A fluorescence ratiometric sensor for hypochlorite based on a novel dual-fluorophore response approach Original Research Article

A fluorescence ratiometric sensor for OCl− has been developed based on a novel dual fluorophore response approach. The sensor molecule contains a coumarin fluorophore and a rhodamine fluorophore, and the two fluorophores are directly linked to an OCl− recognition group. The structure of the sensor was characterized by ESI-MS, NMR, and X-ray crystallographic analysis. Upon treatment with OCl−, both fluorophores in the sensor responded simultaneously at two separate optical windows, with large enhancement of the fluorescence ratio (I578/I501) from 0.01 to 39.55. The fluorescence ratios for the sensor showed a good linearity with the concentration of OCl− in the range of 0.2–40 μM and the detection limits is 0.024 μM (S N−1 = 3). Investigation of reaction products indicated that the sensor reaction with OCl− produced two new fluorescent molecules, which were responsible for the fluorescence changes in two optical windows. In addition, the sensor showed high selectivity to OCl− over other reactive oxygen species, reactive nitrogen species, cations, and anions. The sensor has also been successfully applied to detection of OCl− in natural water samples with satisfactory recovery.