An acylhydrazone-based fluorescent sensor for sequential recognition of Al³⁺ and H₂Po₄ ⁻

A novel acylhydrazone-based fluorescent sensor NATB was designed and synthesized for consecutive sensing of Al³⁺ and H₂ PO₄⁻. NATB displayed fluorometric sensing to Al³⁺ and could sequentially detect H₂ PO₄⁻ by fluorescence quenching. The limits of detection for Al³⁺ and H₂ PO₄⁻ were determined to be 0.83 and 1.7 µM, respectively. The binding ratios of NATB to Al³⁺ and NATB-Al³⁺ to H₂ PO₄⁻ were found to be 1:1. The sequential recognition of Al³⁺ and H₂ PO₄ − by NATB could be repeated consecutively. In addition, the practicality of NATB was confirmed with the application of test strips. The sensing mechanisms of Al³⁺ and H₂ PO₄⁻ by NATB were investigated through fluorescence and UV–Visible spectroscopy, Job plot, ESI-MS,¹ H NMR titration, and DFT calculations.