A rhodamine-based colorimetric and reversible fluorescent chemosensor for selectively detection of Cu2+ and Hg2+ ions

A bifunctional colorimetric and fluorescent chemosensor RbCS has been successfully designed and synthesized by simple condensation of 3,5-dichlorosalicylaldehyde and rhodamine B hydrazide. In aqueous media, chemosensor RbCS exhibits remarkably enhanced absorbance intensity and color change from colorless to pink for Cu 2+ , and shows significant “off–on” fluorescence accompanied with color changes from colorless to red upon binding to Hg 2+ . The absorbance and fluorescence signals of RbCS can be restored with addition of EDTA disodium into solutions of RbCS–Cu 2+ and RbCS–Hg 2+ , showing that the binding of chemosensor RbCS and Cu 2+ /Hg 2+ is chemically reversible.