▎ 摘　　要

A facile one-pot solvothermal method based on exfoliating and disintegrating treatments for graphite oxide was developed to prepare water-soluble graphene quantum dots. Dimethylformamide served as a solvent and source of nitrogen, the as-prepared nitrogen-doped graphene quantum dots (N-GQDs) exhibited bright green emission under ultraviolet irradiation (similar to 365 nm). More importantly, an ultrasensitive paper-based electrochemiluminescence (ECL) immunoassay was developed with green-luminescent N-GQDs as ECL labels and alpha-fetoprotein antigen (AFP) as model protein. The N-GQDs were promising ECL labels because of their low anodic ECL potential of +0.84 V and high biocompatibity, which can facilitate highly sensitive ECL bioassays. A novel paper working electrode was fabricated through a seed-mediated growth approach and served as a promising platform for antibodies attachment. Upon the immunorecognition of the immobilized AFP to its antibody labeled with N-GQDs, the proposed immunoassay displayed increasing ECL intensity, leading to a wide calibration range of 0.005-100 ng mL(-1) with a detection limit of 1.2 pg mL(-1) [signal-to-noise ratio (S/N) =3]. The ECL immunoassay for real samples displayed very similar results with the commercial ECL immunoassay, which provided a powerful avenue for the design of the ultrasensitive detection method for clinical application. (C) 2015 Published by Elsevier B.V.