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Subnanometre ligand-shell asymmetry leads to Janus-like nanoparticle membranes



Self-assembly of nanoparticles at fluid interfaces has emerged as a simple yet efficient way to create two-dimensional membranes with tunable properties1,2,3,4,5,6. In these membranes, inorganic nanoparticles are coated with a shell of organic ligands that interlock as spacers and provide tensile strength. Although curvature due to gradients in lipid-bilayer composition and protein scaffolding7,8 is a key feature of many biological membranes, creating gradients in nanoparticle membranes has been difficult. Here, we show by X-ray scattering that nanoparticle membranes formed at air/water interfaces exhibit a small but significant 6 Å difference in average ligand-shell thickness between their two sides. This affects surface-enhanced Raman scattering and can be used to fold detached free-standing membranes into tubes by exposure to electron beams. Molecular dynamics simulations elucidate the roles of ligand coverage and mobility in producing and maintaining this asymmetry. Understanding this Janus-like membrane asymmetry opens up new avenues for designing nanoparticle superstructures.

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Figure 1: Folding of a detached Au nanoparticle membrane into tubes induced by SEM.
Figure 2: Qualitative surface-enhanced Raman scattering (SERS) measurement showing the asymmetric ligand shell of the membrane.
Figure 3: GISAXS results and analyses on draped and stamped monolayers.
Figure 4: Coarse-grained molecular dynamics simulations showing asymmetry in ligand distribution for single nanoparticles and their self-assembled array residing at the air/water interface.


  1. McGorty, R., Fung, J., Kaz, D. & Manoharan, V. N. Colloidal self-assembly at an interface. Mater. Today 13, 34–42 (June, 2010).

    Article  CAS  Google Scholar 

  2. Bresme, F. & Oettel, M. Nanoparticles at fluid interfaces. J. Phys. Condens. Matter 19, 413101–413133 (2007).

    Article  CAS  Google Scholar 

  3. Lin, Y., Skaff, H., Emrick, T., Dinsmore, A. D. & Russell, T. P. Nanoparticle assembly and transport at liquid–liquid interfaces. Science 299, 226–229 (2003).

    Article  CAS  Google Scholar 

  4. Boker, A., He, J., Emrick, T. & Russell, T. P. Self-assembly of nanoparticles at interfaces. Soft Matter 3, 1231–1248 (2007).

    Article  Google Scholar 

  5. Cheng, W. et al. Free-standing nanoparticle superlattice sheets controlled by DNA. Nature Mater. 8, 519–525 (2009).

    Article  CAS  Google Scholar 

  6. Dong, A., Chen, J., Vora, P. M., Kikkawa, J. M. & Murray, C. B. Binary nanocrystal superlattice membranes self-assembled at the liquid–air interface. Nature 466, 474–477 (2010).

    Article  CAS  Google Scholar 

  7. Zimmerberg, J. & Kozlov, M. M. How proteins produce cellular membrane curvature. Nature Rev. Mol. Cell Biol. 7, 9–19 (2006).

    Article  CAS  Google Scholar 

  8. McMahon, H. T. & Gallop, J. L. Membrane curvature and mechanisms of dynamic cell membrane remodelling. Nature 438, 590–596 (2005).

    Article  CAS  Google Scholar 

  9. Mueggenburg, K. E., Lin, X. M., Goldsmith, R. H. & Jaeger, H. M. Elastic membranes of close-packed nanoparticle arrays. Nature Mater. 6, 656–660 (2007).

    Article  CAS  Google Scholar 

  10. He, J. B. et al. Fabrication and mechanical properties of large-scale freestanding nanoparticle membranes. Small 6, 1449–1456 (2010).

    Article  CAS  Google Scholar 

  11. Lin, Y. et al. Ultrathin cross-linked nanoparticle membranes. J. Am. Chem. Soc. 125, 12690–12691 (2003).

    Article  CAS  Google Scholar 

  12. Hill, W. & Wehling, B. Potential-dependent and Ph-dependent surface-enhanced Raman-scattering of p-mercaptoaniline on silver and gold substrates. J. Phys. Chem. 97, 9451–9455 (1993).

