Abstract
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.
Access options
Subscribe to Journal
Get full journal access for 1 year
$169.00
only $14.08 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
from$8.99
All prices are NET prices.




References
- 1.
Yuyama, K.-I., George, J., Thomas, K. G., Sugiyama, T. & Masuhara, H. Two-dimensional growth rate control of l-phenylalanine crystal by laser trapping in unsaturated aqueous solution. Cryst. Growth Des. 16, 953–960 (2016).
- 2.
Yuyama, K., Rungsimanon, T., Sugiyama, T. & Masuhara, H. Selective fabrication of α- and γ-polymorphs of glycine by intense polarized continuous wave laser beams. Cryst. Growth Des. 12, 2427–2434 (2012).
- 3.
Niinomi, H. et al. Plasmonic heating-assisted laser-induced crystallization from a NaClO3 unsaturated mother solution. Cryst. Growth Des. 17, 809–818 (2017).
- 4.
Murdaugh, A. E., Liddelow, M., Schmidt, A. M. & Manne, S. Two-dimensional crystal growth from undersaturated solutions. Langmuir. 23, 5852–5856 (2007).
- 5.
Zhang, W. et al. Unexpected stable stoichiometries of sodium chlorides. Science 342, 1502–1505 (2013).
- 6.
Dong, X. et al. A stable compound of helium and sodium at high pressure. Nat. Chem. 9, 440–445 (2017).
- 7.
Zhang, L., Wang, Y., Lv, J. & Ma, Y. Materials discovery at high pressures. Nat. Rev. Mater. 2, 17005 (2017).
- 8.
Bykov, M. et al. High-pressure phase transformations in TiPO4: a route to pentacoordinated phosphorus. Angew. Chem. Int. Ed. 55, 15053–15057 (2016).
- 9.
Zimmermann, N. E. R., Vorselaars, B., Quigley, D. & Peters, B. Nucleation of NaCl from aqueous solution: critical sizes, ion-attachment kinetics, and rates. J. Am. Chem. Soc. 137, 13352–13361 (2015).
- 10.
Wang, Y. & Ma, Y. Perspective: crystal structure prediction at high pressures. J. Chem. Phys. 140, 040901 (2014).
- 11.
Lanaro, G. & Patey, G. Birth of NaCl crystals: insights from molecular simulations. J. Phys. Chem. B 120, 9076–9087 (2016).
- 12.
Tassel, C. et al. High-pressure synthesis of manganese oxyhydride with partial anion order. Angew. Chem. Int. Ed. 55, 9667–9670 (2016).
- 13.
Eda, G., Fanchini, G. & Chhowalla, M. Large-area ultrathin films of reduced graphene oxide as a transparent and flexible electronic material. Nat. Nanotechnol. 3, 270–274 (2008).
- 14.
Brar, V. W. et al. Gate-controlled ionization and screening of cobalt adatoms on a graphene surface. Nat. Phys. 7, 43–47 (2011).
- 15.
Profeta, G., Calandra, M. & Mauri, F. Phonon-mediated superconductivity in graphene by lithium deposition. Nat. Phys. 8, 131–134 (2012).
- 16.
Kim, H. W. et al. Selective gas transport through few-layered graphene and graphene oxide membranes. Science 342, 91–95 (2013).
- 17.
Liu, G., Jin, W. & Xu, N. Graphene-based membranes. Chem. Soc. Rev. 44, 5016–5030 (2015).
- 18.
Lozada-Hidalgo, M. et al. Sieving hydrogen isotopes through two-dimensional crystals. Science 351, 68–70 (2016).
- 19.
Liang, L., Xu, Y., Lei, Y. & Liu, H. 1-dimensional AgVO3 nanowires hybrid with 2-dimensional graphene nanosheets to create 3-dimensional composite aerogels and their improved electrochemical properties. Nanoscale 6, 3536–3539 (2014).
- 20.
