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

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 (I-578/I-501) 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 mu M and the detection limits is 0.024 mu M (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. (C) 2013 Elsevier B.V. All rights reserved.