Polyethyleneimine/Graphene Multilayer Film Supported Ferric Cobalt Modified Electrode for High-Performance Sensing of L-cysteine

One novel chemically modified electrode (CME) was prepared through fabricating polyethyleneimine/oxidized graphene multilayers on indium tin oxide (ITO) slide via layer-by-layer assembly followed by electrochemically depositing cobalt hexacyanoferrate. A large range of methods were used to characterize the morphology and electrochemical properties of the electrode including field-emission scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction, cyclic voltammetry, differential pulse voltammetry (DPV), electrochemical impedance spectroscopy and chronoamperometry. Under optimized conditions, the oxidation current of DPV (typically at 0.2 V vs. saturated calomel electrode) increased linearly in the range of 5 × 10 −5 to 2 × 10 −3 mol L −1 . And the limit of detection and the limit of quantity were 4.6 × 10 −7 mol L −1 and 1.5 × 10 −6 mol L −1 (based on signal-to-noise ratio of 3 and 10), respectively. Average recoveries from (spiked) commercial mask were between 98.1% and 104.5% with relative standard derivations less than 3.14% (n = 3) at three spiked levels. The method was validated by HPLC. Furthermore, the possible mechanism of L-Cys detection was studied based on chronoamperometric experiments.