Larquet Clément, Nguyen Anh-Minh, Ávila-Gutiérrez Mario, Tinat Lionel, Lassalle-Kaiser Benedikt, Gallet Jean-Jacques, Bournel Fabrice, Gauzzi Andrea, Sanchez Clément, Carenco Sophie
Sorbonne Universités, UPMC Univ Paris 06, CNRS, Collège de France , Laboratoire de Chimie de la Matière Condensée de Paris, 4 place Jussieu, 75005 Paris, France.
Sorbonne Universités, UPMC Univ Paris 06, CNRS, IRD, MNHN , Institut de Minéralogie, de Physique des Matériaux et de Cosmologie, 4 place Jussieu, 75005 Paris, France.
Inorg Chem. 2017 Nov 20;56(22):14227-14236. doi: 10.1021/acs.inorgchem.7b02336. Epub 2017 Nov 1.
Lanthanide oxysulfide nanoparticles have recently attracted interest in view of their potential applications, such as lighting devices and MRI contrast agents, which requires a good stability in air and a controlled surface. In order to address these issues, in this work, air-sensitive CeOS nanoparticles of hexagonal shape were successfully prepared and characterized under inert conditions. Bimetallic GdCeOS nanoparticles of similar shape and size were also synthesized for the whole composition range (y from 0 to 1). X-ray diffraction structural data are found to follow Vegard's law up to y = 0.4, which is attributed to the loss of stability in air of Ce-rich nanocrystals beyond this threshold. This picture is supported by X-ray absorption spectra taken at the S K-edge and Ce L-edge that show the partial oxidation of sulfide species and of Ce to Ce in the presence of air or water. A complementary near-ambient-pressure X-ray photoelectron spectroscopy study shows that at least two types of oxidized sulfur species form on the nanoparticle surface. Even in GdOS nanoparticles that are generally considered to be air-stable, we found that sulfide ions are partially oxidized to sulfate in air. These results unveil the physicochemical mechanisms responsible for the surface reactivity of lanthanide oxysulfides nanoparticles in air.
鉴于镧系元素硫氧化物纳米颗粒在照明设备和MRI造影剂等潜在应用中的价值，它们最近受到了关注，这些应用要求颗粒在空气中具有良好的稳定性以及可控的表面性质。为了解决这些问题，在本研究中，成功制备了对空气敏感的六边形CeOS纳米颗粒，并在惰性条件下对其进行了表征。还合成了形状和尺寸相似的双金属GdCeOS纳米颗粒，其组成范围为y从0到1。发现X射线衍射结构数据在y = 0.4之前遵循维加德定律，这归因于富铈纳米晶体在此阈值以上在空气中失去稳定性。在S K边和Ce L边采集的X射线吸收光谱支持了这一现象，光谱显示在空气或水存在的情况下，硫化物物种和Ce会部分氧化为Ce。一项补充性的近常压X射线光电子能谱研究表明，纳米颗粒表面至少形成了两种类型的氧化硫物种。即使在通常被认为对空气稳定的GdOS纳米颗粒中，我们也发现硫化物离子在空气中会部分氧化为硫酸盐。这些结果揭示了镧系元素硫氧化物纳米颗粒在空气中表面反应性的物理化学机制。
