A novel ratiometric fluorescent probe for selective and sensitive detection of Cu2+ in complete aqueous solution

- A novel hemicyanine-based ratiometric fluorescent probe 3 for Cu2+ was developed.
- The probe could detect Cu2+ in complete aqueous solution.
- The detection limit of 3 for Cu2+ was found to be 1.1 nM.
- The probe exhibited a large Stokes shift.

A novel hemicyanine-based ratiometric fluorescent probe 3 for Cu2+ was described. The probe exhibited fluorescence emission at 448 nm. Upon addition of Cu2+, the emission at 448 nm quenched and simultaneously generated a significant bathochromic shift of the emission maximum to 503 nm due to the Cu2+-triggered hydrolysis reaction of the picolinate moiety. Thus, a single-excitation, dual-emission ratiometric measurement with a large red shift in emission (Δ55 nm) and remarkable changes in the ratio (F503nm/F448nm) of the emission intensity (R/R0 up to 22-fold) could be established. Moreover, the probe exhibited a large Stokes shift, high sensitivity (detection limit of 1.1 nM), and high selectivity for Cu2+ over other metal ions in complete aqueous solution.

693 can detect Cu2+ in complete aqueous solution with ratiometric fluorescence signal output, high sensitivity, and high selectivity over other metal ions.