SERS from Sharp Silver

CHEMISTRY Surface-enhanced Raman scattering (SERS) is observed on a variety of silver and gold surfaces where nanoscale roughness creates high local fields, and giant enhancements have been observed in “hot spots” created between two nanoparticles. However, even single nanoparticles can create fields large enough to enable single-molecule detection. To better understand the origin of this effect, McLellan et al. have deposited silver nanoparticles of various shapes on silicon substrates that have registration marks. Scanning electron microscopy was used to determine the orientation of the particles so that the effect of laser polarization on SERS spectra could be studied. For nanocubes, the SERS intensity of adsorbed 1,4-benzenedithiol varied greatly with the direction of polarization, and the spectra were more intense when the field cut across the cube's corners; more rounded truncated cubes showed little variation with polarization direction. Similar effects were seen in simulations of the local fields for these particles. — PDS Nano Lett. 7 , 10.1021/nl070157q (2007).