SERS from two-tier sphere segment void substrates

Sphere segment void, or inverse opal, films prepared from a variety of coinage metals have shown promise as reliable and reproducible substrates for surface enhanced Raman spectroscopy (SERS). Sphere segment void substrates are prepared from colloidal templates consisting of one or more layers of polystyrene spheres. In this paper, we investigate the reflection spectra and SERS for a gold film consisting of two-tiers of spherical cavities, and show that the best SERS enhancements are obtained from substrates consisting of just a single layer of sphere segment voids.