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Development of an efficient fluorescent probe for sensing hypochlorite in water samples and biological samples is highly demanded. However, the currently reported fluorescent probes for hypochlorite frequently suffered from the problem of high background fluorescence. Herein, based on the combined effect of two different fluorescence quenching groups, we rationally developed a novel fluorescent probe for hypochlorite with extremely low background fluorescence. Notably, due to the doubly quenching groups, the probe could even keep low background fluorescence in a solution with high viscosity. Furthermore, the probe displayed highly sensitive and selective response to hypochlorite, with the detection limits calculated to be 10.5 nM. Practical application demonstrated that the probe was able to quantitatively detect hypochlorite in various water samples with good recovery. Significantly, the probe showed extremely low background fluorescence in living cells and was capable of detecting minor variation of endogenous hypochlorite in RAW 264.7 cells. Moreover, the fluorescence imaging different concentration of hypochlorite in zebrafish has been successfully conducted. The probe developed herein will be widely used as a reliable tool to accurately monitor the variation of hypochlorite in living organism. Image 1 • The fluorescent probe displayed extremely low background fluorescence by a novel doubly-quenching strategy. • The fluorescent probe showed highly sensitive and selective response to hypochlorite even with no perturbation by viscosity. • The fluorescent probe has been applied for fluorescence imaging of hypochlorite in living cells and zebrafish. [ABSTRACT FROM AUTHOR]

Herein, two compounds (1 a and 1 b) were rationally constructed as novel reaction-based fluorescent probes for CN(-) by making use of the electron-withdrawing ability of the cyano group that was formed from the sensing reaction. Notably, this design strategy was first employed for the development of fluorescent CN(-) probes. The experimental details showed that probe 1 a exhibited a fluorescence turn-on response to CN(-), whereas other anions, biological thiols, and hydrogen sulfide gave almost no interference. The detection limit of probe 1 a for CN(-) was found to be 0.12 μM. The sensing reaction product of 1 a with CN(-) was characterized by NMR spectroscopy and mass spectrometry. TD-DFT calculations demonstrated that the formed cyano group drives the intramolecular charge transfer (ICT) process from coumarin dye to the cyano group and thus the original strong ICT from the coumarin dye to the 3-position pyridyl vinyl ketone substituent is weakened, which results in recovery of coumarin fluorescence. The practical utility of 1 a was also examined. By fabricating paper strips, probe 1 a can be used as a simple tool to detect CN(-) in field measurements. Moreover, probe 1 a has been successfully applied for quantitative detection of endogenous CN(-) from cassava root., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)