UC Davis

The utilization of plasmonic nanomaterials has inspired scientists for decades due to their unique optical phenomenon, known as localized surface plasmon resonance (LSPR). This phenomenon is one of the driving forces behind the creation of new nanostructures due to their material, size-, and shape-dependent properties. Significant research, in the field of nanoplasmonics, has been done to create nanomaterials used for various applications in catalysis, surface enhanced Raman scattering (SERS), and LSPR-based sensors. Gold nanorod (AuNRs) are of exceptional interest due to their shape dependent properties which allow the longitudinal mode of the LSPR to be tuned from the visible to the near infrared region. Chapter 1 reviews the common synthetic methods for gold nanorods and the importance of surface modification.Chapter 2 provides an in-depth analysis of the theoretical simulations of the LSPR for gold nanostructures for both analytical and numerical methods. Insights on the shape, size, and refractive index dependence for the LSPR is addressed. Furthermore, in the subsequent chapters, the extinction efficiencies are calculated for all the synthesized nanomaterials presented in this dissertation using discrete dipole approximation (DDA) method, introduced in this chapter. The focus of Chapter 3 is on the controlled etching of silica coated gold nanorods into twelve different gold nanostructures. This chapter highlights how shape control is crucial to fine tune the optical properties of a nanostructure. Investigation into the mechanisms to synthesize each of these nanostructures was done via UV-Vis-NIR spectroscopy, NMR spectroscopy, and optical microscopy imaging. Chapter 4 introduces a unique nanomaterial called Agu, which has less than 2 nm layer of silver coating on spherical gold nanoparticles. For 100 nm gold nanoparticle with a silver coating between 0.5 and 2 nm, the shift in the surface plasmonic resonance (SPR) peak follows a sigmoidal function as a function of silver thickness on gold. This nanomaterial was used to detect X-ray irradiation etching of silver. The final chapter offers concluding remarks on the various nanostructures which have been synthesized throughout this dissertation. Description of the future work and applications are given.