Environmental Engineering Reference
In-Depth Information
Verticillium sp. (Mukherjee et al. 2001 , 2002 ;
Ahmad et al. 2003a ). Monodisperse particles
have been synthesized using alkalotolerant
Rhodococcus sp. under extreme biological con-
ditions like alkaline and slightly elevated tem-
perature conditions (Ahmad et al. 2003b ).
Aggregated forms of nanoparticles like gold
nanotriangles have been reported in lemon grass
extracts and tamarind leaf extracts (Ankamwar
et al. 2005b ). Extracellular synthesis of gold
nanoparticles has also been observed using
Emblica offi cinalis fruit extract as a reducing
agent (Ankamwar et al. 2005a ). Synthesis of
gold nanostructures in different shapes (spheri-
cal, cubic, and octahedral) has been possible by
the use of fi lamentous cyanobacteria from Au
(I)-thiosulfate and Au (III)-chloride complexes
(Lengke et al. 2006 ). Dead biomass of Humulus
lupulus and leaf extract of Ocimum basilicum
also produce gold nanoparticles (Lopez et al.
2005 ; Singhal et al. 2012 ). Gold nanoparticles
are being developed for fuel cell applications
which would be useful in automotive and display
industry (Thompson 2007 ). Gold nanoparticles
embedded in porous manganese oxide act as
room temperature catalyst to break down volatile
organic pollutants in air. Palladium-coated gold
nanoparticles are very effective catalysts for
removing trichloroethane (TCE) from ground-
water 2,200 times better than palladium alone
(Tiwari et al. 2008 ). The use of gold nanoparti-
cles in colorimetric sensors enables identifi ca-
tion of foods suitable for consumption. Other
methods, such as surface-enhanced Raman spec-
troscopy, exploit gold nanoparticles as substrates
to enable the measurement of vibrational ener-
gies of chemical bonds, which can be used for
the detection of proteins, pollutants, and other
label-free molecules (Ali et al. 2012 ).
(Kowshik et al. 2003 ). Silver nanoparticles have
been reported from Pleurotus sajor caju along
with its antimicrobial activity (Nithya and
Raghunathan 2009 ). Extracellular biosynthesis
of silver nanoparticles has been reported using
marine cyanobacterium Oscillatoria willei
NTDM01 that reduces silver ions and stabilizes
the silver nanoparticles by a secreted protein (Ali
et al. 2011 ). Silver nanoparticles have been pro-
duced in the form of a fi lm or produced in solu-
tion or accumulated on cell surface of Verticillium ,
Fusarium oxysporum , or Aspergillus fl avus
(Senapati et al. 2004 ; Bhainsa and D'Souza 2006 ;
Vigneshwaran et al. 2007 ; Jain et al. 2011 ). Silver
nanoparticles with potential antimicrobial activ-
ity against Escherichia coli , Vibrio cholerae ,
Salmonella typhimurium , Pseudomonas putida ,
P. vulgaris , and P. aeruginosa have been reported
from leaves of Acalypha indica and Nicotiana
tabacum , peels of Citrus sinensis , and stem of
Allium cepa (Krishnaraj et al. 2010 ; Saxena et al.
2010 ; Konwarh et al. 2011 ; Prasad et al. 2011 ).
Silver nanoparticles produced with the aid of
zeolite are a good sorbent for the removal of
vapor-phase mercury from the fl ue gas of coal-
fi red power plants (Dong et al. 2009 ). They are
effective antimicrobial compounds against coli-
form found in wastewater and incorporated as an
antimicrobial, antibiotic, and antifungal agent in
coatings, nanofi ber, fi rst-aid bandages, plastics,
soaps, and textiles, in the treatment of certain
viruses, in self-cleaning fabrics, as conductive
fi ller, and in nanowire and certain catalyst appli-
cations (Jain and Pradeep 2005 ; Tiwari et al.
2008 ). The effect of loaded silver nanoparticles
on TiO 2 has been studied for the degradation of
Acid Red 88 (Anandan et al. 2008 ). Their pres-
ence has been found to signifi cantly enhance
DP25-TiO 2 -mediated photodegradation of
methyl orange at pH 6.6 (Gomathi Devi and
Mohan Reddy 2010 ). The behavior of silver
nanoparticles in a pilot wastewater treatment
plant fed with municipal wastewater was investi-
gated. TEM analyses confi rmed the sorption of
silver nanoparticles to wastewater biosolids, both
in the sludge and effl uent, and freely dispersed
particles were observed only during the initial
pulse spike in the effl uent. XAS measurements
6.2
Silver Nanoparticles
Pseudomonas stutzeri AG 259 isolated from sil-
ver mine formed silver nanoparticles when placed
in silver nitrate solution (Klaus-Joerger et al.
2001 ). High quantity of silver nanoparticles is
obtained using silver-tolerant yeast strains MKY3
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