Ratiometric detection of hypochlorite applying the restriction to 2-way ESIPT: simple design for “naked-eye” tap water analysis

Abstract

We have designed an ESIPT-based ratiometric sensor (3-(benzo[d]thiazol-2-yl)-2-hydroxybenzylidene)thiosemicarbazide (BTHT) for detecting OCl⁻ with high selectivity and sensitivity and a “naked-eye” colour change (from orange to blue under UV light). Here, strong H-bonding-mediated inhibition of 2-way excited-state intramolecular proton transfer (ESIPT) in BTHT is observed over other anions and oxidants in aqueous solution. The sensor is remarkably efficient for the sensitive recognition of hypochlorites present in differentially treated tap water.