Nanoparticle assemblies attract increasing interest because of the possibility of tuning their properties by adjusting the overall size and shape, the stacking of the individual nanoparticles, and the distances between them.[1]

Transmission electron microscopy is an important technique to characterize materials at the nanometer scale and below. However, it conventionally only allows for the acquisition of two-dimensional (2D) projections of three-dimensional (3D) objects, which is not sufficient for a quantitative characterization of complex 3D nanostructures. Electron tomography has therefore been developed to overcome this strict limitation, becoming a versatile and powerful tool, increasingly used in the field of materials science.[2]

For the characterization of nano-assemblies, electron tomography is nowadays a standard technique, yielding a 3D description of the morphology and inner structure.[3] Despite the valuable information that can be obtained, as the synthetized systems become more complex, an accurate characterization of the structure becomes more demanding. For example, 3D reconstructions based on classical algorithms, suffer from a number of restrictions that hamper an accurate characterization of closed-packed nanoparticles assemblies.

Here, we present a novel approach that enables us to determine the coordinates of each nanoparticle in an assembly, even when the assembly consists of up to 10,000 (spherical) particles.[4, 5] This technique will have a major impact as it enables a straightforward quantification of inter-particle distances and 3D symmetry of the stacking. Furthermore, the outcome of these measurements can be used as an input for modelling studies that predict the final 3D structure as a function of the parameters used during the synthesis.

[1]          N. A. Kotov, P. S. Weiss, ACS Nano 2014, 8, 3101.

[2]          P. Midgley, M. Weyland, Ultramicroscopy 2003, 96, 413.

[3]          A. Sánchez-Iglesias, M. Grzelczak, T. Altantzis, B. Goris, J. Perez-Juste, S. Bals, G. Van Tendeloo, S. H. Donaldson Jr, B. F. Chmelka, J. N. Israelachvili, ACS Nano 2012, 6, 11059.

[4]          B. de Nijs, S. Dussi, F. Smallenburg, J. D. Meeldijk, D. J. Groenendijk, L. Filion, A. Imhof, A. van Blaaderen, M. Dijkstra, Nature materials 2015, 14, 56.

[5]          D. Zanaga, F. Bleichrodt, T. Altantzis, N. N. Winckelmans, W. J. Palenstijn, J. Sijbers, B. van Nijs, M. van Huis, A. van Blaaderen, K. Joost Batenburg, Sara Bals, Gustaaf Van Tendeloo, Nanoscale 2015.

Acknowledgements

The authors acknowledge financial support from European Research Council (ERC Starting Grant # 335078-COLOURATOMS, ERC Advanced Grant # 291667 HierarSACol and ERC Advanced Grant 267867 – PLASMAQUO), the European Union under the FP7 (Integrated Infrastructure Initiative N. 262348 European Soft Matter Infrastructure, ESMI and N. 312483 ESTEEM2), and from the Netherlands Organisation for Scientific Research (NWO), project number 639.072.005 and NOW CW 700.57.026. Networking support was provided by COST Action MP1207.

Figures:

Figure 1: SSR reconstructions of Fe-Co-O nanoparticles assemblies with different size: a) 50nm diameter containing 70 particles. b) 100nm diameter containing 574 particles. c) 150nm diameter containing 1305 particles. The icosahedral symmetry of the particle is clear from this view. d) 300nm diameter containing 9301 particles.

Figure 2: (a) 3D visualization of the SIRT reconstruction of an assembly of about 9,000 Co-Fe-O particles. (c) orthoslice acquired through the SIRT reconstruction, missing wedge artifacts are highlighted by the red rectangle. (b, d) 3D visualization and orthoslice of the corresponding SSR reconstruction.

Figure 3: (a) 3D visualization of the rhombicosidodecahedral outer structure. (b) icosahedral core consisting of 20 tetrahedra with particles in an fcc stacking. (c) orthoslice through the reconstruction showing only the particles in an fcc stacking. The red triangle highlights a defect in two tetrahedra, which causes a deformation of the Mackay icosahedral core. (d) particles with icosahedral packing, the tetrahedra visualized by the blue particles are arranged in five-fold symmetry. (e) fcc stacked particles composing part of the outer shell. (f) orthoslice through a 3D visualization of the particles forming the twin planes (hcp stacking).

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EMC Abstracts - https://emc-proceedings.com/abstract/quantitative-3d-analysis-of-huge-nanoparticles-assemblies/