Electrochemical Sensor: L-Cysteine Induced Selectivity Enhancement of Electrochemically Reduced Graphene Oxide-Multiwalled Carbon Nanotubes Hybrid for Detection of Lead (Pb2+) Ions

The selectivity improvement of Electrochemically reduced Graphene Oxide-Multiwalled Carbon Nanotubes-L-cysteine (ErGO-MWNTs-L-cys) nanocomposite modified Glassy Carbon Electrode (GCE) using drop casting method for electrochemical detection of lead (Pb2+) ions was investigated. Initially, the graphene oxide-Multiwalled Carbon Nanotubes-L-cysteine (GO-MWNTs-L-cys) nanocomposite was synthesized by a facile and cost-effective method at room temperature. The as-prepared, GO-MWNTs-L-cys exhibited good stable aqueous dispersions due to high hydrophilic nature of GO components which led to inhibiting the hydrophobicity of MWNTs. Then, the electrochemical conductivity of ErGO-MWNTs-L-cys nanocomposite modified GCE (ErGO-MWNTs-L-cys/GCE) was improved by the direct electrochemical reduction of GO-MWNTs-L-cys nanocomposite. The GO-MWNTs-L-cys nanocomposites and its individual components were characterized by Attenuated Total Reflection Infrared (ATR-IR), Ultraviolet-visible spectroscopy, Raman spectroscopy, Atomic Force Microscopy, and X-ray diffraction (XRD). The synergistic effect of ErGO-MWNTs-L-cys nanocomposite was confirmed by Cyclic Voltammetry (CV) and Electric Impedance Spectroscopy (EIS) measurements in [Fe(CN)(6)](3-/4-) redox. Experimental parameters, such as pH, accumulation time and electrochemical reduction degrees, were optimized. Under optimal conditions, the electrochemical performance of modified electrodes toward Pb2+ ions was examined and it exhibited appreciable improvement at the ErGO-MWNTs-L-cys/GCE. In terms of applications, Differential Pulse Anodic Stripping Voltammetry (DPASV) was employed for the determination of Pb2+ ions on ErGO-MWNTs-L-cys/GCE. The calibration plots between anodic current and Pb2+ ions exhibited linear relationship in the range of 0.2-40 mu gL(-1) with the detection limit calculated to be 0.1 mu gL(-1) (S/N = 3). Finally, the ErGO-MWNTs-L-cys/GCE showed satisfied selectivity and stable results, and the Relative Standard Deviation (RSD) was calculated to be (RSD = 2.15%).