A dual-model fluorescent Zn2+/Cu2+ ions sensor with in-situ detection of S2−/(PO4)− and colorimetric detection of Fe2+ ion

A simple (R)-(−)-2-phenylglycinol functionalized Schiff base exhibited a dual response to Zn 2+ , Cu 2+ and Fe 2+ ions in water:methanol, (90:10 v/v). The compound displays an “off–on” fluorescent effect with Zn 2+ ions. The emission response decreased with Cu 2+ forming a Cu 2+ /Zn 2+ specie. The fluorescence signal is restored upon addition of sulfide anion (S 2 − ) using the Cu 2+ displacement approach , forming again the Zinc complex. Additionally, the sensor exhibits a second channel (colorimetric) response with Fe 2+ even in the presence of competing Fe 3+ ions. The pH profiles allowed to determine the p K a values and the pH-dependent change in the sensor recognition process. In addition, TD-DFT quantum chemical calculations were implemented to analyze the sensing mechanism by means of Natural Transition Orbital (NTO) analysis. Flow cytometry experiments demonstrated that the sensor successfully detects either exogenous or endogenous (natural) Zn 2+ ions in Jurkat cells with high sensitivity.