PHYS01200704032 Debes Ray - Homi Bhabha National Institute

Time-dependent Absorbance
Chapter 2: Block Copolymer-mediated Synthesis of Gold Nanoparticles
the block copolymer and gold salt concentrations, temperature, chemical structure of block
copolymer, pH etc [96,98,146]. The molar ratio of block copolymer to gold salt required is
quite high, typically of the order of 10 and higher. Most of the syntheses carried out using
block copolymers have sizes reported in the range 10 to 50 nm [96,98,146].
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Time (min.)
Figure 2.9. The evolution of formation of gold nanoparticles in block copolymer-mediated
synthesis.
A typical evolution of formation of gold nanoparticles in block copolymer-mediated
synthesis is shown in Figure 2.9. The formation of nanoparticle starts after some time (few
minutes) on mixing the block and gold salt solutions. The initial region of nanoparticle
formation is followed by a linear region where the yield increases almost linearly with time
and finally slowing down on approaching the saturation. It has been found that the typical
time for the synthesis to complete is in the range of 1–3 hrs for most of the block copolymers.
The self-assembly of block copolymers can be utilized in tuning the formation rate as well as
the size of the nanoparticles [95-98].
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