A spirobifluorene-based water-soluble imidazolium polymer for luminescence sensing

Abstract

With increasing industrial development, heavy metal ions have been widely released, and fluorescence detection is an effective approach owing to its high selectivity and sensitivity. Herein, a water-soluble luminescent sensor based on a spirobifluorene-based imidazolium polymer (IMSPF-Br-COOH) is developed from tetraimidazole spirobifluorene and 3-bromo-2-bromomethylpropionic acid through a quaternization reaction. IMSPF-Br-COOH has an imidazolium cationic network and carboxyl coordination groups. Consequently, fluorescence quenching of IMSPF-Br-COOH exhibits high selectivity for Fe³⁺ and Cr₂O₇²⁻via coordination and anion exchange. The corresponding quenching coefficient (K_sv) is 2.0772 × 10³ L mol⁻¹ for Fe³⁺ and 1.0081 × 10⁴ L mol⁻¹ for Cr₂O₇²⁻. The detection limit (LOD) is calculated to be 170.56 μmol L⁻¹ for Fe³⁺ and 100.81 μmol L⁻¹ for Cr₂O₇²⁻. This work provides a novel approach for metal ion detection by water-soluble polymers.