Ultrasensitive and simultaneous detection of heavy metal ions based on three-dimensional graphene-carbon nanotubes hybrid electrode materials.

A green and facile method was developed to prepare a novel hybrid nanocomposite that consisted of one-dimensional multi-walled carbon nanotubes (MWCNTs) and two-dimensional graphene oxide (GO) sheets. The as-prepared three-dimensional GO-MWCNTs hybrid nanocomposites exhibit excellent water-solubility owing to the high hydrophilicity of GO components; meanwhile, a certain amount of MWCNTs loaded on the surface of GO sheets through π-π interaction seem to be "dissolved" in water. Moreover, the graphene(G)-MWCNTs nanocomposites with excellent conductivity were obtained conveniently by the direct electrochemical reduction of GO-MWCNTs nanocomposites. Seeing that there is a good synergistic effect between MWCNTs and graphene components in enhancing preconcentration efficiency of metal ions and accelerating electron transfer rate at G-MWCNTs/electrolyte interface, the G-MWCNTs nanocomposites possess fast, simultaneous and sensitive detection performance for trace amounts of heavy metal ions. The electrochemical results demonstrate that the G-MWCNTs nanocomposites can act as a kind of practical sensing material to simultaneously determine Pb(2+) and Cd(2+) ions in terms of anodic stripping voltammetry (ASV). The linear calibration plots for Pb(2+) and Cd(2+) ranged from 0.5 μg L(-1) to 30 μg L(-1). The detection limits were determined to be 0.2 μg L(-1) (S/N=3) for Pb(2+) and 0.1 μg L(-1) (S/N=3) for Cd(2+) in the case of a deposition time of 180 s. It is worth mentioning that the G-MWCNTs modified electrodes were successfully applied to the simultaneous detection of Cd(2+) and Pb(2+) ions in real electroplating effluent samples containing lots of surface active impurities, showing a good application prospect in the determination of trace amounts of heavy metals.