Effect of Halide Ion Adsorption upon Plasmon-Mediated Photoelectron Emission at the Silver/Solution Interface

Abstract

The effect of the roughening of the silver surface upon photoemission observed in the presence of two different scavengers dissolved in an aqueous solution, CO2 and NO3 - ions, was re-examined. The quantum yield of the photocurrent exhibits a sharp maximum at 370−380 nm in the frequency range of surface plasmons on silver. These photoyields were strongly affected by the extent of the roughening of the Ag surface and reached an unusually large value of 0.05 electron per incident photon. Electrochemical oxidation/reduction roughening performed in the presence of Cl-, Br-, and ClO4 - ions, similar to that employed in enhanced Raman scattering (SERS) experiments, affected the maximum of the photocurrent and in some cases also its onset potential. Photocurrents arising at potentials more negative than the potential of zero charge (pzc) of silver were principally influenced by changing morphology of the surface resulting from more or less deep roughening performed in different solutions. On the other hand, the photoelectrochemical behavior of silver at potentials positive with respect to the pzc was clearly affected by the specific adsorption of anions of the supporting electrolyte. It was, in particular, the Br- anion that caused in this potential region the strongest enhancement of the photocurrent, associated with the reduction of scavengers and led to an apparent positive shift of the onset potential. The role played by the specifically adsorbed anions is interpreted in terms of slowing down the reverse reactions of solvated electrons and of reaction intermediates (such as, for example, the NO3 2- anion) returning to the electrode.

Plasmon‐Mediated Syntheses of Metallic Nanostructures

“…This physical process has been known for some time, but it is difficult to utilize because the lifetime of the electron-hole pairs is very short. [55,[97][98][99][100][101][102] Typically, surface plasmons dephase within femtoseconds and subsequently undergo electronic thermalization and relax via coupling to lattice phonons within picoseconds. [59,[103][104][105] Nonetheless, this phenomenon has led to the development of systems that exhibit plasmoninduced charge separation.…”

The Role of Photon Energy and Semiconductor Substrate in the Plasmon-Mediated Photooxidation of Citrate by Silver Nanoparticles

“…2,3 Nonetheless, photochemistry mediated by hot metallic carriers has been extensively studied in high vacuum surface science experiments, 2,4−6 and hot carrier photochemistry at metal electrodes has also been reported. 7,8 Additional examples of hot carrier photochemistry come from surface-enhanced Raman spectroscopy (SERS). In SERS, Raman scattering from molecules adsorbed on noble metal nanoparticles or roughened surfaces is enhanced by orders of magnitude.…”

Visible laser–induced photoreduction of silver 4‐nitrobenzenethiolate revealed by Raman scattering spectroscopy

“…The detailed mechanism of the nitro-to-amine conversion on Ag is a matter of conjecture, but photoelectrons are known to be readily ejected from Ag even by a visible laser. It has been observed by Fedurco et al [44] that the surface roughening of Ag results in a drastic increase of the photocurrent for the wavelength close to the surface plasmon frequency. On the other hand, it is known that when photoreaction occurs for aromatic nitro molecules in a solution phase, a chemical species from which hydrogen atom(s) can be abstracted is needed.…”