A colorimetric and ratiometric fluorescent probe for Cu2+ with a large red shift and its imaging in living cells

The ester derived from picolinic acid and 4-hydroxynaphthalimide has been developed as a colorimetric and ratiometric fluorescent probe for the detection of Cu2+. Upon exposure to Cu2+ in a buffered solution, the probe displays a large red shift both in its absorption (110 nm) and emission (143 nm) spectra. This novel probe has a high sensitivity and an excellent selectivity for Cu2+ ions over competing metal ions (K+, Na+, Zn2+, Ni2+, Mn2+, Mg2+, Ca2+, Hg2+, Cd2+, Pb2+, Fe2+, Co2+, Ba2+, Ag+ and Fe3+). Most importantly, this new picolinate probe can successfully detect Cu2+ in living cells.