confirmed the antibacterial property of NPs, but the exact mechanism of their mode of
action is still to be deciphered.
Table 4 Bacterial growth inhibition monometallic and bimetallic nanoparticles
prepared by plasma chemical treated Grape fruit extract
Bacteria species
Bacterial growth inhibition, %
Control
(Extract)
Ag
Ag/Au
Escherichia coli
13.0
97.5
93.1
Staphylococcus aureus
10.0
98.3
95.1
Aqueous extract of Grape fruit have been utilized in the syntheses of copper-silver
bimetallic nanoparticles (Ag/Cu NPs).
The dark brownish colouration confirms the
reduction of Ag
+
ions to Ag
0
and in the case of bimetallic mixture, gray precipitates
with dark greenish colouration at the top was observed. The SEM reveals uniform
microspheres of anisotropic particles for Ag/Cu NPs.
CONCLUSION
Green chemistry approach towards the synthesis of nanoparticles has many
advantages such as, ease with which the process can be scaled up and economic
viability. Monometallic and bimetallic nanoparticles were prepared in aqueous
precursors solutions by using of contact non-equilibrium low-temperature plasma and
different stabiliser agents as capping agent.
1. The possibility of applying the discharge of contact nonequilibrium low-
temperature plasma for synthesizing metal nanodispersions from water AgNO
3
solutions is established. The efficiency of plasma-chemical synthesis without the use
of additional reducing reagents and in the presence of stabilizing reagent is shown. The
process is more efficient in the presence of the stabilizer. The formation of MNPs
colloidal solutions in the presence of capping agent is characterized by the presence of
peak in the spectra.
2. It is found that the yield of silver nanoparticles in the plasma-chemical synthesis
is higher by 1.5-2 % and 75-78 %, in comparison with the conventional method of
chemical reduction in solutions and photochemical precipitation, respectively. At the
same time, the duration of the synthesis process is reduced almost 3 times. It is found
that the introduction of stabilizer contributes to the increase of the yield of silver
nanoparticles and allows synthesizing stable colloidal silver solutions.
3. The thermodynamics analysis of formation of silver nanoparticles in aqueous
solutions using various methods for calculating the Gibbs free energy is carried out.
Depending on the method of calculation of
0
Ag
(
s)
NP
f
G
, it is from –9.43 to –14.48 J/mol
and 36.5–50.6 KJ/mol. The pattern is revealed: the Gibbs free energy in aqueous
solutions increases with decreasing size of silver particles. Comparison of the
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