EFFECT OF THE SURFACE-ROUGHNESS ON THE SPECTRAL DISTRIBUTION OF PHOTOEMISSION CURRENT AT THE SILVER/SOLUTION CONTACT

The use of an aqueous electrolyte containing dissolved CO2 enabled revealing of an unusually intense photoemission from a bulk silver electrode. The observed cathodic photocurrent exhibits a sharp peak at ∼360 nm corresponding to the energy of surface plasmons in silver. The amount and the spectral distribution of the photocurrent are strongly affected by the extent of roughness of the silver surface. In particular, an electrochemical roughening procedure, analogous to that leading to the surface enhancement of Raman scattering (SERS) at silver, causes appearance of a long tail on the low-energy side of the photoemission spectra. In consequence, significant photocurrents, corresponding to a quantum yield of ∼7×10-3, are observed for the deliberately roughened silver electrodes illuminated with the wavelength of 514 nm, most frequently used in SERS experiments. It is postulated that this intense photoemission, discovered in the presence of CO2 in the solution, equally takes place in the absence of scavengers. However, in the latter case no significant photocurrents can be detected as most of the photoemitted electrons (solvated or not) return back to the electrode. © 1995 American Institute of Physics.