Size and Shape Control of Silver Nanostructures -- Studies of Clusters, Icosahedra, Prisms and Flower-like Morphologies

The work presented in this thesis 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 nanoparticle morphologies investigated include different types of prisms: flower-like platelets and icosahedra. Starting at atomic size control, small (<2 nm), monodisperse silver clusters composed of a thiolate shell and a metal core were produced synthetically. These clusters were the first single-species silver clusters (proven by a single band in gel electrophoresis) with well-defined optical transitions reported. This original discovery involved the novel procedure of cluster synthesis based on a cyclic reduction in oxidative conditions. The cluster chirality imprinted by ligands was characterized by circular dichroism spectroscopy. Further cluster advancement was a one-stage preparation using a combination of chiral ligands which provided an increase in stability and achieved tuning of chirality. 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. Further developments of this synthetic methodology gave rise to the preparation of flower-like morphologies. These regularly-faceted hexagonal platelets prepared by selective growth are the first such structure reported 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 protocol involving modifications 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 reported 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 optical properties promising in sensing, catalysis and optical applications.