Solution Synthesis of Actinide Chalcogenide and Oxychalcogenide Nanoparticles

We report the synthesis and characterization of a series: UOS, UOSe and β-US₂, the first examples of uranium-chalcogen-containing nanomaterials using colloidal synthetic techniques. The challenge to these syntheses is the oxophilicity of uranium, as uranium dioxide is difficult to avoid and the only actinide nanomaterial reported previously. All reagents, the metal, chalcogen source and solvent, were investigated to understand phase formation in solution. We found a post-synthetic modification, commonly known as digestive ripening, that led to size control of the β-US₂ nanoparticles. The phases were confirmed using powder x-ray diffraction and Rietveld analysis, as well as microscopy ( transmission electron microscopy), and magnetic susceptibility measurements. The oxychalcogenide nanomaterials are antiferromagnetic, in contrast to previously reported UO₂ nanoparticles. As found in bulk β-US₂, the nanoparticles are paramagnetic, with a moment consistent with localized f electrons.