A novel colorimetric and ratiometric fluorescent probe for detection of Cu2+ with large stokes shift in complete aqueous solution

A novel colorimetric and ratiometric fluorescent probe 1 for Cu2+ was designed and synthesized. 1 exhibited maximum absorption and fluorescence emission peaks at 385 nm and 495 nm respectively, with large Stokes shift of 110 nm. In sensing of Cu2+, the maximum absorption and fluorescence emission peaks generated bathochromic shift to 415 nm and 560 nm respectively, due to the Cu2+-induced hydrolysis reaction of the picolinate moiety in 1. Meanwhile, the solution of 1 turned from pale yellow to yellow in visible light and from pale green to orange under a 365 nm UV lamp. 1 displayed remarkable change in the ratio (F560 nm/F495 nm) of the fluorescence intensity (R/R0 up to 23-fold), high sensitivity (detection limit of 0.62 μM), fast response time (within 2 min), and excellent selectivity for Cu2+ over other metal ions in complete aqueous solution.