Development of Fabrication and Synthetic Protocols to Produce Substrate-Immobilized Plasmonic Nanomaterials

This dissertation serves to advance the fabrication techniques and synthesis protocols of plasmonic nanomaterials directly on substrate surfaces. The work presented here aimed, (i) to add novel pathways for obtaining plasmonic nanostructures with tunable properties that use substrate-immobilized seeds as a starting point and (ii) to provide further understanding of the nanoplate growth mechanism of seed-mediated approaches. The beginning segment aims to provide the required context for understanding what plasmonic nanomaterials are and express the importance of researching such structures and their properties. Plasmonic nanostructures composed of gold and silver are mentioned specifically due to the significant attention they have garnered within the field. A subclassification of plasmonic nanostructures, referred to as nanogap nanostructures, are then introduced and their desirable properties are described. The difficulties associated with their fabrication from multiple approaches are brought forth along with a novel pathway to overcome said limitations that are illustrated. The first of two syntheses is subsequently presented, defining a three-reagent liquid-phase gold nanotriangle synthesis with substantially higher yield than previously reported. The resulting structures are epitaxially aligned with atomically flat surfaces and sharp vertices. Their optical properties and topography are investigated through extensive characterization. The following section introduces an adapted silver nanoplate synthesis that greatly surpasses prior attempts to produce deterministically placed silver nanoplates on substrates. The prerequisites for plate formation are more thoroughly explained, and the importance of high-quality seeds is further emphasized. The penultimate chapter details an in-depth analysis of the growth mechanism that drives a gold hexagonal nanoplate synthesis by controlling light conditions through the use of a custom-made reflective chamber with interchangeable light emitting diodes. The results obtained through various illumination and reaction conditions support the existence of a never-before-seen growth mechanism. The final section summarizes the experimental data presented and reiterates the significance of the conclusions drawn.