Chemistry and Biochemistry
M.Sc. Thesis Defence-Nicole Cathcart-Jan. 18-1:30-4:00 pm, N1053
M.Sc. Thesis Defence
January 18th, 2011, 1:30-4:00 pm, N1053
Name of the Student: Nicole Cathcart
Size and Shape Control of Silver Nanostructures – Studies into Icosahedron, Thick Prism and Flower-like Morphologies
The thesis research deals with the experimental study of nanoscale silver ranging from the synthesis of monodisperse clusters to morphology control and the tailoring of the optical properties of nanoparticles. The silver morphologies investigated include different types of prisms: flower-like platelets and icosahedra. Starting at atomic size control, small (<2 nm), monodisperse silver clusters comprising of a thiolate shell and a metal core were produced synthetically. These clusters were the first single-species silver clusters (proven by electrophoresis) with well-defined optical transitions reported in the field. The monodisperse clusters were further explored as nanoparticle precursors; the controlled aggregation of clusters enabled the formation of monodisperse thick silver prisms with narrow tunable plasmon resonances and remarkable self-assembly and flower-like morphologies. These regularly-faceted hexagonal platelets prepared by selective growth are the first such structure developed and are promising for surface-enhanced Raman spectroscopy. Also prepared for the first time were silver icosahedra where successful combinations of chemical and photochemical approaches have been utilized. In another advancement, precise tuning of the plasmon resonance in planar twinned silver nanoparticles was effectively accomplished using two-stage modification protocol with a combination of halides. The plasmon resonance maxima were reliably and reproducibly tuned from 405 to <900 nm with the precision of greater than 0.5% for the first time. The developed, robust methodology of plasmon control has provided a basis for the successful realization of a first-year chemistry laboratory experiment of preparation and studies of a silver nanorainbow. Overall, successful synthetic protocols have been developed to prepare several types of well-defined silver nanoscale morphologies with tunable advanced optical properties promising in sensing, catalysis and optical applications.