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_4,5-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_4,5-edge white lines (883, 901 eV). White line intensity ratio (M₅/M₄) along with changes in the fine structure on M_4,5-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 (Ce⁴⁺and Ce³⁺) changing with low and high Ce-load. Graphical abstract: [Figure not available: see fulltext.]