Qian Yongchao, Zhang Zhen, Tian Wei, Wen Liping, Jiang Lei
Key Laboratory of Space Applied Physics and Chemistry, Ministry of Education, Shanxi Key Laboratory of Macromolecular Science and Technology, School of Science, Northwestern Polytechnical University, Xi'an 710072, P. R. China.
Faraday Discuss. 2018 Oct 1;210(0):101-111. doi: 10.1039/c8fd00025e.
The existence of heavy ions, such as Pb2+, in the external environment is potentially hazardous as these can be highly toxic to the human body. Inspired by the highly efficient ability of biological ion channels to recognize the metal ion, much effort has been devoted to investigating biomimetic ionic gates based on engineered solid-state conical nanopores/nanochannels. However, the reported system generally displays relatively poor functionality and low stability due to the limited functional region. This article describes an ionic gate with enhanced stability and improved sensitivity based on an emerging advanced funnel-shaped nanochannel system. The ionic gate is developed by anchoring the Pb2+ ion-responsive functional molecules, 4'-aminobenzo-18-crown-6 (4-AB18C6), onto the inner surface of a funnel-shaped polyethylene terephthalate (PET) nanochannel. The system can selectively recognize Pb2+ with an ultra-low concentration of down to approximately 10-15 M and displays excellent stability. The Pb2+ ions will form positively charged complexes through specific association with 4-AB18C6, which would screen the negative charge existing on the channel walls, resulting in a decreased ionic current and also an "OFF state". Since the ability of EDTA to associate with Pb2+ is much stronger than that of 4-AB18C6, the nanochannel can also achieve reversible switching upon the alternating addition of Pb2+ ions and EDTA. The switching behaviors of the system were reflected by the good reproducibility of the tunable rectifying effect. The stability of the conical and funnel-shaped nanochannels is also compared using current scanning under constant voltage. The results have shown that the stability of the funnel-shaped nanochannel is much better than that of the conical nanochannel, and this can be ascribed to its much longer critical region. Consequently, the funnel-shaped nanochannels with enhanced stability and improved sensitivity can potentially be applied in ion transportation, sensors, drug release, and energy conversion.
外部环境中存在的重金属离子，如Pb2+，具有潜在危害，因为它们对人体可能具有高毒性。受生物离子通道识别金属离子的高效能力启发，人们致力于研究基于工程化固态锥形纳米孔/纳米通道的仿生离子门。然而，由于功能区域有限，已报道的系统通常表现出相对较差的功能和较低的稳定性。本文介绍了一种基于新兴的先进漏斗形纳米通道系统的具有增强稳定性和更高灵敏度的离子门。该离子门是通过将Pb2+离子响应功能分子4'-氨基苯并-18-冠-6（4-AB18C6）锚定在漏斗形聚对苯二甲酸乙二醇酯（PET）纳米通道的内表面而开发的。该系统能够以低至约10-15 M的超低浓度选择性识别Pb2+，并表现出优异的稳定性。Pb2+离子通过与4-AB18C6的特异性结合形成带正电的络合物，这将屏蔽通道壁上存在的负电荷，导致离子电流降低，从而处于“关闭状态”。由于乙二胺四乙酸（EDTA）与Pb2+结合的能力比4-AB18C6强得多，因此该纳米通道在交替添加Pb2+离子和EDTA时也能实现可逆切换。系统的切换行为通过可调整流效应的良好重现性得以体现。还使用恒压下的电流扫描比较了锥形和漏斗形纳米通道的稳定性。结果表明，漏斗形纳米通道的稳定性远优于锥形纳米通道，这可归因于其更长的临界区域。因此，具有增强稳定性和更高灵敏度的漏斗形纳米通道在离子传输、传感器、药物释放和能量转换方面具有潜在应用价值。
