Page 91 - Environmental Nanotechnology Applications and Impacts of Nanomaterials

Nanomaterials Fabrication 77

H PtCl and FeCl together with hydrazine and a surfactant such as
2
2
6
sodium dodecyl sulfate (SDS) or CTAB, are mixed in water. Heating at
70 C allows reduction and forms fcc-structured Fe-Pt nanoparticles
[148]. Reduction of FeCl and Pt(acac) mixtures in diphenylether by
2
2
superhydride, LiBEt H, in the presence of oleic acid, oleylamine, and
3
1,2-hexadecanediol at 200 C has led to 4 nm Fe-Pt nanoparticles [59].
The initial molar ratio of the metal precursor allows control of the com-
position of the final particles more easily than in the polyol process.
However, a major drawback of using borohydride is the contamination
of the final product by boron.
Another process used to produce Fe-Pt nanoparticles is the thermal
decomposition of Fe(CO) and reduction of Pt(acac) by 1,2-alkanediol
2
5
[59]. The mixture is heated to reflux (297 C). Oleic acid and oleylamine
are used for surface passivation and stabilization of particles. The com-
position of particles is controlled by the Fe/Pt ratio and fine-tuning of
particle size between 2 and 5 nm is achieved by controlling the surfac-
tant to metal ratio. Alternatively, to make larger Fe-Pt nanoparticles,
a seed-mediated growth method has been used [59].

Carbon Based Nanomaterials
Although nanomaterials had been known for many years prior to the dis-
covery of C , the field of nanoscale science was really founded upon this
60
seminal discovery and that of subsequent carbon nanomaterials. Part of
the reason for this explosion in nanochemistry is that the carbon mate-
rials range from well-defined nano-sized molecules (i.e., C ) to tubes with
60
lengths in hundreds of microns range. Despite this range of scale, carbon
nanomaterials have common reaction chemistry: that of the field of
organic chemistry. This provides them with almost infinite functionality.
molecule is like every other
A further advantage is that since every C 60
12 13
one, ignoring C and C isotope effects, C provides a unique monodis-
60
persed prototype nanostructure assembly with particle size of 0.7 nm. In
no other nanomaterial system is there the ability to prepare true monodis-
persed material.
The previously unknown allotrope of carbon, C 60 , was discovered in
1985 [1], and in 1996, Curl, Kroto, and Smalley were awarded the Nobel
Prize in Chemistry for this discovery. The other allotropes of carbon are
2 3
graphite (sp ) and diamond (sp ). C 60 , commonly known as the “bucky-
ball” or buckminsterfullerene, has a spherical shape comprising of highly
2
pyramidalized sp carbon atoms. The C 60 variant is often compared to
the typical white and black soccer ball, hence buckyball, however, this
is also used for higher derivatives. Fullerenes are similar in structure
to graphite, which is composed of a sheet of linked hexagonal rings, but
they contain pentagonal (or sometimes heptagonal) rings that prevent