The carbon paste electrode was prepared by mixing fine graphite
powder with paraffin (70:30, w/w) in a mortar and pestle. A portion
of the composite mixture was packed into the end of a glass tube
(3.4 mminner diameter). Electrical contact wasmade by forcing a copperwire
down into the tube and into the back of the composite. A small
amount of carbon paste was forced out fromthe tube and cut off with a
scalpel. The electrode surface was smoothed by polishing on a piece of
graph paper while a slight manual pressure was applied to the piston.
To prepare the modified composite electrode, 500 mg of the graphite
powder was mixed with 3 mL of GN solution. This modified composite
was air dried for 24 h and then used in the sameway as the unmodified
composite. TEM image is shown in Fig. 4.