We report a full characterization of PuO₂ nanoparticles at the atomic level and probe their local and electronic structure by a variety of methods available at the synchrotron and theoretical approaches.

Here we provide evidence that the formation of PuO 2 nanoparticles from oxidized Pu VI under alkaline conditions proceeds through the formation of an intermediate Pu V solid phase,s imilar to NH 4 PuO 2 CO 3 ,w hich is stable over ap eriod of several months.F or the first time,s tate-of-the-art experiments at Pu M 4 and at L 3 absorption edges combined with theoretical calculations unambiguously allowt od etermine the oxidation state and the local structure of this intermediate phase.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.org/10.

X-ray absorption experiments at Ce L3 and M5 edges and theoretical calculations demonstrate that in addition to the nanoceria charge stability, the formation of hydroxyl groups at the surface affects the chemical performance of nanomaterials.