Metal Oxysulfides: From Bulk Compounds to Nanomaterials.

This review summarizes the syntheses and applications of metal oxysulfides. Bulk compounds of rare earth and transition metals are discussed in the section Introduction. After a presentation of their main properties and applications, their structures are presented and their syntheses are discussed. The section Bulk Materials and Their Main Applications is dedicated to the growing field of nanoscaled metal oxysulfides. Synthesis and applications of lanthanide-based nanoparticles are more mature and are discussed first. Then, works on transition-metal based nanoparticles are presented and discussed. Altogether, this review highlights the opportunities offered by metal oxysulfides for application in a range of technological fields, in relation with the most advanced synthetic routes and characterization techniques.

Different Reactivity of Rutile and Anatase TiO2 Nanoparticles: Synthesis and Surface States of Nanoparticles of Mixed-Valence Magnéli Oxides.

Magnéli phases Tin O2n-1 (3

Synthesis of Ce2O2S and Gd2(1-y)Ce2yO2S Nanoparticles and Reactivity from in Situ X-ray Absorption Spectroscopy and X-ray Photoelectron Spectroscopy.

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 Ce2O2S nanoparticles of hexagonal shape were successfully prepared and characterized under inert conditions. Bimetallic Gd2(1-y)Ce2yO2S 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 L3-edge that show the partial oxidation of sulfide species and of CeIII to CeIV 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 Gd2O2S 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.