Single source precursors for heterometallic fluoride nanomaterials
Résumé
The nanostructured and functionalized inorganic fluorides nanomaterials, ranging from nanoparticles or glass-ceramics to thin layers and coatings, find many important applications. However, due to scarcity of suitable metallic precursors, the chemical routes to heterobimetallic fluorides remain almost un-explored. We report new Na-Ln trifluoroacetate complexes with glyme ligands as excellent single source precursors for lanthanide-doped NaY(Gd)F4 upconverting nanocrystals, which efficiently convert near infra-red radiation to shorter wavelength UV-visible region. These heterometallic precursors have multiple advantages over the extensively used homometallic Ln(TFA)3(H2O)3 for above upconverting nanomaterials. These include their being anhydrous (presence of water molecules is detrimental for the up-converting properties), having comparatively low decomposition temperature and containing glyme ligand, which acts as a capping-reagent during decomposition to provide controlled size and stable dispersion of nanocrystals in organic solvents. A comparative study on the decomposition behaviour of the Na-Y and Na-Gd precursors shows that the hexagonal phase of the NaY(Gd)F4 matrix, which is many fold more efficient for the upconversion process, is easily obtained at much lower temperature for the latter. Catalytic applications of these nanocrystals, either as support for gold calalysts in the oxidation reactions or their nanocomposites with titania for NIR-driven photocatalysis will be discussed.