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Instruments / Technical Area	Publication Details	Published
I20-Scanning-X-ray spectroscopy (XAS/XES)	Thermally stable surfactant-free ceria nanocubes in silica aerogel Francesco Caddeo , Alberto Casu , Danilo Loche , Lucy M. Morgan , Gavin Mountjoy , Colm O'Regan , Maria F. Casula , Shusaku Hayama , Anna Corrias , Andrea Falqui Journal Of Colloid And Interface Science DOI: 10.1016/j.jcis.2020.09.044 Diamond Proposal Number(s): [19013] Open Access Show Abstract ▼ Abstract: Surfactant-mediated chemical routes allow one to synthesize highly engineered shape- and size-controlled nanocrystals. However, the occurrence of capping agents on the surface of the nanocrystals is undesirable for selected applications. Here, a novel approach to the production of shape-controlled nanocrystals which exhibit high thermal stability is demonstrated. Ceria nanocubes obtained by surfactant-mediated synthesis are embedded inside a highly porous silica aerogel and thermally treated to remove the capping agent. Powder X-ray Diffraction and Scanning Transmission Electron Microscopy show the homogeneous dispersion of the nanocubes within the aerogel matrix. Remarkably, both the size and the shape of the ceria nanocubes are retained not only throughout the aerogel syntheses but also upon thermal treatments up to 900 °C, while avoiding their agglomeration. The reactivity of ceria is measured by in situ High-Energy Resolution Fluorescence Detected - X-ray Absorption Near Edge Spectroscopy at the Ce L3 edge, and shows the reversibility of redox cycles of ceria nanocubes when they are embedded in the aerogel. This demonstrates that the enhanced reactivity due to their prominent {100} crystal facets is preserved. In contrast, unsupported ceria nanocubes begin to agglomerate as soon as the capping agent decomposes, leading to a degradation of their reactivity already at 275 °C.	Sep 2020
B18-Core EXAFS	Determining the maximum lanthanum incorporation in the fluorite structure of La-doped ceria nanocubes for enhanced redox ability Danilo Loche , Lucy M. Morgan , Alberto Casu , Gavin Mountjoy , Colm O'regan , Anna Corrias , Andrea Falqui Rsc Advances 9, 6745 - 6751 DOI: 10.1039/C8RA09766F Diamond Proposal Number(s): [14239] Open Access Show Abstract ▼ Abstract: Ceria nanocubes have been doped with increasing amounts of lanthanum to enhance their redox ability. X-ray diffraction and transmission electron microscopy techniques provide a consistent picture indicating that there is an upper limit to the lanthanum that can be incorporated in the fluorite structure of ceria nanocubes, which is close to 7.5 mol% La. This limited loading is nevertheless able to produce a significant enhancement of the ceria redox ability as evidenced by use of X-ray absorption spectroscopy to determine the Ce3+/Ce4+ ratio in samples submitted to a degassing treatment at room temperature.	Feb 2019
B18-Core EXAFS	Evidence of a cubic iron sub-lattice in t-CuFe2O4 demonstrated by X-ray Absorption Fine Structure Francesco Caddeo , Danilo Loche , Maria F. Casula , Anna Corrias Scientific Reports 8 DOI: 10.1038/s41598-017-19045-8 Diamond Proposal Number(s): [11086] Open Access Show Abstract ▼ Abstract: Copper ferrite, belonging to the wide and technologically relevant class of spinel ferrites, was grown in the form of t-CuFe2O4 nanocrystals within a porous matrix of silica in the form of either an aerogel or a xerogel, and compared to a bulk sample. Extended X-ray absorption fine structure (EXAFS) spectroscopy revealed the presence of two different sub-lattices within the crystal structure of t-CuFe2O4, one tetragonal and one cubic, defined by the Cu2+ and Fe3+ ions respectively. Our investigation provides evidence that the Jahn-Teller distortion, which occurs on the Cu2+ ions located in octahedral sites, does not affect the coordination geometry of the Fe3+ ions, regardless of their location in octahedral or tetrahedral sites.	Jan 2018
B18-Core EXAFS	Cation Distribution and Vacancies in Nickel Cobaltite Danilo Loche , Claudia Marras , Daniela Carta , Maria Francesca Francesca Casula , Gavin Mountjoy , Anna Corrias Phys. Chem. Chem. Phys. DOI: 10.1039/C7CP02260C Diamond Proposal Number(s): [5820] Show Abstract ▼ Abstract: Samples of nickel cobaltite, a mixed oxide occurring in the spinel structure which is currently extensively investigated because of its prospective application as ferromagnetic, electrocatalytic, and cost-effective energy storage material were prepared in the form of nanocrystals stabilized in a highly porous silica aerogel and as unsupported nanoparticles. Nickel cobaltite nanocrystals with average size 4 nm are successfully grown for the first time into the silica aerogel provided that a controlled oxidation of the metal precursor phases is carried out, consisting in a reduction under H2 flow followed by mild oxidation in air. The investigation of the average oxidation state of the cations and of their distribution between the sites within the spinel structure, which is commonly described assuming the Ni cations are only located in the octahedral sites, has been carried out by X-ray Absorption Spectroscopy providing evidence for the first time that the unsupported nickel cobaltite sample has a Ni:Co molar ratio higher than the nominal ratio of 1:2 and a larger than expected average overall oxidation state of the cobalt and nickel cations. This is achieved retaining the spinel structure, which accommodates vacancies to counterbalance the variation in oxidation state.	Jun 2017

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