Nanoscale Materials - Nanotechnology and the Environment - page 15

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Dendrimers.(branched.structures)
Composites
Other.(e.g.,.spherical)

Some. authorities. further. subdivide. these. general. structural. categories.. For.
example,.the.National.Institute.for.Occupational.Safety.and.Health.(NIOSH).deines.
11.categories.of.nanomaterial.structure.[6]:

. 1.. Agglomerated.spheres

. 2.. Colloids

. 3.. Crystalline

. 4.. Films

. 5.. Nanohorns

. 6.. Nanorods

. 7.. Nanotubes

. 8.. Nanowires

. 9.. Quantum.dots

. 10.. Spherical

. 11.. Other

Others. classify. nanoparticles. by. dimension. [7-9].. According. to. this. classiication.
scheme,.one-dimensional.structures.include.nano.ilms,.two-dimensional.nanomate-
rials.include.nanotubes,.and.three-dimensional.shapes.include.fullerenes.

2.2.3 F ree versus F ixed n anOpartiCles

Free.nanoparticles,.as.the.name.implies,.are.in.solution.or.suspension..As.a.result,.
exposure.can.occur.during.manufacture,.use,.and.after.disposal..Commercial.prod-
ucts.containing.free.nanoparticles.include:

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Diesel.fuel.containing.cerium.oxide.to.reduce.emissions
Certain.sunscreens.containing.titanium.dioxide.and.a.face.cream.contain-
ing.fullerenes
Drugs.containing.dendrimers.for.targeted.delivery
Certain.food.products,.for.example.vegetable.oils,.containing.nanodrops.of.
components.such.as.vitamins,.minerals,.and.phytochemicals

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Free.nanoparticles.are.likely.to.be.released.into.the.environment.through.a.vari-
ety.of.pathways.as.materials.are.used.and.disposed.
Alternatively,.manufacturing.processes.may.ix.nanoscale.particles.into.a.solid,.
as.in.the.following.examples:

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Composite.tennis.rackets.strengthened.with.carbon.nanotubes
Rubber.products.reinforced.with.carbon.black
Computer.chips.containing.nanoscale.transistors