Ultrasensitive colorimetric/fluorescence dual-mode sensing platform based on quasi-NENU-5 for specific detection of glyphosate

Herein, a colorimetric/fluorescence dual-mode sensor was developed for ultrasensitive detection of glyphosate, utilizing a Cu-based quasi-metal-organic framework NENU-5 (QN-5) and green-emissive carbon dots (GCDs). QN-5 mimics laccase activity by catalyzing the conversion of oxygen (O 2 ) into superoxide radical (·O 2 − ), which then oxidizes the phenolic substrate 2,4-dichlorophenol (2,4-DP) in the presence of 4-aminoantipyrine (4-AP) to generate a distinct red quinone imine (λ Abs  = 510 nm, QI). The generated QI quenches the fluorescence of GCDs via the inner filter effect. However, the strong complexation between glyphosate and Cu 2+ inhibits the catalytic activity of QN-5, thereby reversing the colorimetric and fluorescence signals. The developed dual-mode sensor exhibits excellent sensitivity, achieving detection limits of 11 nM in fluorescence mode and 17 nM in colorimetric mode, with recoveries ranging from 92.50 % to 102.85 %. This sensor also exhibits satisfactory selectivity and anti-interference in real samples of soybean, soil, and river water.