Selective detection of Fe2+ by combination of CePO4:Tb3+nanocrystal–H2O2 hybrid system with synchronous fluorescence scan technique

Abstract

A new method for quenching kinetic discrimination of Fe²⁺ and Fe³⁺, and sensitive detection of trace amount of Fe²⁺ was developed by using synchronous fluorescence scan technique. The principle of this assay is based on the quenching kinetic discrimination of Fe²⁺ and Fe³⁺ in CePO₄:Tb³⁺ nanocrytals–H₂O₂ hybrid system and the Fenton reaction between Fe²⁺ and H₂O₂. Stable, water-soluble and well-dispersible CePO₄:Tb³⁺ nanocrystals were synthesized in aqueous solutions, and characterized by transmission electron microscopy (TEM) and electron diffraction spectroscopy (EDS). We found that both Fe²⁺ and Fe³⁺ could quench the synchronous fluorescence of CePO₄:Tb³⁺ nanocrytals-H₂O₂ system, but their quenching kinetics velocities were quite different. In the presence of Fe³⁺, the synchronous fluorescent intensity was unchanged after only one minute, but in the presence of Fe²⁺, the synchronous fluorescent intensity decreased slowly until 28 min later. The Fenton reaction between Fe²⁺ and H₂O₂ resulted in hydroxyl radicals which effectively quenched the synchronous fluorescence of the CePO₄:Tb³⁺ nanocrystals due to the oxidation of Ce³⁺ into Ce⁴⁺ by hydroxyl radicals. Under optimum conditions, the linear range for Fe²⁺ is 3 nM–2 μM, and the limit of detection is 2.0 nM. The method was used to analyze water samples.