A derivative of fluorescein was designed, synthesized, and characterized by FT-IR, 1H, 13C NMR, mass spectrometry, and quantum chemical calculations. When applied to the set of solutions containing different cations, it has shown a selective colorimetric and fluorescence response for Cu2+. A visible color change from colorless to purple and from non-fluorescent to red fluorescence was observed. A linear relationship between Cu2+ concentration and absorbance or fluorescence intensity was demonstrated with low detection limits (0.64 and 0.24 μM, respectively) in the acetonitrile/water mixture. Test strips are made by impregnating filter paper with acetonitrile chemosensor 1 solution and used to detect Cu2+ in water. The strips noticeably change their color from colorless to purple.
