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Intrinsic properties of a compound (e.g. electronic structure, crystallographic structure, optical and magnetic properties) define notably its chemical and physical behavior. In the case of nanomaterials, these fundamental properties depend on the occurrence of quantum mechanical size effects and on the considerable increase of the surface to bulk ratio. However, the literature on this size-dependence and on the involved mechanisms is quite elusive and scarce. Here, we explore the size-dependence of both crystal and electronic properties of CeO2 nanoparticles (NPs) with different sizes by state-of-the art spectroscopic techniques. XRD, XPS and HERFD-XANES demonstrate that the as-synthesized NPs crystallize in the fluorite structure and they are predominantly composed of Ce IV ions. The strong dependence of the lattice parameter with the NPs size was attributed to the presence of adsorbed species at the NPs surface thanks to FTIR and TGA measurements. In addition, the size-dependence of the t2g level in the Ce LIII XANES spectra was experimentally observed by HERFD-XANES and confirmed by theoretical calculations.

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Thin layers of PuSb and PuSe were studied by photoelectron spectroscopy. X-ray photoelectron spectroscopy and high-resolution valence-band ultraviolet photoelectron spectroscopy spectra show localization of the 5f states and a low density of states at E(F) in PuSb. In PuSe, which can be classified as a heavy fermion system with low carrier density, we observed three narrow peaks in the valence band, which can be related to the 5f emission. These three features are very sensitive to stoichiometry deviations and disappear for PuSe prepared at T = 77 K.

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The around-mean-field LSDA+U correlated band theory is applied to investigate the electronic and magnetic structure of f cc-Pu-Am alloys. Despite a lattice expansion caused by the Am atoms, neither tendency to 5f localization nor formation of local magnetic moments on Pu atoms in PuAm alloys are found. The 5f -manifolds in the alloys are calculated being very similar to a simple weighted superposition of elemental Pu and Am 5f -states.