PHYS01200704032 Debes Ray - Homi Bhabha National Institute

g I () -1
Chapter 4: Optimization of the Block Copolymer-mediated Synthesis of Gold Nanoparticles
system. The analysis shows that P85 micelles have a PPO core radius of R c = 3.70 ± 0.05 nm
and radius of gyration of PEO chain as R g = 1.2 ± 0.1 nm. These micellar parameters of P85
are in good agreement with those reported in the literatures earlier [124,198-201].
1.0 1 wt% P85
1 wt% P85 + 0.003 wt% HAuCl4.3H2O
1 wt% P85 + 0.005 wt% HAuCl4.3H2O
1 wt% P85 + 0.007 wt% HAuCl4.3H2O
0.8
1 wt% P85 + 0.01 wt% HAuCl4.3H2O
0.6
0.4
0.2
0.0
1 10 100
(s)
Figure 4.7. Plots of the intensity autocorrelation functions in DLS data of 1 wt% P85 with
varying concentration of HAuCl 4 .3H 2 O in aqueous solution. The solid curve is a theoretical
fit to the experimental data.
It has been found that a large ratio of block copolymer-to-gold salt concentration is
required for the formation of gold nanoparticles whereas only a very small fraction of block
copolymers remains part of the gold nanoparticles. These results have been further confirmed
by DLS. Figure 4.7 shows the DLS data of the intensity autocorrelation function [g I ()] of
the nanoparticle systems. The data do not show any significant change with the addition of
salt. The functionality of the autocorrelation function depends on the diffusion coefficient of
the particles and the data suggest that it is dominated by only one type of the particles (i.e.
micelles). The analysis shows that the micelles have a diffusion coefficient of 30 10 -6
cm 2 /sec, which corresponds to the hydrodynamic size of 9 nm. This hydrodynamic size of the
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