Construction of an ultrasensitive hypochlorite fluorescent probe based on a novel chromophore fragmentation strategy

•LAB core is utilized as a recognition unit for HClO based on a novel chromophore fragmentation sensing mechanism.•The colorimetric and ratiometric fluorescence “turn on” signals for naked eyes are shown.•The practical applications in real samples (water and vegetable) are demonstrated.•The fluorescence “turn on” imaging for detection of HClO in mung bean sprout is successfully achieved. The excess intake of hypochlorite (ClO−) in the human body and excessive emission in wastewater can pose serious health risks and environmental pollution. Therefore, it is vital to develop an efficient method for detecting ClO− in foodstuff and water. In this work, we reported a lactam-fused aza-BODIPY (LAB1) for ultrasensitive ClO− detection based on novel chromophore fragmentation strategy for the first time. It exhibited distinct advantages of good selectivity, high sensitivity, fast response (60 s) and low detection limit of 9.65 nM. The sensing mechanism revealed LAB1 core was fragmented by ClO−, leading to significantly colorimetric and ratiometric fluorescence changes. As a result, 320 nm blue-shift in absorption maximum (from green to colorless) and 340 nm blue-shift in emission maximum (from dark to bright blue) allowed for visual detection by the naked eyes. The potential applicability of LAB1 for ClO− detection with satisfactory recovery in the real samples (tap water and lake water) and vegetables (spinach, lettuce, Chinese cabbage, bean sprouts), and fluorescence “turn on” imaging in mung bean sprout were demonstrated. In addition, LAB1-loaded test paper was suitable for semi-quantitative scanning ClO− analysis by using color recognition APP in a smartphone. Therefore, this work highlights a promising approach based on novel sensing mechanism for monitoring ClO− in food samples.