Novel optical properties and emerging applications of metal nanostructures

This paper provides a brief overview of recent research activities concerning metal nanomaterials, including their synthesis, structure, surface plasmon absorption, surface enhanced Raman scattering (SERS), electron dynamics, emerging applications, and the historical context by which to view these subjects. We emphasize coinage metals, particularly silver and gold. Silver and gold nanostructures exhibit fascinating optical properties due to their strong optical absorption in the visible as a result of the collective oscillation of conduction band electrons, known as the surface plasmon. This is the origin of many interesting physical phenomena and related applications such as surface plasmon resonance (SPR) and SERS useful in chemical and biomedical detection and analysis. SERS offers high sensitivity and molecular specificity that are attractive for sensing and imaging applications. Electron dynamics in metal nanostructures have been studied using ultrafast laser techniques to gain fundamental insight into electron-phonon interaction as well as coherent lattice oscillation in different metal nanostructures. Relevant theoretical work and models are also discussed in conjunction with the related experimental work. Synthesis and structural characterization are also discussed to make this paper self-contained and easier to follow. The paper ends with some emerging applications of optical properties of metal nanomaterials including photothermal therapy for cancer.