A novel fluorescent Fe3+ sensor based on a europium complex

A novel Eu3+ complex (EuL) based on 1,10-phenanthroline-2-carboxylic was successfully synthesized, and gave a characteristic red emission. The complex was shown to act as a selective luminescence quencher for Fe3+, as shown by the “on/off” switch phenomenon. The quenching curve showed a double-exponential well decay with the increase of Fe3+ ions. The stability constant of EuL/Fe3+ was calculated as 8.6 × 103 L mol−1(lg β/L mol−1 = 3.93). The response showed high selectivity for Fe3+ compared with other metal ions; the complex therefore has the potential to be applied as a fluorescent sensor for Fe3+.

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► A novel Fe3+ luminescent “on–off” sensor is developed based on a Eu3+ complex.
► A 1:1 binding model between the Eu3+ complex and the Fe3+ ion is proposed.
► The binding constant of EuL/Fe3+ is 8.6 × 103 L mol−1(lg β/L mol−1 = 3.93).