Moon, I. K., Lee, J., Ruoff, R. S. & Lee, H. Reduced graphene oxide by chemical graphitization. Nat. Commun. 1, 73 (2010).
- 21.
Swanson, H. E. et al. Standard X-ray Diffraction Powder Patterns Vol. 2, Circular 539 (National Bureau of Standards, Washington, 1953).
- 22.
Lee, D. K. et al. Water-soluble epitaxial NaCl thin film for fabrication of flexible devices. Sci. Rep. 7, 8716 (2017).
- 23.
Ma, J. C. & Dougherty, D. A. The cation–π interaction. Chem. Rev. 97, 1303–1324 (1997).
- 24.
Xiu, X., Puskar, N. L., Shanata, J. A. P., Lester, H. A. & Dougherty, D. A. Nicotine binding to brain receptors requires a strong cation–π interaction. Nature 458, 534 (2009).
- 25.
Shi, G. et al. Ion enrichment on the hydrophobic carbon-based surface in aqueous salt solutions due to cation–π interactions. Sci. Rep. 3, 3436 (2013).
- 26.
Mahadevi, A. S. & Sastry, G. N. Cation–π interaction: its role and relevance in chemistry, biology, and material science. Chem. Rev. 113, 2100–2138 (2013).
- 27.
Shi, G. et al. Molecular-scale hydrophilicity induced by solute: molecular-thick charged pancakes of aqueous salt solution on hydrophobic carbon-based surfaces. Sci. Rep. 4, 6793 (2014).
- 28.
Liu, J., Shi, G., Guo, P., Yang, J. & Fang, H. Blockage of water flow in carbon nanotubes by ions due to interactions between cations and aromatic rings. Phys. Rev. Lett. 115, 164502 (2015).
- 29.
Shi, G. et al. Unexpectedly enhanced solubility of aromatic amino acids and peptides in an aqueous solution of divalent transition-metal cations. Phys. Rev. Lett. 117, 238102 (2016).
- 30.
Gebbie, M. A. et al. Tuning underwater adhesion with cation–π interactions. Nat. Chem. 9, 473–479 (2017).
- 31.
Chen, L. et al. Ion sieving in graphene oxide membranes via cationic control of interlayer spacing. Nature 550, 380–383 (2017).
- 32.
Patra, N., Wang, B. & Král, P. Nanodroplet activated and guided folding of graphene nanostructures. Nano Lett. 9, 3766–3771 (2009).
- 33.
Falk, K., Sedlmeier, F., Joly, L., Netz, R. R. & Bocquet, L. Molecular origin of fast water transport in carbon nanotube membranes: superlubricity versus curvature dependent friction. Nano Lett. 10, 4067–4073 (2010).
Acknowledgements
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.
Author information
Affiliations
Contributions
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.
Corresponding authors
Ethics declarations
Competing interests
The authors declare no competing interests.
Additional information
Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
About this article
Cite this article
Shi, G., Chen, L., Yang, Y. et al. Two-dimensional Na–Cl crystals of unconventional stoichiometries on graphene surface from dilute solution at ambient conditions. Nature Chem 10, 776–779 (2018). https://doi.org/10.1038/s41557-018-0061-4
Received:
Accepted:
Published:
Issue Date:
Further reading
-
Artificial channels for confined mass transport at the sub-nanometre scale
Nature Reviews Materials (2021)
-
Toward two-dimensional ionic crystals with intrinsic ferromagnetism
Physics Letters A (2021)
-
Association of Lennard-Jones particles in nanoconfined aqueous solution: Theory and molecular dynamics simulations
Physica A: Statistical Mechanics and its Applications (2021)
-
Remarkable Antibacterial Activity of Reduced Graphene Oxide Functionalized by Copper Ions
Advanced Functional Materials (2021)
-
Poly(vinyl alcohol)/Carboxyl Graphene Membranes for Ethanol Dehydration by Pervaporation
Chemical Engineering & Technology (2020)