Chemistry Reference
In-Depth Information
Fig. 3. SEM images of graphene-Au-Ag alloy nanocomposites with compositions 1:1
(left), 1:8 (right) respectively. The scale bars correspond to 20 µm.
3.1.
Electrochemical detection of dopamine using
graphene-alloy nanocomposites
The need to detect neurotransmitters such as dopamine and ascorbic acid
is over emphasized in the literature. However, preparation of an electrode
that requires minimum surface treatment with good response is still a
challenge. The response of dopamine (DA) on bare glassy carbon
electrode (GCE) and on graphene-Au-Ag alloy composite modified GCE
is followed by cyclic voltammetry. The composite colloid is drop coated
(50 µL) on the surface of GCE (0.2 cm
2
area) and the solvent is
subsequently evaporated to result in a stable alloy colloidal film on the
surface. Typical cyclic voltammograms of DA are recorded in phosphate
buffer, pH = 7.0 (Fig. 4). It is clear that well-defined and resolved
voltammetric peak is observed for DA oxidation on alloy composite
modified electrode in comparison to bare GCE. DA shows an irreversible
redox reaction on bare GCE while well-defined, sharp redox pair with
obviously increased current response is obtained for DA on the alloy
composite modified GCE. For example, the negatively shifted anodic
peak potential (
E
pa = 184 mV) and the positively shifted cathodic
peak potential (
E
pc = 97 mV) results in small
∆E
p
value (67 mV) for a
concentration of 1 mM DA in the buffer. The negative shifts of the
oxidation potentials together with the formation of well-defined redox
peaks clearly indicate the favorable electrocatalysis for the oxidation of
