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.