A coumarin derivative-based turn-on fluorescent probe for real-time applications of hydrazine detection in environment and bioimaging

Increasing the concentration of hydrazine is a major toxic threat to living beings and the environment. Thus, a potential probe was designed, including coumarin-integrated N-(diethylamino)salicylaldehyde (Cou) and 2,4-dinitrobenzoate (DNP), to develop the Cou-DNP probe sensor. The probe can react with hydrazine through the nucleophilic substitution reaction with the elimination of an ester (O–CO-) group besides achieving a “turn-on” fluorescence. This enhanced emission is because of the intramolecular charge transfer (ICT) sensing mechanism that exists between Cou and DNP. Also, the cleavage of an ester bond and the result of coumarin phenol (Cou) were verified through characterizations of 1H NMR, HR-MS, and density-functional theory (DFT) calculations. The application of Cou-DNP was effectively demonstrated by tracking gaseous hydrazine with paper strips; also, soil and actual samples (food, water) were examined to detect hydrazine in the solution phase. Moreover, a time-dependent study was conducted in HeLa cells to monitor the exo- and endogenous (in situ) hydrazine levels using hydrazine solution and isoniazid as a metabolite of hydrazine release, respectively. The probe-pretreated onion epidermal cells were imaged with hydrazine in the time interval of 0–5 min. We anticipate that a probe with the aid of a new recognition unit will provide a replacement for the traditional methods in detecting the toxic analyte hydrazine in real and bio-samples.