Department of Chemistry, Manipur University, Imphal-795003, India.
J Am Chem Soc. 2011 Mar 9;133(9):2998-3004. doi: 10.1021/ja1092437. Epub 2011 Feb 10.
YPO(4) nanoparticles codoped with Eu(3+) (5 at. %) and Bi(3+) (2-10 at. %) have been synthesized by a simple coprecipitation method using a polyethylene glycol-glycerol mixture, which acts as capping agent. It has been found that the incorporation of Bi(3+) ions into the YPO(4):Eu(3+) lattice induces a phase transformation from tetragonal to hexagonal, and also a significant decrease in Eu(3+) luminescence intensity was observed. This is related to the association of the water molecules in the hexagonal phase of YPO(4) in which the nonradiative process from the surrounding water molecules around Eu(3+) is dominating over the radiative process. On annealing above 800 °C, luminescence intensity recovers due to significant removal of water. 900 °C annealed Bi(3+) codoped YPO(4):Eu(3+) shows enhanced luminescence (2-3 times) as compared to that of YPO(4):Eu(3+). When sample was prepared in D(2)O (instead of H(2)O), 4-fold enhancement in luminescence was observed, suggesting the extent of reduction of multiphonon relaxation in D(2)O. This study illustrates the stability of water molecules even at a very high temperature up to 800 °C in Eu(3+) and Bi(3+) codoped YPO(4) nanoparticles.
采用简单的共沉淀法，以聚乙二醇-甘油混合物作为包覆剂，合成了 YPO(4)纳米粒子共掺 Eu(3+)（5 原子%）和 Bi(3+)（2-10 原子%）。研究发现，Bi(3+)离子掺入 YPO(4):Eu(3+)晶格中会引起从四方相到六方相的转变，同时观察到 Eu(3+)发光强度显著降低。这与 YPO(4)中六角相水分子的缔合有关，其中来自周围水分子的非辐射过程在 Eu(3+)的辐射过程中占主导地位。在 800°C 以上退火时，由于大量去除水，发光强度恢复。与 YPO(4):Eu(3+)相比，900°C 退火的 Bi(3+)共掺 YPO(4):Eu(3+)显示出增强的发光（2-3 倍）。当在 D(2)O（而不是 H(2)O）中制备样品时，观察到发光强度增强了 4 倍，表明在 D(2)O 中多声子弛豫的程度降低了。这项研究表明，即使在高达 800°C 的非常高的温度下，Eu(3+)和 Bi(3+)共掺 YPO(4)纳米粒子中的水分子也很稳定。
