摘要： In this work, a kind of down/up-conversion luminescent F-doped carbon dots (F-CDs) with high fluorescence quantum yield was prepared by one-step hydrothermal treatment of perfluorooctanoic sulfonate (PFOS) and was used for the label-free detection of Fe3+. The obtained F-CDs have a uniform and monodispersed size at 4 nm, and show good properties such as down/up-conversion luminescence, good water-solubility, anti-photo-bleaching, salt tolerance, and high fluorescence quantum yield of about 35.2%. The down/up-conversion photoluminescence emissions both are independent on the excitation and both the emission peaks are at 447 nm, which indicates it is promising to be used as fluorescent whitening agent. Based on the quenching effect of iron ions, a simple, sensitive, low-cost and label-free fluorescent assay for iron ions has been developed with a liner range of 1–100 μM and a limit of detection (LOD) of 10 nM. Furthermore, the label-free nanoprobe has been successfully applied for the detection of Fe3+ in real samples.