| An important aspect of nanotechnology involves the development of macroscopic materials that retain the unique nanoscale optical, electronic, thermal, magnetic, catalytic, or phase properties of the 1-100 nm building blocks that comprise them. Because these nanoscale properties result from the concerted effects of size, shape, composition, and surface properties, control of these descriptors is requisite for gains in both the fundamental understanding of nanoscale materials, and for the construction of controllable nanostructured macroscopic materials. This dissertation work focuses on understanding the factors controlling nanoparticle size, monodispersity, and surface composition when smaller-size thiolate-capped gold nanoparticles (e.g. 2 nm) are thermally processed to form larger core sizes (3-10 nm). Herein, molecularly-tuned core-size control and selectivity have been demonstrated by the manipulation of alkanethiol concentrations and chain length effects on interparticle aggregative growth. In addition, the cohesive interactions between alkanethiols have been shown to play an important role in regulating the interparticle aggregative reactivity. The high monodispersity and size selectivity of the thermally-processed nanoparticles obtained enables the exploration of many applications requiring a high uniformity of nanoparticle properties. The utilization of NMR and UV-visible spectroscopic methods for the quantitative determination of capping-shell thiolates before and following thermally activated processing are described to provide better insight into the aggregative coalescence mechanism and the surface properties of the resulting particles. The applicability of the thermal processing route to the fabrication of gold-coated iron oxide nanoparticles is also discussed for the purpose of creating bio-compatible magnetic nanoparticles useful for enhanced bio-separation, and surface enhanced Raman spectroscopic detection of biomolecules. |
