Nonhydrolytic Synthesis and Electronic Structure of Ligand-Capped CeO2-δ and CeOCl Nanocrystals

A novel and versatile nonhydrolytic approach is developed for the synthesis of ligand-passivated CeO2-delta and CeOCl nanocrystals soluble in nonpolar organic solvents based on the condensation of cerium alkoxides with cerium halides. The alkyl group on the metal alkoxides and the specific halide used in the synthesis are observed to considerably influence the composition and size of the obtained nanocrystals. The obtained nanocrystals are <3 nm in diameter and, owing to their surface-capping groups, yield homogeneous and clear solutions in nonpolar organic solvents with no evidence of agglomeration. The electronic structure of the obtained CeO2-delta nanocrystals has been studied using optical absorption spectroscopy and near-edge X-ray absorption fine structure spectroscopy at Ce M- and O K-edges. The latter technique provides detailed insight into the metal valence, geometric structure, and atom-projected density of states in these nancrystals. Finally, this synthesis method has been expanded to explore the doping of La to form solid-solution CexLa1-xO2-delta nanocrystals.