Dual-emission fluorescent probe with sequential two-step ESIPT activation mechanism for selective hydrazine detection and multifunctional applications

Abstract

Hydrazine is a commonly used chemical in various industries, including pharmaceuticals, agriculture, and aerospace. However, its high toxicity may cause serious harm to the natural environments and human health. The development of new methods for sensitive and selective detection of hydrazine is of great significance. In this study, we present a fluorescent probe that employs a unique two-step excited-state intramolecular proton transfer (ESIPT) activation mechanism for hydrazine detection. This probe integrates a phthalimide group into benzothiazole scaffold with its fluorescence initially quenched due to the inhibition of ESIPT process and photo-induced electron transfer (OFF state). Upon exposure to hydrazine, the nucleophilic cleavage of the phthalimide group activates the first ESIPT process, yielding yellow emission (ON1 state). A subsequent deprotection step triggers the second ESIPT process, producing blue fluorescence (ON2 state). These three states fluorescent change along with dual-emission signal output provide a highly sensitive and reliable method for hydrazine detection and monitoring, with a limit of detection (LOD) of 18 nM. Moreover, this probe showed versatile applications in environmental monitoring, food sample analysis, plant imaging, and bioimaging, including a convenient smartphone-assisted quantitative assay. The dual-activation mechanism offers valuable insights for the design of novel ESIPT probes, paving the way for promoting their applications in chemical, biological, and environmental fields.