Environmental Engineering Reference
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narrow size range of 45-75 nm. h e synthesized nanoparticles were highly
active against a range of fungal pathogens such as
Puccinia graminis tritci
,
Aspergillus l avus
,
Aspergillus niger
and
Candida albicans.
Basavegowda
et
al.
[95] have used pineapple (
Ananas comosus
L.) fruit extracts to produce
gold nanoparticles. h e authors demonstrated very high inhibitory activ-
ity of the synthesized gold nanoparticles against some important human
pathogens like
E. coli
and
Streptobacillus sp.
At a low temperature, Song
et al.
[47] reported production of a mixture
of plate (triangles, pentagons, and hexagons) and spherical nanoparticles
(size, 5-300 nm) using leaf extracts
of
Magnolia kobus
and
Diopyros kaki
.
Castro
et al.
[96] synthesized gold nanowires by using pulp of sugar beet as
reducing and capping agent. Khalil
et al.
[97] have elucidated that olive leaf
extract synthesized gold nanoparticles (AuNPs) of various shapes (triangle,
hexagonal, and spherical). Rastogi and Arunachalam [98] have produced
gold nanoparticles via reduction of HAuCl
4
by using aqueous extract of
garlic cloves as reducing/stabilizing agent. Similarly, Singh
et al.
[99] used
a rapid, reproducible and a green biogenic approach for the biosynthesis
of gold and silver nanoparticles by using biomolecules present in the leaf
extract of
Dalbergia sissoo
as a reducing material.
In a recent research study, Babu and coworkers [27] reported a controlled
biosynthesis of gold nanoparticles by using ethanolic leaf extract of
Bacopa
monnieri
[27] and UV irradiation. h e X-ray dif raction, UV-Visible spec-
tra and TEM demonstrated the particles were crystalline in nature whose
size ranged from 3-45 nm with a mean diameter of 11 nm.
10.2.3
Gold/Silver Bimetallic Nanoparticles
In recent research carried out by Mondal
et al.
[100], the role of aque-
ous extract of dried leaves of mahogany (
Swietenia mahogani
Ja.) in the
rapid synthesis of stable monometallic Au and Ag nanoparticles and also
Au-Ag bimetallic alloy nanoparticles were investigated. h e reduction of
aqueous Ag
+
and AuCl
4
−
ions was ascribed to the presence of various poly-
hydroxy limonoids in the extract. Extracellular synthesis of pure metallic
silver, gold nanoparticles and bimetallic Au-Ag nanoparticles using neem
(
Azadirachta indica
) leaf broth has been reported by Shankar and cowork-
ers [25]. Synthesis of bimetallic Au core-Ag shell nanoparticles in solution
takes place when Au3
+
and Ag
+
ions are present simultaneously in the solu-
tion, with silver nanoparticles being adsorbed onto the gold nanoparticles.
In a related report, Sheny
et al.
[101] have investigated the biosynthesis of
Au, Ag and Au-Ag bimetallic nanoparticles with the aqueous extract and
dried leaf of
Anacardium occidentale.
h ey characterized the synthesized
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