Rational design of a FRET-based ratiometric fluorescent chemosensor for detecting ClO− with large Stokes based on rhodamine and naphthalimide fluorophores

Abstract The design and synthesis of high selective and sensitive fluorescence chemosensor for the determination of ClO− has received great efforts due to its critically important role in the immune system, however, most of chemosensor for detecting ClO− by using single-channel fluorescent signal, which is susceptible to many factors. Herein, a fluorescence resonance energy transfer (FRET)-based ratiometric and colormetric chemosensor containing a 1,8-naphthalimide fluorophore and a rhodamine fluorophore is designed and synthesized for the detection of ClO−, and its structure is characterized by NMR and ESI-MS. The reaction between ClO− and thiosemicarbazide causes the transform of the rhodamine fluorophore from the ring-closed form to the ring-opened form, showing a FRET process with the fluorescence color change from blue to orange. The chemosensor is successfully used for the quantitative detection of ClO− based on the ratio between the fluorescence emission intensities of the two forms, and exhibits a wide linear range of 0–60 μM (R = 0.996) and the detection of limit as low as 4.50 nM. In addition, the detection is highly selective and not significantly affected by various reactive oxygen species (ROS), RNS and other anions in DMSO/PBS buffer (6/4, v/v). The chemosensor can be used for cell staining.