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Two-dimensional Na–Cl crystals of unconventional stoichiometries on graphene surface from dilute solution at ambient conditions

Nature Chemistryvolume 10pages776779 (2018) | Download Citation


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–π interaction between the ions and the π-conjugated system in the graphitic surface, which promotes the ion–surface adsorption. The strong Na+π 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.

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We thank P. Ball, Y. Tu, R. Wan and Y. Gao for their constructive suggestions. Support from the National Science Fund for Outstanding Young Scholars (no. 11722548), the National Natural Science Foundation of China (no. 11574339, 41430644, 11404361 and 21671131), the Scientific Research and Developed Fund of Zhejiang A & F University (no. 2017FR032), the Key Research Program of the Chinese Academy of Sciences (no. KJZD-EW-M03), the Key Research Program of Frontier Sciences of the Chinese Academy of Sciences (no. QYZDJ-SSW-SLH053), the Deepcomp7000 and ScGrid of the Supercomputing Center, Computer Network Information Center of Chinese Academy of Sciences, the Special Program for Applied Research on SuperComputation of the NSFC-Guangdong Joint Fund (the second phase) and the Supercomputer Center of CAS is acknowledged.

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Author notes

  1. These authors contributed equally to this work: Guosheng Shi, Liang Chen and Yizhou Yang.


  1. Division of Interfacial Water and Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, China

    • Guosheng Shi
    • , Yizhou Yang
    • , Deyuan Li
    • , Shanshan Liang
    • , Long Yan
    •  & Haiping Fang
  2. Shanghai Applied Radiation Institute, Shanghai University, Shanghai, China

    • Liang Chen
    • , Zhe Qian
    •  & Minghong Wu
  3. Zhejiang Provincial Key Laboratory of Chemical Utilization of Forestry Biomass, Zhejiang A&F University, Linan, China

    • Liang Chen
  4. Institute for Frontier Materials (IFM), Deakin University, Victoria, Australia

    • Lu Hua Li


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H.-P.F. had the idea to observe Na–Cl crystals in the rGO membranes in salt solutions of concentrations below the saturated concentration based on the ion–π interactions. H.-P.F., M.-H.W., G.-S.S. and L.Y. conceived and designed the experiments and simulations. L.C., G.-S.S., D.-Y.L. and Z.Q. performed the experiments. G.-S.S. and Y.-Z.Y. performed the simulations. G.-S.S., L.C., H.-P.F., S.-S.L. and L.-H.L. analysed the data, G.-S.S., L.C., H.-P.F. and M.-H.W. co-wrote the paper. All the authors discussed the results and commented on the manuscript.

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The authors declare no competing interests.

Corresponding authors

Correspondence to Minghong Wu or Haiping Fang.

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