| Nanometer-sized metal particles have attracted considerable interest in recent years due to their unique, size-dependent properties. Currently, nanoparticle research is increasingly directed towards novel applications of these materials such as nanoelectronics, sensors, catalysts, and taggents for biomolecules. Two crucial requirements must be met to use nanoparticles in any of these applications. Synthetic methods must be developed to provide convenient access to specifically functionalized nanoparticles of controlled core size, and the controlled organization of individual nanoparticles into ordered structures must be achieved. This dissertation describes a versatile approach for the synthesis of a wide range of functionalized gold nanoparticles and demonstrates the controlled, rationally designed self-assembly of these materials into well-ordered, low-dimensional structures along DNA scaffolds.; The approach for the synthesis of functionalized gold nanoparticles presented herein utilizes facile ligand exchange reactions of readily available, phosphine-stabilized precursor nanoparticles with o-functionalized thiols. It is applicable for nanoparticles with various core sizes (e.g., 0.8 nm and 1.5 nm) and tolerates a wide variety of functional groups. In addition to the general nature of the approach and the ease of preparation, the resulting thiol-stabilized nanoparticles show increased stability while preserving the core size of the precursor nanoparticles. Mechanistic studies reveal core size-dependent differences in the chemistry of the ligand exchange and provide important information how to control the progression of these reactions.; The organization of individual nanoparticles into extended, well-ordered structures is achieved using a biomolecular nanolithography approach that employs the self-assembly of cationic nanoparticles along DNA templates. This assembly method results in the formation of low-dimensional assemblies in which the nanoparticles form close-packed structures along the DNA template. The interparticle spacing can be precisely controlled over a range of 1.4 to 2.8 nm through the ligand shell thickness of the nanoparticle. The dimensions of the nanoparticle assembly are strictly dictated by the DNA template which is demonstrated by the formation of monodisperse nanoparticle polymers along monodisperse DNA templates. The versatility and the high degree of control inherent in the described template-directed self-assembly approach will prove highly useful for the realization of nanoparticle-based devices.; This dissertation includes both previously published and unpublished co-authored materials. |
