PHYS01200704032 Debes Ray - Homi Bhabha National Institute

Chapter 6: High-Yield Synthesis of Gold Nanoparticles
Gold Nanoparticle System
Diffusion
Coefficient
D × 10 -6 (cm 2 /sec)
Hydrodynamic
Size
(nm)
1% P85 + 0.05% HAuCl 4 .3H 2 O + 0.05% Na 3 Ct 18.3 30.4
1% P85 + 0.1% HAuCl 4 .3H 2 O + 0.1% Na 3 Ct 16.1 34.6
1% P85 + 0.5% HAuCl 4 .3H 2 O + 0.5% Na 3 Ct 14.6 38.2
DLS has also been used to confirm the coexistence of gold nanoparticles and micelles
during the synthesis. The measured intensity autocorrelation functions of gold nanoparticles
at different salt concentrations are shown in Figure 6.16. It shows that the autocorrelation
function broadens with the increase in the gold salt concentration with respect to that from
pure block copolymer solution. It has been already found using SANS studies that structure
of block copolymer micelle does not change significantly during the synthesis of gold
nanoparticles and these changes in the autocorrelation function are believed to be because of
the presence of gold nanoparticles. The DLS data have been fitted with two exponentials
I
using the equation of intensity autocorrelation function g ( ) 1 exp( 2 )
where one
exponential corresponds to that from pure block copolymer micelles has been kept fixed and
second for gold nanoparticles varies with gold salt concentration. The fitted parameters for
the system of block copolymer P85 with varying gold salt and Na 3 Ct concentration obtained
from DLS data are shown in Table 6.4. The sizes measured by DLS are comparatively larger
than those measured directly. This arises as DLS measures overall size consisting gold
nanoparticles covered by block copolymer coating and hydration attached it.
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