A novel metastable pentavalent plutonium solid phase on the pathway from aqueous Pu(VI) to PuO2 nanoparticles

We report here experimental evidence that the formation of PuO2 nanoparticles from oxidized Pu(VI) under environmentally relevant conditions proceeds through the formation of an intermediate Pu(V) solid phase, similar to NH4PuO2CO3, which is stable over a period of several months. State-of-the-art experiments at Pu M4 and L3 absorption edges combined with theoretical calculations unambiguously allowed us to determine the oxidation state and the local structure of this intermediate phase