Hybrid diamond/graphite films as electrodes for anodic stripping voltammetry of trace Ag+ and Cu2+

Abstract

Hybrid diamond/graphite nanostructures were synthesized in CH4/H2 mixture gas using microwave plasma enhanced chemical vapor deposition (MPCVD) at a power of 10kW. The microstructure and the composition of the films were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), Raman spectroscopy and X-ray diffraction (XRD). The as-deposited diamond films at high methane level in hydrogen plasma show good conductivity and excellent electrochemical activity, owing to the co-existence of diamond and graphite phases in the films. The largest electrochemical potential window of the hybrid diamond/graphite films is 3.1V, which is comparable with the B-doped diamond. The films exhibit quasi-reversible, mass controlled electrode reactions in both aqueous and organic solutions. In the application of trace heavy metal ion detection, the hybrid diamond/graphite electrodes present low background currents and detection limits (S/N≥3): ∼1.5μA/cm2 and 5.8ppb for Ag+, ∼4.7μA/cm2 and 5.6ppb for Cu2+. The diamond/graphite electrodes also possess good linearity over a wide concentration range from 10ppb to 1ppm. In addition, the simultaneous determination of silver and copper ions was also successful. The good recovery values for the analysis of the tap water samples with standard addition method demonstrate the accuracy of the hybrid diamond/graphite electrodes. Hence, the hybrid diamond/graphite films are promising for electrochemical applications such as trace heavy metal ions detection because of its wide potential window, lower background current and high sensitivity.