Ionic-liquid-stabilized fluorescent probe based on S-doped carbon dot-embedded covalent-organic frameworks for...

An ionic-liquid-stabilized fluorescent probe for histamine is described. Sulfur-doped carbon dots (S-CDs) were incorporated into a covalent organic framework (COF) that was prepared from 1,3,5-triformylphloroglucinol and 2,5-dimethyl-p-phenylenediamine by one-pot hydrothermal polymerization in the dark. The blue fluorescence of the S-CDs (with excitation/emission maxima at 350/440 nm) is enhanced (compared to undoped CDs) due to element doping by ionic-liquid modification. The COF is resistant to acids, bases, and boiling water. The fluorescence of the probe is statically quenched by histamine, and quenching follows the Stern-Volmer equation. The normalized fluorescence of the probe drops in the 10 to 1000 μg kg^-1 histamine concentration range, and the limit of detection is 5.3 μg kg^-1. The probe was successfully applied to the analysis of wine and fermented meat products. The recoveries from spiked samples range between 84.6 and 115.3%. The method is selective, sensitive, stable and repeatable. The mechanisms of the fluorometric response and molecular recognition were explored. Graphical abstractSchematic presentation of ionic-liquid-stabilized fluorescent probe based on S-doped carbon dot-embedded covalent organic framework for determination of histamine. The ionic liquid [VBIm][BF₄] reacts with MPTS-modified carbon dots to enhance the fluorescence signal for analyte recognition.