Biomedical Engineering Reference
In-Depth Information
Figure 10.5
Photograph showing the deep wine-red color solution of Au NPs.
nanospheres. h e most popular one for a long time has been that of using
sodium citrate reduction of HAuCl4 in water. Adding freshly prepared tri-
sodium citrate in boiled HAuCl4 will produce deep wine-red color solu-
tion (see Figure 10.5), At er the reaction was complete, the nanoparticles
were centrifuged with water and ethanol and redispersed in water.
10.5.2 AgNanoparticles
Silver nanoparticles were synthesized by a chemical reduction method
using trisodium citrate [43] as well as sodium borohydride [44]. Sodium
borohydride being a very strong reducing agent, reaction takes place
almost instantly and small particles are produced. Reduction using sodium
borohydride is done at room temperature, while trisodium citrate needs
a higher temperature (around 80
C)
for the reduction. Trisodiumcitrate
(Na
3
C
6
H
5
O
7
) was added to the silver nitrate solution and the resulting mix-
ture was rel uxed at 80
C
for 30 min. Pale-yellow color solution of silver
nanoparticles will be formed. Figure 10.6 shows the golden yellow color
solution of Ag NPs.
10.6 Core-ShellMaterial
Core-shell nanocomposite materials are essentially dei ned as the parti-
cles containing a core and a shell and have dimensions in the nanome-
ter range. Core-shell nanomaterials ot en exhibit improved physical and
chemical properties over their single-component counterparts, and hence
are potentially useful in a broad range of applications. h ey constitute a
class of materials with potential application in chemically stabilizing col-
loidal particles, catalysis, l uorescent diagnostics, photonic band-gap
materials, preparation of biconjugates, etc. [45]. Core-shell nanomaterials
can be synthesized in a variety of combinations such as dielectric-metal
