title: Subnanometre ligand-shell asymmetry leads to Janus-like nanoparticle membranes.
abstract: Self-assembly of nanoparticles at fluid interfaces has emerged as a simple yet efficient way to create two-dimensional membranes with tunable properties. 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 scaffolding 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.
authors.affiliation: Advanced Photon Source, Argonne National Laboratory, 9700 South Cass Avenue Argonne, Illinois 60439, USA.
authors.forename: Zhang
authors.initials: Z
authors.lastname: Jiang
authors.affiliation: Department of Physics and James Franck Institute, The University of Chicago, 929 East 57th Street Chicago, Illinois 60637, USA.
authors.forename: Jinbo
authors.initials: J
authors.lastname: He
authors.affiliation: Center for Nanoscale Materials, Argonne National Laboratory, 9700 South Cass Avenue Argonne, Illinois 60439, USA.
authors.forename: Sanket A
authors.initials: SA
authors.lastname: Deshmukh
authors.affiliation: Department of Physics and James Franck Institute, The University of Chicago, 929 East 57th Street Chicago, Illinois 60637, USA.
authors.forename: Pongsakorn
authors.initials: P
authors.lastname: Kanjanaboos
authors.affiliation: Center for Nanoscale Materials, Argonne National Laboratory, 9700 South Cass Avenue Argonne, Illinois 60439, USA.|Department of Chemistry, University of Missouri, 601 South College Avenue Columbia, Missouri 65211, USA.
authors.forename: Ganesh
authors.initials: G
authors.lastname: Kamath
authors.affiliation: Department of Physics and James Franck Institute, The University of Chicago, 929 East 57th Street Chicago, Illinois 60637, USA.
authors.forename: Yifan
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Center for Nanoscale Materials, Argonne National Laboratory, 9700 South Cass Avenue Argonne, Illinois 60439, USA.
authors.forename: Subramanian K R S
authors.initials: SK
authors.lastname: Sankaranarayanan
authors.affiliation: Advanced Photon Source, Argonne National Laboratory, 9700 South Cass Avenue Argonne, Illinois 60439, USA.
authors.forename: Jin
authors.initials: J
authors.lastname: Wang
authors.affiliation: Department of Physics and James Franck Institute, The University of Chicago, 929 East 57th Street Chicago, Illinois 60637, USA.
authors.forename: Heinrich M
authors.initials: HM
authors.lastname: Jaeger
authors.affiliation: Center for Nanoscale Materials, Argonne National Laboratory, 9700 South Cass Avenue Argonne, Illinois 60439, USA.
authors.forename: Xiao-Min
authors.initials: XM
authors.lastname: Lin