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Your search keyword '"Cafun, Jean-Daniel"' showing total 12 results
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12 results on '"Cafun, Jean-Daniel"'

1. Photomagnetic CoFe prussian blue analogues: role of the cyanide ions as active electron transfer bridges modulated by cyanide-alkali metal ion interactions

Author

Cafun, Jean-Daniel, Champion, Guillaume, Arrio, Marie-Anne, dit Moulin, Christophe Cartier, and Bleuzen, Anne

Subjects
Electron transport -- Analysis, Iron alloys -- Chemical properties, Iron alloys -- Magnetic properties, Iron alloys -- Optical properties, Prussian blue (Chemical compound) -- Chemical properties, Prussian blue (Chemical compound) -- Optical properties, Cobalt alloys -- Chemical properties, Cobalt alloys -- Magnetic properties, Cyanides -- Chemical properties, Cyanides -- Electric properties, Chemistry
Abstract

Several ligand field multiplet calculations are conducted to explain the different properties exhibited by the different states of the three photomagnetic CoFe Prussian blue analogues. The significance of the various cyanide ions as efficient active electron transfer bridges during the metal ion interactions is also analyzed.

Published
2010

11. Absence of Ce3+Sites in Chemically Active Colloidal Ceria Nanoparticles

Author

Cafun, Jean-Daniel, Kvashnina, Kristina O., Casals, Eudald, Puntes, Victor F., and Glatzel, Pieter

Abstract

The catalytic performance of ceria nanoparticles is generally attributed to active sites on the particle surface. The creation of oxygen vacancies and thus nonstoichiometric CeO2−δhas been proposed to result in Ce3+sites with unpaired f electrons which can be oxidized to spinless Ce4+ions during catalytic reactions. We monitored the Ce electronic structure during the synthesis and catalase mimetic reaction of colloidal ceria nanoparticles under in situconditions. By means of high-energy resolution hard X-ray spectroscopy, we directly probed the Ce 4f and 5d orbitals. We observe pronounced changes of the Ce 5d bands upon reduction of the particle size and during the catalytic reaction. The Ce 4f orbitals, however, remain unchanged, and we do not observe any significant number of spin-unpaired Ce3+sites even for catalytically active small (3 nm) particles with large surface to bulk ratio. This confirms strong orbital mixing between Ce and O, and the Ce spin state is conserved during the reaction. The particles show an increase of the interatomic distances between Ce and O during the catalytic decomposition of hydrogen peroxide. The redox partner is therefore not a local Ce3+site, but the electron density that is received and released during the catalytic reaction is delocalized over the atoms of the nanoparticle. This invokes the picture of an electron sponge.

Published
2013
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