Core-Shell Upconversion Nanoparticle@Metal–Organic Framework Fluorescent Nanoprobes for the Detection of Ferric Ions and Ferrous Ions

In this study, we report a core-shell fluorescent nanoprobe consisting of upconversion nanoparticles (UCNPs) NaGdF₄ : Yb³⁺, Er³⁺ and metal-organic frameworks (MOFs) ZIF-8. ZIF-8 can specifically bind to ferric ions (Fe³⁺) to change the ultraviolet-visible absorption spectrum of the probe, as a result the fluorescence of the probe was quenched and achieve the detection of Fe³⁺. At the same time, since rhodamine B (RhB) can quench the fluorescence of this probe, by introducing ferrous ions (Fe²⁺) and hydrogen peroxide, based on Fenton reaction, the fluorescence signal of this probe can be recovered after the degradation of RhB, so it also can be used to detect Fe²⁺. Importantly, as the first report of UCNP@MOF probes for detecting Fe³⁺ and Fe²⁺, respectively, this method exhibits a good selectivity and anti-interference capability. Finally, it was used to detect Fe³⁺ and Fe²⁺ in the serum with excellent recoveries.