EELS post-processing and multiplet calculation for Ce4+, Ce3+ valency determination in nanomaterials

Analytical transmission electron microscopy is a well-established methodology with which thoroughly characterize nowadays nanomaterials, particularly the crystalline kind. Further from micrograph imaging, chemical characterization on the nanometer scale is done by spectroscopies such as electron energy-loss spectroscopy (EELS). In this regard, cerium doped mesoporous silica materials (Ce-MCM-41) has been used in the present work to determine the oxidation state (Ce4+, Ce3+) in CeO2 nanoparticles incorporated into the compounds MCM-41:Ce (2.9, 13.2 wt%). The Ce M-4,M-5-edge fine structure was studied by energy-loss near-edge spectroscopy (ELNES). after removing plural scattering and the continuum contribution at the base of Ce M-4,M-5-edge white lines (883, 901 eV). White line intensity ratio (M-5/M-4) along with changes in the fine structure on M-4,M-5-edge help on determination of cerium oxidation state. The atomic multiplet calculation was performed using the CTM4XAS software based on code by Cowan. It was found the CeO2 nanoparticles have mixed oxidation states (Ce(4+)and Ce3+) changing with low and high Ce-load.