As a new form of fluorescent carbon nanomaterials, carbon dots (CDs) have many advantages such as simplicity of synthesis, low biological toxicity, resistance to photobleaching, excellent in biocompatibility and easy to modify.As the most inorganic mineral of human hard tissues including bone and tooth, calcium phosphate(CaP) materials have high biocompatibility and good biodegradability.The hydroxyapatite (HA), a common type of calcium phosphate, has been widely used in drug delivery, removal of heavy metal ions, gene transfection and other biomedical fields.Herein, a novel method for preparation of fluorescent calcium phosphate/carbon dot (CaP/CD) hybrid composites was described.We first prepared CDs with a quantum yield of 51.5 % by carbonization of citric acid with polyethylenimine (PEI) in one step.Next, the fluorescent CaP/CD hybrid composites upon UV excitation were obtained in the presence of carboxymethyl cellulose (CMC) as a template and CD as a cotemplate.The asprepared CaP/CD hybrid composites consisted of irregularly shaped nanorods with a length of 50 ~ 140 nm and a diameter of 10 ~ 25 nm were characterized by transmitted electron microscopy (TEM).And the highly magnified TEM image of CaP/CD hybrid composites showed that tens of CDs in shape of nanodot indeed existed in the CaP/CD hybrid composites.More importantly, CDs enabled the CaP/CD hybrid composites to emit bright blue fluorescence under UV irradiation.In addition, the result of Xray powder diffraction (XRD) patterns indicated that the crystalline phase of CaP/CD hybrid composites were in good agreement with those of hexagonal HA (JCPDS Data Card 090432).Moreover, it was found that the assynthesized CaP/CD hybrid composites were potentially useful in detecting the concentration of Cu 2 + and imaging the cell with nontoxic as potential fluorescent probes.