ZrO 2 Nanoflowers Decorated with Graphene Quantum Dots for Electrochemical Immunosensing

In the present work, hybrid nanostructures of graphene quantum dots decorated zirconia (GQDs@ZrO 2 ) were synthesized by a facile one-pot hydrothermal method and utilized as an efficient electrochemical sensing probe. The hydrothermal method involved carbonization of citric acid into GQDs and growth of ZrO 2 NPs, simultaneously. The electron microscopic images visualized a nanoflower structure of GQDs@ZrO 2 nanostructures having an average diameter of 17 ± 3 nm. X-ray photoelectron spectroscopy, zeta potential, UV–visible, and fluorescence characterizations have also validated the existence of ZrO 2 NPs and GQDs in the synthesized GQDs@ZrO 2 nanostructures. The GQDs@ZrO 2 hybrid prevented restacking of GQDs and provided adequate availability of functional groups and a high electron transport rate, which resulted in improved electrochemical biosensing performance. The oxygen moieties associated with the GQDs@ZrO 2 /ITO electrode offer an excellent environment for covalent attachment of antibodies. A fabricated BSA/anti-OTA/GQDs@ZrO 2 /ITO immunosensor revealed enhanced biosensing parameters such as a detection range of 1–20 ng/mL, sensitivity of 5.62 μA mL/ng cm 2, limit of detection of 0.38 ng/mL, and an average of 95% recovery of ochratoxin-A from the spiked coffee sample.