2.2. Preparation of the electrodes
At the beginning, a bare glassy carbon electrode (BGCE) was
polished with 0.05 mm aluminum oxide slurry on a cloth and
then rinsed with double-distilled water. The electrode was
then consecutively inserted in 1:1 nitric acid, absolute
ethanol, and double-distilled water in an ultrasonic bath for
2 minutes.
A silver nanoparticles modified GCE (SNPs-GCE) was prepared
by immersing a BGCE in a solution containing 100mM
nitric acid and 1mM silver nitrate; a continuous cyclic potential
from 0.7 V to 1.9 V at a sweep rate of 80 mV/s for eight
cycles was also applied [19]. As the final point, the modified
electrode was rinsed with double-distilled water and dried in
air.
A delphinidin silver nanoparticles modified GCE (DSNPs-
GCE) was prepared by immersing a SNPsGCE in a 0.10mM
solution of delphinidin in a 0.10M phosphate buffer (pH 7.0)
and modified by 16 cycles of a potential scan in the range of
0.25 V to 0.7 V at 20 mV/s (Figure 2), in which the delphinidin
modified glassy carbon electrode (DGCE) was based on placing
the BGCE in a 0.10mM solution of delphinidin in a 0.10M
phosphate buffer (pH 7.0), and modified in the same procedure
as described for the DSNPs-GCE.
In addition, to ensure the electrode modification steps,
scanning electron microscope (SEM) imaging was performed
using the MIRA3 Tescan SEM (Tescan, Brno-Kohoutovice,
Czech Republic) for the silver nanoparticle modified electrode
and for delphinidin immobilized on the silver nanoparticles
on the GCE.