A novel ratiometric fluorescence probe based on the FRET-ICT mechanism for detecting fluoride ions and viscosity.

Fluoride ion is not only important for dental health, but also a contributing factor in a variety of diseases. At the same time, fluoride ions and cell viscosity are both important to the physiological environment of mitochondria. We developed a dual-response ratiometric fluorescent probe BDF based on Förster resonance energy transfer (FRET) and intramolecular charge transfer (ICT) mechanism for the detection of F and viscosity. BDF has an outstanding intramolecular energy transfer efficiency of 97.7% and shows excellent performance for fluorine ion detection. In addition, when the system viscosity increases, the fluorescence emission intensity of BDF is greatly heightened, indicating the possibility of viscosity detection. Finally, based on the fluorescence properties of BDF, we used the probe to detect F in the toothpaste sample and image exogenous fluoride ions in HeLa cells.