Wang Xin-Yao, Yin Hua-Qing, Yin Xue-Bo
State Key Laboratory of Medicinal Chemical Biology and Tianjin Key Laboratory of Biosensing and Molecular Recognition, College of Chemistry, Nankai University, Tianjin 300071, P. R. China.
ACS Appl Mater Interfaces. 2020 May 6;12(18):20973-20981. doi: 10.1021/acsami.0c04147. Epub 2020 Apr 22.
Aggregation-caused quenching (ACQ) is often observed in covalent organic frameworks (COFs) for their low emission. Here, we propose that limited COF layers form on UiO-66 to eliminate the ACQ by the formation of UiO@COF composites. UiO-66 is selected because this metal-organic framework (MOF) is easily prepared in nanosize with Zr ion and 2-aminoterephthalic acid (BDC-NH). The high affinity of the Zr ion to phosphate species improves sensing selectivity. The surface -NH reacts with 2,4,6-triformylphloroglucinol (Tp) to integrate COF1 and COF2, which are prepared with Tp and phenylenediamine or tetraamino-tetraphenylethylene, respectively. The hydrogen bond formed between the hydroxyl group in Tp and imine nitrogen realizes excited-state intramolecular proton transfer; therefore, multiemission is observed from the enol and keto states of the COFs and UiO-66 at 360, 470, and 613 nm for UiO@COF1 and at 370, 470, and 572 nm for UiO@COF2. When phosphate ion is added in the composites, the emissions from the COFs keep stable, while that from UiO-66 is enhanced. However, adenosine-5'-triphosphate (ATP) improves the emissions from UiO-66 and COF's enol state, but that from the keto state keeps stable. The differentiation and ratiometric fluorescence detection of ATP and phosphate ion are therefore realized with the multiemission, the affinity of Zr ions, and the structural selectivity of the COFs. Thus, UiO@COF is a novel strategy to integrate multiemission, affinity, and structural selectivity to improve the sensing performance for differentiation and ratiometric detection.
聚集诱导猝灭（ACQ）现象在共价有机框架（COF）中较为常见，因其发射率较低。在此，我们提出在UiO - 66上形成有限的COF层，通过形成UiO@COF复合材料来消除ACQ。选择UiO - 66是因为这种金属有机框架（MOF）易于通过锆离子和2 - 氨基对苯二甲酸（BDC - NH）制备成纳米尺寸。锆离子对磷酸根物种的高亲和力提高了传感选择性。表面的 - NH与2,4,6 - 三甲基间苯三酚（Tp）反应以整合COF1和COF2，它们分别由Tp与苯二胺或四氨基四苯乙烯制备而成。Tp中的羟基与亚胺氮之间形成的氢键实现了激发态分子内质子转移；因此，对于UiO@COF1，在360、470和613 nm处观察到来自COF和UiO - 66的烯醇态和酮态的多发射，对于UiO@COF2，在370、470和572 nm处观察到多发射。当向复合材料中加入磷酸根离子时，COF的发射保持稳定，而UiO - 66的发射增强。然而，腺苷 - 5'-三磷酸（ATP）提高了UiO - 66和COF烯醇态的发射，但酮态的发射保持稳定。因此，利用多发射、锆离子的亲和力以及COF的结构选择性实现了ATP和磷酸根离子的区分及比率荧光检测。所以，UiO@COF是一种整合多发射、亲和力和结构选择性以提高区分及比率检测传感性能的新策略。
