A Dual-Responsive Julolidine-Barbituric Acid Platform for Environmental Hydrazine Detection

Hydrazine is a highly toxic and carcinogenic compound widely used in industrial, agricultural, and pharmaceutical applications, necessitating rapid, sensitive, and selective detection methods for environmental and safety monitoring. In this study, we report the design and synthesis of a novel Julolidine-barbituric acid-based fluorescent chemosensor (JB) via a simple Knoevenagel condensation reaction for the selective detection of hydrazine hydrate. The probe exhibits high selectivity toward hydrazine over competing analytes, accompanied by a distinct colorimetric change from orange to colorless under visible light and a fluorescence shift from yellow to blue with significant enhancement in emission intensity under UV irradiation. The sensor showed a linear response over the concentration range of 0-2.0 × 10^- 5 M, with limits of detection of 7.78 × 10^- 6 M from UV-visible spectroscopy and 508 nM from fluorescence measurements, indicating high sensitivity for trace-level detection. The sensing mechanism was investigated using ¹H-NMR and HRMS spectroscopic techniques, confirming hydrazine-induced nucleophilic cleavage of the conjugated system. Additionally, the sensor demonstrated practical applicability through JB-coated paper strips for rapid, on-site detection, as well as successful detection of hydrazine in real soil samples. These results highlight JB as a cost-effective, portable, and efficient platform for real-time monitoring of hydrazine hydrate in environmental systems.