PHYS01200704032 Debes Ray - Homi Bhabha National Institute

Chapter 6: High-Yield Synthesis of Gold Nanoparticles
6.3.2. Additional Reductant Method
Figure 6.4. Photograph of gold nanoparticles in aqueous solutions of 1 wt% P85 + 0.02 wt%
HAuCl 4 .3H 2 O with varying trisodium citrate (Na 3 Ct) concentration. The labels show the
concentration of Na 3 Ct in wt%.
This method makes use of additional reductant to improve the reduction otherwise weak in
the block copolymer-mediated synthesis of gold nanoparticles. Trisodium citrate (Na 3 Ct), one
of the most widely used reducing agents, is used for additional reduction [208]. The
optimization of Na 3 Ct for the synthesis is carried out by measuring the yield by varying its
concentration for fixed block copolymer and gold salt concentrations. Figure 6.4 shows the
photograph of the yield improvement of the gold nanoparticles in 1 wt% P85 with 0.02 wt%
HAuCl 4 .3H 2 O by varying the Na 3 Ct concentration. It is seen that the nanoparticle yield
increases with the increase in Na 3 Ct concentration and has maximum around 0.02 wt%.
Figure 6.5 shows the variation of SPR peak absorbance of the gold nanoparticles in 1
wt% P85 with 0.01 wt% HAuCl 4 .3H 2 O with varying Na 3 Ct concentration. It may be
mentioned that a dilute gold nanoparticle system (1 wt% P85 with 0.01 wt% HAuCl 4 .3H 2 O)
had been chosen in Figure 6.5 as the UV-visible spectroscopy in these systems can be directly
measured. However, one can also take the higher HAuCl 4 .3H 2 O concentrations but will
require the dilution to avoid the saturation in the measurement of absorbance during UVvisible
spectroscopy. These results give that the yield is maximum approximately for 1:1 wt
ratio of Na 3 Ct-to-gold salt concentration which is also consistent with the similar molecular
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