title: Three-dimensional valency mapping in ceria nanocrystals.
abstract: Using electron tomography combined with electron energy loss spectroscopy (EELS), we are able to map the valency of the Ce ions in CeO2-x nanocrystals in three dimensions. Our results show a clear facet-dependent reduction shell at the surface of ceria nanoparticles; {111} surface facets show a low surface reduction, whereas at {001} surface facets, the cerium ions are more likely to be reduced over a larger surface shell. Our generic tomographic technique allows a full 3D data cube to be reconstructed, containing an EELS spectrum in each voxel. This possibility enables a three-dimensional investigation of a plethora of material-specific physical properties such as valency, chemical composition, oxygen coordination, or bond lengths, triggering the synthesis of nanomaterials with improved properties.
authors.affiliation: EMAT, University of Antwerp , Groenenborgerlaan 171, B-2020 Antwerp, Belgium.
authors.forename: Bart
authors.initials: B
authors.lastname: Goris
authors.forename: Stuart
authors.initials: S
authors.lastname: Turner
authors.forename: Sara
authors.initials: S
authors.lastname: Bals
authors.forename: Gustaaf
authors.initials: G
authors.lastname: Van Tendeloo
keywords: EELS; catalysis; ceria; redox; tomography