A colorimetric/ratiometric chemosensor based on an aggregation-induced emission strategy for tracing hypochlorite in vitro and in vivo

Excessive levels of hypochlorite (ClO⁻) negatively affect environmental and biological systems. Thus, it is essential to develop sensors that can identify ClO⁻ in various systems such as the environment and living organisms. In this study, we report the development and evaluation of a novel aggregation-induced emission (AIE) strategy-based colorimetric and ratiometric fluorescent chemosensor 2,2′-(((1E,1′E)-[2,2′-bithiophene]− 5,5′-diylbis(methanylylidene))bis(hydrazin-1-yl-2-ylidene))bis(N,N,N-trimethyl-2-oxoethan-1-aminium) chloride (BMH-2∙Cl) for detecting ClO⁻. BMH-2∙Cl enabled highly selective ClO⁻ detection through a color change from yellow to colorless and a fluorescence color change from turquoise to blue in a perfect aqueous solution. BMH-2∙Cl exhibited low limits of detection (2.4 ×10⁻⁶ M for colorimetry and 2.9 ×10⁻⁷ M for ratiometric fluorescence) for detecting ClO⁻ with a rapid response within 5 s. The detection mechanism for ClO⁻ and an AIE property change of BMH-2∙Cl were demonstrated by ¹H NMR titration, ESI-MS, variation of water fraction (f_w) and theoretical calculations. In particular, we confirmed not only the practicality of BMH-2∙Cl by using test strips, but also demonstrated the potential for efficient ClO⁻ detection in biological and environmental systems such as real water samples, living zebrafish and bean sprouts.