A fluorescent sensor for Cu2+ and Fe3+ based on multiple mechanisms

A new fluorescent sensor for the selective and sensitive sensing of Cu2+ and Fe3+ based on the rational control of multiple mechanisms has been developed. Sensor L is weakly-fluorescent (phi = 0.029) due to the C=N isomerization and PET process. Upon binding with Cu2+, the complex L + Cu2+ can give a remarkable fluorescence enhancement (phi = 0.182) with a limit of detection down to 1.3 x 10(-8) mol L-1 because of both inhibition of the C=N isomerization and PET process. However, upon binding with Fe3+, the original weak fluorescence of L is completely quenched (phi = 0.002) due to the paramagnetic quenching property. In addition, the complex L + Cu2+ could be further used as a new platform for the ultrasensitive detection of Fe3+ based on the fluorescence turn-off response with a limit of detection down to 2.4 x 10(-8) mol L-1 in aqueous solution.