Selective sensing of Fe³⁺ ions in aqueous solution by a biodegradable platform based lanthanide metal organic...

As a significant metal ion in the environmental and biological systems, excess or shortage of Fe³⁺ from the organism can cause a host of diseases. So it is very urgent to explore an explicit, rapid and recoverable method for the detection of Fe³⁺ ions. Herein, a novel and flexible ligand containing 12 carboxyl groups (BHM-COOH) is used for the structure of a series of luminescent Eu³⁺/Tb³⁺-metal-organic frameworks (MOFs). A reliable and convenient luminescent detection platform is constructed by combining polylactic acid (PLA) film with Eu_0.24Tb_0.76-BHM-COOH. More importantly, the luminescent platform can highly sensitive to sense Fe³⁺ ions through fluorescence quenching (Stern-volmer constant Ksv = 1.27 × 10⁴ M^-1 for Fe(NO₃)₃), and detection limit can be as low as 4.47 μM. The sensing mechanism is ascribed to the fluorescence quenching caused by the competitive absorption between Eu_0.24Tb_0.76-BHM-COOH and Fe³⁺ ion. At the same time, the sensor can be reused many times. These exciting results indicate that Eu_0.24Tb_0.76-BHM-COOH film can serve as a promising multi-responsive luminescent sensor for environmental pollutant monitoring.