Nanofluidics and Ultrafiltration with track-etched Graphen-Polymer Composite Membranes

膜可用于多种应用。作为渗透选择性屏障，它们可以用作分离膜，例如，超滤，透析，水净化或气体分离。在更一般的情况下，它们也可以用作化学、物理或电屏障，例如，在保护膜、电容器或传感器中。对于所有这些应用，使膜尽可能薄，同时在机械和化学上尽可能坚固是有利的。根据这些标准，石墨烯似乎代表了理想的材料，因为它的机械强度和无限小的厚度只有3 Å。完美的石墨烯对所有气体和液体都是不渗透的，而穿孔的石墨烯在过滤应用中具有前所未有的传输速率，因为准二维选择性膜将表现出可以忽略不计的壁间相互作用。因此，对于膜技术来说，基于石墨烯的新型复合材料可以提供传统材料无法实现的显著改进。本提案的主要目标如下：我们的目标是开发一种由石墨烯和聚合物膜组成的坚固复合材料的制造工艺，该复合材料将被进一步加工以生产与技术分离相关的超滤（UF）或纳滤（NF）膜，其中选择性元素是单个人工穿孔的石墨烯层。将对这些超滤膜和纳滤膜的性能进行评估，并阐明其制造和分离过程的潜在机制。复合材料的穿孔将通过一种成熟的技术来实现，即用快速重离子照射，从而控制石墨烯的孔隙密度和大小。这些孔隙将具有非常窄的尺寸分布（等孔），它们的尺寸可以在5到50 nm^2的范围内选择，从而提供了高度的选择性。通过使用另一种被称为轨迹蚀刻的成熟技术，选择性屏障孔将连接到支撑聚合物膜上的较大孔，从而产生独特的UF或NF复合膜。孔入口的功能化，特别是带电荷基团的功能化，可以用来进一步提高选择性，这样甚至可以使水脱盐。由于通过二维势垒层的传输不受壁面相互作用的阻碍，因此需要非常低的压力。因此，预计超滤膜或纳滤膜的目标原型将比现有材料的性能高出约100倍（就相同选择性下的更高通量而言），这将大大节省能源。然而，将这种高通量膜集成到模块中的适当概念也是绝对必要的，因此在这个项目中，基于石墨烯的微/纳米流体分离系统将被设计和研究，作为实现这种全新膜的第一步。

Membranes can be used in a plethora of applications. As permeation-selective barrier they may serve as a separation membrane, for e.g., ultrafiltration, dialysis, water purification, or gas separation. In a more general context, they can also be used as a chemical, physical, or electrical barrier, e.g., in protective films, capacitors, or as sensors. For all these applications it is advantageous to make the membrane as thin as possible and at the same time as mechanically and chemically robust as possible. With respect to these criteria, graphene seems to represent the ideal material due to its mechanical strength and infinitesimal thickness of only 3 Å. Perfect graphene is impermeable for all gases and liquids and perforated graphene promises an unprecedented level of transport rates in filtering applications as the quasi two-dimensional selective membrane would exhibit negligible wall interactions. Thus, for membrane technologies novel composites based on graphene can offer significant improvements unachievable by conventional materials. The main goals of this proposal are the following: We aim to develop a process for the manufacturing of robust composites consisting of graphene and a polymer film, which will be processed further to produce ultrafiltration (UF) or nanofiltration (NF) membranes with relevance for technical separations, where the selective element is a single, artificially perforated layer of graphene. The performance of these UF and NF membranes will be assessed and the underlying mechanisms of manufacturing and separation processes will be elucidated. The perforation of the composite will be achieved by an established technology, i.e. the irradiation with swift heavy ions, enabling to control pore density and size in graphene. These pores will have a very narrow size distribution (isoporous) and their size can be selected in the range from 5 to 50 nm^2 thus offering a high degree of selectivity. By using another established technology known as track-etching, the selective barrier pores will be connected to larger pores in the supporting polymer film, yielding a unique composite UF or NF membrane. Functionalization of the pore entrance, in particular with charged groups, can be used to further increase selectivity so that even desalination of water may be feasible. As the transport through the 2D barrier layer is not hindered by wall interactions very low pressures are needed. It is therefore expected that the targeted membrane prototypes for UF or NF will outperform current materials by a factor of ~100 (in terms of higher fluxes at same selectivity) which would enable substantial energy savings. However, appropriate concepts for integration of such high flux membranes into modules are also absolutely necessary and therefore in this project micro-/nanofluidic separation systems based on graphene will be designed and investigated as first steps towards implementation of such radically novel membranes.