A novel phenolphthalein-based fluorescent chemosensor for pyrophosphate detection via an Al³⁺ displacement approach...

Herein, we report a new phenolphthalein appended Schiff base (PASB) as reversible fluorescent sensor for the detection of pyrophosphate (PPi) ions through the metal displacement mechanism. PASB showed sensing exclusively toward Al³⁺ ions in DMF/H₂O (v/v = 1/4, pH 5.5) solution, which resulted in a significant fluorescence enhancement at 540 nm. The 1: 2 binding stoichiometry for the complex formation between PASB and Al³⁺ was confirmed by Job's plot and mass spectroscopic studies. Moreover, a solution of the in situ formed PASB-Al³⁺ complex displayed a high selectivity to PPi. The addition of PPi to PASB-Al³⁺ ensemble significantly quenched its fluorescence. Thus, a dual response was established based on "Off-On-Off" strategy for detection of both Al³⁺ and PPi. The detection limit is 5.86 nM and 26 nM for Al³⁺ and PPi, respectively. On this basis, we use PASB to detect Al³⁺ in food samples. Furthermore, PASB was successfully applicable to detect Al³⁺ and PPi for intracellular imaging in Human liver cancer cells.