Yang Qian, Lin Xingyu, Su Bin
Institute of Analytical Chemistry, Department of Chemistry, Zhejiang University , Hangzhou 310058, China.
Anal Chem. 2016 Oct 18;88(20):10252-10258. doi: 10.1021/acs.analchem.6b02968. Epub 2016 Oct 7.
An ideal molecular filtration membranes should be highly permeable and selective, thus desiring the membranes to be ultrathin, be highly porous, and consists of small and uniform pores or channels. In this work, we report the molecular filtration by free-standing ultrathin silica nanochannel membranes (SNMs) using a U-shaped cell and spectrophotometric detection, focusing on the quantitative evaluation of permeability and selectivity of SNMs. Thanks to the ultrasmall channel size, namely, ∼2-3 nm, and the negatively charged channel surface arising from the deprotonation of silanol groups, the SNM displayed excellent size and charge selectivity for molecular filtration. The selectivity coefficient for separation of small methyl viologen from large cytochrome c is as high as 273, because of the uniform pore/channel size. The charge-based filtration can be modulated by the salt concentration and solution pH, which control the overlap of radial electrical double layer and surface charge sign/density, respectively. Owing to the high relative pore density, namely, 16.7%, and the straight and vertical channel orientation, the SNM is highly permeable, displaying a molecule flux much higher than commercially available dialysis membrane and others reported previously. In addition, we demonstrated that, by biasing a small voltage across the SNM, both the flux and separation selectivity could be significantly enhanced.
理想的分子过滤膜应具有高渗透性和选择性，因此希望膜超薄、高度多孔且由小而均匀的孔或通道组成。在这项工作中，我们报告了使用U形池和分光光度检测对独立式超薄二氧化硅纳米通道膜（SNM）进行分子过滤，重点是对SNM的渗透性和选择性进行定量评估。由于通道尺寸极小，即约2-3纳米，以及硅醇基团去质子化产生的带负电的通道表面，SNM在分子过滤方面表现出优异的尺寸和电荷选择性。由于孔/通道尺寸均匀，从小甲基紫精中分离大细胞色素c的选择性系数高达273。基于电荷的过滤可以通过盐浓度和溶液pH值进行调节，它们分别控制径向双电层的重叠以及表面电荷的符号/密度。由于相对孔密度高，即16.7%，且通道方向笔直且垂直，SNM具有高渗透性，其分子通量远高于市售透析膜和先前报道的其他膜。此外，我们证明，通过在SNM上施加小电压，通量和分离选择性都可以显著提高。
