Department of Chemistry, Manipur University, Imphal-795003, India.
J Am Chem Soc. 2010 Mar 3;132(8):2759-68. doi: 10.1021/ja909578s.
Ce(3+)- and Eu(3+)-doped YPO(4) nanorods have been prepared at relatively low temperature (120 degrees C). A detailed investigation of the role of Ce(3+) concentration up to 10 atom % on the luminescence intensity of Eu(3+) in Ce(3+)- and Eu(3+)-doped YPO(4) has been carried out. Phase transformation from a tetragonal to a hexagonal structure occurs with increasing Ce(3+) concentrations, and water molecules are also associated during phase transformation. Thermal study shows that water can be retained up to 800 degrees C in the hexagonal structure. Interestingly, the hexagonal structure returns to the tetragonal structure on annealing above 900 degrees C. As-prepared and 500 degrees C heated samples show uniform sized nanorods, whereas a 900 degrees C heated sample shows distorted nanorods in which pores are present. Initially, the luminescence intensity decreases sharply with increasing Ce(3+) concentrations, even for 2 atom %. This is related to the enhanced nonradiative rate as compared to the radiative rate, since multiphonon relaxation to surrounding water molecules increases. This is not due to the possible oxidation-reduction process between Eu(3+) and Ce(3+) to give Eu(2+) and Ce(4+), as confirmed by X-ray photoelectron spectroscopy and luminescence studies. Then, a significant enhancement of luminescence intensity occurs on annealing above 900 degrees C. This can be ascribed to the loss of water molecules during a phase transformation from the hydrated hexagonal to the dehydrated tetragonal phase. To the authors' knowledge, we for the first time performed a luminescent study with a change of solvent from H(2)O to D(2)O, and significant enhancement in luminescence is found.
Ce(3+) 和 Eu(3+) 掺杂的 YPO(4) 纳米棒已在相对较低的温度（120°C）下制备。详细研究了 Ce(3+) 浓度高达 10 原子%时对 Ce(3+) 和 Eu(3+)掺杂的 YPO(4)中 Eu(3+)发光强度的影响。随着 Ce(3+)浓度的增加，会发生从四方相到六方相的相变，并且在相变过程中也会结合水分子。热研究表明，在六方结构中水可以保留到 800°C。有趣的是，在高于 900°C 的退火温度下，六方结构会回到四方结构。制备的和在 500°C 下加热的样品显示出均匀尺寸的纳米棒，而在 900°C 下加热的样品显示出扭曲的纳米棒，其中存在孔。最初，随着 Ce(3+)浓度的增加，发光强度急剧下降，即使是 2 原子%。这与增强的非辐射速率有关，因为多声子弛豫到周围的水分子会增加。这不是由于 Eu(3+)和 Ce(3+)之间可能的氧化还原过程导致 Eu(2+)和 Ce(4+)，正如 X 射线光电子能谱和发光研究所证实的那样。然后，在高于 900°C 的退火温度下，发光强度显著增强。这可以归因于在水合六方相向脱水四方相的相变过程中水分子的损失。据作者所知，我们首次进行了从 H(2)O 到 D(2)O 的溶剂变化的发光研究，并发现发光强度显著增强。
