Amidani Lucia, Vaughan Gavin B M, Plakhova Tatiana V, Romanchuk Anna Yu, Gerber Evgeny, Svetogorov Roman, Weiss Stephan, Joly Yves, Kalmykov Stepan N, Kvashnina Kristina O
The Rossendorf Beamline at ESRF, The European Synchrotron, CS40220, 38043, Grenoble Cedex 9, France.
Institute of Resource Ecology, Helmholtz Zentrum Dresden-Rossendorf (HZDR), PO Box 510119, 01314, Dresden, Germany.
Chemistry. 2021 Jan 4;27(1):252-263. doi: 10.1002/chem.202003360. Epub 2020 Nov 12.
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 ThO 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 ThO small units similar to thorium hexamer clusters mixed with 1 nm ThO 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 ThO NPs. HERFD XANES analysis at the thorium M 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.
锕系元素纳米颗粒（NPs）的结构表征至关重要且难以实现，特别是对于那些粒径小于3 nm的非均匀样品。通过结合高能X射线散射（HEXS）和高能分辨荧光探测X射线吸收近边结构（HERFD XANES）分析，我们首次对通过化学沉淀法制备的ThO NPs的短程和中程有序结构进行了表征。运用这种方法，我们对NPs在其形成不同阶段的结构有了全新的认识。对分布函数显示，在形成的初始阶段，存在高浓度类似于钍六聚体簇的ThO小单元，且与1 nm的ThO NPs混合在一起。在约150 °C下干燥沉淀物促进了最小单元重结晶为热力学上更稳定的ThO NPs。在钍M边进行的HERFD XANES分析是对f态的直接探测，其显示出的变化与钍原子周围局部对称性的破坏相关，这很可能涉及表面原子。总之，HEXS和HERFD XANES是研究锕系元素NPs及其形成机制的有力方法。
