Biomedical Engineering Reference
In-Depth Information
Figure 13.7
Iron - and platinum - containing polymers used for
the synthesis of FePt nanoparticle fi lms. Reproduced with
permission from Ref. [58]; © Wiley-VCH Verlag GmbH & Co.
KGaA.
The thermal decomposition of polymer
P2
at 500 °C resulted in a release of Fe
and Pt atoms and the formation of FePt nanoparticles. Aggregation of the nanopar-
ticles was suppressed by the surrounding carbonaceous matrix. An increase in the
pyrolysis duration or temperature led to a predictable increase in FePt nanoparticle
size and polydispersity. One advantage of the metallopolymer precursor approach
to metal alloy nanoparticle synthesis was the potential synthetic control over the
location of metal nanoparticle formation using lithographic techniques. Electron-
beam lithography has been used to control the deposition of precursor
P2
as a
negative resist, affording FePt nanoparticles patterned with strong shape retention
(Figure 13.8). The use of metal-containing polymers and various lithographic
techniques to form patterned arrays of metal alloy nanoparticles with composi-
tional and particle density control may become important in device and catalyst
applications.
Ni
Pt nanoparticles of variable stoichiometry have been synthesized by the
polyol reduction of nickel acetate and platinum acetylacetonate in the presence of
stabilizing agents, such as oleic acid and oleylamine. Other stabilizing agents,
including adamantanecarboxylic acid ( ACA ),
n
- tetradecylphosphonic acid ( TDPA ),
and trioctylphosphine oxide (TOPO), in combination with other primary amines
and carboxylic acids, form colloids having a variety of shapes (Figure 13.9).
Variation of the oleic acid and oleylamine relative concentrations as capping
agents affects NiPt nanoparticle growth. For example, increasing the oleic acid
concentration with a constant amount of oleylamine leads to a decrease in the alloy
nanoparticle size, whereas increasing the oleic acid concentration relative to the
oleylamine concentration produces polycrystalline and irregularly shaped parti-
cles. The colloid particle size or stability appears to be infl uenced most by the oleic
acid concentration, while nanoparticle shape is determined by the oleylamine
−
