Anisotropic Noble Metal Nanomaterials for Analytical Surface Enhanced Raman Spectroscopy
Payne, Courtney Michelle
Hafner, Jason H
Doctor of Philosophy
Noble metal mesoscale and nanoscale materials exhibit unique optical properties that are of interest to a wide variety of fields including sensing, imaging, biomedicine, and catalysis. The properties of the nanomaterial are strongly dependent on the size, morphology, composition, and local molecular environment of the material, all of which can be controlled by material design and synthesis. A novel nanomaterial referred to as a gold nanobelt was synthesized and characterized. Gold nanobelts synthesized in cetyltrimethylammonium bromide and sodium dodecylsulfate and with sub-100 nm rectangular cross sections were found to exhibit a strong transverse plasmon peak at visible wavelengths. Unlike larger diameter silver nanowires, these nanobelts exhibit sharp, tunable plasmon resonances similar to those of nanoparticles. The gold nanobelt crystal structure contains a mixture of face centered cubic and hexagonally close packed lattice phases that can be isolated and examined individually due to the unique nanobelt size and shape. The nanobelt synthesis is very sensitive to temperature which is likely due to the transition of the surfactant solution from wormlike micelles to spherical micelles. The electromagnetic field enhancing properties of gold nanobelts, silver nanowires, gold microplates, and gold nanorods were used to fabricate platforms for analytical surface enhanced Raman spectroscopy. Gold nanobelts and silver nanowires were deposited on glass substrates and when used alone or in combination with a gold microplate demonstrate surface enhancing capabilities. A thin film of gold nanorods was shown to be easily modifiable and provide surface enhanced Raman spectra of the local chemical environment.