Ag nanoparticles are easily prepared by conventional
chemical reduction methods. The citrate (Turkevich
method) [229, 255, 256] and NaBH4 [255, 257–259] reduction
method are the two standard chemical preparation
routes. The synthesis of silver nanoparticles in AOT reverse
micelles by mixing AOT reverse micellar solutions at the
same water content containing Ag(AOT) and N2H4 or
NaBH4 offers a stable Ag colloidal solution and facile control
of particle size [260]. Following the treatment by a
size-selected precipitation process, nearly monodispersed Ag
nanoparticles are accessible [261, 262]. Shape-controllable
synthesis is always a challenging subject in nanoparticle
preparation. This is, without exception, for the synthesis of
silver nanoparticles. An amazing result of the shape control
of Ag nanoparticles was reported by Mirkin and co-workers
recently [263]. In the presence of bis(p–sulfonatophenyl)
phenyl–phosphine dihydrate dipotassium salt (BSPP) (as a
stabilizing agent), they observed that large quantities of
silver nanoprisms evolve from the initial spherical nanoparticles
through the fluorescent light irradiation. The
production of Ag nanoprisms lies in the light-induced ripening
process in which the small nanoprisms act as seeds, and
then grow as the small spherical nanocrystals are digested, as
shown in Figure 2. Most recently, one arresting experiment
shows that triangular Ag nanoprisms are obtained by boiling
AgNO3 in N,N–dimethyl formamide (a powerful reducing
agent against Ag+ ions) in the presence of PVP [264]. The
optimal experimental conditions are chosen ([AgNO3 =
0022 M, [PVP = 006 mM) so that a large population of
(mainly) triangular, and in general polygonal, nanoprisms
are formed in solution. Another attractive experiment shows
that truncated triangular Ag nanoplates can be synthesized
in large quantities through a seed-mediated growth (by
reduction of Ag+ ions with ascorbic acid on silver seeds
in a basic solution) in the presence of highly concentrated
micelles of CTAB [115, 265]. It is noticeable that, in these
cases, the optical properties of Ag nanoprisms or triangular
nanoplates varied in contrast to that of spheroidal Ag nanoparticles.
An intensive in-plane dipole resonance absorption
peaks at 550–675 nm, which gives a red- or blue-colored
colloidal solution. Another breakthrough in the shape control
of Ag nanoparticles was achieved by Xia and co-workers
[266]. They fabricated monodisperse Ag nanocubes in large
quantities by reducing silver nitrate with ethylene glycol in
the presence of PVP. Here, the concentration of AgNO3
was high enough (0.25 M), and the molar ratio between the
repeating unit of PVP and AgNO3 was kept at 1.5. Meanwhile,
the presence of PVP and its molar ratio (in terms
of repeating unit) relative to silver nitrate both played key
roles in the determination of the geometric shape and size of
the product. The generated single-crystalline Ag nanocubes
were characterized by a slightly trunctated shape bounded by
{100}, {110}, and {111} facets. Other techniques, including
pulsed laser irradiation [21, 267],  irradiation [68], pulsed
sonoelectrochemistry [58, 268], and ultraviolet irradiation
[117], have proven to be efficient methods to control the
shapes of Ag nanoparticles.