Materials Science Division, Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, United States.
Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments, School of Mechanical Engineering, Southeast University, Nanjing 211189, China.
ACS Nano. 2020 May 26;14(5):6269-6275. doi: 10.1021/acsnano.0c02423. Epub 2020 May 4.
Inner pores of carbon nanotubes combine extremely fast water transport and ion selectivity that could potentially be useful for high-performance water desalination and separation applications. We used dye-quenching halide assays and stopped-flow spectrometry to determine intrinsic permeability of three small monovalent halide anions (chloride, bromide, iodide) and one pseudohalide anion (thiocyanate) through narrow 0.8 nm diameter carbon nanotube porins (CNTPs). These measurements revealed unexpectedly strong differential ion selectivity with permeabilities of different ions varying by up to 2 orders of magnitude. Removal of the negative charge from the nanotube entrance increased anion permeability by only a relatively small factor, indicating that electrostatic repulsion was not a major determinant of CNTP selectivity. First principle molecular dynamics simulations revealed that the origin of this strong differential ion selectivity is partial dehydration of anions upon entry into the narrow CNTP channels.
碳纳米管的内孔具有极快的水传输和离子选择性，这可能对高性能海水淡化和分离应用非常有用。我们使用染料猝灭卤化物测定法和停流光谱法来确定三种单价小卤化物阴离子（氯离子、溴离子、碘离子）和一种拟卤化物阴离子（硫氰酸根离子）通过狭窄的 0.8nm 直径碳纳米管孔蛋白（CNTP）的固有渗透率。这些测量结果显示出出人意料的强离子选择性，不同离子的渗透率差异高达 2 个数量级。从纳米管入口处去除负电荷仅使阴离子渗透率增加了相对较小的因子，这表明静电排斥不是 CNTP 选择性的主要决定因素。第一性原理分子动力学模拟表明，这种强离子选择性的起源是阴离子进入狭窄的 CNTP 通道时的部分脱水。
