▎ 摘　　要

The current work demonstrates the fabrication and optimization of a fluorescence-based immunosensor for ferritin estimation wherein amine-functionalized graphene quantum dots (afGQDs) and methyl orange are used as a fluorophore-quencher couple. The synthesis of afGQDs is achieved by the hydrothermal method. The synthesized QDs were characterized using analytical techniques such as UV-vis, fluorescence, FTIR, and Raman spectroscopies, XRD diffraction studies, elemental analysis, and morphological studies through transmission electron microscopy. The QDs showed a quantum yield of 51%, which is one of the highest reported for this class of material. Exploiting the high fluorescence of this material, these afGQDs, were conjugated with antiferritin antibodies (Ab) for specific fluorescence-based immunosensing of ferritin. The conjugation was confirmed from contact angle measurements and electrophoresis, which confirmed successful bioconjugation. With methyl orange (MO) as the quencher, the Stern-Volmer plot showed a linear upward trend indicating a static quenching process. After elucidating the quenching mechanism, a nanoprobe-based fluorophore-quencher (Ab@ afGQDs-MO) couple was employed for ferritin sensing. Using a dynamic linear range from 10 to 4000 ng.mL(-1) with an R-2 value of 0.994, a limit of detection of 0.723 ng.mL(-1) is achieved. With optimization of other input parameters, the ferritin is estimated in spiked serum samples as well.