A TICT-based phenothiazine probe for smartphone-enabled on-site detection of hydrazine in environmental and biological systems.

Hydrazine (N2H4) is a highly toxic pollutant and potential carcinogen, demanding sensitive, rapid, and field-deployable detection methods for environmental and food safety monitoring. Herein, we rationally designed a twisted intramolecular charge transfer (TICT)-based fluorescent probe PS featuring a phenothiazine scaffold for selective N2H4 sensing. The probe exhibits a prominent "turn-on" fluorescence response via a nucleophilic addition-elimination mechanism, verified by 1H NMR, HRMS, FTIR, and DFT/TD-DFT calculations. PS delivers a low detection limit (47.54 nM), rapid response (<11.5 min), excellent selectivity, good photostability (12h), and wide pH tolerance (3-12). To meet on-site demands, we developed multiple field-ready formats: direct visual screening on food/plant surfaces, colorimetric/fluorometric test strips for aqueous and gaseous N2H4, and a smartphone-integrated platform for portable quantitative analysis of soil and water. The probe achieved accurate N2H4 quantification in real environmental and food samples (tap/lake/river/wastewater, sandy/farmland/campus soil, and food samples) with satisfactory recoveries (94.89-109.97%). Beyond environmental monitoring, PS exhibits good biocompatibility, enabling sensitive bioimaging in HepG2 cells, plant tissues, and zebrafish for toxicity assessment. Collectively, this work provides a field-deployable molecular tool that integrates environmental monitoring, food safety screening, and biological imaging, bridging laboratory research and practical application.