Localized surface plasmon resonance of nanoporous gold

We report the plasmonic properties of free-standing nanoporous gold (NPG) films with an intricate bicontinuous nanostructure. Two characteristic plasmon bands of NPG have been detected in absorption spectra. One at similar to 490 nm, resulting from the resonant absorption of gold films, is independent of nanopore sizes and dielectric surroundings. The other at similar to 550-650 nm, arising from the excitation of localized surface plasmon resonance, shows obvious band shift with the nanopore sizes and dielectric indices of surrounding media, suggesting that NPG is a promising candidate as plasmonic sensors for organic and biologic molecule detection. This study also shines light on the underlying mechanisms of surface enhanced spectroscopy of NPG. (C) 2011 American Institute of Physics. [doi:10.1063/1.3560482]