Environmental Engineering Reference
In-Depth Information
Synthesis of nanoparticles using plant extract is very cost ef ective, and
therefore can be used as an economic and valuable alternative for large-
scale production of metal nanoparticles. Extract from plants can act both
as reducing and capping agent in nanoparticle synthesis. Shastry
et al.
have
studied bioreduction of gold and silver ions by leaf broth of
Pelargonium
graveolens
and
Azadirachta indica
[92].
Silver nanoparticles were successfully synthesized from AgNo
3
through a simple green and natural route using the latex of 6 differ-
ent plant taxa belonging to 6 different families [93]. Some specific
plant parts or whole plant, especially angiospermic plants, are used for
great synthesis of nanoparticles. Alfalfa roots are capable of absorbing
Ag (0) from agar medium and transferring them to the shoot of the
plant in the same oxidation state. In the shoot these Ag atoms arrange
themselves to form nanoparticles by joining themselves to form larger
arrangements. With the use of
Emblica officinalis
fruit extract as reduc-
ing agent, the extracellular synthesis of highly stable Ag and AuNPs has
been achieved [94].
Achlypha indica
leaf extracts have produced silver nanoparticles (20-
30nm) in 30 min. h ese nanoparticles had excellent antimicrobial activity
against waterborne pathogens like
E.coli
and
V. cholera
[95].
12.12.1
Extraction of Nanoparticles
At er synthesizing nanoparticles by using plant extract, methods such as
freezing, osmotic shock and heating are used in order to extract them
from cells.
In addition to this, in the case of extracellular production of nanopar-
ticles, centrifugation could be used for extraction and purii cation of
nanoparticles.
12.13
Characterizations of Nanoparticles
h ere are several techniques to analyze nanoparticles such as atomic
absorbtion spectroscopy (AAS), TEM, surface characterization through
X-ray photoelectron spectroscopy, dynamic light scattering, etc., some of
which are described below.
•
X-ray dif erentiation:
XRD is a noncontact, nondestructive
technique, which can be used to determine the crystalline
phases presented in materials.
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