3 research outputs found
Elucidating Self-Assembly Mechanisms of Uranyl–Peroxide Capsules from Monomers
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>)Â(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
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>OÂ(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
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