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The properties of materials are determined by the positions of the atoms, their chemical nature and the bonding between them. Therefore, reaching atomic resolution in 3D has been the ultimate goal in the field of electron tomography for many years. One of the possibilities to perform electron tomography with atomic resolution is by applying reconstruction algorithms based on compressive sensing [1,2]. The methodology was applied to high angle annular dark field scanning transmission electron microscopy (HAADF-STEM) images acquired from defect-free Au nanorods [1]. Also nanostructures that include defects can be investigated in this manner. Going further than determining the positions of atoms is the aim to determine the type of individual atoms in hetero-nanoparticles. Again using a combination of HAADF-STEM and compressive sensing, we were able to distinguish individual Ag from Au atoms in core-shell Au@Ag nanorods, even at the metal-metal interface [2]. Also energy dispersive X-ray (EDX) mapping can be combined with electron tomography and the use of the Super-X system is hereby very beneficial. EDX tomography was applied to obtain qualitative information concerning a galvanic replacement reaction in AuAg nanoparticles and to investigate the 3D composition of Fe and Co in nanodumbbells [3,4]. Quantification 3D EDX results can be considered as the next crucial step. Finally, by combining electron tomography with electron energy-loss spectroscopy at high energy resolution, we were able to determine the valency of the Ce ions in CeO2-x in 3D [5]. We kindly acknowledge Prof. L. M. Liz-Marzán and Prof. K. Soulantica for the provision of the samples.
[1] B. Goris, S. Bals, W. Van den Broek, E. Carbo-Argibay, S. Gomez-Grana, L. M. Liz-Marzan, G. Van Tendeloo, Nature Mater. 11 (2012) 930
[2] B. Goris, A. De Backer, S. Van Aert, S. Gómez-Graña, L. M. Liz-Marzán, G. Van Tendeloo, S. Bals, Nano Lett. 13 (2013) 4236
[3] N.Liakakos, Ch. Gatel, Th. Blon, Th. Altantzis, S. Lentijo-Mozo, C. Garcia-Marcelot, L.-M. Lacroix, M. Respaud, S. Bals, G. Van Tendeloo, K. Soulantica Nano Lett.14 (2014) 2747
[4] B. Goris, L. Polavarapu, S. Bals, G. Van Tendeloo, L. M. Liz-Marzán Nano Lett. 14 (2014) 3220
[5] B. Goris, S. Turner, S. Bals, G. Van Tendeloo ACS Nano 8 (2014) 10878
