A dual recognition site-based ratiometric fluorescent probe with reversible mechanochromism and acetochromism for ultra-sensitive hypochlorite detection

Existing hypochlorite (ClO^-) probes often rely on a single recognition site, limiting their sensitivity and versatility. To address this, we designed and synthesized a phenothiazine-benzothiazole hydrazine-based ratiometric chemodosimeter (PBT-1) with dual hypochlorite recognition sites, achieving enhanced detection capabilities with an ultra-low detection limit of 0.026 nM. The probe exhibits greenish-yellow fluorescence and detects hypochlorite <i>via</i> sulfur oxidation followed by oxidative intramolecular cyclization, forming a non-fluorescent triazole product (PBT-1+ClO-). It also features reversible mechanochromism, acetochromism, positive solvatochromism, excellent stability, rapid response (1 second), and high selectivity over competing analytes. Mechanistic insights were supported by DFT calculations, ESI-MS, and ¹H NMR titration, with electrochemical sensing achieving an LOD of 1.105 nM. Practical applications included test strips, paddy roots, bean sprouts, and vegetables, showcasing its versatility and effectiveness. This dual-recognition strategy establishes a new benchmark for hypochlorite detection with superior sensitivity and multifunctionality.