Tailored coordination chemistry: A novel Zn(II)-fluorescent coordination material for highly selective and sensitive detection of Hg²⁺ ions in aqueous environments

The pursuit of advanced sensing materials for precisely detecting heavy metal ions remains a critical imperative in environmental science. This manuscript deal with a novel fluorescent material, ZU-1, designed for the selective and sensitive detection of Hg²⁺ ions in aqueous suspension. Employing the Hard-Soft Acid-Base (HSAB) concept, Zn²⁺ serves as the d¹⁰ metal ion, and ZU-1 is synthesized with a −S donor ligand (NaSCN) and 2-pyridine methanol (Hhmp). The fluorescence sensing elucidates a unique detection mechanism, unveiling the distinctive coordination facilitated by the larger ionic radius and soft acid characteristics of Hg²⁺ with the −S donor sites in ZU-1. Fluorescence titration experiments validate ZU-1’s outstanding ability to selectively quench fluorescence intensity in the presence of Hg²⁺, even amidst interference from other metal ions. The quantitative analysis yields a Stern-Volmer constant (K_sv) of 7.5 × 10⁸ M⁻¹ and an exceptional limit of detection for Hg²⁺ at ∼0.60 ppm. ZU-1 further distinguishes itself through outstanding recyclability over four cycles, underscoring its potential as a sustainable and reusable sensor for real-time Hg²⁺ detection. Beyond its practical implications, this research contributes fundamental insights into design principles for materials exhibiting heightened selectivity and sensitivity to heavy metal ions.