A dual-platform phenothiazine-based fluorescent probe for hydrazine (N₂H₄) bioimaging in multiple organisms and...

Hydrazine (N₂H₄), a potent environmental pollutant and carcinogen, demands sensitive and on-site monitoring methods. Herein, we present a new fluorescent "off-on" probe N'-((10-propyl-10H-phenothiazin-3-yl)methylene)pyrimidine-4-carbohydrazide (PP) for dual-mode N₂H₄ detection. Probe PP operates via a nucleophilic addition-elimination mechanism, achieving rapid (<40 s) and ultrasensitive detection of N₂H₄ with a low detection limit of 35.3 nM. Probe PP enables on-site visual detection of N₂H₄ on food/plant surfaces, and has been further incorporated into colorimetric test strips for rapid on-site monitoring of aqueous/gaseous N₂H₄. Moreover, PP was capable of not only accurately quantifying N₂H₄ levels in diverse soil and water samples but also performing sensitive bioimaging in various biological systems, including bacteria, live cells, plants, and zebrafish, demonstrating its excellent biocompatibility and versatile applicability. Furthermore, a smartphone-assisted platform based on PP test strips allows quick, on-site quantitative detection of N₂H₄ in soil/water samples without relying on laboratory instruments, making it a practical tool for environmental monitoring and industrial safety applications. This work not only provides a robust molecular tool for N₂H₄ tracing across biological and environmental matrices but also delivers a field-deployable strategy that bridges the gap between laboratory research and practical application.