奈米孔道的離子電流整流：孔道形狀, pH 與鹽類性質的影響

Ionic Current Rectification of Nanochannels: Effects of Channel Geometry, pH, and Salt Conditions

林采葳(Tsai-Wei Lin)

指導教授 ： 徐治平

國立臺灣大學/工學院/化學工程學研究所/碩士(2019年)

https://doi.org/10.6342/NTU201901022

摘要

擁有高度應用潛力，奈米流體裝置近年來已受到須多研究團隊的重視。而為了提供給實驗團隊重要的結果以促進奈米流體裝置的實際應用，我們利用數值模擬研究這些奈米孔道中的離子傳輸行為。其中，離子電流整流行為為們主要研究對象。在第一章節中，我們探討許多因素對錐狀奈米孔道的電流整流行為的影響，囊括了孔道幾何與電解質濃度種類影響。在此研究中，我們討論的離子種類為：KCl、NaCl 及 LiCl。我們發現，當電解質濃度較低，且開口角度很小的奈米孔道中，LiCl 溶液有最佳的電流整流行為；然而，加大開口角度或是提高電解質濃度時，則是 KCl 的電流整流行為最佳。此研究成果已發表於 Journal of Physical Chemistry C.

第二章節中，利用表面塗佈有 pH 可調節聚電解質的圓柱狀奈米孔道，我們提出了同時施以外加電壓與外加酸鹼值 pH 梯度下，此奈米孔道的離子電流整流機制。我們觀察到，當施加較強的 pH 梯度，此圓柱狀奈米孔道的整流方向會隨著外加電壓大小而反轉；施加較弱的 pH 梯度，藉由提升聚電解質的接枝密度，可改變奈米孔道的整流方向。我們所提出的機制討論與研究結果已發表於 Journal ofPhysical Chemistry C.

關鍵字

奈米流體 ； 離子電流整流 ； 電導度 ； 可調節聚電解質 ； 酸鹼值梯度

並列摘要

Nanofludic devices have gained much attention for its applicability in many fields. To advance nanodevices’ applications and provide significant results for experimental groups, we develop numerical models to simulate ion transport behaviors in naopores. Ion current rectification (ICR) of nanopores is particularly focused in our studies. In the first part, the effects of nanopores’ geometry, bulk salt concentration, and types of salt on ICR of conical nanopores are discussed in detail. Three types of salt are considered: KCl, NaCl, and LiCl. With sufficiently low salt concentration and small half cone angle, LiCl shows the best current rectifying behavior. The reverse of the trend is observed if we increases either the salt concentration or half cone angle. The above results was published in Journal of Physical Chemistry C.

In the second part, we provide a mechanism for ICR performance of a nanopore simultaneously applied with an electric potential and a pH gradient. A cylindrical nanopore functionalized with homogeneous (single) pH-tunable polyelectrolyte brushes is adopted in our study. We show that homogeneously modified nanopores can also exhibit ion current rectification behavior when applied an external pH gradient. The preferential direction of ionic current can be tuned by increasing level of applied electric potential if pH gradient is strong. For nanopores with weak pH gradient, an increase in grafting density of the polyelectrolyte chains can reverse preferential direction. The results and the discussion are published in Journal of Physical Chemistry C.

並列關鍵字

Nanofludic devices ； Ion current rectification ； Nanopore conductance ； pH-tunable polyelectrlyte ； pH gradient

參考文獻

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