Nanoparticle assemblies with long-range packing order and preferred crystallographic orientation of building blocks, i.e., mesocrystals, are of high interest not only because of their unique physical properties but also due to their complex structure and morphogenesis. In this study, faceted mesocrystals have been assembled from the dispersion of truncated cubic-shaped iron oxide nanoparticles stabilized by oleic acid (OA) molecules using the nonsolvent "gas phase diffusion technique"into an organic solvent. The effects of synthesis conditions as well as of the nanoparticle size and shape on the structure and morphogenesis of mesocrystals were examined. The interactions of OA-capped iron oxide nanoparticles with solvent molecules were probed by analytical ultracentrifugation and double difference pair distribution function analysis. It was shown that the structure of the organic shell significantly depends on the nature and polarity of solvent molecules. For the nonpolar solvents, the interaction of the aliphatic chains of OA molecules with the solvent molecules is favorable and the chains extend into the solvent. The solvation shell around the nanoparticles is more extended in nonpolar and more compact in polar solvents. There is a clear trend for more spherical particles to be assembled into the fcc superlattice, whereas less truncated cubes form rhombohedral and tetragonal structures. The observed changes in packing symmetry are reminiscent of structural polymorphism known for "classical"(atomic and molecular) crystals.
Bibliographical noteFunding Information:
We hereby acknowledge the DFG (Deutsche Forschungsgemeinschaft) for financial support (SFB1214 Project B1). We thank Clara Schlotheuber for editorial help and fruitful discussions. We also thank Dr. Danny Haubold and Ramon Zimmermanns for being a great help in laboratory work. S.S. and A.L. acknowledge funding from the European Research Council (ERC) under the Horizon 2020 research and innovation program of the European Union (Grant Agreement Number 715620). M.Z. acknowledges support by the Bavarian Academy for Sciences and Humanities. M.Z. and S.T. acknowledge beamtime at ID15-ERH at European Synchrotron Radiation Facility and I15-1 at Diamond Lightsource, as well as support from the respective beamline scientists Gavin Vaughan and Phil Chater. We acknowledge DESY (Hamburg, Germany), a member of the Helmholtz Association HGF, for the provision of experimental facilities. Parts of this research were carried out at PETRA III synchrotron facility, and we would like to thank the beamline staff and especially Michael Sprung for assistance in using Coherence Application P10 beamline. This work was supported by the Helmholtz Associations Initiative Networking Fund (Grant No. HRSF-0002) and the Russian Science Foundation (Grant No. 18-41-06001). We also gratefully acknowledge the Gauss Center for Supercomputing e.V. ( www.gauss-centre.eu ) for providing computing time through the John von Neumann Institute for Computing (NIC) on the GCS Supercomputer JUWELS at the Jülich Supercomputing Center (JSC), which was used to receive the models in ULRASCAN for AUC data. E.V.S. thanks the Zukunftskolleg at the University of Konstanz and “Konstanzia Transition” programme of equal opportunity council for financial support. Last but not least, we thank the Bio Imaging Center Constance and Stefan Helfrich to help us to evaluate light microscope images, quantitatively.
All Science Journal Classification (ASJC) codes
- Chemical Engineering(all)
- Materials Chemistry