The structure of plutonium(iv) oxide as hydrolysed clusters in aqueous suspensions

Abstract

The behavior of plutonium still puzzles scientists 70 years after its discovery. There are several factors making the chemistry of plutonium interesting including its ability to keep several oxidation states. Another unique property is that the oxidation states +III, +IV, +V and +VI may exist simultaneously in solution. Another property plutonium shares with some other tetravalent metal ions is the ability to form stable polynuclear complexes or colloids. The structures of freshly prepared and five-year old plutonium(IV) colloids are compared with crystalline plutonium(IV) oxide using Pu L(3)-edge EXAFS. It was shown that as the plutonium colloids age they do in fact shrink in size, contrary to previous expectations. The aged colloidal particles are indeed very small with only 3-4 plutonium atoms, and with a structure very similar to solid plutonium(IV) oxide, but with somewhat shorter mean Pu-O bond and Pu···Pu distances indicating a partial oxidation. The very small size of the colloidal particles is further supported by the fact that they do not sediment on heavy ultra-centrifugation.

The Rise of Magnetically Recyclable Nanocatalysts

“…The structural parameters of all samples contain eight oxygen distances at 2.31 ± 0.02 Å. This is in good agreement with the theoretical value of eight coordinated oxygen atoms to each Pu IV atom in the PuDFOE complex,28 PuO 2 (cr)31,44,45 and Pu IV complexes on kaolinite surfaces 46. These Pu–O distances can be clearly observed in the Fourier Transforms (FTs) at ca.…”

“…The CN and R values for the Pu–Pu shell are 2.13 and 3.74 ± 0.02 Å, respectively. As many as twelve Pu atoms are typical for Pu–Pu interactions in a crystalline PuO 2 solid,44,45 thus we do not believe that our results are skewed by the presence of colloidal Pu. The Pu–Pu distance observed in these studies agrees with those previously observed for small Pu oxo–hydroxo–aqua oligomer species 31.…”

Insights into the sonochemical synthesis and properties of salt-free intrinsic plutonium colloids

“…The preparation of intrinsic Pu colloids with controlled composition and properties is still a great challenge. In general, colloidal Pu species obtained by hydrolysis of Pu(IV) salts are composed of 2–5 nm PuO 2 -like nanoparticles (NPs) coated by Pu(IV) ions coordinated to water molecules, OH − groups, and anions originating from electrolyte salts78910. In organic solvents, ~5 nm PuO 2 nanoparticles obtained by thermolysis of Pu(VI) in a mixture of benzyl ether, oleic acid, and oleylamine was shown to be stabilized by oleate-anions adsorbed at the surface of PuO 2 NPs11.…”

Trace-level plutonium(IV) polymer stability and its transport in coarse-grained granites

“…2a), the polymer size decreased over the aging period. Typically, P >450nm declined to ~2% at t = 135 d. This trend towards decreasing sizes was also observed in relatively high concentrations of Pu(IV) polymers (~10 −3 mol/L Pu)(Abdel-Fattah et al, 2013;Ekberg et al, 2013). Such polymers (plutonium oxide nanoclusters) with chemical structures very similar to that of crystalline PuO 2 contained 38…”

“…Based on the experimental results of DLS and EXAFS, Abdel-Fattah et al (2013) and Ekberg et al (2013) indicated decreased size of aged polymers. However, an opposite trend in their size was shown according to the results of DLS (Triay et al, 1991), XRD (Delegard, 2013), LIBD (Rothe et al, 2004), and ultracentrifuge (Ichikawa and Sato, 1984).…”