Plasmonic Materials for Surface-Enhanced and Tip-Enhanced Raman Spectroscopy

The chapter focuses on the fabrication and characterization of plasmonic materials that show promise in chemical/biological sensing and surface-enhanced spectroscopy applications. Plasmonics is an emerging branch of nano-optics and nano-photonics that examines the properties of collective electronic excitations in noble metal films or nanoparticles known colloquially as surface plasmons. The chapter briefly reviews the simple, massively parallel method of nanosphere lithography and its use in the fabrication of size- and shape-controlled nanostructures. The essential physics of the localized surface plasmon resonance (LSPR) and the theoretical methods used to understand it are described, and key results concerning the short- and long-range distance dependencies of the electromagnetic fields surrounding the nanoparticles are summarized in the chapter. The relationship between LSPR spectroscopy and surface-enhanced Raman spectroscopy (SERS) is analyzed in the chapter. SERS provides a systematic reproducible way to optimize the signal intensity in SERS experiments. These experiments are directly relevant to optimization of tip-enhanced Raman spectroscopy (TERS) experiments, where the electromagnetic enhancement mechanism is expected to play a crucial role. The chapter also presents some initial works on force dependence in TERS.