Ion Transport through Atomically Thin Cap74illaries

我建议以几埃为主要尺度研究离子通过毛细血管的尺寸效应（Å）。离子筛分在许多自然系统（亚纳米离子通道在细胞膜中发挥重要作用）和许多技术（包括海水淡化、化学分离、透析、生物分析等）中具有极其重要的意义。到目前为止，创造这种大小的人工通道，根据需要调整它们的属性并研究它们的功能只是一个遥远的目标。传统上，沸石和多孔聚合物膜用于离子和分子筛分，但大尺寸分布和对智能膜的追求推动了这一领域的研究。尽管在过去的几十年里取得了进步，包括使用纳米管和先进的纳米光刻技术，但这一目标甚至无法实现，因为在有限的几何形状和有限的材料中，器件尺寸很少达到真正的纳米尺度。这是一个艰巨的挑战，但也是参与这个迷人研究领域的主要原因，我想通过使用二维原子晶体来解决这个挑战。二维原子晶体非常吸引人，并提供了一条通过范德华异质结构组装制造“设计器件”的途径，通过选择材料调整其特性。如果将单个原子平面从块状晶体中移除，留下选定高度的扁平空洞；这个微小的空间在操纵流体、液体、气体、粒子和离子方面提供了如此多的东西。这不仅是纳米流体领域的突破性技术进步，而且重要的是，所提出的毛细血管为研究最终受限空间中离子传输的基本科学现象提供了一个平台。本研究的主要目的是：(1)深入研究本征离子通过这些毛细血管的输运，包括空间效应的作用、离子进出效应（尤其是当离子大小与毛细血管大小相当时）、“量子”约束对毛细血管内离子周围水化壳的影响等。如此深入的分析之所以成为可能，只是因为所提出的毛细血管是原子清洁的，并且涉及很少的表面电荷，而不像之前研究的实验系统（例如纳米管）以后者为主。(2)从离子通过这些狭缝传输的基本原理中获得见解，智能毛细血管将被构建在离子可以被垂直电场操纵的地方。该项目将在曼彻斯特大学（UoM）凝聚态物理组、率先开展石墨烯/ 2d材料研究的物理学院和国家石墨烯研究所执行。在UoM，石墨烯小组分布在物理、化学、计算机科学、材料和生命科学的许多学院，扩大了智能毛细血管可能的目标应用范围，使该项目真正成为跨学科项目。如提案中所述，我们的埃级毛细管制造方法为设计和复杂工程提供了极大的灵活性、可重复性和可能性。特别是，我们的制造过程为已经激动人心的纳米流体领域提供了一个新的方向，而不仅仅局限于一个领域。通过解决核心问题，即理解固有离子传输，同时克服利用Å-scale有限空间进行尺寸选择性离子分离的主要障碍，我的研究将影响包括海水淡化在内的广泛领域和技术，为未来具有深远社会和经济意义的应用铺平道路。

I propose to study the size effect in ion transport through capillaries with principal dimensions of few angstroms (Å). Ion sieving is of extreme importance in many natural systems (sub-nm ion channels perform important functions in cellular membranes) and in many technologies including desalination, chemical separation, dialysis, bio-analytics, etc. It has so far been only a distant goal to create artificial channels of this size, tune their properties as required and investigate their functioning. Traditionally, zeolites and porous polymer membranes are used for ionic and molecular sieving but the large size distribution and quest for smart membranes has driven the research in this area. Despite all the progress during the last decades, including the use of nanotubes and advanced nanolithography techniques, this goal could not be even approached, with device dimensions rarely reaching the true nanoscale in a limited number of geometries and with a limited number of materials. This is a formidable challenge, but also a central reason to engage in this fascinating area of research and I want to address this challenge by the use of 2D-atomic crystals. 2D-atomic crystals are highly fascinating and offer a route to the fabrication of "devices-by-design" through van der Waals heterostructure assembly with their properties tuned via chosen materials. If individual atomic planes were removed from a bulk crystal leaving behind flat voids of a chosen height; the tiny empty space has so much to offer in terms of manipulation of fluids, liquids, gases, particles and ions.Not only is this a groundbreaking technological advancement of the field of nanofluidics but also importantly the proposed capillaries offer a platform for studying fundamental scientific phenomenon of ionic transport in ultimately confined spaces. The key aims of this proposal are (1) investigation of in-depth intrinsic ion transport through these capillaries, including the role of steric effects, ion entry-exit effects especially when the size of ion is comparable to the capillary size, effect of 'quantum' confinement on the hydration shells surrounding the ions inside capillaries, etc. Such in-depth analysis is possible only because the proposed capillaries are atomically clean and involve little surface charge, unlike the previously studied experimental systems (e.g., nanotubes) dominated by the latter. (2) Gaining insights from the fundamentals of ion transport through these slits, smart capillaries will be constructed where the ions can be manipulated by a perpendicular electric field. The project will be executed at the University of Manchester (UoM) in condensed matter physics group, school of physics which has pioneered graphene/2D-materials research and National Graphene Institute. At the UoM, the graphene group is spread across many schools in the faculty of physics, chemistry, computer science, materials and life sciences, widening the scope of the possible target applications of the smart capillaries and making the project truly interdisciplinary. Our fabrication approach of angstrom-scale capillaries offers a great flexibility, reproducibility and possibility for design and sophisticated engineering, as described in the proposal. In particular, our fabrication procedures provide a new direction for the already exciting large field of nanofluidics but are not limited to only one area. By tackling a core issue i.e., understanding the intrinsic ion transport, alongside overcoming the primary obstacle to exploiting Å-scale confined spaces for size-selective ion separation, my research will impact across a broad range of fields and technologies including desalination, paving the way to future applications of far-reaching social and economic importance.