Biomedical Engineering Reference
In-Depth Information
for 16 chosen metal nanorods. The predictions are expected not only
to clearly portrait the material-dependent spectral behaviors, but
also to facilitate the material design for future applications of the
noble metal nanoparticles.
1
.
2
Synthesis of Gold Nanoparticles
The development in nanosynthesis of nearly monodispersed gold
nanocrystals with controlled sizes and shapes is vital for both
fundamental science and their applications. The preparation of
dispersed gold nanoparticles in aqueous solution described by
Faraday
15
is so far the irst well-documented method. Since then,
synthesis of other types of noble metal nanocrystals
16-21
and, lately,
growth of size- and shape-controlled gold nanocrystals through
electrochemical method
13,14,22
and seeded growth
23-25
have also
been developed in aqueous solution.
We then focus on the preparation methodologies of gold
nanoparticles for the use of biomedical applications, ranging from
immunoassay rapid test technology, biomolecular sensing to recent
simultaneous cancer diagnosis and therapy. The gold nanostruc-
tures aiming for the above applications cover from spherical particles
to nanoshells and nanorods.
Synthesis of nearly monodispersed gold nanoparticles in aqueous
by the use of standard citrate reduction (SCR) method is probably the
most well-known bottom-up wet chemical approach. Its historical
development irst by Turkevich
et al
.
26
in 1951, and later by Frens
27
in 1973, has been widely recognized. The ingredients and their
functions associated with this method have been clearly described
and re-investigated recently.
28
The synthesis of gold nanorods was irst demonstrated by using
the co-surfactant system under an electrochemical method.
13,14
Thus, the prepared nanorods suspended in an aqueous solution
were synthesized inside an electrochemical cell and were stabilized
by the cationic co-surfactant capping molecules. Such co-surfactant
system is composed of tetradodecylammonium bromide and
hexadecyltrimethylammonium bromide. The aspect ratios of gold
nanorods can be inely controlled; subsequently the resulting peak
absorption of their surface plasmon resonance can be precisely
tuned.
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