ZrO2 Nanoflowers Decorated with GrapheneQuantum Dots for Electrochemical Immunosensing

In the present work, hybrid nanostructures of graphene quantum dots decorated zirconia (GQDs@ZrO2) 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 ZrO2 NPs, simultaneously. The electron microscopic images visualized a nanoflower structure of GQDs@ZrO2 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 ZrO2 NPs and GQDs in the synthesized GQDs@ZrO2 nanostructures. The GQDs@ZrO2 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@ZrO2/ITO electrode offer an excellent environment for covalent attachment of antibodies. A fabricated BSA/anti-OTA/GQDs@ZrO2/ITO immunosensor revealed enhanced biosensing parameters such as a detection range of 1–20 ng/mL, sensitivity of 5.62 μA mL/ng cm2, limit of detection of 0.38 ng/mL, and an average of 95% recovery of ochratoxin-A from the spiked coffee sample.