Dual-mode fluorescence and colorimetric sensor based on a novel Wurster-type twisted covalent organic framework for determination of HSO4ˉ with excellent selectivity and sensitivity in water and serum

Abstract

A novel wurster-type twisted covalent organic framework (TNCOF) composed of N, N, N', N'-tetrakis(4-aminophenyl)-1,4-benzenediamine and 2,6-naphthalenedicarbaldehyde was synthesized and characterized. TNCOF exhibits exceptional crystallinity, as well as remarkable thermal and chemical stability. TNCOF in 1,4-dioxane exhibits highly selective and sensitive “on-off” fluorescent and colorimetric sensing ability towards HSO4ˉ over the other anions with fast response time. The fluorescence color of TNCOF suspension changes from pink to blue under the 365 nm UV lamp. Meanwhile, the color also changes under day light from grapefruit color to colorless. Both the fluorescence intensity at 597 nm and absorbance at 255 nm are linear relationship against the concentration of HSO4ˉ over a broad range, with lower limits at the micromolar level. The XPS, FTIR spectra and DFT calculation prove that TNCOF forms complex with HSO4ˉ via the hydrogen bonding. TNCOF demonstrates high recovery for detecting HSO4ˉ in practical water samples and serum, making it a suitable chemosensor for the identification and detection of HSO4ˉ.