    Article  CAS  Google Scholar 

  13. Liu, G. K. et al. Laser-induced formation of metal–molecule–metal junctions between Au nanoparticles as probed by surface-enhanced Raman spectroscopy. J. Phys. Chem. C 112, 6499–6508 (2008).

    Article  CAS  Google Scholar 

  14. Narayanan, S., Wang, J. & Lin, X. M. Dynamical self-assembly of nanocrystal superlattices during colloidal droplet evaporation by in situ small angle x-ray scattering. Phys. Rev. Lett. 93, 135503 (2004).

    Article  Google Scholar 

  15. Vegso, K. et al. Silver nanoparticle monolayer-to-bilayer transition at the air/water interface as studied by the GISAXS technique: Application of a new paracrystal model. Langmuir 28, 9395–9404 (2012).

    Article  CAS  Google Scholar 

  16. Smith, D. K., Goodfellow, B., Smilgies, D. M. & Korgel, B. A. Self-assembled simple hexagonal AB(2) binary nanocrystal superlattices: SEM, GISAXS, and defects. J. Am. Chem. Soc. 131, 3281–3290 (2009).

    Article  CAS  Google Scholar 

  17. Pietra, F. et al. Semiconductor nanorod self-assembly at the liquid/air interface studied by in situ GISAXS and ex situ TEM. Nano Lett. 12, 5515–5523 (2012).

    Article  CAS  Google Scholar 

  18. Jiang, Z., Lin, X. M., Sprung, M., Narayanan, S. & Wang, J. Capturing the crystalline phase of two-dimensional nanocrystal superlattices in action. Nano Lett. 10, 799–803 (2010).

    Article  CAS  Google Scholar 

  19. Jiang, Z., Lee, D. R., Narayanan, S., Wang, J. & Sinha, S. K. Waveguide-enhanced grazing-incidence small-angle x-ray scattering of buried nanostructures in thin films. Phys. Rev. B 84, 075440 (2011).

    Article  Google Scholar 

  20. McCarley, R. L., Dunaway, D. J. & Willicut, R. J. Mobility of the alkanethiol-gold (111) interface studied by scanning probe microscopy. Langmuir 9, 2775–2777 (1993).

    Article  CAS  Google Scholar 

  21. Norgaard, K., Weygand, M. J., Kjaer, K., Brust, M. & Bjornholm, T. Adaptive chemistry of bifunctional gold nanoparticles at the air/water interface. A synchrotron X-ray study of giant amphiphiles. Faraday Discuss. 125, 221–233 (2004).

    Article  CAS  Google Scholar 

  22. Glogowski, E., He, J. B., Russell, T. P. & Emrick, T. Mixed monolayer coverage on gold nanoparticles for interfacial stabilization of immiscible fluids. Chem. Commun. 32, 4050–4052 (2005).

    Article  Google Scholar 

  23. Pensa, E. et al. The chemistry of the sulfur–gold interface: In search of a unified model. Acc. Chem. Res. 45, 1183–1192 (2012).

    Article  CAS  Google Scholar 

  24. Tay, K. A. & Bresme, F. Wetting properties of passivated metal nanocrystals at liquid–vapor interfaces: A computer simulation study. J. Am. Chem. Soc. 128, 14166–14175 (2006).

    Article  CAS  Google Scholar 

  25. Lane, J. M. D. & Grest, G. S. Spontaneous asymmetry of coated spherical nanoparticles in solution and at liquid–vapor interfaces. Phys. Rev. Lett. 104, 235501 (2010).

    Article  Google Scholar 

  26. Freund, L. B. & Suresh, S. Thin Film Materials: Stress, Defect Formation and Surface Evolution (Cambridge Univ. Press, 2003).

