Flavones Fluorescence-Based Dual Response Chemosensor for Metal Ions in Aqueous Media and Fluorescence Recovery

Responsiveness of sensing materials 3-hydroxyflavone (3HF) towards metal ions in aqueous medium has been explored following photoexcitation. 3HF exhibited both colorimetric and fluorescence (FL) turn-off response towards Cu2+ and Fe2+ with high sensitivity and selectivity. Meanwhile, the distinct colour change and the rapid quenching of FL intensity provide naked-eye detection. On successive addition of Cu(2+)and Fe2+ ions, FL of 3HF was turned off, whereas there is no change in wavelength of FL bands. Quenching efficiencies for Cu(2+)and Fe2+ ions are 88% and 49%, respectively. The detection limit of the sensor towards Cu2+ and Fe2+ was 1.54 mu M and 1.98 mu M, respectively. The binding strategy between 3HF and metal ions (Cu2+, Fe2+) and the nature of quenching have been explored with the Benesi-Hildebrand and Stern-Volmer plots, respectively. The FL of 3HF significantly quenched in the presence of Cu2+ ions, and then recovered upon addition of HCl, providing the possibility of constructing a sensitive Cu2+-HCl off-on fluorescent probe. Moreover, the proposed simple, quick response and visual test strip-based chemosensor could be used for the detection of Fe2+ and Cu2+ ions.