Dual Recognition Site-Based Ratiometric Fluorescent Probe with Reversible Mechanochromism and Acetochromism for Ultra-Sensitive Hypochlorite Detection

Abstract

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 via 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