Optical Properties and Applications of Nanoporous Metals
In this chapter, we introduce the optical properties of dealloyed nanoporous metals and their applications in surface-enhanced spectroscopy for detection and identification of organic and biological molecules. Similar to those of other nanostructured metals, the excellent optical properties of nanoporous metals originate from the surface plasmon resonance (SPR) as a result of coherent oscillations of conduction electrons excited by electromagnetic radiation at a metal–dielectric interface. The intensity and peak position of SPR strongly depend on the characteristic lengths (nanopore and ligament sizes) of nanoporous metals, giving rise to the nano-size effects in surface-enhanced Raman/fluorescence spectra of nanoporous metals. In addition to the nanopore size effect, the optical properties of nanoporous metals can be further improved by optimizing the geometric structure and chemical composition. As new plasmonic substrates, dealloyed nanoporous metals with superior reproducibility, excellent chemical/structural stability and facile synthesis promise to be ideal candidates for a wide range of applications in ultrasensitive instrumentations for molecular diagnosis, food safety, and environmental protection.