PHYS01200704032 Debes Ray - Homi Bhabha National Institute

d/d (cm -1 )
Chapter 6: High-Yield Synthesis of Gold Nanoparticles
3.2
2.8
2.4
2
1% HAuCl 4
.3H 2
O + 1% Na 3
Ct
0.7% HAuCl 4
.3H 2
O + 0.7% Na 3
Ct
0.5% HAuCl 4
.3H 2
O + 0.5% Na 3
Ct
0.2% HAuCl 4
.3H 2
O + 0.2% Na 3
Ct
0.1% HAuCl 4
.3H 2
O + 0.1% Na 3
Ct
0.05% HAuCl 4
.3H 2
O + 0.05% Na 3
Ct
0.02% HAuCl 4
.3H 2
O + 0.02% Na 3
Ct
1.6
1.2
0.01 0.1
Q (Å -1 )
Figure 6.12. SANS data of 1 wt% P85 with varying (HAuCl 4 .3H 2 O + Na 3 Ct) concentration
at 15 o C. The block copolymers are contrast-matched to the solvent (15% D 2 O). The solid
curves are theoretical fits to the experimental data.
To simplify the analysis, SANS data have also been taken for block copolymers
contrast-matched to the solvent (85% H 2 O in H 2 O and D 2 O mixture) as in Figure 6.12. In
this case, no scattering from block copolymers is seen and whatever is measured is the
scattering from gold nanoparticles. The scattering increases as the number density of the gold
nanoparticles increases with increasing gold salt concentration. The gold nanoparticles are
fitted with polydispersed spherical particles. Although we do not directly measure the
adsorbed block copolymers on the nanoparticle surface but their stability particularly
observed at higher temperature do suggest that the hydrophobic PPO should be covering the
surface of the gold nanoparticles surrounded by the solvated PEO. Na 3 Ct remain uniformly
dissolved in the solution as it is highly soluble in aqueous solution (Solubility in water ~ 42.5
gm/100 ml at 25 °C). The particle size is found to increase with decrease in polydispersity
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