Environmental Engineering Reference
In-Depth Information
A.variation.on.the.nanoprobe.is.based.on.the.light-scattering.technique.known.as.
surface-enhanced.Raman.spectroscopy.(SERS)..This.probe.can.detect.and.analyze.
chemicals,.including.explosives.and.drugs.on.surfaces,.at.a.theoretical.single-mol-
ecule.level..This.capability.makes.the.nanoprobe.far.more.selective,.sensitive,.and.
accurate. than. conventional. analytical. techniques.. The. SERS. nanoprobe. is. being.
developed. for. nanotechnology. applications. from. military. and. water. monitoring.
applications.to.medical.environments.
2.4.4 C
arbOn
b
laCk
Carbon.black.comprises.ine.particles.of.elemental.carbon..It.is.arguably.one.of.the.
oldest. nanomaterials. in. commercial. use. and. certainly. the. most. widely. used.. The.
Chinese.manufactured.an.impure.form.of.carbon.black.more.than.3500.years.ago.by.
burning.vegetable.oils.in.lamps..Modern.manufacturers.still.produce.carbon.black.
from.the.incomplete.combustion.or.thermal.decomposition.of.hydrocarbons.(usually.
heavy.aromatic.oils)..Worldwide,.manufacturers.produced.approximately.18.billion.
pounds.of.carbon.black.in.2004..About.90%.of.this.output.found.use.in.rubber.prod-
ucts,.where.it.serves.as.a.iller.and.a.strengthening.or.reinforcing.agent..Carbon.black.
also.is.used.in.plastics,.coatings,.and.inks.[22,.23].
Carbon. black.consists.of.more.than.97%. elemental. carbon.. Carbon. black.par-
ticles,.or.nodules,.comprise.stacks.of.graphite-like.sheets.of.carbon..Carbon.black.
products.are.characterized.by.their.structure,.size,.surface.area,.surface.activity,.and.
particle.size.[22].
Carbon.black.particles.generally.range.in.size.from.tens.to.a.few.hundred.nano-
meters..As.a.result,.many.classify.carbon.black.as.a.nanomaterial.(e.g.,.[3,.22,.24])..
The.International.Carbon.Black.Association,.however,.holds.a.different.view.[23];.
it.holds.that.while.the.initial.particle.size.may.be.on.the.nanoscale,.van.der.Waals.
forces.cause.these.particles.to.rapidly.aggregate.into.“basic.indivisible.entities”.of.
carbon.black.approximately.85.to.500.nm.in.size..These.aggregates.then.adhere.to.
form.stable.agglomerates.on.the.order.of.1.to.over.100.µm.in.size..Manufacturers.
shape. these. aggregates. into. carbon. black. pellets. between. 0.1. and. 1.0. mm. in. size.
before. shipment. to. their. customers.. The. International. Carbon. Black. Association.
indicates.that.nanoparticles.of.carbon.black.“are.not.found.outside.the.reactor,.nor.
are.they.found.as.a.component.dust.fraction.in.inal.manufactured.carbon.blacks.”
These.differences.in.the.categorization.of.carbon.black.illustrate.two.important.
points.regarding.nanotechnology:
.
1.. Strong.attractive.forces.can.cause.individual.particles.to.agglomerate.read-
ily,.changing.their.characteristics.and.limiting.their.transport.in.the.envi-
ronment..(See.Chapter.6.for.further.discussion.of.the.forces.that.govern.the.
behavior.of.nanoparticles.)
.
2.. Literature. reports. on. nanotechnology. warrant. careful. reading. to. ascer-
tain. the. actual. particle. size. and. form. under. discussion,. and. to. determine.
whether. experimental. conditions. correspond. accurately. to. the. form. of. a.
material. that. is. actually. commercially. available. or. used.. (Chapter. 8. dis-
cusses.some.of.the.techniques.used.to.suspend.nanoparticles.in.solution.for.
