Curcumin as a colorimetric and fluorescent chemosensor for selective recognition of fluoride ion

The binding properties of curcumin with anions in acetonitrile were examined for the first time by UV–vis absorption and fluorescence spectroscopies. The results showed that curcumin highly and selectively responded to F− over other anions such as AcO−, H2PO4− and Cl− because of anionic complex formation via hydrogen bond. Curcumin gave rise to the red-shift of absorption spectra and its fluorescence was quenched with concomitant color change from yellow to purple upon addition of F−, which was detected by naked eyes. The addition of other anions such as AcO−, H2PO4−, HSO4−, NO3−, Cl− and Br− did not result in observable spectral change and solution color change. The binding constant between curcumin and F− was 2.0×105 mol−1 L and the recognizing mechanism was investigated as well.