Ratiometric fluorescence sensor based on europium-organic frameworks for selective and quantitative detection of cerium ions

Yaohui Wang; Yi Zheng; Feng Huo; Qian Zhang; Xiupei Yang; Pran Gopal Karmaker

doi:10.1016/j.aca.2023.342131

Ratiometric fluorescence sensor based on europium-organic frameworks for selective and quantitative detection of cerium ions

Anal Chim Acta. 2024 Jan 25:1287:342131. doi: 10.1016/j.aca.2023.342131. Epub 2023 Dec 13.

Authors

Yaohui Wang¹, Yi Zheng¹, Feng Huo², Qian Zhang¹, Xiupei Yang³, Pran Gopal Karmaker⁴

Affiliations

¹ College of Chemistry and Chemical Engineering, Chemical Synthesis and Pollution Control Key Laboratory of Sichuan Province, China West Normal University, Nanchong, 637000, China.
² College of Chemistry and Chemical Engineering, Chemical Synthesis and Pollution Control Key Laboratory of Sichuan Province, China West Normal University, Nanchong, 637000, China; School of Chemistry and Chemical Engineering, Analytical Testing Center, Institute of Micro/Nano Intelligent Sensing, Neijiang Normal University, Neijiang, 641100, China.
³ College of Chemistry and Chemical Engineering, Chemical Synthesis and Pollution Control Key Laboratory of Sichuan Province, China West Normal University, Nanchong, 637000, China. Electronic address: xiupeiyang@cwnu.edu.cn.
⁴ College of Chemistry and Chemical Engineering, Chemical Synthesis and Pollution Control Key Laboratory of Sichuan Province, China West Normal University, Nanchong, 637000, China. Electronic address: pranchem2012@gmail.com.

PMID: 38182353
DOI: 10.1016/j.aca.2023.342131

Abstract

Background: Due to the unavoidable use of cerium in daily life, the accumulation of cerium in the environment increases health risks for humans. Therefore, it is crucial to develop a chemical sensing technology for the rapid, sensitive, and selective detection of cerium ions.

Results: In this research work, a novel two-dimensional chain structure of a europium-based metal organic framework (Eu-MOF) [Eu₂(tcpa)(Htcpa)₂] was synthesized by using 3,4,5,6-tetrachloro-1,2-benzenedicarboxylic acid (H₂TCPA) as the ligand and europium nitrate as the metal source. The results of powder X-ray diffraction and thermogravimetric analysis show that the synthesized Eu-MOF has excellent chemical and thermal stability. When the Eu-MOF suspension was excited by ultraviolet light at 292 nm, four fluorescence emissions were observed at 420, 595, 620 and 705 nm. It was particularly interesting that when cerium ions (Ce³⁺/Ce⁴⁺) were added to the Eu-MOF suspension, the fluorescence intensity at 420 nm was enhanced, while the fluorescence at 620 nm was quenched. On this basis, a ratiometric fluorescent sensor for detecting cerium ions was constructed, which has a good linear relationship in the range of 0.05-15 μM and a detection limit of 16 nM. The plausible mechanism of the change in the fluorescence characteristics of Eu-MOF caused by cerium ions was discussed in detail. Through the study of fluorescence lifetime and ultraviolet absorption, it was proven that the mechanism of Ce³⁺-quenching Eu-MOF fluorescence is the inner filter effect. Photoinduced electron transfer and internal filtering effects lead to fluorescence quenching at 620 nm, while redox reactions lead to fluorescence enhancement of the ligand at 420 nm.

Significance: The proposed ratiometric fluorescence sensor was successfully employed for the detection of cerium ions in real water samples, confirming that it can be used as an alternative method for the detection of Ce³⁺ and Ce⁴⁺ in environmental samples.

Keywords: Cerium ions; Chemosensor; Eu-MOF; Fluorescence quenching; Inner filter effect.