PHYS01200704032 Debes Ray - Homi Bhabha National Institute

Integrated Absorbance / Yield (a.u.)
Int. Absorbance / Yield (a.u.)
Chapter 4: Optimization of the Block Copolymer-mediated Synthesis of Gold Nanoparticles
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Time (min.)
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0.5 wt% P85 + 0.004 wt% HAuCl4.3H2O
1 wt% P85 + 0.008 wt% HAuCl4.3H2O
2 wt% P85 + 0.016 wt% HAuCl4.3H20
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Time (min.)
Figure 4.11. Comparison of integrated intensity of SPR peaks as a function of time for 0.5, 1
and 2 wt% P85 at their corresponding gold salt concentrations of maximum yield. All these
data show three different regions (i) Formation, (ii) Saturation and (iii) Stability. Inset:
Enlarged view of the formation region of the gold nanoparticles.
The evolution of synthesis is examined by time-dependent UV-visible spectroscopy
over a wide period of time (up to 20 hrs) similar to as shown in Figure 4.5. The integrated
absorbance or yield of the synthesis has been calculated from the area under the SPR peak
covering wavelength range 450 to 800 nm. The comparison of the synthesis for three block
copolymer concentrations is shown in Figure 4.11. The time-dependence of nanoparticles
synthesis shows three distinct regions for all the concentrations: (i) Formation region, (ii)
Saturation region and (iii) Stability region. In the formation region, the yield of nanoparticles
increases linearly with time. Higher the values of block copolymer concentration, higher will
be its tendency to nucleate and hence faster formation rate of nanoparticles (inset of Figure
4.11). The saturation region is obtained when most of the gold ions have been utilized in the
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