PHYS01200704032 Debes Ray - Homi Bhabha National Institute

nanoparticle-protein conjugate confirms the adsorption of protein on nanoparticles. The
changes in the scattering data arise due to the formation of core-shell structure of adsorbed
protein on gold nanoparticles.
Finally the last 8 th Chapter gives the summary of the thesis. This thesis reports the
results on synthesis and characterization of block-copolymer mediated gold nanoparticles for
understanding the role of different components in tuning the various synthesis parameters
(formation rate, yield, stability, shape and size of nanoparticles). A multi-technique approach
(combination of UV-visible spectroscopy, TEM, SAXS, SANS and DLS) has been used for
the detailed characterization of gold nanoparticles. The main results are:
i. The optimization of synthesis has been carried out by varying gold salt and block
copolymer concentrations. A minimum ratio of block copolymer-to-gold salt is required
for maintaining the synthesis. The maximum yield by varying the gold salt or block
copolymer concentration is limited by the aggregation of large sized nanoparticles formed
at high block copolymer concentrations.
ii. The role of self-assembly of block copolymer on the synthesis of gold nanoparticles has
been investigated. The higher propensity of block copolymer to self-assemble enhances
the formation of gold nanoparticles. For block copolymer to self-assemble or mediate in
nanoparticle synthesis is driven by different forces.
iii. Two novel methods (step addition method and additional reductant method) for stable
high-yield synthesis of gold nanoparticles have been developed. These methods can
enhance nanoparticle yield by manifold than those earlier synthesis methods.
iv. The gold nanoparticles have been used to examine their interaction with two model
proteins lysozyme and BSA. The strong interaction between lysozyme with nanoparticle
leads to phase separation whereas BSA adsorption on nanoparticle form a stable complex
under physiological conditions.
To conclude, this thesis presents an extensive study of block copolymer-mediated
synthesis of gold nanoparticles and their characterization by a combination of spectroscopy,
microscopy and scattering techniques. The synthesis has advantages that it is fast, easy to
tune and environmentally benign. The role of various components (gold salt, block
copolymer and additional reductant) and solution conditions (concentration and temperature)
on the optimization various parameters of synthesis such as formation rate, yield, stability,
structure of gold nanoparticles has been established. Two novel methods (step addition
method and additional reductant method) to achieve stable high yield of gold nanoparticles
xxi