Embedding carbon dots in Eu 3+ ‐doped metal‐organic framework for label‐free ratiometric fluorescence detection of Fe 3+ ions

Abstract Fluorescent detection is a new spectroscopic measurement for ions sensing due to the advantages of real‐time determination with high selectivity, accuracy, and low cost. However, chemosensors based on fluorescent detection are usually determined by absolute intensity from a monochromatic emission signal, which is easy to be fluctuated by the external environment, especially for Fe 3+ detection in complex fluids. Herein, we rationally design a dual‐emission Eu 3+ : CDs@ZIF‐8 to construct a ratiometric fluorescent sensor with self‐calibrating ability for Fe 3+ determination. High efficient carbon dots (CDs) are embedded in europium ions (Eu 3+ )‐doped MOF by simple stirring preparation at room temperature. The label‐free ratiometric fluorescent probe (I CDs@ZIF‐8 /I Eu ) exhibits simultaneous blue and red emission under the same excitation at 365 nm. Remarkably, Eu 3+ : CDs@ZIF‐8 displays the superiority of high selectivity to Fe 3+ , which shows ratiometric fluorescence characteristics (I 0 /I) in a range of 0‐6 μmol\L with a low limit of detection (LOD) of 0.897 μmol\L. Besides, the CDs‐MOF nanocomposite holds good aqueous dispersibility and low cytotoxicity, which shows great potential applications in medical aid including biological detection and clinical diagnosis.