    Google Scholar 

  27. Schmidt, Q. G. & Eberl, K. Thin solid films roll up into nanotubes. Nature 410, 168 (2001).

    Article  CAS  Google Scholar 

  28. Tadaki, T., Otsuka, K. & Shimizu, K. Shape memory alloys. Annu. Rev. Mater. Sci. 18, 25–45 (1988).

    Article  CAS  Google Scholar 

  29. Deserno, M. Fluid lipid membranes: From differential geometry to curvature stresses. Chem. Phys. Lipids 185, 11–45 (2015).

    Article  CAS  Google Scholar 

  30. Kanjanaboos, P., Joshi-Imre, A., Lin, X. M. & Jaeger, H. M. Strain patterning and direct measurement of Poisson’s ratio in nanoparticle mono layer sheets. Nano Lett. 11, 2567–2571 (2011).

    Article  CAS  Google Scholar 

  31. Scheffer, L., Bitler, A., Ben-Jacob, E. & Korenstein, R. Atomic force pulling: Probing the local elasticity of the cell membrane. Eur. Biophys. J. 30, 83–90 (2001).

    Article  CAS  Google Scholar 

  32. Blees, M., Rose, P., Barnard, A., Roberts, S. & McEuen, P. L. American Physical Society March Meeting (2014);

    Google Scholar 

  33. Zharnikov, M. & Grunze, M. Modification of thiol-derived self-assembling monolayers by electron and X-ray irradiation: Scientific and lithographic aspects. J. Vac. Sci. Technol. B 20, 1793–1807 (2002).

    Article  CAS  Google Scholar 

  34. Zhou, C., Trionfi, A., Hsu, J. W. P. & Walker, A. V. Electron-beam-induced damage of alkanethiolate self-assembled monolayers (SAMs): Dependence on monolayer structure and substrate conductivity. J. Phys. Chem. C 114, 9362–9369 (2010).

    Article  CAS  Google Scholar 

  35. Marrink, S. J., Risselada, H. J., Yefimov, S., Tieleman, D. P. & de Vries, A. H. The MARTINI force field: Coarse grained model for biomolecular simulations. J. Phys. Chem. B 111, 7812–7824 (2007).

    Article  CAS  Google Scholar 

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The authors thank S. McBride and E. Barry for many stimulating discussions. We also benefited from discussions with Y. Rabin of Ilan University, Israel, and R. Salvarezza of INIFTA, Argentina. This work was performed at the Center of Nanoscale Materials and 8-ID at the Advanced Photon Source, a US Department of Energy, Office of Science, Office of Basic Energy Sciences User Facility under Contract No. DE-AC02-06CH11357. The work at the University of Chicago was supported by the NSF through grant DMR-1207204 and through the Chicago MRSEC, under NSF DMR-1420709. This research used resources of the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the US Department of Energy under Contract No. DE-AC02-05CH11231. This research also used resources of the Argonne Leadership Computing Facility, which is a DOE Office of Science User Facility supported under Contract DE-AC02-06CH11357.

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Authors and Affiliations



Z.J., J.H. and X-M.L. performed the GISAXS experiments and Z.J. and J.W. analysed the data. P.K., Y.W. and X-M.L. carried out the SEM study of the membrane-folding experiment. J.H. performed the Raman study of the monolayer. X-M.L. synthesized the nanoparticles used. S.K.R.S.S. guided the simulation effort. S.A.D., G.K. and S.K.R.S.S. performed and analysed the coarse-grained molecular dynamics simulation. J.W., H.M.J. and X-M.L. conceived the project and designed the experiments. All authors contributed to the preparation of the manuscript.

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Correspondence to Xiao-Min Lin.

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Jiang, Z., He, J., Deshmukh, S. et al. Subnanometre ligand-shell asymmetry leads to Janus-like nanoparticle membranes. Nature Mater 14, 912–917 (2015).

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