A hybrid conjugate of reduced graphene oxide/ferrous-ferric oxide nanoparticles (rGO-Fe3O4 NPs) is characterized and assembled with chitosan and laccase to form a layered functional superstructure. After its characterization by field-effect scanning electron microscopy, energy-dispersive X-ray analysis, X-ray photoelectron spectroscopy, attenuated total reflectance Fourier transform infrared, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS), the nanocomposite has been deposited on glassy carbon for the enzyme-mediated electrochemical determination of the endocrine disruptor bisphenol A (BPA). Proof-of-concept assays conducted by using CV, EIS, and square wave voltammetry reveal that the enzymatic biosensor provides linear response in a wide range of BPA concentrations (6-228 ppb), very high sensitivities, and excellent durability (over 1-month storage). Using amperometric detection, remarkable sensitivities (2080 μA μM-1 cm-2) and detection limits (18 nM) are attained. Applications to real samples of bottled water proved feasible with recoveries in the range 107-124%. Graphical abstract Reduced graphene oxide conjugated with magnetite nanoparticles (rGO-Fe3O4) was assembled with laccase (wine-colored dots) and chitosan for the electrochemical determination of bisphenol A. The enzymatic biosensor exhibited excellent linearity (6-228 ppb) and stability. Best sensitivity (2080 μA μM-1 cm-2, detection limit 18 nM) was obtained by amperometry.
Keywords: ATR-FTIR; Chronoamperometry; Cyclic voltammetry; Electrochemical impedance spectroscopy; Enzymatic biosensors; FESEM; Graphene nanomaterials; Graphene-nanoparticle conjugates; Magnetite nanoparticles; Square wave voltammetry; XPS.