Interface electronic structure from ellipsometry coupled with differential capacity measurements

Spectroscopic Real-Time Ellipsometry of Putidaredoxin Adsorption on Gold Electrodes

“…The latter effect is insignificant in our dilute buffer solution containing only anions of low specific adsorptivity on gold . Our (Δ,Ψ) vs E also shows the same asymmetry around the point-of-zero-charge ( E pzc = 0.05 V) observed by Chao et al , wherein positive charging ( E > 0.05 V) exhibits a stronger optical effect (steeper (Δ,Ψ) vs E slope) than does negative charging ( E < 0.05 V). Positive charging of the metal surface provides a transition layer of constant index of refraction ň tr but increasing thickness d tr , while negative charging provides for a very thin region (about 0.3 Å) where electrons are increasingly accumulated .…”

“…reported similar results for gold electrodes and analyzed them in terms of the charged surface layer model. , They interpreted the variation of (Δ,Ψ) with electrode potential E as due to modulation of the complex index of refraction of the electrode surface layer where accumulation or depletion of free electrons occurs, as well as due to changes on the solution side because of modifications in adsorption of solution components . The latter effect is insignificant in our dilute buffer solution containing only anions of low specific adsorptivity on gold . Our (Δ,Ψ) vs E also shows the same asymmetry around the point-of-zero-charge ( E pzc = 0.05 V) observed by Chao et al , wherein positive charging ( E > 0.05 V) exhibits a stronger optical effect (steeper (Δ,Ψ) vs E slope) than does negative charging ( E < 0.05 V).…”

“…Chao et al. reported similar results for gold electrodes and analyzed them in terms of the charged surface layer model. , They interpreted the variation of (Δ,Ψ) with electrode potential E as due to modulation of the complex index of refraction of the electrode surface layer where accumulation or depletion of free electrons occurs, as well as due to changes on the solution side because of modifications in adsorption of solution components . The latter effect is insignificant in our dilute buffer solution containing only anions of low specific adsorptivity on gold .…”

Combined Spectroscopic Ellipsometry and Voltammetry of Tetradecylmethyl Viologen Films on Gold

“…Δ and Ψ versus potential dependencies were recorded for bare gold in buffer solution during the potentiodynamic scan from −0.2 to −0.9V before the introduction of the adsorbate. They were similar to the previously published ellipsometry data for gold in the double-layer region. , C 14 MV was injected close to the electrode surface at open circuit potential using 0.5 mL portions of 10 mM deaerated solution. The solution was continuously purged with argon during the experiment, thus ensuring rapid mixing of the adsorbate with buffer solution.…”

Voltage-Induced Adsorbate Damping of Single Gold Nanorod Plasmons in Aqueous Solution

“…The capacitance of (19 ± 4) μF/cm 2 fits well to similar results obtained by surface plasmon resonance (SPR) or ellipsometric measurements on thin gold films at potentials below the PZC. 37,38 In contrast, surface capacitances as high as 80 μF/cm 2 are frequently reported for noble metal nanoparticles 23,24 or for SPRs when the gold films are charged above the PZC. 38 Indeed, we observe a substantial deviation from the linear dependence of the NPPR position on the applied potential in the second potential range (ii) between +0.3 V and approximately 1.1 V (Figure 2a).…”