Plasmonic Nanostructures Synthesized by On-Wire Lithography: Smaller Sizes and New Materials and Applications

On-Wire Lithography (OWL) is a powerful synthetic method for the preparation of nanostructure arrays with highly tunable particle size and interparticle spacing. While a number of different types of materials can be created with OWL, the work in this dissertation focuses on the synthesis of plasmonic gold and silver nanostructure ensembles, where we take advantage of OWL's unique control over geometry for fundamental plasmonic investigations and applications in detection, nanoscale encoding, and authentication.;In Chapter 2, previous work on the synthesis of gold nanodisk dimers using OWL for surface-enhanced Raman scattering (SERS) is extended to silver, which leads to an increase in the sensitivity of the structures for SERS. Several challenges in the OWL process for the preparation of controlled and well-defined silver segments are addressed, and the impact the increased sensitivity of silver has on the SERS properties of the dimers for detection and nanoscale encoding of materials are investigated.;In Chapter 3, an altered OWL process is presented for the synthesis of smaller metal nanostructure arrays, surpassing the previous limit of 270 nm in diameter. Applying important alterations to the OWL process presented in this chapter, we demonstrate for the first time the ability to synthesize arrays with tailorable diameters down to as small as 35 nm, which has important implications in a number of important applications of OWL due to the enhancement of many nanoscale properties at these length scales. One example presented in this chapter illustrates the ability to study how the plasmon resonances of gold nanorods couple with one another across very short distances in a way that had not been achieved with any other synthesis/fabrication methods.;In Chapters 4–6, several applications of the smaller OWL structures are demonstrated for fundamental and applied investigations. In Chapter 4, OWL-synthesized Au nanorod dimer and trimer structures are used to study the interactions of closely spaced plasmonic structures, which leads to new insights about the nature of plasmon coupling. In Chapters 5 and 6, 35 nm diameter Au OWL dimers are applied as unique and powerful SERS substrates for a number of novel applications.