A novel free-standing CVD graphene platform electrode modified with AuPt hybrid nanoparticles and L-cysteine for the selective determination of epinephrine

A novel free-standing graphene platform electrode (GPE) was prepared directly by transferring a chemical vapor deposition (CVD) graphene film from Cu foils to polyethylene terephthalate substrates with the aid of polymethyl-methacrylate. AuPt hybrid nanoparticles (AuPtNPs) and L-cysteine (L-Cys) were electrodeposited simultaneously on the GPE. The successful formation of AuPtNPs-Cys/GPE was confirmed by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), Raman microscope and X-ray diffraction (XRD). The electrocatalytic activity and enhanced conductivity of AuPtNPs-Cys/GPE sensor was evaluated by determining epinephrine (EP) in the presence of ascorbic acid (AA), dopamine (DA), uric acid (UA) in phosphate buffer solution by various techniques, including cyclic voltammetry (CV), differential pulse voltammetry (DPV) and chronoamperometry. Further, the proposed sensor not only achieved the selective determination of EP, but also separated the voltammetric signals of AA, DA, EP and UA with potential differences of 266, 250 and 183 mV, respectively. The amperometric current response was increased linearly with increasing EP concentration in the range of 0.2 to 1000 mu M with a detection limit of 0.0157 mu M (S/N = 3). In addition, the as-obtained sensor delivered extraordinary stability, reproducibility, as well as high resistance to interferences, and was successfully utilized in determining real samples.