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Fluorescent probes for detection of CN− still have many limitations, such as small Stokes shift, irreversible, and background interference, which hamper their applications for on‐site detection and bioimaging of CN−. In this work, we design a new CN−‐activatable fluorescent probe (named AHMM) containing an ESIPT (excited‐state intramolecular proton transfer) and hydrogen bond features, which show a large Stokes shift (225 nm) and molecular structural reversible detection. The probe AHMM exhibits an excellent selectivity for CN− without any interference from other anions in aqueous DMSO system. Furthermore, the mechanism of the interaction of AHMM with CN− is concluded by various experiments. The limit of detection of AHMM for CN− is calculated as low as 4.47 × 10−8 M, lower than the concentration of CN− deemed acceptable by WHO (World Health Organization). AHMM can recognize CN− in tap water quantitatively and on‐site by a smartphone APP. Moreover, food samples such as almond and cassava including CN− are visualized by fluorescence imaging. In addition, the probe shows practical applications of CN− imaging in cells and mice. This concept can be applied for designing multifunctional fluorescent probes with ESIPT and reversible characteristics for detection of CN−. [ABSTRACT FROM AUTHOR]

It's important to pay great attention to the detection of CN− due to its high toxicity. Based on ESIPT characteristics, we design, synthesize and characterize the colorimetric and fluorescence "turn-on" probe AHAM to recognize CN−, which has the large Stokes shift (228 nm), exhibits high sensitivity and excellent selectivity. The limit detection of the probe AHAM for CN− was 1.94 × 10−8 M, which was much lower than the standard set by WHO and many previously reported probes. The recognition mechanism between AHAM and CN− was investigated by spectroscopic analysis, 1H NMR titration and mass spectrometry. To our surprise, AHAM could not only identify CN− reversibly, but also recognize CN− accurately in test paper and silica gel plate applications. Furthermore, AHAM was successfully used for fluorescence imaging in C. elegans and mice. It provides the new easy, fast and accurate method to detect CN−. [Display omitted] • The Stokes shift of AHAM toward CN− reached 228 nm. • AHAM recognized CN− with low LOD selectively, sensitively and reversibly. • AHAM achieved to visualize CN− in C. elegans and mice. [ABSTRACT FROM AUTHOR]