title: Substantial Difference in Ordering of 10, 15, and 20 nm Iron Oxide Nanoparticles on a Water Surface: In Situ Characterization by the Grazing Incidence X-ray Scattering.
abstract: In the present study, for the first time, a unique combination of in situ grazing incidence small-angle X-ray scattering and X-ray reflectivity, accompanied by the pressure-area isotherm analysis, Brewster angle microscopy, and ex situ scanning electron microscopy, was applied for investigation of two-dimensional superlattices of magnetic nanoparticles as they form on a water surface in a Langmuir trough. Iron oxide particles of different sizes stabilized with a single layer of oleic acid were used. It is demonstrated that monodisperse 10 nm particles on a water surface reproducibly form identical highly ordered monolayers in a wide range of experimental conditions, while monodisperse 20 nm particles always form compact three-dimensional clusters and never the monolayers. Monodisperse particles of an intermediate size, 15 nm in diameter, build a metastable monolayer, which shows a tendency for spontaneous transformation to bi-, tri-, and multilayer islands. The importance to use both grazing incidence small-angle X-ray scattering and X-ray reflectivity together with the complementary techniques, to avoid misinterpretation of separate experimental data sets, is underlined.
authors.affiliation: Department of Physics and Astronomy, Uppsala University , Box 516, 751 20 Uppsala, Sweden.|European Synchrotron Radiation Facility , 71 Avenue des Martyrs, CS 40220, 38043 Grenoble Cedex 9, France.
authors.forename: A
authors.initials: A
authors.lastname: Vorobiev
authors.affiliation: European Synchrotron Radiation Facility , 71 Avenue des Martyrs, CS 40220, 38043 Grenoble Cedex 9, France.|Organic Materials and Devices, Friedrich-Alexander-Universität Erlangen-Nürnberg , Martensstraße 7, 91058 Erlangen, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Khassanov
authors.affiliation: Department of Physics and Astronomy, Uppsala University , Box 516, 751 20 Uppsala, Sweden.|Petersburg Nuclear Physics Institute , Orlova Roscha, Gatchina, St. Petersburg 188300, Russia.
authors.forename: V
authors.initials: V
authors.lastname: Ukleev
authors.affiliation: European Synchrotron Radiation Facility , 71 Avenue des Martyrs, CS 40220, 38043 Grenoble Cedex 9, France.
authors.forename: I
authors.initials: I
authors.lastname: Snigireva
authors.affiliation: European Synchrotron Radiation Facility , 71 Avenue des Martyrs, CS 40220, 38043 Grenoble Cedex 9, France.
authors.forename: O
authors.initials: O
authors.lastname: Konovalov