Ratiometric fluorescence assay for sulfide ions with fluorescent MOF-based nanozyme

• Published in: Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy Molecular and biomolecular spectroscopy, 2023-07, Vol.295, p.122620, Article 122620
• Main Authors: Zhu, Nianlei, Deng, Tinghui, Zuo, Ya-Nan, Sun, Jing, Liu, Huwei, Zhao, Xian-En, Zhu, Shuyun
• Format: Article
• Language: English
• Subjects: Autocatalytic reaction; Inner filter effect; Metal-organic framework; Oxidase-mimic; Ratiometric fluorescence; Sulfide ions
• ISSN: 1386-1425
• DOI: 10.1016/j.saa.2023.122620

A ratiometric fluorescence strategy has been designed for the detection of sulfide ions with fluorescent MOF-based nanozyme, which acts as fluorescence reporter as well as biomimetic oxidase. [Display omitted] •A ratiometric nanosensor for S2- based on multifunctional MOF was established for the first time.•NH2-Cu-MOF exhibits biomimetic oxidase activity besides its intrinsic fluorescence.•The presence of S2- inhibits the oxidase-like activity of MOF due to the formation of CuS.•The in situ-formed fluorophore can avoid additional synthesis of another probe. A novel ratiometric fluorescence strategy for sulfide ions (S2-) analysis has been developed using metal–organic framework (MOF)-based nanozyme. NH2-Cu-MOF displays blue fluorescence (λem = 435 nm) originating from 2-amino-1,4-benzenedicarboxylic acid ligand. Besides, it possesses oxidase-like activity due to Cu2+ node, which can trigger chromogenic reaction. o-Phenylenediamine (OPD), as a common enzyme substrate, can be oxidized by NH2-Cu-MOF to form luminescent products (oxOPD) (λem = 570 nm). Inner filter effect occurs between oxOPD and MOF. Upon exposure to S2-, oxidase-like activity of MOF is depressed significantly because of the generation of CuS. On one hand, the amount of free Cu2+ decreases, affecting the yielding of oxOPD. On the other hand, CuNPs with larger size are obtained during the oxidation–reduction reaction between Cu2+ and OPD, which show weaker autocatalytic ability for OPD oxidation. These result in the decrease and increase of intensities at 570 and 435 nm, respectively. This method exhibits sensitive and selective responses towards S2- with LOD of 0.1 μM. Furthermore, such ratiometric strategy has been applied to detect S2- in food samples.