Résumé
While recent studies have provided a wealth of information on the structure of oxide nanoparticles resulting from Pu(IV) hydrolysis, little is known about their formation mechanism. This article describes the stabilization and characterization of a reaction intermediate observed during the formation of PuO2 colloidal nanoparticles in aqueous solution. The intermediate was captured by a kinetic blocking of the started hydrolysis reaction by dilution of the reacting medium into DOTA (pH 3.5), glycine (pH 2.0) or acetic acid (pH 1) aqueous solutions. Such an approach allowed to stabilize hexameric polynuclear structures of Pu(IV) that were thoroughly characterized using laboratory and synchrotron techniques (SAXS, L3-edge XAS, M4-edge HERFD-XANES). Beyond the new insight given about the contribution of [Pu6O4(OH)4]12+ cluster during the aqueous formation of colloidal PuO2 nanoparticles in aqueous conditions, this study confirms the added value of synchrotron radiations for the characterization of very dilute and strongly radioactive nanostructures, paving the way for further research in the domain.