Embedding carbon dots in Eu3+-doped metal-organic framework for label-free ratiometric fluorescence detection of Fe3+ ions

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.