Biomedical Engineering Reference
In-Depth Information
nanoparticles. Simply put, gold salt, reducing agent and citrate
are stirred in water and metal nanospheres are reduced.
2HAuCl
4
+ 3C
6
H
8
O
7
(citric acid)
2Au + 3C
5
H
6
O
5
(3-ketoglutaric acid) +
8HCl + 3CO
2
During the process, the temperature, the ratio of gold to citrate, and the
order of addition of the reagents control the size distribution of gold nano-
spheres. h e most popular one for a long time has been that using sodium
citrate reduction of HAuCl
4
in water.
Citrate
reduction
method
Synthesis
of gold
nanoparticles
Nanosphere
lithography
Two phase
reactions
Biological
method
Nanosphere lithography
[50] method is an inexpensive synthetic proce-
dure to generate arrays of metal nanoparticles. Polystyrene nanospheres are
drop-coated onto piranha-cleaned and base-treated glass substrates and are
allowed to dry, forming a hexagonal closed-packed monolayer or spheres.
Such monolayer can act as a template or deposition mask for metal deposition.
Metal is then deposited onto and in between the spheres by thermal evapo-
ration, creating particles in the voids of the polystyrene spheres. Following
metal deposition, the samples are sonicated in ethanol to remove the polysty-
rene nanosphere mask, leaving an array of triangular shaped metal nanopar-
ticles on the substrate. h is generates monodisperse, uncapped nanoparticles
in geometric arrays over a large surface area of the substrate [51].
Two phase reactions
[49, 52] method has been widely used to produce
small nanoparticles (1-5 nm) with narrow dispersity. A gold-thiol bond is
used to stabilize these particles. Samples generated with this method are
