▎ 摘　　要

Graphene quantum dot-NaYF4:Yb,Er was made via hydrothermal synthesis. The resulting hybrid shows good water-solubility, small particle size of 11.5 nm and significant enhancement of upconversion emission. Further, the hybrid was designed as an upconversion biosensing nanoplatform for detection of carcinoembryonic antigen based on the exonuclease III-aided target recycling amplification. Firstly, the linker DNA (LDNA) is covalently attached to the hybrid surface. Then, the upconversion emission of LDNA-modified hybrid is effectively quenched through the hybridization of gold nanoparticles with hairpin DNA (H-p) via the fluorescence resonance energy transfer. Finally, the H-p on the nanoassembly is specially opened by signal DNA (SDNA) and leads to rapid recovery of the quenched upconversion emission. In addition, the exonuclease III-aided target cycling amplification strategy is introduced to generate the SDNA and release the carcinoembryonic antigen. The released carcinoembryonic antigen is circularly used to produce more SDNA, resulting in a significant signal amplification. The as-proposed biosensor displays good analytical performance in the detection of carcinoembryonic antigen with a wide linear range of 5.0 x 10(-17)-1.0 x 10(-8) g ml(-1) giving a low detection limit of 2.4 x 10(-17) g ml(-1) (S/N = 3) along with a high specificity. Its practicality has been verified by the analysis results of carcinoembryonic antigen in human serum.