Surface-enhanced Raman scattering: comparison of three different molecules on single-crystal nanocubes and nanospheres of silver.

We have investigated the surface-enhanced Raman scattering (SERS) of chemically prepared single-crystal nanocubes and nanospheres of Ag with three different molecules to quantitatively understand the effect of sharp features on the SERS enhancement factor. Both experimental measurements and theoretical calculations confirmed a higher SERS activity for the nanocubes as a result of sharp features on their surfaces. We also found major discrepancies between the measured SERS intensities and those predicted from the electromagnetic mechanism. Through analysis of SERS bands, we concluded that sharp features on the Ag nanocubes could greatly increase the contribution of the chemical enhancement to the SERS intensity.