SAXS study of the formation and structure of polynuclear thorium(IV) colloids and thorium dioxide nanoparticles

Abstract

Stable actinide colloids and nanoparticles are of interest because of their potential to affect the transportation of radionuclides in the near-field of a nuclear waste repository. At high concentrations, thorium(IV) can precipitate to form intrinsic colloids. In the present study, polynuclear thorium colloids and thorium dioxide crystallites, formed by the condensation of hydrolyzed Th4+ solutions (3 mM; initial pH 5.5) aged for up to 18 months, were studied using small-angle X-ray scattering. Scattering profiles were fitted using a unified Guinier/power-law model (Beaucage model) to extract the radii of gyration and Porod exponents. Analysis of the scattering profiles from a dispersion aged for 5 months indicated that both polymer coils and more compacted structures (radius of gyration R g ≃ 10 nm) were present, which translated in the Kratky plots as a plateau and a peak maximum, respectively. After 18 months, the SAXS data were consistent with the presence of agglomerates of ThO2 particles suspended in aqueous solution (pH 3.2; [Th] = 1.45 mM). The measured radius of gyration (R g) of the agglomerates was 5.8 nm, whereas the radius of the ThO2 particles was 2.5 nm.

Synthesis and multi-scale properties of PuO2 nanoparticles: recent advances and open questions

“…146 The stabilization of these very small and low concentration aggregates with the DOTA ligand (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) allowed their characterization with a good signal-to-noise ratio, thus demonstrating the technical capacity of the mutual approach. Scattering techniques are obviously strongly considered in modern actinide science [147][148][149] but remain poorly applied for trans-uranium oxide nanoparticles and we expect a stronger interest for the technique in the near future. The results recently provided by Zhai et al on the formation and structure of ThO 2 colloidal nanoparticles could be helpful for understanding the properties of analogous nanosized An oxides.…”

“…12 nm in diameter. 149 It is important to emphasize that the various analytical techniques used to probe the PuO 2 nanoparticles may offer several advantages and drawbacks thus highlighting the observed interest of most of the authors in the combination of approaches when characterizing PuO 2 nanoparticles. For instance, slight variations in the nanoparticle sizes are generally noticed when comparing both XRD and TEM techniques.…”

Synchrotron Radiation Techniques and their Application to Actinide Materials

“…A SAXS experiment is sensitive to microstructural details up to a few thousand Å and provide information on the surface, volume, and shape of the inhomogeneities, on the distribution of their sizes, and on the inter-particle correlation. In actinide science, SAXS has been used, for instance, to study the formation of atomic clusters (Burns et al, 2005), polynuclear colloidal particles (Zhai et al, 2022), the interactions between natural colloidal organic matter and actinides in solutions (Tian et al, 2020), and the solution speciation of metal-oxo clusters (Nyman, 2017).…”

“…The technique can be applied to samples in solid or liquid forms, including nanoparticles (Gerber et al, 2020) and colloidal forms (Micheau et al, 2020), with element sensitivity down to tens of ppm. In combination with small angle x-ray scattering (SAXS) measurements, XAS provides detailed information on the local structure, size, shape, and interfacial properties of atomic clusters and intrinsic colloidal particle (Micheau et al, 2020;Nyman, 2017;Tian et al, 2020;Zhai et al, 2022).…”

Foreword to the special virtual issue on Actinide physics and chemistry with synchrotron radiation

“…Anna Romanchuk and co-workers proposed a new core-shell approach for the actinide and lanthanide dioxide nanoparticles with calculated effective coordination numbers from Ce K-edge and Th and Pu L 3 -edge EXAFS (Romanchuk et al, 2022). Baihui Zhai and co-authors studied the formation and structure of polynuclear thorium(IV) colloids and thorium dioxide nanoparticles by SAXS (Zhai et al, 2022).…”