Directional Raman scattering spectra of metal–sulfur bonds at smooth gold and silver substrates

Abstract

AbstractThe gold–sulfur (Au–S) and silver–sulfur (Ag–S) bonds are integral to the surface modification of metal films with alkanethiol monolayers. Although the metal–sulfur bond can be characterized with surface‐enhanced Raman spectroscopy (SERS) at roughened metal films, some applications require or perform better when using a smooth metal surface, which is not suitable for SERS signal enhancement. Directional‐surface‐plasmon‐coupled Raman scattering (directional Raman scattering) is an approach to measure metal–sulfur bonds on smooth metal films with sub‐monolayer sensitivity. The metal–sulfur bonds formed from a benzenethiol monolayer on smooth planar gold or silver films are observed in the directional Raman scattering spectra between 240 and 270 cm−1; the signal‐to‐noise ratio of the Au–S Raman peak is 60. Importantly, the directional Raman scattering signal measured with smooth metal surfaces can be simply modeled and easily compared across many samples. Directional Raman scattering can also be measured at roughened metal films, which makes it applicable for many analyses.