Nanostructure Restoration of Thermally Reduced Graphene Oxide Electrode upon Incorporation of Nafion for Detection of Trace Heavy Metals in Aqueous Solution

High performance reduced graphene oxide (RGO)-Nafion (N) thin film electrodes coated on silicon (Si) substrates (RGO-N/Si) were successfully developed through thermal reduction of GO-N without delamination from the substrates. The restoration of the RGO-N nanostructure upon the addition of Nafion was proven by Raman spectroscopy (RS) and field emission scanning electron microscopy, and the restoration mechanism of the RGO-N nanostructure was proposed. Through the investigation using x-ray photoelectron spectroscopy (XPS), the polyfluorocarbon from Nafion possessed a function that could prevent the delamination of the RGO sheets from the substrates during the thermal reduction. The RGO-N/Si samples were later used for the determination of trace heavy metals, such as divalent lead, cadmium and copper ions (Pb2+, Cd2+ and Cu2+, respectively) using square wave anodic stripping voltammetry in a 0.1M acetate buffer solution (pH 5). Based on the electroanalytical measurements, the RGO-N/Si samples exhibited a highly linear behavior in the detection of Cd2+, Pb2+ and Cu2+ over the concentration range of 50 nM to 300 nM with detection limits at nM levels. In addition, the RGO-N/Si samples presented good recoveries of target metals in tap water samples.