The missing pieces of the PuO2 nanoparticles puzzle

The nanoscience field often produces results more mystifying than any other discipline. It has been argued that changes of the plutonium dioxide (PuO2) particle size from bulk to nano can have a drastic effect on PuO2 properties. Here we report a full characterization of PuO2 nanoparticles (NPs) at the atomic level, explore their stability and probe their local and electronic structure. The particles were synthesized from precursors with different oxidation states (Pu III, IV and V) under various environmentally and waste storage relevant conditions (pH 8 and pH 12). We demonstrate that well dispersed, crystalline NPs with a size of ~2.5 nm in diameter are always formed in spite of diverse chemical conditions. Identical crystal structures and the presence of only Pu(IV) oxidation state in all NPs indicate that their fundamental properties, rather than being fancy and exotic, are identical to those of the bulk PuO2.