A polyspirooxazine fluorescent probe for Fe2+/Fe3+ detection based on aggregation-caused quenching

Abstract

Iron ions are important species in biological, environmental and industrial systems, and fluorescent probes with simple preparation and clear signal output are desirable for their detection. Herein, a polyspirooxazine fluorescent material, denoted PSO, was synthesized from a diisatin monomer, diethyl acetylenedicarboxylate and a diisoquinoline monomer under mild conditions. NMR, FT-IR and GPC analyses confirmed the successful formation of PSO, which was obtained in 94.3% yield with an Mw of 13000 g mol−1 and a Ð of 1.41. PSO showed absorption at 300 – 400 nm and fluorescence emission at 400 – 600 nm under 320 nm excitation, together with typical aggregation-caused quenching behavior. Among the tested metal ions, Fe2+ and Fe3+ induced pronounced turn-off fluorescence responses, with detection limits of 9.90 and 6.33 μM, respectively. DLS and EDTA-2Na competition experiments suggested that iron-ion coordination with multiple accessible N/O sites arranged along the spirocyclic polymer backbone induces polymer-chain aggregation, leading to fluorescence quenching. These results demonstrate the potential of PSO as a polyspirooxazine-based fluorescent material for Fe2+/Fe3+ detection.