3 research outputs found

    Elucidating Self-Assembly Mechanisms of Uranyl–Peroxide Capsules from Monomers

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    Self-assembly of uranyl peroxide polyoxometalates (POMs) in alkaline peroxide solutions has been known for almost a decade, but in these dynamic solutions that contain high concentrations of base and peroxide the reaction pathway could never be discerned, mixed species are obtained, and reproducibility is sometimes a challenge. Here we elucidate the reaction mechanisms utilizing self-assembly of the U<sub>24</sub> cluster, [UO<sub>2</sub>(O<sub>2</sub>)­(OH)]<sub>24</sub><sup>24‑</sup>, from monomers as a model system. Using Raman as our main spectroscopic probe, we learned that the monomeric species is persistent in water at room temperature indefinitely. However, if a redox-active transition metal catalyst (copper (Cu<sup>2+</sup>) or cobalt (Co<sup>2+</sup>)) is added, self-assembly is accelerated in a significant manner, forming U<sub>24</sub> peroxide clusters in several hours, which is a good time scale for studying reaction mechanisms. From semiquantitative treatment of the spectroscopic data, we elucidate reaction mechanisms that are consistent with prior structural and computational studies that suggest uranyl peroxide rings templated by alkalis are the building units of clusters. By understanding aqueous speciation and processes, we are moving toward assuming control over cluster self-assembly that has been mastered for decades now in the analogous transition-metal POM systems

    Insight into Hydrogen Bonding of Uranyl Hydroxide Layers and Capsules by Use of <sup>1</sup>H Magic-Angle Spinning NMR Spectroscopy

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    Solid-state <sup>1</sup>H magic-angle spinning (MAS) NMR was used to investigate local proton environments in anhydrous [UO<sub>2</sub>(OH)<sub>2</sub>] (α-UOH) and hydrated uranyl hydroxide [(UO<sub>2</sub>)<sub>4</sub>O­(OH)<sub>6</sub>·5H<sub>2</sub>O (metaschoepite). For the metaschoepite material, proton resonances of the μ<sub>2</sub>-OH hydroxyl and interlayer waters were resolved, with two-dimensional (2D) double-quantum (DQ) <sup>1</sup>H–<sup>1</sup>H NMR correlation experiments revealing strong dipolar interactions between these different proton species. The experimental NMR results were combined with first-principles CASTEP GIPAW (gauge including projector-augmented wave) chemical shift calculations to develop correlations between hydrogen-bond strength and observed <sup>1</sup>H NMR chemical shifts. These NMR correlations allowed characterization of local hydrogen-bond environments in uranyl U<sub>24</sub> capsules and of changes in hydrogen bonding that occurred during thermal dehydration of metaschoepite

    Development of <sup>225</sup>Ac Production from Low Isotopic Dilution <sup>229</sup>Th

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    The promise of 225Ac targeted alpha therapies has been on the horizon for the last two decades. TerraPower Isotopes are uniquely suited to produce clinically relevant quantities of 225Ac through the decay of 229Th. Herein, a rapid processing scheme to isolate radionuclidic and radioisotopically pure 225Ac in good yield (98%) produced from 229Th that contains significant quantities of 228Th activity is described. The characterization of each step of the process is presented along with the detailed characterization of the resulting 225Ac isotopic starting material that will support the cancer research and development efforts
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