A novel fluorescein derivative as a colorimetric chemosensor for detecting copper(II) ion

A novel fluorescein derivative, synthesized by the reaction of fluorescein hydrazide and 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone, was evaluated as a chemoselective metal ion sensor. Addition of Cu2+ to an aqueous solution of the fluorescein derivative resulted in a rapid color change from colorless to deep yellow together with a distinctive change in UV–vis absorption spectrum. However, other common alkali-, alkaline earth-, transition- and rare earth metal ions induced no or minimal spectral changes. The stoichiometry of the reaction and association constant of the fluorescein derivative with Cu2+ are described. Experimental results indicate that the fluorescein derivative could provide a rapid, selective and sensitive response to Cu2+, and could be used as a potential Cu2+ colorimetric chemosensor in aqueous solution.