Date of Award
Doctor of Philosophy (PhD)
Creager , Stephen
Christensen , Kenneth
Pennington , William
Silver nanoparticles interact with light via the excitation of plasmon resonances that are the collective oscillations of the free electron density. This excitation represents the most efficient mechanism for the interaction of light with matter and therefore the nanoparticles are of great interest for both fundamental and practical points of view. In the following dissertation, silver nanoparticles, core-shell nanoparticles, and silver nanoparticle clusters were synthesized and there optical properties were investigated.
Chapter 1 contains general background information about the optical properties of bulk and silver nanoparticles. It also contains a concise description of two of my collaborative projects that did not go into the main body of the dissertation. The results from these projects are published and relate to the detection of the germination of the B. subtilis endospores using surface-enhanced Raman scattering as well as plasmon assisted enhancement of light emission from semiconductor quantum wells. This chapter also contains a brief overview of the main body of the dissertation.
In Chapter 2, carbon nanoparticles between 10 - 50 nm in diameter and carbon shells of various thickness around silver nanoparticles were synthesized by the hydrothermal reaction of fructose. The effect of the carbon shells on the plasmon resonance of the silver nanoparticles and their stability in sodium chloride solutions was investigated. The shell thickness can be adjusted to have insignificant damping of the plasmon resonance and provide stabilization of the particles in solutions with high ionic strength. Hydrazine-carbonyl cross-linking reactions were performed to link fluorescent dye molecules to carbonyl groups on the carbon shell surface.
In Chapter 3, binary polymer nanoparticles were synthesized by the reprecipitation of poly(4-vinylpyridine) in the presence of poly(diallyldimethylammonium chloride) and further used to make polymer coated silver nanoparticles. Polymer shells around silver nanoparticles were formed by two methods: the reduction of silver(I)oxide in the presence of the polymer nanoparticles and by mixing the polymer nanoparticles with already made silver nanoparticles. The resulting nanoparticles were coated with layers of the two polymers with the hydrophilic polymer on the outside providing their stability in water. The exposure of the polymer coated silver nanoparticles to unmodified silver nanoparticles resulted in spontaneous self-assembly due to electrostatic attraction. The polymer coated nanoparticles and the nanoparticle assemblies were characterized by UV-Vis, surface enhanced Raman scattering spectroscopy, and transmission electron microscopy.
Chapter 4 is devoted to the fundamental studies of depolarized light scattering from non-spherical silver nanoparticles. Depolarized scattering spectra in the visible/near- IR spectral regions from individual silver nanoparticles were recorded as a function of the incident polarization angle relative to the particle orientation. The same individual nanoparticles were also imaged with scanning electron microscopy and the recorded spectra were correlated to the nanoparticles' shape, size and orientation. It was found that the intensity of depolarized scattered light from non-spherical silver nanoparticles strongly depends upon particle shape and orientation relative to the polarization vector. The intensity of depolarized scattered light also increases with increasing the aspect ratio of the nanoparticles. The wavelengths of the depolarized scattered light can be tuned by changing the particles' size.
Heckel, John, "Synthesis and Optical Properties of Silver Nanostructures" (2010). All Dissertations. 653.