Supramolecular self-assembly enhanced europium(III) luminescence under visible light.
Supramolecular self-assembly enhanced europium(III) luminescence under visible light.
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DOI：
10.1039/c4sm00335g
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发表时间：
2014-06
期刊：
影响因子：
3.4
通讯作者：
Limin Xu;Liangzhu Feng;Yuchun Han;Yu Jing;Zhaoyang Xian;Zhuang Liu;Jianbin Huang;Yun Yan
中科院分区：
文献类型：
--
作者：
Limin Xu;Liangzhu Feng;Yuchun Han;Yu Jing;Zhaoyang Xian;Zhuang Liu;Jianbin Huang;Yun Yan
本文报道了在水介质中用可见光直接激发Eu离子的发光。当用双位配体1，11-bis(2，6-dicarboxypyridin-4-yloxy)-3，6，9-trioxaundecane(L2EO4)取代所有围绕中心Eu离子配位的水分子时，有效地消除了水分子的猝灭，提供了相当大的Eu发射。通过与带正电的嵌段聚电解质按化学计量混合，带负电荷的L2EO4-Eu配位络合物可以转变为配位聚合物，同时由于荧光寿命测量表明L2EO4配位Eu(III)的比例增加，形成的静电胶束进一步增强了Eu的荧光发射。这种方法避免了经常使用紫外线作为辐射源的天线效应的使用。我们进一步将这些胶束用于生物成像，并首次展示了使用直接激发的含Eu的纳米探针在可见激发下对小动物进行体内荧光成像。虽然文献结果表明，在配位配体存在的情况下，Eu离子在水中的直接激发可能会导致发射，但由于配位球中剩余的水分子，这些发射太弱而不能应用。我们的工作指出，在排除配位球中所有水分子的情况下，Eu的直接激发可以产生相当大的Eu发射，这不仅大大减少了实验室合成天线分子的繁琐工作，而且有利于Eu在可见光下在水介质中的应用。
In this paper, we report on the luminescence of europium by directly exciting europium ions with visible light in aqueous medium. Upon replacing all the water molecules that coordinate around a central europium ion with a ditopic ligand 1,11-bis(2,6-dicarboxypyridin-4-yloxy)-3,6,9-trioxaundecane (L2EO4), the quenching from water molecules is efficiently eliminated, offering considerable europium emission. By stoichiometrically mixing with a positively charged block polyelectrolyte, the negatively charged L2EO4-Eu coordinating complex can be transformed into a coordination 'polymer', which simultaneously forms electrostatic micelles with further enhanced europium fluorescence emission, owing to the increased fraction of L2EO4-coordinated Eu(III) as revealed by the fluorescence lifetime measurements. This approach avoids the use of the antenna effect that often utilizes UV light as the irradiation source. We further use those micelles for bio-imaging, and for the first time demonstrate the use of directly excited Eu-containing nano-probes for in vivo fluorescence imaging in small animals under visible excitation. Although literature results have shown that the direct excitation of europium ions in water may lead to emissions in the presence of coordinating ligands, those emissions were too weak to be applied due to the remaining water molecules in the coordination sphere. Our work points out that the direct excitation of europium can generate considerable europium emission given that all the water molecules in the coordination sphere are excluded, which does not only greatly reduce tedious lab work in synthesizing antenna molecules, but also facilitates the application of europium in aqueous medium under visible light.