PHYS01200704032 Debes Ray - Homi Bhabha National Institute

d/d (cm -1 )
Chapter 4: Optimization of the Block Copolymer-mediated Synthesis of Gold Nanoparticles
minutes and remains almost unchanged thereafter. The integrated absorbance or yield
(proportional to nanoparticle concentration) of the synthesis has been calculated from the area
under the SPR peak in wavelength range 450 to 800 nm. The evolution of formation of gold
nanoparticles as a function of time is shown in the inset of Figure 4.5. This figure shows two
distinct regions of synthesis (i) Formation region and (ii) Saturation region. In the formation
region, the yield of nanoparticles increases almost linearly with time while the saturation
region is obtained when most of the gold ions have been utilized in the formation of
nanoparticles. The constant value in the saturation region suggests the formation of highly
stable nanoparticles in these systems.
1.6
1.2
1 wt% P85
1 wt% P85 + 0.005 wt% HAuCl4.3H2O
1 wt% P85 + 0.01 wt% HAuCl4.3H2O
1 wt% P85 + 0.015 wt% HAuCl4.3H2O
1 wt% P85 + 0.02 wt% HAuCl4.3H2O
0.8
0.4
0.0
0.015 0.1
Q (Å -1 )
Figure 4.6. SANS 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.
SANS has been used to examine the role of block copolymer in the formation of gold
nanoparticles. Figure 4.6 shows the SANS data of pure 1 wt% P85 and with the addition of
varying HAuCl 4 .3H 2 O concentration. The data without and with the addition of salt have
similar features. Block copolymers in salt solutions can either participate in the formation of
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