A ratiometric fluorescent probe for hypochlorous acid determination: Excitation and the dual-emission wavelengths at NIR region

An interesting ratiometric fluorescent probe with unique optical performance was reported in this work. By modifying on the bridge-head of heptamethine cyanine chromophore with an N-phenyl-N'-ethylene amine thiourea substituent as a chemodosimetric recognition unit, the probe exhibited ratiometric fluorescent response towards hypochlorous acid (HClO). Upon addition of HClO, the absorbance spectra showed a great red shift as large as 150 nm from 650 nm to 800 run. Employing the isosbestic absorption point at 730 nm as an excitation wavelength, a ratiometric fluorescent sensing mode with two long emission wavelengths at 760 nm and 820 nm was acquired, and thus the probe displayed significant behavior with both the excitation wavelength and the dual-emission wavelengths located at NIR (650-900 nm) region exclusively. Also, the probe showed excellent performance in high sensitivity and good selectivity towards HClO over other reactive oxygen species and a wide variety of coexist species in biological pH condition and had been successfully used to detect hypochlorous acid in serum samples and tap water samples.