A Reversible Colorimetric and Fluorescence "Turn-Off" Chemosensor for Detection of Cu and Its Application in Living Cell Imaging.

Dual-function chemosensors that combine the capability of colorimetric and fluorimetric detection of Cu are still relatively rare. Herein, we report that a 3-hydroxyflavone derivative ()-2-(4-(dimethylamino)styryl)-3-hydroxy-4-chromen-4-one (), which is a red-emitting fluorophore, could serve as a reversible colorimetric and fluorescence "turn-off" chemosensor for the detection of Cu. Upon addition of Cu to in neutral aqueous solution, a dramatic color change from yellow to purple-red was clearly observed, and its fluorescence was markedly quenched, which was attributed to the complexation between the chemosensor and Cu. Conditions of the sensing process had been optimized, and the sensing studies were performed in a solution of ethanol/phosphate buffer saline (/ = 3:7, pH = 7.0). The sensing system exhibited high selectivity towards Cu. The limit of naked eye detection of Cu was determined at 8 × 10 mol/L, whereas the fluorescence titration experiment showed a detection limit at 5.7 × 10 mol/L. The complexation between and Cu was reversible, and the binding constant was found to be 3.2 × 10 M. Moreover, bioimaging experiments showed that could penetrate the cell membrane and respond to the intracellular changes of Cu within living cells, which indicated its potential for biological applications.