Magnetic field-assisted assembly of iron oxide mesocrystals: a matter of nanoparticle shape and magnetic anisotropy

• Julian J. Brunner,
• Marina Krumova,
• Helmut Cölfen and
• Elena V. Sturm (née Rosseeva)

Beilstein J. Nanotechnol. 2019, 10, 894–900, doi:10.3762/bjnano.10.90

• superparamagnetic nanoparticles and how a magnetic field can be used to design anisotropic mesocrystals with different structures. Keywords: directed assembly; magnetite; mesocrystal; nanoparticle; transmission electron microscopy; Findings In materials science, nanoparticles and their assemblies belong to the

• single crystal-like fast Fourier transforms (FFTs) and texture-like EDs are shown in Figure 3. The large yellow circles indicate the position from which the FFTs and EDs are obtained. The symmetry of the projected mesocrystal surface, which is parallel to the substrate can be described either in p4mm

• their corresponding EDs and FFTs are presented. A “self-assembled mesocrystal” is shown next to two “directed mesocrystals”, whereby all superlattices show a projected p4mm symmetry of the basal surface, which is parallel to the substrate. Nevertheless, the orientational order of magnetite nanocrystals

Oriented attachment explains cobalt ferrite nanoparticle growth in bioinspired syntheses

• Annalena Wolff,
• Walid Hetaba,
• Marco Wißbrock,
• Stefan Löffler,
• Nadine Mill,
• Katrin Eckstädt,
• Axel Dreyer,
• Inga Ennen,
• Norbert Sewald,
• Peter Schattschneider and
• Andreas Hütten

Beilstein J. Nanotechnol. 2014, 5, 210–218, doi:10.3762/bjnano.5.23

• primary-building-block-like substructures as well as mesocrystal-like structures, were observed in HRTEM measurements. These structures display regions of substantial orientation and possess the same shape and size as the resulting discs. An increase in orientation with time was observed in electron

• compositional changes occur. Discussion Intermediate phases, such as oriented subunits within incomplete crystals as well as mesocrystal-like structures (Figure 3, bottom), were observed in addition to the final discs throughout the growth process. The intermediate phases are of non-stoichiometric compositions

• matches the description of an oriented attachment process. Crystal growth via oriented attachment as well as mesocrystal formation have been described previously for biomineralization and biomimetic syntheses [19][25]. A schematic of this multistep process can be found in Figure 5. Nanoparticle growth via