Environmental Engineering Reference
In-Depth Information
FiguRe .
Micrograph.of.a.nanowire.curled.into.a.loop.in.front.of.a.strand.of.human.hair..
(From.Macmillan.Publishers.Ltd.,.Tong,.L..et.al..2003..Subwavelength-diameter.silica.wires.
for.low-loss.optical.wave.guiding..
Nature,
.426.(18.December):.816-819..With.permission.)
.
deFinitions
A.nanometer.(nm).is.one.billionth.of.a.meter..This.size.scale.can.be.dificult.to.grasp.
and. is. perhaps. best. understood. by. analogy. to. common. materials.. A. nanometer. is.
about.100,000.times.smaller.than.either.the.diameter.of.a.human.hair.(Figure.2.1).
or.the.thickness.of.a.sheet.of.paper..A.red.blood.cell.is.approximately.5000.nm.in.
size..Another.way.to.grasp.the.relative.scale.of.nanoparticles.is.this:.the.diameter.of.
a.fullerene,.which.is.a.spherical.nanoparticle.1.nm.in.diameter.comprising.60.carbon.
atoms,.is.approximately.10
8
.times.smaller.than.a.soccer.ball,.which.in.turn.is.about.
10
8
.smaller.than.the.planet.Earth.
ASTM.International.[2].deines.nanotechnology.as.“a.term.referring.to.a.wide.
range. of. technologies. that. measure,. manipulate,. or. incorporate. materials. and/or.
features.with.at.least.one.dimension.between.approximately.1.and.100.nanometers.
(nm)..Such.applications.exploit.the.properties,.distinct.from.bulk/macroscopic.sys-
tems,.of.nanoscale.components.”.A.nanoparticle.is
“a.sub-classiication.of.ultraine.
particle.with.lengths.in.two.or.three.dimensions.greater.than.0.001.micrometer.(1.
nanometer).and.smaller.than.about.0.1.micrometer.(100.nanometers).and.which.may.
or.may.not.exhibit.a.size-related.intensive.property.”.The.U.S..Environmental.Pro-
tection. Agency. (U.S.. EPA). cites. a. slightly. different. deinition. of. nanotechnology:.
“research.and.technology.development.at.the.atomic,.molecular,.or.macromolecular.
levels.using.a.length.scale.of.approximately.one.to.one.hundred.nanometers.in.any.
dimension;.the.creation.and.use.of.structures,.devices.and.systems.that.have.novel.
properties. and. functions. because. of. their. small. size;. and. the. ability. to. control. or.
manipulate.matter.on.an.atomic.scale.”.[3].These.deinitions.suggest.three.critical.
aspects.of.nanotechnology:.(1).size,.(2).functionality.due.to.that.size,.and.(3).inten-
tional. manufacture.. As. the. Nanoforum. notes. [4],. “nanotechnology. should. not. be.
viewed.as.a.single.technique.that.only.affects.speciic.areas..It.is.more.of.a.'catch-all'.
term.for.a.science.which.is.beneiting.a.whole.array.of.areas,.from.the.environment,.
to.healthcare,.to.hundreds.of.commercial.products.”
