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

• The Schiff base detect Zn2+, with a 10−7 M limit of detection.
• The sensor exhibits a multifunctional approach for Zn2+, Cu2+ and Fe2+.
• Reversibility and cyclability properties for the continuous detection of Zn2+.
• Natural (endogenous) Zn2+ detection in live Jurkat cells.
• TD-DFT revealed highly efficient charge transfer properties.

A simple (R)-(−)-2-phenylglycinol functionalized Schiff base exhibited a dual response to Zn2+, Cu2+ and Fe2+ ions in water:methanol, (90:10 v/v). The compound displays an “off–on” fluorescent effect with Zn2+ ions. The emission response decreased with Cu2+ forming a Cu2+/Zn2+ specie. The fluorescence signal is restored upon addition of sulfide anion (S2−) using the Cu2+displacement approach, forming again the Zinc complex. Additionally, the sensor exhibits a second channel (colorimetric) response with Fe2+ even in the presence of competing Fe3+ ions. The pH profiles allowed to determine the pKa 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) Zn2+ ions in Jurkat cells with high sensitivity.

Sensor L1 displays a dual-model response via turn off–on fluorescence effect upon addition of Zn2+ and Cu2+ metal ions and phosphates and S2− anions. The sensor presents a rapid and reversible fluorescent response suitable for the continuous detection of natural (endogenous) Zn2+ ions in a live cell line.Figure optionsDownload as PowerPoint slide