A simple ratiometric fluorogenic and chromogenic chemodosimeter for hydrazine detection in pure aqueous solution:...

Hydrazine is a significant chemical reagent utilized across various fields. It is, however, highly toxic and poses substantial hazards of environmental contamination throughout its manufacturing, transportation, application and disposal processes. Long-term exposure to hydrazine has serious consequences for human health. Thus, there is a necessity for fast, sensitive and selective detection techniques for hydrazine. Here, a simple and effective water-soluble fluorescent chemodosimeter CD was developed for selective detection of hydrazine in 100 % aqueous solution. The chemodosimeter CD exhibited a remarkable colorimetric and ratiometric fluorescent response to hydrazine relative to the other twenty competing analytes. In the presence of hydrazine, CD resulted in a decrease of the absorption peaks at 551 nm and 296 nm, along with an increase in the peak at 369 nm, which led to a color change from purple to colorless. Upon addition of hydrazine to the aqueous solution of CD, the fluorescence intensity of CD at 623 nm decreased, and a new blue-shifted band appeared at 454 nm, accompanied by the generation of strong cyan fluorescence. The changes in optical properties primarily resulted from the nucleophilic addition of hydrazine to the CC double bond of the chemodosimeter CD. The proposed sensing mechanism of CD for hydrazine was validated using NMR spectroscopy, mass spectrometry, FTIR and Job's plot analysis. The CD detection limit for hydrazine was found to be 1.25 μM and 0.72 μM, respectively, based on UV-Vis and fluorescence titration data. For quick on-site visual hydrazine detection, we created CD-based test kits and CD-treated silica gel. The cotton buds loaded with the chemodosimeter CD were developed for the visual and fluorescent recognition of gaseous hydrazine. Furthermore, CD was utilized to effectively detect N₂H₄ in mung bean sprouts, rice grains and soil samples. In addition, chemodosimeter CD was employed in a smartphone-assisted RGB analysis for hydrazine detection. These findings demonstrated that the chemodosimeter CD effectively detects hydrazine in aqueous and vapor phases, as well as in environmental samples.