A new quinoline-derived highly-sensitive fluorescent probe for the detection of hydrazine with excellent large-emission-shift ratiometric response

Hydrazine is an important industrial material yet highly toxic and extremely harmful to people's health when over-exposed in the environment, thus monitoring hydrazine is of great significance. In this work, a novel highly fluorescent fluorophore BQ-OH, based on hydroxyl- and benzo[d]oxazole-substituted quinoline structure, was synthesized and esterified with 4-biomobutyric acid to afford a fluorescent probe BQABr for the selective detection of hydrazine. The probe follows SN2(nucleophilic substitution)-cyclization sensing mechanism with remarkable response, excellent sensitivity and selectivity. Spectra experiments in aqueous solutions demonstrated that BQABr exhibited an excellent ratiometric fluorescence response toward hydrazine with two well separated emission bands before/after sensing reaction. Emission peak shifted over 130 nm from 387 nm to 521 nm, and unexpectedly outstanding ratio signal enhancement over 3000-fold was achieved. Due to the large spectra response, a very low detection limit of 5.8 nM (0.19 ppb) was obtained. Selectivity experiment was performed, showing BQABr had nearly no spectra response to other possible disturbing analytes. The probe-coated test papers were fabricated and successfully applied to detect gaseous hydrazine. Furthermore, potential application for the detection of hydrazine in both environmental samples and biological samples (living cells) has been demonstrated.