▎ 摘　　要

A ball milling method which is green with simple. manipulation and low. cost was used to prepare graphene as precursor for graphene quantum dots (GQDs) synthesis. Subsequently, GQDs with good dispersibility, uniform size distribution, average diameter of (4.80 +/- 0.20) nm and 1-3 layers were prepared by one-step hydrothermal method. The morphology, structure and optical properties of the GQDs were characterized by high-resolution transmission electron microscopy (HRTEM), atomic force microscope (AFM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), UV-Vis absorption and fluorescence spectroscopy. Furthermore, the GQDs were used in label. free and specific detection of ferric ion (Fe3+) with broad linear ranges of 2.0 x 10(-6) -7.0 x 10(-4) mol/L and low detection limit of 1.8 x 10(-6) mol/L (S/N = 3). The possible mechanism was also discussed and the application of GQDs for Fe3+ detection in tap water was demonstrated. Finally, based on their low cytotoxicity and excellent biocompatibility, the as. prepared GQDs were successfully applied to efficient cell imaging. This work provides a new way for preparation of carbon. based nanomaterials and build a foundation for deepening applications of GQDs in bio-/chem- analysis, bioimaging, etc.