Environmental Engineering Reference
In-Depth Information
a soccer ball and has 60 carbon atoms arranged as 12 pentagons and 20 hexagons.
Otherfullerenenanoparticlesalsoexist(e.g.,C
70
, C
74
, C
76
, C
78
, etc.). Fullerenes are
hydrophobic and have application as organic photovoltaics, antioxidants, catalysts,
polymers,inwaterpuriication,bio-hazardprotectiveagents,andinvariousmedical
and pharmaceutical applications (Yadav and Kumar
2008
). Carbon nanotubes
(CNTs) are also important. CNTs include single- and multi-walled nanotubes
(SWNTsandMWNTs)thatarecylindricalinshape.CNTspossessexcellenttensile
strengthandelasticityandshowdifferentmetallicandkineticpropertiesthatvaryby
theirsize.Forexample,hightensilestrengthcarbonnanotubes(CNTs)haveappli-
cationsintheelectronicandpolymerindustries(Koehleretal.
2008
; Wu et al.
2004
;
Table
2
). Moreover, the energy sector and the consumer goods industries are doing
research with this unique material (Koehler et al.
2008
). CNTs promise to have
interestingfutureapplicationsbybeingintegratedintopolymers(Changetal.
2005
)
andintolithiumionsecondarybatteries(Ouellette
2003
). The demand for carbon-
basednanoparticlesinthemarket,especiallyintheelectronicsandpolymersectors,
isenormousandisestimatedtoreach$1.096billionby2015(Garland
2009
).
Metalnanoparticlesaremadebymanipulatingheavymetalslikegold,silver,iron
and platinum. Such ENPs possess specific properties that are based on their shape,
size and dissolution medium. Different routes have been used to synthesize these
nanoparticles;recently,greensynthesismethodshavebeenutilizedtomakesilver
andironnanoparticles(Ramtekeetal.
2010
,
2012
; Sahu et al.
2012
;Shankaretal.
2003
). Metal nanoparticles have many uses and new ones are routinely being discov-
ered. For example, colloidal gold is used to treat rheumatoid arthritis in an animal
model(Tsaietal.
2007
),isusedasadrugcarrier(Gibsonetal.
2007
) and as an agent
fordetectingtumors(Qianetal.
2008
). Colloidal gold has also been used as a con-
trastagentforbiologicalprobeslikeantibodies,nucleicacids,glycansandreceptors
(HorisbergerandRosset
1977
)(Table
2
). Silver nanoparticles are used in medicine
(Table
2
)asadisinfectant,antiseptic,insurgicalmasks,andinwounddressingsthat
have anti-bacterial activity (Chopra
2007
). Many textiles, keyboards, cosmetics,
waterpuriierappliances,plasticsandbiomedicaldevicesarenowknowntocontain
silvernanoparticlesthatprovideprotectionagainstmicroorganisms(Lietal.
2010
).
Ironnanoparticlesareutilizedinmagneticrecordingmediaandtapes,asacata-
lyst in Fischer-Tropsch synthesis, in drug-delivery applications, in magnetic reso-
nanceimaging(MRI)andintreatinghyperthermia(Huber
2005
). Iron nanoparticles
have been used to remediate industrial sites that were contaminated with chlorinated
organiccompounds(Zhang
2003
)(Table
2
). Platinum nanoparticles exhibit antioxi-
dant properties, but what applications they are to be put to is as yet undeciphered.
Although no applications have yet emerged, it is interesting to note that platinum
NPshaveantioxidantactivitythatincreasesroundwormlongevity(Kimetal.
2008
;
Table
2
).Thetotalmarketfornanoparticlesinbiotechnology,drugdiscoveryand
development was valued at $17.5 billion in 2011. The value is predicted to reach
approximately$53.5billionin2017(BCCResearch
2012
).
The commercially important metal oxide nanomaterials include TiO
2
, ZnO,
Fe
2
O
3
, Fe
3
O
4
, SiO
2
, MgO and Al
2
O
3
. These nanomaterials increasingly have appli-
cations as catalytic devices, sensors, uses in environmental remediation and in
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