A selectively fluorescein-based colorimetric probe for detecting copper(II) ion.

Abstract A novel fluorescein derivative 3-bromo-5-methylsalicylaldehyde fluorescein hydrazone (BMSFH) has been synthesized by reacting fluorescein hydrazide with 3-bromo-5-methylsalicylaldehyde and was developed as a new colorimetric probe for detection of Cu 2+ . In the presence of Cu 2+ the BMSFH exhibits a rapid color change from colorless to yellow together with an obvious new band appeared at 502 nm in the UV–vis absorption spectra. However, other common alkali-, alkaline earth-, transition- and rare earth metal ions induced no or minimal spectral changes. This change is attributed to BMSFH via coordination with Cu 2+ in a 1:1 stoichiometry and this binding to Cu 2+ is reversible, as indicated by the bleaching of the color when the Cu 2+ is extracted with EDTA. Experimental results indicate that the BMSFH can provide a rapid, selective and sensitive response to Cu 2+ with a linear dynamic range 3.0–330 μmol/L and can be used as a potential Cu 2+ colorimetric probe in aqueous solution.