Environmental Engineering Reference
In-Depth Information
room temperature. h e nanoparticles produced were found to be in the
size range of 20-60 nm and crystallized in face-centered cubic symme-
try. More recently, Mallikarjuna and coworkers [107] examined the one-
pot synthesis of palladium (4 ± 1 nm)
nanoparticles using a leaf extract
of
Piper betle.
Fourier transform infrared (FTIR) spectroscopy revealed
that the water soluble l avonoids of
P. b e t l e
are responsible for reduction
of palladium nanoparticles. h e produced nanoparticles displayed high
antifungal activity. In another study, Raut
et al.
[108] reported extracellu-
lar synthesis of platinum and palladium nanoparticles, of spherical shape,
using root extract of
Asparagus racemosus
L
.
h e
palladium nanoparticles
synthesized were characterized using UV-Visible spectroscopy, transmis-
sion electron microscopy (TEM) and cyclic voltammetry (CV) techniques.
h e authors found that both the nanoparticles are produced within 5 min,
having crystalline form, and are in the size range of 1-6 nm.
10.2.5
Synthesis of Other Transition Metal Nanoparticles
Many other transition metal nanoparticles such as copper, zinc and
c
ad-
mium oxide have attracted huge attention due to their applications in cataly-
sis, solar cells, sensors and other photonic devices [109, 110]. h e common
routes for their production involve chemical reductions using synthetic
agents [111]. h e use of plants in their synthesis is not well documented in
the literature; however Lee and coworkers [58] have reported the synthesis
of stable copper nanoparticles (37-110 nm) by treating aqueous solution of
CuSO
4
.5H
2
O with the leaf extract of
Magnolia kobus
as a reducing material.
Sangeetha
et al.
[112] have produced polydispersed zinc oxide nanopar-
ticles having an average size of 25-40 nm by using leaf extract of
Aloe
barbadensis
Miller plant. h eir results have proved that a leaf broth con-
centration of greater than 25% could result in more than 95% conservation
of zinc salts to zinc nanoparticles. Likewise, spherical zinc oxide nanopar-
ticles (50-200 nm) have been produced by Samat and colleagues [113]
using extracts of
Citrus aurantifolia.
10.3 Proposed Mechanisms
Several mechanisms for the synthesis of nanoparticles using plants have
been proposed, however, an exact mechanism is still not known. An
emerging area of scientii c research being developed is the investigation
of the role of biomolecules in the synthesis of transition metal nanopar-
ticles. Scientists all around the world are of the opinion that the presence of
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