Two-dimensional Na-Cl crystals of unconventional stoichiometries on graphene surface from dilute solution at ambient conditions
Two-dimensional Na-Cl crystals of unconventional stoichiometries on graphene surface from dilute solution at ambient conditions
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DOI：
10.1038/s41557-018-0061-4
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发表时间：
2018-07-01
期刊：
影响因子：
21.8
通讯作者：
Fang, Haiping
中科院分区：
文献类型：
--
作者：
Shi, Guosheng;Chen, Liang;Fang, Haiping
在环境条件下，化学计量比为1:1的氯化钠是钠 - 氯晶体唯一已知的稳定形式，非1:1的钠 - 氯物质只能在极端条件下（如高压）形成。在此，我们报道在环境条件下，从远低于饱和浓度的盐溶液中，在还原氧化石墨烯膜以及天然石墨粉末表面，观察到了Na₂Cl和Na₃Cl作为二维（2D）钠 - 氯晶体与常规氯化钠一同存在。分子动力学和密度泛函理论计算表明，这种非常规的结晶过程源于离子与石墨表面的π共轭体系之间的阳离子 - π相互作用，这种作用促进了离子 - 表面吸附。强烈的Na⁺ - π相互作用和电荷转移导致化学计量比中Na⁺过量。由于具有独特的电子和自旋分布以及化学键合，所得到的二维晶体可能具有不寻常的电学、磁学、光学和力学性质。
NaCl in a 1:1 stoichiometry is the only known stable form of the Na-Cl crystal under ambient conditions, and non-1:1 Na-Cl species can only form under extreme conditions, such as high pressures. Here we report the direct observation, under ambient conditions, of Na2Cl and Na3Cl as two-dimensional (2D) Na-Cl crystals, together with regular NaCl, on reduced graphene oxide membranes and on the surfaces of natural graphite powders from salt solutions far below the saturated concentration. Molecular dynamics and density functional theory calculations suggest that this unconventional crystallization process originates from the cation-pi interaction between the ions and the pi-conjugated system in the graphitic surface, which promotes the ion-surface adsorption. The strong Na+-pi interaction and charge transfer lead to stoichiometries with an excess of Na+. With unique electron and spin distributions and bonding, the resulting 2D crystals may have unusual electronic, magnetic, optical and mechanical properties.