PHYS01200704032 Debes Ray - Homi Bhabha National Institute

Nanoparticle Yield (a.u.)
Chapter 6: High-Yield Synthesis of Gold Nanoparticles
improved the reduction and subsequently the concentration of the gold nanoparticles, which
only works in presence of block copolymer. The nanoparticle concentration is now shown to
increase with gold salt concentration in presence of additional reductant.
9
8
1% P85 + C% HAuCl4 + C% Na3Ct
C% HAuCl4 + C% Na3Ct
6
4
2
0
0.0 0.2 0.4 0.6 0.8 1.0
C (wt%)
Figure 6.8. The calculated yield of gold nanoparticles in 1 wt% P85 with varying
(HAuCl 4 .3H 2 O + Na 3 Ct) concentration. The comparison of nanoparticle concentration
without the use of block copolymer is also shown.
The high-yield nanoparticles have been characterized using SANS and SAXS. Unlike
the case of neutrons where the scattering from hydrogenous system is high, X-rays are useful
probe for such systems. The differences in scattering for neutrons and X-rays arise due to the
fact that while neutrons are scattered by the nucleus of an atom, X-rays are scattered by the
electron clouds around the nucleus. Table 6.1 gives the calculated scattering length densities
of different components of the block copolymer-mediated gold nanoparticle system for X-
rays compared with neutrons. It is clear from the variation in scattering length density for
neutrons that there exists a strong contrast for the block copolymers with respect to that from
the gold nanoparticles in D 2 O whereas this contrast is reversed when the solvent is H 2 O. On
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