Journal of Fluorescence ( IF 2.6 ) Pub Date : 2022-10-12 , DOI: 10.1007/s10895-022-03036-8 Manpreet Kaur 1 , Mohamad Yusuf 1 , Ashok Kumar Malik 1
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In this research, Zn- or Cd-based metal–organic frameworks (coded ZnMOF-1 and CdMOF-1) containing benzene-1,4-dicarboxylic acid (H2bdc) and pyridyl-based Schiff base (4-pyridylcarboxaldehydeisonicotinoylhydrazone (L)) dual ligands were successfully assembled via a conventional solvothermal method. The photoluminescence quenching response of ZnMOF-1 and CdMOF-1 and their sensing sensitivity and selectivity towards various inorganic anions were evaluated in aqueous media. Crystallographic and thermogravimetric studies confirm the formation of both MOFs with good crystallinity and thermal stability. Photoluminescence studies also verify the selectivity of ZnMOF-1 and CdMOF-1 for efficient sensing of inorganic oxyanions (like chromate/dichromate: CrO42− and Cr2O72−). Further, it was noted that only chromate/dichromate (CrO42−/Cr2O72−) anions showed a significant turn-off quenching effect while other anions (like F−, Br−, I−, Cl−, ClO4−, SCN−, SO42−, NO3−, and NO2−) have a low/negligible effect on the photoluminescence intensity of both MOFs. The limit of detection (LOD) of chromate/dichromate by ZnMOF-1 and CdMOF-1 was 9.79/10.94 µM and 2.68/1.48 µM, respectively. A probable mechanism for turn-off quenching response towards chromate and dichromate anions could be attributed to the spectral overlap of both excitation and emission spectra of ZnMOF-1/CdMOF-1 with the absorption spectra of chromate/dichromate anions. As a result, the energy transfer from ZnMOF-1 or CdMOF-1 to the target chromate and dichromate anions decreased fluorescence intensity (i.e., fluorescence quenching effect).
Graphical Abstract
中文翻译：
席夫碱功能化金属有机骨架选择性检测水中的铬酸盐和重铬酸盐
在这项研究中，基于 Zn 或 Cd 的金属有机框架（编码为 ZnMOF-1 和 CdMOF-1）含有苯-1,4-二羧酸（H 2 bdc）和基于吡啶基的席夫碱（4-吡啶基甲醛异烟酰腙（L )) 双配体通过传统的溶剂热法成功组装。在水性介质中评估了 ZnMOF-1 和 CdMOF-1 的光致发光猝灭响应及其对各种无机阴离子的传感灵敏度和选择性。晶体学和热重研究证实了两种 MOF 的形成都具有良好的结晶度和热稳定性。光致发光研究还验证了 ZnMOF-1 和 CdMOF-1 对无机氧阴离子（如铬酸盐/重铬酸盐：CrO 4 2−和 Cr 2O 7 2 -）。此外，注意到只有铬酸盐/重铬酸盐 (CrO 4 2- /Cr 2 O 7 2- ) 阴离子显示出显着的关断淬灭效应，而其他阴离子（如 F -、Br -、I -、Cl -、ClO 4 -、SCN -、SO 4 2-、NO 3 -和NO 2 -) 对两种 MOF 的光致发光强度的影响很小/可以忽略不计。ZnMOF-1 和 CdMOF-1 对铬酸盐/重铬酸盐的检测限 (LOD) 分别为 9.79/10.94 µM 和 2.68/1.48 µM。对铬酸盐和重铬酸盐阴离子的关闭猝灭响应的可能机制可归因于 ZnMOF-1/CdMOF-1 的激发和发射光谱与铬酸盐/重铬酸盐阴离子的吸收光谱的光谱重叠。结果，从 ZnMOF-1 或 CdMOF-1 到目标铬酸盐和重铬酸盐阴离子的能量转移降低了荧光强度（即荧光猝灭效应）。
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