Ankara : The Department of Chemistry and the Graduate School of Engineering and Science of Bilkent University, 2011.Thesis (Ph. D.) -- Bilkent University, 2011.Includes bibliographical references leaves 77-84.In this study, light-assisted synthesis of gold nanoparticles in polymer films is demonstrated
and characterization of gold nanoparticle-polymer composites using various techniques is
shown. There are various methods introduced for the synthesis of gold nanoparticles in
solution and their integration to the polymer films afterwards. However, synthesizing gold
nanoparticles directly inside the polymer matrix is more advantageous for the production of
polymer-nanoparticle composites.
An advantage of synthesizing gold nanoparticles within polymer films is the opportunity of
photo-patterning. Films having patterns made of regions with and without gold nanoparticles
can be produced, using masks designed to cut off the radiation at desired places. Such
patterned films were investigated with scanning electron microscope (SEM) and dark regions
between irradiated regions and masked regions were observed. These dark regions are shown
to be “ion depleted regions”, where gold ions diffuse through irradiated regions during the
irradiation. These regions of about 10 m width, suggests a very large distance for gold ions
to diffuse through a rigid matrix like Poly(methyl methacrylate)(PMMA), which is very
interesting. Supporting evidence for the existence of these regions was obtained from
fluorescence studies with Rhodamine 6G molecule and x-ray electron spectroscopy (XPS).
The observations made through the formation of ion depleted regions can be used to estimate
the diffusion constant of gold ions inside the PMMA matrix. Also the presence of ion
depleted regions indicate the stability of photo-patterns created on the polymer film against smearing during light exposure after the production, by setting an upper limit to the critical
feature size.
During the characterization of gold nanoparticle-polymer composites, the electrical properties
of PMMA with and without gold nanoparticles were investigated using charge resolved XPS,
while applying external bias to the films with and without gold nanoparticles to probe the
charging properties of the films. An enhancement of conductivity of PMMA films containing
gold nanoparticles was observed using this technique. Additionally charge resolved XPS
technique was also used to determine the charge storage characteristics of the polymer
surfaces, which is important for the identification of charging mechanisms during contact and
other electrification processes. It was shown that the PMMA surface is very susceptible to
negative charging and even native negative charges on the PMMA surface can be observed
prior to any treatment. Also when the surface is charged carbon and oxygen atoms of the
carbonyl and methoxy groups of PMMA were observed to behave differently from the
backbone of the polymer, which shows the chemical specificity of the charge accumulating
spots on the surface.Yılmaz, EdaPh.D
