Comprehensive Solid-State Characterization of Rare Earth Fluoride Nanoparticles

The combination of multinuclear solid-state NMR spectroscopy and powder X-ray diffraction has been applied to characterize the octahedron-shaped crystalline nanoparticle products resulting from an inverse micelle synthesis. Rietveld refinements of the powder X-ray diffraction data from the nanoparticles revealed their general formula to be (H3O)Y3F10 center dot xH(2)O. H-1 magic-angle spinning (MAS) NMR experiments provided information on sample purity and served as an excellent probe of the zeolithic incorporation of atmospheric water. F-19 MAS NMR experiments on a series of Monodisperse. nanoparticle. samples of various Sizes yielded spectra featuring three unique F-19 resonances arising from three different fluorine sites within the (H3O)Y3F10 center dot xH(2)O crystal structure. Partial removal of zeolithic water from the internal cavities and tunnels of the nanoparticles led to changes in the integrated peak intensities in the F-19 MAS NMR spectra; the origin of this behavior is discussed in terms of F-19 longitudinal relaxation. F-19-Y-89 variable-amplitude cross-polarization (VACP) NMR experiments on both stationary samples and samples under MAS conditions indicated that two distinct yttrium environments are present, and on the basis of the relative peak intensities, the population of one of the two sites is closely linked to the nanoparticle size. Both F-19 MAS and F-19-Y-89 VACP/MAS experiments indicated small amounts of an impurity present in certain nanoparticles; these are postulated to be spherical amorphous YF3 nanoparticles. We discuss the importance of probing molecular-level structure in addition to microscopic structure and how the combination of these characterization methods is crucial for understanding nanoparticle design, synthesis, and application.