Chemistry Reference
In-Depth Information
using NaOH. To the above solution, 2.0 mL each of 10.0 mM AuCl
3
and
AgNO
3
solutions (depending on the alloy composition) were added and
stirred for 20 minutes at 25°C. Subsequently, 4.0 mL of ice cold NaBH
4
(50 mM) was added and vigorously stirred for 1 hour. Instantaneous
colour change from dark brown to black was observed. The black colour
is due to the reduction of EGO to reduced EGO. The as-synthesized
nanocomposite was washed with ethanol to remove any by-product and
the material thus obtained was dried and used for subsequent
characterization. Au-Ag alloy nanocomposites with different molar ratios
such as 0.6:0.4, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8 and 1:9 were prepared
by similar procedure. Monometallic graphene-Au nanocomposite and
graphene-Ag nanocomposite were also prepared using a similar protocol
for comparative purposes.
2.3.
Synthesis of GO-Co
3
O
4
composite
500.0 mg of Co(NO
3
)
2
was dissolved in 40.0 mL of hexanol which
formed a red colour solution. To this, 100 mg of EGO was added and
dispersed by ultrasonication for 3 hours. The solution was then refluxed
at 120°C for about 10 hours.
29
After cooling down to room temperature,
the as-synthesized product was washed with ethanol repeatedly to
remove any by-product and dried.
2.4.
Synthesis of EGO-RuOx composite
The preparation of EGO and ruthenium oxide composite was based on
the method proposed for the preparation of sol-gel derived RuO
x
.xH
2
O.
30
500 mg of EGO was suspended in a mixture of 1:1 (by volume)
methanol: water (100 mL) containing 60 mg of RuCl
3.
The mixture was
stirred for 2 hours and the pH of the solution was adjusted to 7 by using 1
M NaOH. During the process ruthenium hydroxide particles precipitated
out and got dispersed on EGO. It was centrifuged and washed several
times with distilled water to remove NaCl completely. The material was
subsequently dried in vacuum at room temperature and subsequently at
300°C for 2 hours.
