title: Tuning the structure and habit of iron oxide mesocrystals.
abstract: A precise control over the meso- and microstructure of ordered and aligned nanoparticle assemblies, i.e., mesocrystals, is essential in the quest for exploiting the collective material properties for potential applications. In this work, we produced evaporation-induced self-assembled mesocrystals with different mesostructures and crystal habits based on iron oxide nanocubes by varying the nanocube size and shape and by applying magnetic fields. A full 3D characterization of the mesocrystals was performed using image analysis, high-resolution scanning electron microscopy and Grazing Incidence Small Angle X-ray Scattering (GISAXS). This enabled the structural determination of e.g. multi-domain mesocrystals with complex crystal habits and the quantification of interparticle distances with sub-nm precision. Mesocrystals of small nanocubes (l = 8.6-12.6 nm) are isostructural with a body centred tetragonal (bct) lattice whereas assemblies of the largest nanocubes in this study (l = 13.6 nm) additionally form a simple cubic (sc) lattice. The mesocrystal habit can be tuned from a square, hexagonal to star-like and pillar shapes depending on the particle size and shape and the strength of the applied magnetic field. Finally, we outline a qualitative phase diagram of the evaporation-induced self-assembled superparamagnetic iron oxide nanocube mesocrystals based on nanocube edge length and magnetic field strength.
authors.affiliation: Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, Sweden. erik.wetterskog@angstrom.uu.se gersal@protonmail.com and Department of Engineering Sciences, Ångström Laboratory, Uppsala University, Sweden.
authors.forename: Erik
authors.initials: E
authors.lastname: Wetterskog
authors.affiliation: Jülich Centre for Neutron Science JCNS and Peter Grünberg Institut PGI, JARA-FIT, Forschungszentrum Jülich, 52425 Jülich, Germany.
authors.forename: Alice
authors.initials: A
authors.lastname: Klapper
authors.affiliation: Department of Chemistry, Universität zu Köln, 50939 Köln, Germany.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Disch
authors.affiliation: Jülich Centre for Neutron Science JCNS and Peter Grünberg Institut PGI, JARA-FIT, Forschungszentrum Jülich, 52425 Jülich, Germany and Helmholtz-Zentrum Dresden-Rossendorf, Institute of Ion Beam Physics and Materials Research, Bautzner Landstr. 400, 01328 Dresden, Germany.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Josten
authors.affiliation: Jülich Centre for Neutron Science JCNS and Peter Grünberg Institut PGI, JARA-FIT, Forschungszentrum Jülich, 52425 Jülich, Germany and Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, 37831 Tennessee, USA.
authors.forename: Raphaël P
authors.initials: RP
authors.lastname: Hermann
authors.affiliation: Jülich Centre for Neutron Science JCNS and Peter Grünberg Institut PGI, JARA-FIT, Forschungszentrum Jülich, 52425 Jülich, Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Rücker
authors.affiliation: Jülich Centre for Neutron Science JCNS and Peter Grünberg Institut PGI, JARA-FIT, Forschungszentrum Jülich, 52425 Jülich, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Brückel
authors.affiliation: Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, Sweden. erik.wetterskog@angstrom.uu.se gersal@protonmail.com.
authors.forename: Lennart
authors.initials: L
authors.lastname: Bergström
authors.affiliation: Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, Sweden. erik.wetterskog@angstrom.uu.se gersal@protonmail.com.
authors.forename: German
authors.initials: G
authors.lastname: Salazar-Alvarez