圓錐形奈米孔道：角度對離子整流效應的影響與 離子擴散方向對濃鹽差發電的影響

Abstract

圓錐形奈米孔道在生物科技上有著高潛力的應用，它能夠產生特殊的電動力學現象，如離子濃度極化(ICP)和離子整流效應(ICR)。在第一章節中，我們利用數值模擬的方式，研究圓錐形奈米孔道的開口角度對離子整流效應所造成的影響。改變角度時有兩種方式，第一種方式是固定孔道尖端的開口尺寸，改變末端的開口尺寸;而第二種則是固定末端的開口尺寸，改變尖端的開口尺寸。我們發現，第一種改變角度的方式，對孔道的離子整流效應影響較顯著，而且隨著角度加大時，奈米孔道的整流效應係數會出現先增加後減低的結果。第二章節，我們則是討論運用圓錐形奈米孔道的逆電析法來進行海水鹽差能發電，透過這種方式能取得乾淨的能源，是一種具有前景的再生能源。由於圓錐形奈米孔道有著不對稱形狀的特性，因此我們考慮兩種相反的離子擴散方向對海水鹽差能的影響，一種是離子從孔道的尖端往末端擴散，另一種是離子從孔道末端往尖端擴散。結果顯示第二種擴散方向能產生較好的海水鹽差能發電效果。

Due to its potential applications in biotechnology, ion current rectification (ICR) arising from the asymmetric nature of ion transport in a nanochannel has drawn the attention of researchers in various fields. In the former, the influences of the cone angle, surface charge density, and bulk salt concentration on this behavior are investigated, and mechanisms proposed to explain the results obtained. We show that if the cone angle is enlarged by fixing the nanopore tip radius and raising its base radius, the ICR ratio has a local maximum. This behavior may not present if the cone angle is enlarged by fixing the nanopore base radius and raising its tip radius. This ratio also has a local maximum as the surface charge density varies and the larger the cone angle the higher the surface charge density at which the local maximum in the ICR ratio occurs. In the latter, to assess the possibility of energy harvesting through reverse electrodialysis (RED), we consider the electrokinetic behavior of the ion transport in a pH-regulated conical nanopore connecting two large reservoirs having different bulk salt concentrations. In particular, the influences of the ion diffusion direction, the solution pH, and the bulk concentration ratio on that behavior are examined in detail, and the underlying mechanisms discussed. We show that the geometrically asymmetric nature of the nanopore yields profound and interesting phenomena arising mainly from the distribution of ions in its interior. We show that a power of 18.3 pW can be generated, and the maximum power efficiency of 0.53 achieved from a PET nanopore