stirring of the biphasic mixture, the ODA molecules bind to the gold nanoparticles,
thereby rendering them hydrophobic and dispersible in the organic phase. The
ODA-capped gold nanoparticles could be separated in the form of a dry powder by
rotary evaporation of the toluene phase and could be readily redispersed in organic
solvents such as chloroform, benzene, carbon tetrachloride etc. [67].
A drop of the toluene phase with the ODA-capped gold nanoparticles was placed
on a TEM grid and analyzed after solvent evaporation. Figure 3.5 shows the image
obtained wherein a well ordered hexagonal, close-packed configuration of gold
nanoparticles can be seen. The ordered domains are not particularly large due
to the fact that the monodispersity of the gold particles in the aqueous phase was
ca. 15%. It is interesting to observe the separation of the gold nanoparticles into
domains based on their size (Figure 3.5).
A
B
Fig. 3.4. (A) Picture showing the two-phase
gold hydrosol–ODA containing toluene layers
before (test tube on the right) and after (test
tube on the left) phase transfer of the gold
particles into toluene. (B) UV–vis spectra
recorded from the toluene phase (curve 2) and
the aqueous phase before (curve 3) and after
(curve 1) phase transfer of the gold colloidal
particles into toluene (Figure 3.4A, solutions
taken from the test tube on the right).
(Reprinted with permission from [67], 8 2001,
Elsevier Science).
3.4 Moving Gold Nanoparticles Around 39
thereby rendering them hydrophobic and dispersible in the organic phase. The
ODA-capped gold nanoparticles could be separated in the form of a dry powder by
rotary evaporation of the toluene phase and could be readily redispersed in organic
solvents such as chloroform, benzene, carbon tetrachloride etc. [67].
A drop of the toluene phase with the ODA-capped gold nanoparticles was placed
on a TEM grid and analyzed after solvent evaporation. Figure 3.5 shows the image
obtained wherein a well ordered hexagonal, close-packed configuration of gold
nanoparticles can be seen. The ordered domains are not particularly large due
to the fact that the monodispersity of the gold particles in the aqueous phase was
ca. 15%. It is interesting to observe the separation of the gold nanoparticles into
domains based on their size (Figure 3.5).
A
B
Fig. 3.4. (A) Picture showing the two-phase
gold hydrosol–ODA containing toluene layers
before (test tube on the right) and after (test
tube on the left) phase transfer of the gold
particles into toluene. (B) UV–vis spectra
recorded from the toluene phase (curve 2) and
the aqueous phase before (curve 3) and after
(curve 1) phase transfer of the gold colloidal
particles into toluene (Figure 3.4A, solutions
taken from the test tube on the right).
(Reprinted with permission from [67], 8 2001,
Elsevier Science).
3.4 Moving Gold Nanoparticles Around 39