4. Conclusions
In summary, the hybrid diamond/graphite films have been
synthesized at a high CH4/H2 ratio with a microwave power of
10 kW by MPCVD without nitrogen addition. The TEM, Raman
and XRD results show that the as-grown films contain both
diamond and graphite phases. The diamond nanostructures are
surrounded by graphite which greatly enhances its electrical conductivity.
We confirm that the morphology change from granular
to nanostructure and the electricity promotion from insulate to
metallic conductivity of the films are because of the high CH4 concentration
and microwave power. The hybrid electrode exhibits
quasi-reversible, mass controlled electrode reactions in aqueous
and organic solutions and have a wide potential window of about
3.1 V. It shows good linearity with r2 ≥
0.997 over a wide range and
low detection limits with 5.8 ppb for Ag+ and 5.6 ppb for Cu2+ as
electrochemical electrode in heavy metal ions detection. The good
recovery values in tap water samples demonstrate the accuracy and
feasibility of the hybrid diamond/graphite electrodes. The hybrid
diamond/graphite electrode is thus a potential candidate for trace
heavy metal ions detection.