Key Laboratory of Chemistry of Northwestern Plant Resources and Key Laboratory for Natural Medicine of Gansu Province, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences , Lanzhou 730000, China.
Institute of Modern Physics, Chinese Academy of Sciences , Lanzhou 730000, China.
Anal Chem. 2016 Oct 18;88(20):10002-10010. doi: 10.1021/acs.analchem.6b02175. Epub 2016 Sep 22.
Graphene-coated plastic substrates, such as polyethylene terephthalate (PET), are regularly used in flexible electronic devices. Here we demonstrate a new application of the graphene-coated nanoporous PET membrane for the selective separation of metal ions in an ion exchange manner. Irradiation with swift heavy ions is used to perforate graphene and PET substrate. This process could create graphene nanopores with carboxyl groups, thus forming conical holes in the PET after chemical etching to support graphene nanopores. Therefore, a monolayer nanoporous graphene membrane with a PET substrate is constructed successfully to investigate its ionic selective separation. We find that the permeation ratio of ions strongly depends on the temperature and H concentration in the driving solution. An electric field can increase the permeation ratio of ions through the graphene nanopores, but it inhibits the ion selective separation. Moreover, the structure of the graphene nanopore with carboxyl groups is resolved at the density functional theory level. The results show the asymmetric structure of the nanopore with carboxyl groups, and the analysis indicates that the ionic permeation can be attributed to the ion exchange between metal ions and protons on the two sides of graphene nanopores. These results would be beneficial to the design of membrane separation materials made from graphene with efficient online and offline bulk separation.
石墨烯涂覆的塑料基底，如聚对苯二甲酸乙二醇酯（PET），常用于柔性电子设备。在这里，我们展示了石墨烯涂覆的纳米多孔 PET 膜在离子交换方式下选择性分离金属离子的新应用。利用高速重离子辐照来穿孔石墨烯和 PET 基底。这一过程可以在化学刻蚀后在 PET 上形成具有羧基的石墨烯纳米孔，从而支撑石墨烯纳米孔。因此，成功构建了具有 PET 基底的单层纳米多孔石墨烯膜，以研究其离子选择性分离。我们发现，离子的渗透比强烈依赖于驱动溶液中的温度和 H 浓度。电场可以增加离子通过石墨烯纳米孔的渗透比，但会抑制离子的选择性分离。此外，通过密度泛函理论水平解析了具有羧基的石墨烯纳米孔的结构。结果表明，具有羧基的纳米孔具有不对称结构，分析表明离子的渗透可以归因于金属离子与石墨烯纳米孔两侧质子之间的离子交换。这些结果有助于设计具有高效在线和离线整体分离的石墨烯膜分离材料。
