Lifting of the (̄3 × 22) surface reconstruction of Au(1 1 1) as a sensitive probe to monitor adsorption of cyclodextrin and its complexes in halide solutions

Stabilization of the (̄3×22) reconstruction of Au(1 1 1) in halide solutions by adsorbed, uncharged organic molecules was investigated using cyclic voltammetry. In aqueous solutions containing either iodide, bromide, or chloride, the presence of α-cyclodextrin (α-CD), β-cyclodextrin (β-CD), or a ferrocene inclusion complex of the latter (Fc·β-CD) was found to shift the potential of the (̄3×22) to (1 × 1) transition positive by several tens of mV. This shift is explained by the inhibition of halide adsorption due to the need to displace adsorbed cyclodextrin species. The size of the shift follows the trend in the strength of interaction between the three halides and the Au surface. Changes to the CV shapes suggest an influence of the cyclodextrins on both the thermodynamics and kinetics of the reconstruction lifting event. Differences observed in CVs recorded with the three cyclodextrin adsorbates also demonstrate the utility of the potential dependent surface reconstruction processes of Au(1 1 1) as a probe of adsorbed species. Each halide/cyclodextrin combination was further examined by perturbing the electrode surface with potential cycling and subsequently recording CVs to monitor the recovery of the surface to an equilibrium state.