▎ 摘　　要

Herein, the erbium-doped graphene quantum dots (Er-GQDs) with up- and down-conversion fluorescence have, for the first time, been hydrothermally fabricated at lactose-to-erbium pentahydrate ratio of 50, and then employed as the nanosensing probe to detect Fe3+ ions in aqueous and human serum samples. The surface characterization shows that the 1.8 at% Er is successful incorporated into 2-8 nm GQD lattice to form Er-GQD nanoparticles. The Er3+-doped GQDs exhibit both up and down-conversion luminescence properties after excitation with 730-nm visible light and 360-nm UV light, respectively. Both up- and down-conversion fluorescence properties of Er-GQDs show excellent analytical performance toward Fe3+ detection. A wide dynamic range of 4 orders of magnitude with limits of detection of 2.8-11.2 nM is observed when down-conversion property of Er-GQD is used for Fe3+ detection in PBS and human serum. Moreover, both up- and down-conversion fluorescence behaviors exhibit superior selectivity over 16 metal ion and 19 organic interferences. Results clearly indicate the feasibility of using Er-GQDs with both up- and down-conversion fluorescence properties as the nanosensing probe for highly selective and sensitive detection of metal ions in various environmental media, which can extend the application of up-conversion application from inorganic materials to carbon based nanomaterials for label-free detection of analysts in environmental and biological samples.