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 Cu 2+ was described. The probe exhibited fluorescence emission at 448   nm. Upon addition of Cu 2+ , the emission at 448   nm quenched and simultaneously generated a significant bathochromic shift of the emission maximum to 503   nm due to the Cu 2+ -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 (F 503nm /F 448nm ) of the emission intensity (R/R 0 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 Cu 2+ over other metal ions in complete aqueous solution.