Design and synthesis of new coumarin-based fluorescent chemosensors for the dual detection of Hg2+ and Cu2+ in aqueous and biological samples

Abstract

A novel series of coumarin-based Schiff base probes (1a–1d) were designed and synthesized for the highly selective and sensitive dual detection of Hg²⁺ and Cu²⁺ ions in aqueous buffer solutions and human blood serum samples, making them valuable tools in biomedical and environmental applications. These probes exhibited distinct optical responses, a fluorescence “turn-on” mechanism for Hg²⁺ via chelation-enhanced fluorescence (CHEF) and a quenching effect for Cu²⁺ due to paramagnetic interactions. Probe 1d demonstrated exceptional sensitivity, with detection limits of 36.75 nM for Hg²⁺ and 33 nM for Cu²⁺, along with rapid response times (<35 seconds). Selectivity was confirmed through UV-vis and fluorescence spectroscopy measurements, with minimal interference from other ions. Notably, the probes enabled naked-eye detection through visible color changes (green to yellow for Hg²⁺). Reversibility studies using EDTA highlighted their reusability. Practical applicability was validated by successful Hg²⁺/Cu²⁺ quantification in spiked blood serum samples, achieving recoveries 90–99.8% and 91–99.9% in absorption and fluorescence spectra, respectively. The probe complexes with Hg²⁺/Cu²⁺ could detect S²⁻. These findings underscore the potential of coumarin-based probes as efficient, cost-effective tools for real-time environmental monitoring and clinical diagnostics.