Surface Roughness‐dependent Photoelectron Emission Characteristics of Silver Probed by Surface‐enhanced Raman Scattering of 4‐Nitrobenzenethiol#

The surface roughness‐dependent photoelectron emission characteristics of silver were investigated through the surface‐enhanced Raman scattering ( SERS ) spectra of 4‐nitrobenzenethiol (4‐ NBT ) adsorbed on HNO 3 ‐etched Ag foils. The roughness of the etched Ag foil, examined by field emission scanning electron microscopy and atomic force microscopy, was found to be related to the SERS characteristics of 4‐ NBT . In fact, the 4‐ NBT molecules adsorbed on silver showed different SERS spectral patterns depending on the surface roughness of Ag. The symmetric stretching vibration of nitro group of 4‐ NBT gradually lost its intensity, and new peaks attributable to 4‐aminobenzenethiol appeared as the etching time of the Ag foil was increased, suggesting that photoelectrons could be transferred from silver to 4‐ NBT even by the irradiation of a visible laser, more easily upon the increase in the surface roughness.