Zeng Zhenping, Yeh Li-Hsien, Zhang Mingkan, Qian Shizhi
School of Electronic and Optical Engineering, Nanjing University of Science and Technology, Nanjing 210094, P. R. China.
Nanoscale. 2015 Oct 28;7(40):17020-9. doi: 10.1039/c5nr05828g.
Inspired by nature, functionalized nanopores with biomimetic structures have attracted growing interests in using them as novel platforms for applications of regulating ion and nanoparticle transport. To improve these emerging applications, we study theoretically for the first time the ion transport and selectivity in short nanopores functionalized with pH tunable, zwitterionic polyelectrolyte (PE) brushes. In addition to background salt ions, the study takes into account the presence of H(+) and OH(-) ions along with the chemistry reactions between functional groups on PE chains and protons. Due to ion concentration polarization, the charge density of PE layers is not homogeneously distributed and depends significantly on the background salt concentration, pH, grafting density of PE chains, and applied voltage bias, thereby resulting in many interesting and unexpected ion transport phenomena in the nanopore. For example, the ion selectivity of the biomimetic nanopore can be regulated from anion-selective (cation-selective) to cation-selective (anion-selective) by diminishing (raising) the solution pH when a sufficiently small grafting density of PE chains, large voltage bias, and low background salt concentration are applied.
受自然启发，具有仿生结构的功能化纳米孔作为调节离子和纳米颗粒传输应用的新型平台，已引起越来越多的关注。为了改进这些新兴应用，我们首次从理论上研究了用pH可调的两性离子聚电解质（PE）刷功能化的短纳米孔中的离子传输和选择性。除了背景盐离子外，该研究还考虑了H(+)和OH(-)离子的存在以及PE链上官能团与质子之间的化学反应。由于离子浓度极化，PE层的电荷密度分布不均匀，并且显著取决于背景盐浓度、pH值、PE链的接枝密度和施加的电压偏置，从而在纳米孔中产生了许多有趣且意想不到的离子传输现象。例如，当施加足够小的PE链接枝密度、大电压偏置和低背景盐浓度时，通过降低（提高）溶液pH值，仿生纳米孔的离子选择性可以从阴离子选择性（阳离子选择性）调节为阳离子选择性（阴离子选择性）。
