Study of Ag(111) and Au(111) electrodes by optical second-harmonic generation

Abstract

We have measured the potential dependence of optical second-harmonic generation from Ag(111) and Au(111) electrodes at wavelengths below and above the free electron regime. In the free electron regime, the cubic nonlinear susceptibility is dominant, leading to similar effects for positive and negative charging. Above the free electron regime, the quadratic nonlinear susceptibility of the d-electrons is dominant, leading to different effects for positive and negative charging. We also followed the oxidoreduction of Au(111) and found that second-harmonic generation is very sensitive to the different steps of the reaction.

Structure of Au(111) and Au(100) Single-Crystal Electrode Surfaces at Various Potentials in Sulfuric Acid Solution Determined by In Situ Surface X-ray Scattering

“…Information obtained by optical techniques contains contributions not only from the electrode surface but also from the bulk. [27][28][29][30][31][32][33][34][35][36][37] Thus, the surface structures of the single-crystal gold electrodes at atomic resolution for wide potential regions, particularly in the oxide formation potential region, have not been clarified yet.…”

“…The surface structures of the singlecrystal gold electrodes in electrolyte solutions have been investigated using various techniques, including conventional electrochemical methods, [7][8][9][10][11][12][13][14][15] scanning tunneling microscopy (STM), [16][17][18][19][20][21][22][23][24][25][26][27][28] and several optical techniques, [27][28][29][30][31][32][33][34][35][36][37] and were found to be strongly dependent on the potentials. It is well-known that the potential-induced reversible lifting and restoration of surface reconstruction (i.e., ( 3 × 23) for Au(111) and hexagonal closed-packing for Au(100) surfaces) take place around +0.35 V vs Ag/AgCl in a sulfuric acid solution.…”

Excitation Wavelength Dependent Three-Wave Mixing at a CO-Covered Platinum Electrode

“…Consequently, the SHG signal is sensitive to changes at the surface and interface, and therefore, the SHG process is a useful probe of various interfacial phenomena. This technique has been applied to various systems including electrochemical systems to probe the dc field [33][34][35][36] and geometric and electronic structure of interfaces [37][38][39][40][41][42] and is often used to study the adsorption of molecules, ions, and metal atoms on various interfaces in both resonant and nonresonant conditions. 32,[40][41][42] The resonant enhancement of the SHG signal is observed when the electronic transition couples energetically with either the input photon or the output SH photon.…”

Second harmonic generation study on electrochemical deposition of palladium on a polycrystalline gold electrode

“…This enhancement effect is commonly known as electric field induced SH (EFISH) [40]. This effect was found not to be as pronounced on the Au as on the Ag electrode surfaces under both near-IR and visible excitations [59]. This is because the EFISH effect on the Au electrode surface is smaller than the contribution.…”

“…(i) Near-IR excitation: As mentioned earlier, under near-IR excitation, a resonant SHG signal was observed at the Au surface as 2ω photons coupled with either the interband transition (2.25 eV) from the upper edge of the 5d band to the states near the Fermi level located in the 6s band [59,60] or an intraband transition within the sp band [65].…”