A Miniaturized Linear pH Sensor Based on a Highly Photoluminescent Self-Assembled Europium(III) Metal-Organic Framework
A Miniaturized Linear pH Sensor Based on a Highly Photoluminescent Self-Assembled Europium(III) Metal-Organic Framework
复制标题
DOI：
10.1002/anie.200902045
复制
发表时间：
2009-01-01
影响因子：
16.6
通讯作者：
Rocha, Joao
中科院分区：
文献类型：
--
作者：
Harbuzaru, Bogdan V.;Corma, Avelino;Rocha, Joao
具有二维或三维结构的稀土金属有机骨架(LnMOF)的领域正在迅速增长，这是因为新的晶体结构具有有趣的性质，并在催化、[5-13]传感器、[14-19]造影剂、[20]非线性光学、[21，22]显示器、[23]和电致发光器件中具有潜在的应用。将配体和天线的性质结合在一个有机部分中是非常可取的。众所周知，1，10-邻菲咯啉-2，9-二羧酸(H_2PhenDCA)是一种对溶液中的Eu~(3+)离子有很强增敏作用的配体，其中的羧基和邻菲咯啉部分都可以配位到金属中心。[26，27]配位部分之间的接近意味着这种络合剂有形成零维(分子)络合物的趋势，这些络合物在一些基于溶液的分析应用中是有用的，但不能用作固体传感器或发光材料。因此，获得这些零维水溶性络合物的二维或三维不可溶的对应物是有意义的。为了实现这一目标，我们使用了水热合成，这是一种强大的技术来制备用传统方法可能无法获得的亚稳态化合物。[28，29]水热合成还允许使用在373K以下的水中少量溶解的螯合剂，从而增强了配体的稀土配位能力。本文报道了一种新型Eu3+金属有机骨架ITQMOF-3-Eu(ITQMOF=Instituto de Tecnologia Quimica金属有机骨架)的合成、结构和传感性能。Eu3+ITQMOF-3(ITQMOF-3-Eu)的吸收、能量传递和发射速率之间的良好平衡使我们能够制造出在生物感兴趣的范围(5-7.5)内工作的微型pH传感器原型。通过将这种材料与光纤相结合，实现了线性光致发光响应，并允许在此pH范围内对发射信号进行自校准。ITQMOF-3-Eu材料是通过H_2PhenDCA配体与Eu~(3+)盐或氧化物在水热条件下反应得到的(见支持信息)。该晶体在紫外光下具有强烈的红色发光(见图1a)。化学和元素分析表明，该材料的分子式为[Eu3(C14H6N2O4)4(OH)(H2O)4]·2H2O。
The field of lanthanide-based metal–organic frameworks (LnMOFs) with two-or three-dimensional structures [1–4] is rapidly growing because of the discovery of new crystalline structures that exhibit interesting properties and have potential applications in catalysis,[5–13] sensors,[14–19] contrast agents,[20] non-linear optics,[21, 22] displays,[23] and electroluminescent devices.[24] For photoluminescence applications, it is necessary to prepare lanthanide-containing materials with high quantum efficiencies, in order to achieve the required miniaturization and reduce energy losses from undesirable quenching processes.[25] Moreover, it is highly desirable to combine the properties of ligands and antennae in one organic moiety. A well-known powerful sensitizing ligand for Eu3+ ions in solution is 1, 10-phenanthroline-2, 9-dicarboxylic acid (H2PhenDCA), in which both carboxylic and phenanthroline moieties may coordinate to the metal center.[26, 27] The proximity between the coordinative parts means that this chelating agent has the tendency to form zero-dimensional (molecular) complexes that are useful in some solution-based analytical applications, but cannot be applied as solid sensors or light-emitting materials. Thus, it is of interest to obtain the two-or three-dimensional insoluble counterparts of these zero-dimensional water-soluble complexes. To achieve this goal, we have used hydrothermal synthesis, which is a powerful technique for the preparation of metastable compounds that may not be accessible by using conventional methods.[28, 29] Hydrothermal synthesis also allows the use of chelating agents that are sparingly soluble in water at temperatures below 373 K, thus enhancing the lanthanidecoordinating ability of the ligand. Herein, we report the synthesis, structure, and sensing properties of a new Eu3+ metal–organic frameworkITQMOF-3-Eu (ITQMOF= Instituto de Tecnologia Quimica Metal Organic Framework) that contains the ligand 1, 10-phenanthroline-2, 9-dicarboxylic acid. The excellent balance between absorption, energy transfer, and emission rate of the Eu3+ ITQMOF-3 (ITQMOF-3-Eu) allowed the fabrication of a miniaturized pH sensor prototype that functions in the biologically interesting range (5–7.5). By combining this material and an optical fiber, a linear photoluminescence response, which also allows the self-calibration of the emitting signal within this pH range, was achieved. The ITQMOF-3-Eu material was obtained by reacting the H2PhenDCA ligand and the Eu3+ salt or oxide under hydrothermal conditions (see the Supporting Information). The crystal has a strong red luminescence under ultraviolet light (see Figure 1a). Chemical and elemental analyses showed that the formula of the material is [Eu3 (C14H6N2O4) 4 (OH)(H2O) 4]· 2 H2O.