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Simple and Efficient Synthesis of a Nd: LaAlO3 NIR Nanophosphor from Rare Earth Alkoxo-Monoaluminates Ln(2)Al(2)((OPr)-Pr-i)(12)((PrOH)-Pr-i)(2) Single Source Precursors by Bradley Reaction

Pazik, Robert; Seisenbaeva, Gulaim; Gohil, Suresh; Wiglusz, Rafal; Kepinski, Leszek; Strek, Wieslaw; Kessler, Vadim


Nanoparticles of a Nd-doped LaAlO3 perovskite can be obtained rapidly and with quantitative yield using the Bradley (ether elimination) treatment of a mixture of individual Ln(2)Al(2)((OPr)-Pr-i)(12)((PrOH)-Pr-i)(2), Ln = La, Nd, in acetophenone. The initially produced particles are poorly crystalline, but their crystallinity improves strongly on heating to 800 degrees C, which leads also to a controllable aggregation, The prepared nanoparticles are rather solution stable and can easily be surface-modified, which opens prospects for their use as phosphors in bioimaging applications. The precursors, bimetallic isopropoxides of rare earth elements and aluminum with a 1:1 composition, Ln(2)Al(2)((OPr)-Pr-i)(12)((PrOH)-Pr-i)(2), can be prepared with high yields via direct dissolution of metallic lanthanoids in a solution of aluminum isopropoxide in a toluene - isopropanol medium or through a short time reflux of "Ln((OPr)-Pr-i)3" with 1 equiv of Al((OPr)-Pr-i)(3) in toluene. In spite of good volatility and their proper composition, the Ln(2)Al(2)((OPr)-Pr-i)(12)((PrOH)-Pr-i)(2), Ln = La, Nd,do not act as single-source precursors in MOCVD, because of their quantitative transformation into LnAl(3)((OPr)-Pr-i)(12) together with Ln(5)O((OPr)-Pr-i)(13) on evaporation. These molecules are, however, present intact in solution according to variable temperature NMR studies, which permits application of them successfully as single source precursors in the synthesis of Ln:LaAlO3 perovskite nanopowders with compositions thoroughly controlled through the conditions of the synthesis. Luminescent properties of the Nd:LaAlO3 were examined and discussed in detail. The thermal population of the F-4(5/2) and H-2(9/2) states was found as a consequence of the grain size effect causing difficulties in heat dissipation. Moreover, luminescence behavior of the powder annealed at a lowest temperature shows well-defined short-range order.

Publicerad i

Inorganic Chemistry
2010, Volym: 49, nummer: 6, sidor: 2684-2691