The application of HEXS and HERFD XANES for accurate structural characterization of actinide nanomaterials: application to ThO2.,Chemistry - A European Journal

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The application of HEXS and HERFD XANES for accurate structural characterization of actinide nanomaterials: application to ThO2.
Chemistry - A European Journal ( IF 3.9 ) Pub Date : 2020-09-21 , DOI: 10.1002/chem.202003360
Lucia Amidani _{1,

2} , Gavin B M Vaughan ₃ , Tatiana V Plakhova ₄ , Anna Yu Romanchuk ₄ , Evgeny Gerber _{1,

4} , Roman Svetogorov ₅ , Stephan Weiss ₂ , Yves Joly ₆ , Stepan N Kalmykov ₄ , Kristina O Kvashnina _{1,

2,

4}

Affiliation

The structural characterisation of actinide nanoparticles (NPs) is of primary importance and hard to achieve, especially for non‐homogeneous samples with NPs less than 3 nm. By combining high‐energy X‐ray scattering (HEXS) and high‐energy‐resolution fluorescence‐detected X‐ray absorption near‐edge structure (HERFD XANES) analysis, we have characterised for the first time both the short‐ and medium‐range order of ThO₂ NPs obtained by chemical precipitation. By using this methodology, a novel insight into the structures of NPs at different stages of their formation has been achieved. The pair distribution function revealed a high concentration of ThO₂ small units similar to thorium hexamer clusters mixed with 1 nm ThO₂ NPs in the initial steps of formation. Drying the precipitates at around 150 °C promoted the recrystallisation of the smallest units into more thermodynamically stable ThO₂ NPs. HERFD XANES analysis at the thorium M₄ edge, a direct probe for f states, showed variations that we have correlated with the breakdown of the local symmetry around the thorium atoms, which most likely concerns surface atoms. Together, HEXS and HERFD XANES are a powerful methodology for investigating actinide NPs and their formation mechanism.

中文翻译：

HEXS 和 HERFD XANES 在锕系纳米材料精确结构表征中的应用：在 ThO2 中的应用。

锕系元素纳米颗粒 (NP) 的结构表征至关重要且难以实现，特别是对于 NP 小于 3 nm 的非均质样品。通过结合高能 X 射线散射 (HEXS) 和高能分辨率荧光检测 X 射线吸收近边缘结构 (HERFD XANES) 分析，我们首次表征了短程和中程通过化学沉淀获得的ThO ₂ NPs的顺序。通过使用这种方法，人们对纳米颗粒在形成的不同阶段的结构有了新的认识。对分布函数揭示了高浓度的ThO ₂小单元，类似于钍六聚体簇，在形成的初始步骤中与1 nm ThO _{2 NPs混合。}在 150 °C 左右干燥沉淀物可促进最小单元重结晶成热力学更稳定的 ThO ₂纳米颗粒。钍 M ₄边缘的 HERFD XANES 分析（对 f 态的直接探测）显示出与钍原子周围局部对称性破坏相关的变化，这很可能与表面原子有关。HEXS 和 HERFD XANES 共同成为研究锕系纳米粒子及其形成机制的强大方法。

更新日期：2020-09-21

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