A malononitrile-based portable fluorescent probe for ultrasensitive detection of hydrazine in environmental matrices

Hydrazine (N₂H₄), a highly toxic environmental pollutant, demands ultrasensitive detection across gaseous, aqueous, and soil matrices to meet the U.S. EPA safety standard (10 ppb). Existing probes rarely integrate portable detection with field-deployable platforms. Herein, a malononitrile-based fluorescent probe (BTN) was developed for ultrasensitive and portable detection of N₂H₄. By integrating a 2,1,3-benzothiadiazole (BTD) fluorophore and malononitrile recognition unit, BTN achieved a remarkable detection limit of 0.023 μM (S/N = 3) with rapid response (20 min) and excellent anti-interference capability. A smartphone-assisted platform enabled on-site liquid-phase detection using test strips (0.1–10 μM via RGB imaging). Simultaneously, BTN demonstrated gas-phase monitoring through fluorescence quenching and tracked degradation dynamics in soil samples. This work pioneers a low-cost, portable strategy for cross-compartment environmental monitoring.