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首页> 外文期刊>RSC Advances >Origin of blue emission in ThO2 nanorods: exploring it as a host for photoluminescence of Eu3+, Tb3+ and Dy3+
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Origin of blue emission in ThO2 nanorods: exploring it as a host for photoluminescence of Eu3+, Tb3+ and Dy3+

机译：ThO2纳米棒中蓝色发射的起源：将其作为Eu3 +，Tb3 +和Dy3 +的光致发光主体

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Nanorods of ThO2 were synthesized in a reverse micelle technique using cetyl trimethyl ammonium bromide as a surfactant and characterized by X-ray diffraction and transmission electron microscopy. Doping with europium, terbium and dysprosium was performed at a 1.0 mol% level and was confirmed using XRD. Photoluminescence study showed that nanorods of thoria emit blue color on UV-excitation. Lifetime and electron paramagnetic resonance (EPR) spectroscopy showed that this blue emission is because of oxygen vacancy. First principle calculations using projector augmented wave potentials and generalized gradient approximations predicted that the structural relaxation due to neutral and positively charged oxygen defects in bulk thoria leads to symmetric distortion around the vacancy sites and this prediction was experimentally complemented by measuring highly symmetric isotropic signal with g = 1.959 in EPR studies. Density of states analysis showed the presence of defects states mainly attributed to Th d and f states near the conduction band minima for the double positively charged oxygen vacancy. The radiative transitions from these states qualitatively explain blue emission in thoria. On the basis of the time resolved emission data (TRES), it has been inferred that two different types of Ln(3+) ions were present in the thoria nanorods: A long lived species (tau similar to 1.5 ms) was present at cubic site with Oh symmetry and the other was a short lived species (tau similar to 300 mu s) present at the non-cubic site with C-3v symmetry. Most of Eu and Tb are distributed in cubic site with Oh symmetry whereas Dy is mainly localized at the non-cubic site with C-3v symmetry. Under UV light excitation, ThO2:Ln(3+) nanorods show the characteristic f-f transitions of Ln(3+) (Eu, Tb and Dy) ions and give bright red, green, bluish-yellow emission, respectively. In addition, multicoloured luminescence containing white emission has been successfully achieved for tri-doped ThO2:Ln(3+) phosphors by simultaneous doping with all the three lanthanides ions and adjusting their doping concentrations for the simultaneous luminescence of Ln(3+) in the ThO2 host.
机译：以十六烷基三甲基溴化铵为表面活性剂，通过反胶束技术合成了ThO2纳米棒，并通过X射线衍射和透射电镜进行了表征。以1.0mol％的水平掺杂a，ter和，并使用XRD确认。光致发光研究表明，氧化ria的纳米棒在紫外线激发下发出蓝色。寿命和电子顺磁共振（EPR）光谱表明，这种蓝色发射是由于氧空位引起的。使用投影仪增强波势和广义梯度近似进行的第一原理计算预测，由于本体氧化ria中性和带正电的氧缺陷而导致的结构弛豫会导致空位附近的对称畸变，并且该预测通过在实验中通过测量具有g的高对称各向同性信号得到了补充。在EPR研究中= 1.959。态密度分析表明，缺陷态的存在主要归因于双带正电荷的氧空位的导带极小值附近的Th d和f态。这些状态的辐射跃迁定性地解释了氧化ria中的蓝色发射。根据时间分辨发射数据（TRES），可以推断出在氧化ria纳米棒中存在两种不同类型的Ln（3+）离子：立方中存在长寿命物种（tau类似于1.5 ms）具有Oh对称性的位点，另一个是存在于C-3v对称的非立方位点的短寿命物种（tau约300 s）。 Eu和Tb的大部分分布在具有Oh对称性的立方位置，而Dy主要位于具有C-3v对称性的非立方位置。在紫外光激发下，ThO2：Ln（3+）纳米棒显示Ln（3 +）（Eu，Tb和Dy）离子的特征性f-f跃迁，并分别发出亮红色，绿色，蓝黄色。此外，三掺杂ThO2：Ln（3+）荧光粉通过同时掺杂所有三个镧系元素离子并调节其掺杂浓度以实现Ln（3+）同时发光，已经成功实现了三掺杂ThO2：Ln（3+）荧光粉的白色发射。 ThO2主机。

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