A coumarin–chalcone hybrid used as a selective and sensitive colorimetric and turn-on fluorometric sensor for Cd2+ detection
A chalcone-based naked-eye colorimetric chemical sensor, (E)-4-hydroxy-3-(3-(4-methoxyphenyl)acryloyl)-2H-chromen-2-one 1a, was developed for selective and sensitive recognition of Cd2+ in mixed aqueous–organic media. The chemosensor demonstrates a distinct color change as well as a remarkable variation in the absorption and fluorescence enhancement observed in its emission spectra upon interaction with Cd2+. The dual colorimetric and fluorometric responses of the chemosensor 1a towards Cd2+ are attributed to the formation of a 1 : 1, 1a–Cd2+ complex, which eventually affect its optical properties. The association constants for Cd2+ towards receptor 1a obtained from the Benesi–Hildebrand plot and non-linear least square fitting were found to be 9.56 × 105 M−1 and 1.34 (±0.87) × 106 M−1, respectively, with a detection limit of 5.84 × 10−8 M. The fluorescence enhancement of chemosensor 1a upon interaction with Cd2+ was attributed to chelation-enhanced fluorescence (CHEF) occurring at pH 7.0.