LAUSR

Abstract A porphyrin-based receptor to sense fluoride ion via hydrogen bonding has been prepared and investigated in aqueous media. The interactions between receptor and fluoride ion are confirmed by absorption and emission spectroscopy, and the influence of pH on the sensor performance has also been investigated. A dramatic color change from wine red to green, and photoswitching from the fluorescent on-state to the non-fluorescent off-state were observed after addition of fluoride ion to chemosensor POR. The detection limit for fluoride ion was calculated to be around 10 µM by both the colorimetric and fluorometric methods, which is under the tolerable amounts in drinking water by WHO guidelines. The Jobs plot showed a 1:2 reaction stoichiometry between POR and fluoride ion, which was further confirmed by mass analysis. The experimental results are fully supported by the DFT theoretical calculations. Furthermore, the changes in structural alignment of POR during fluoride detection were also proposed.