School of Materials Science and Engineering, State Key Laboratory of New Ceramics and Fine Processing, Key Laboratory of Materials Processing Technology of MOE, ‡Center for Nano and Micro Mechanics, §Department of Engineering Mechanics, and ⊥Department of Mechanical Engineering, Tsinghua University , Beijing 100084, P. R. China.
ACS Nano. 2014 Jan 28;8(1):850-9. doi: 10.1021/nn4055682. Epub 2014 Jan 10.
Graphene and graphene oxide (G-O) have been demonstrated to be excellent filters for various gases and liquids, showing potential applications in areas such as molecular sieving and water desalination. In this paper, the selective trans-membrane transport properties of alkali and alkaline earth cations through a membrane composed of stacked and overlapped G-O sheets ("G-O membrane") are investigated. The thermodynamics of the ion transport process reveal that the competition between the generated thermal motions and the interactions of cations with the G-O sheets results in the different penetration behaviors to temperature variations for the considered cations (K(+), Mg(2+), Ca(2+), and Ba(2+)). The interactions between the studied metal atoms and graphene are quantified by first-principles calculations based on the plane-wave-basis-set density functional theory (DFT) approach. The mechanism of the selective ion trans-membrane transportation is discussed further and found to be consistent with the concept of cation-π interactions involved in biological systems. The balance between cation-π interactions of the cations considered with the sp(2) clusters of G-O membranes and the desolvation effect of the ions is responsible for the selectivity of G-O membranes toward the penetration of different ions. These results help us better understand the ion transport process through G-O membranes, from which the possibility of modeling the ion transport behavior of cellular membrane using G-O can be discussed further. The selectivity toward different ions also makes G-O membrane a promising candidate in areas of membrane separations.
石墨烯和氧化石墨烯（G-O）已被证明是各种气体和液体的优良滤膜，在分子筛和海水淡化等领域有潜在的应用。本文研究了由堆叠和重叠的 G-O 片组成的膜（“G-O 膜”）对碱金属和碱土金属阳离子的选择性跨膜传输性质。离子传输过程的热力学表明，产生的热运动与阳离子与 G-O 片之间的相互作用之间的竞争导致考虑的阳离子（K(+)、Mg(2+)、Ca(2+)和 Ba(2+)）对温度变化的穿透行为不同。基于平面波基密度泛函理论（DFT）方法的第一性原理计算，定量了研究金属原子与石墨烯之间的相互作用。进一步讨论了选择性离子跨膜运输的机制，发现其与生物系统中涉及的阳离子-π相互作用的概念一致。考虑的阳离子与 G-O 膜的 sp(2)簇之间的阳离子-π相互作用与离子的去溶剂化效应之间的平衡，是 G-O 膜对不同离子渗透选择性的原因。这些结果有助于我们更好地理解通过 G-O 膜的离子传输过程，从而可以进一步讨论使用 G-O 对细胞膜离子传输行为进行建模的可能性。对不同离子的选择性也使 G-O 膜成为膜分离领域有前途的候选材料。
