▎ 摘　　要

Chemical sensors relying on graphene-based materials have been widely used for electrochemical determination of metal ions and have demonstrated excellent signal amplification. This study reports an electrochemically reduced graphene oxide (ERGO)/mercury film (HgF) nanocomposite-modified pencil graphite electrode (PGE) prepared through successive electrochemical reduction of graphene oxide (GO) sheets and an in situ plated HgF. The ERGO-PG-HgFE, in combination with dimethylglyoxime (DMG) and square-wave adsorptive cathodic stripping voltammetry (SW-AdCSV), was evaluated for the determination of Ni2+ in tap and natural river water samples. A single-step electrode pre-concentration approach was employed for the in situ Hg-film electroplating, metal-chelate complex formation, and non-electrolytic adsorption at -0.7 V. The current response due to nickel-dimethylglyoxime [Ni(II)-DMG(2)] complex reduction was studied as a function of experimental paratmeters including the accumulation potential, accumulation time, rotation speed, frequency and amplitude, and carefully optimized for the determination of Ni2+ at low concentration levels (mu g L-1) in pH 9.4 of 0.1 M NH3-NH4Cl buffer. The reduction peak currents were linear with the Ni2+ concentration between 2 and 16 mu g L-1. The limits of detection and quantitation were 0.120 +/- 0.002 mu g L-1 and 0.401 +/- 0.007 mu g L-1 respectively, for the determination of Ni2+ at an accumulation time of 120 s. The ERGO-PG-HgFE further demonstrated a highly selective stripping response toward Ni2+ determination compared to Co2+. The electrode was found to be sufficiently sensitive to determine metal ions in water samples at 0.1 mu g L-1, well below the World Health Organization standards.