Optical Properties and Applications of Shape-Controlled Metal Nanostructures

Abstract

Noble metallic materials in the nanoscale size regime display unique optical and electronic properties. In this chapter, we review current synthetic methods for making gold and silver nanostructures of various shapes and sizes and discuss select techniques that have become indispensible for structural characterization of nanomaterials. A fundamental characteristic of metal nanostructures is their interaction with light through surface plasmon resonance (SPR), which can be modulated by shape, surrounding environment, and size. We first address the effect of shape on the SPR and then discuss changes in the extinction spectrum that result from plasmonic coupling between metal nanostructures in close proximity. Changes in the refractive index of media surrounding the nanoparticles and the corresponding effect on the SPR are briefly addressed. We then highlight several applications of metal nanostructures that utilize their unique optical properties, including SPR as a technique for detection, surface-enhanced Raman scattering (SERS), photothermal ablation therapy (PTA), drug delivery, and solar energy conversion. We conclude with a discussion of current challenges and promising research directions in the study and use of metal nanostructures.