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.
| Original language | English |
|---|---|
| Pages (from-to) | 15571-15580 |
| Number of pages | 10 |
| Journal | Nanoscale |
| Volume | 8 |
| Issue number | 34 |
| DOIs | |
| State | Published - Sep 14 2016 |
Funding
We acknowledge SOLEIL for the provision of synchrotron radiation facilities and we would like to thank F. Meneau for assistance in using the beamline SWING. This research was funded by the Swedish Research Council. E. W. acknowledges partial financial support from the FP-7 Nanomag project (FP7-NMP-604448). S. D. acknowledges financial support by the 7th European Community Framework Programme (PIEF-GA-2011-298918), the Fonds der Chemischen Industrie, and the German Research Foundation (DFG: Emmy Noether Grant DI 1788/2-1). R. P. H. acknowledges support from the Materials Sciences and Engineering Division, Office of Basic Energy Sciences, U.S. Department of Energy. G. S. A. thanks the Knut and Alice Wallenberg Foundation for partial financial support within the project 3DEM-NATUR and for financing the microscopy facilities at SU. We thank E. Kentzinger for assistance with the GISAXS measurements at GALAXI. J. Mouzon and M. Agthe are acknowledged for assistance in acquiring a part of the SEM images. P. Svedlindh is acknowledged for performing the magnetometry measurements.