant as the effect of nanoconfinement. Three pairs of CNTs (i.e., (8,8) , 10.85 Å vs (9,7) , 10.88 Å; (9,8) , 11.53 Å vs (10,7) , 11.59 Å; and (9,9) , 12.20 Å vs (10,8) , 12.23 Å) are used to investigate the roles of diameter and metallicity. Specifically, the (9,8) can restrict the hydrogen-bonding-mediated structuring of water and give the highest reduction in carbon-water interaction energy, providing an extraordinarily high water flux, around 250 times that of the commercial reverse osmosis membranes and approximately fourfold higher than the flux of the state-of-the-art boron nitrate nanotubes. Further, the high performance of (9,8) is also reproducible when embedded in lipid bilayers as synthetic high-water flux porins. Given the increasing availability of high-purity CNTs, these findings provide valuable guides for realizing novel CNT-enhanced nanofluidic systems.
碳纳米管（CNTs）具有疏水和亲水的原子平滑内通道，是构建用于能量收集、健康监测和水净化的超高通量纳米流控平台的有前途的材料。传统观点认为，纳米限域效应决定了 CNT 中的水输运。在这里，通过全原子分子动力学模拟，表明 CNT 中的水输运行为与单壁 CNT 的电子特性（金属（met）与半导体（s/c））密切相关，这与纳米限域效应一样重要。使用三对 CNT（即（8,8），10.85 Å 与（9,7），10.88 Å；（9,8），11.53 Å 与（10,7），11.59 Å；和（9,9），12.20 Å 与（10,8），12.23 Å）来研究直径和金属性的作用。具体来说，（9,8）可以限制氢键介导的水分子结构并降低碳-水相互作用能，从而提供极高的水通量，约为商业反渗透膜的 250 倍，大约是最先进的硝酸硼纳米管的四倍。此外，（9,8）的高性能在嵌入脂质双层作为合成高水通量 porin 时也是可重复的。鉴于高纯度 CNT 的可用性不断增加，这些发现为实现新型 CNT 增强纳米流控系统提供了有价值的指导。
