Biomedical Engineering Reference
In-Depth Information
Chemical reduction
is the most common of all methods to obtain silver
nanoparticles. h e most important advantages it of ers include high yield
of non-aggregated nanoparticles, low price and ease of performance. h is
method is based on the reduction of silver nitrate (AgNO
3
) with a reducing
agent in the presence of a suitable amount of stabilizer, which controls the
growth of silver nanoparticles undisturbed by aggregation. h e reducing
agents used are sodium borohydride (NaBH
4
), tri-sodium citrate, hydra-
zine (N
2
H
4
) and glucose [35]. Polyoxyethylene sorbitan monolaurate, a sta-
bilizer commercially known as TWEEN [36] was used to obtain colloidal
silver. h e most important parameters of this method are: starting concen-
tration of AgNO
3
, ratio of molal concentrations of reducing agent to silver
nitrate, and the concentration of the stabilizer [37]. h e most popular and
best known method to obtain nano silver is the reduction of silver nitrate
with a reducing agent e.g. sodium borohydride or tri- sodium citrate.
Photoreduction
with UV light is also one of the leading methods. In addi-
tion, regardless of the vast number of publications on “green” technologies with
which to obtain nanosilver, research into developing a fully environmentally-
friendly production method for Ag NPs is still in progress [39, 40].
Laser ablation
, a new method to obtain nanosilver which has been
frequently analysed in the last decade, involves the superi cial reaction
between liquid and a solid body suspended in it. In this process a pulsat-
ing laser beam directed at the surface of a solid body causes a “discharge”
of material from the surface of the solid body, which then migrates to the
surrounding liquid (reducing liquid medium) in a bubble form. Vacuum
ion sputtering is another method used to synthesize nanosilver.
Microwave irradiation
is another method used to synthesize
nanoparticles, and it was successfully used to obtain nanosilver. When
Figure 4.8
TEM images of silver nanoparticles at various citrate concentrations (a) low
citrate concentration (0.5×10
-4
M) (b) intermediate citrate concentration (1.5×10
-4
M)
while, MT represents multiple twinned particles [38].
