A triphenylamine‐based carbohydrazide hydrazone fluorescent probe for selective detection of hypochlorite and sensing acidic gases

Hypochlorous acid and its hypochlorite are important reactive oxygen species in the body, and are involved in various physiological processes related to immunity; their rapid detection is of great significance. Here, we synthesized a fluorescent probe (TPAS) by condensation of 4‐(diphenylamino)benzaldehyde, carbohydrazide, and salicylaldehyde, which can be used for the detection of ClO − in water and sensing of acidic gas in its solid state. The probe showed strong selective recognition of ClO − in acetonitrile and good tolerance to interference ions. There were good linear responses between the intensity of absorbance and fluorescence and the amount of ClO − . The TPAS solid and its paper strips can emit red fluorescence when exposed to volatile acidic vapours. After being treated with NH 3 , the red fluorescence can be restored to yellow. The response process of TPAS to ClO − and acid gases was characterized using nuclear magnetic resonance, electrospray ionisation mass spectrometry, transmission electron microscopy, and density functional theory calculations. Furthermore, it can be utilized in analyzing ClO − in commercially available bleaching products; the detection results were basically compatible with the labelled values. In addition, the probe is biocompatible and can be applied for imaging ClO − in zebrafish.