Optical Investigations of Film Formation and Removal on Gold Anodes in Acidic Oxalate Solutions
RECENT investigations of the oxidation of oxalate ions in acidic solutions using gold anodes have provided electrochemical evidence for the formation of a film on this anode during steady-state electrolysis at potentials well below that for Au2O3 formation, 1.36 V normal hydrogen electrode1. The determination of the nature of the film on gold at potentials below 1.36 V using electrochemical techniques has introduced uncertainties as to whether the film is a ‘three dimensional’ oxide film or a ‘two dimensional’ chemisorbed oxygen film. Some investigators2–5 using charging curves as their basis conclude that the formation of an oxide occurs only above 1.36 V, the formation of a chemisorbed oxygen film being the process occurring below this potential. The formation of this chemisorbed oxygen film begins at potentials as low as 1 15 V (ref. 6). Other work, however, also based on electrochemical evidence, indicates that the formation of an oxide film does occur below 1.36 V (ref. 7).
Fast scanning spectroelectrochemical ellipsometry: In-situ characterization of gold oxide
Abstract A study of the solid/liquid interface using a fast scanning spectroscopic ellipsometer with an optical multichannel analyzer (SE-OMA) is described. Here, we discuss the basic operating principles of the SE-OMA and, as an example of its application, report the optical properties and growth of monolayer gold oxide films formed on polycrystalline Au surfaces. These studies were performed using a specially-designed spectroelectrochemical cell operated with 0.5M H2SO4 under anodic potential. For the first time, spectroscopic ellipsometry measurements reveal the oxide dielectric function in real time from 1.5 to 3.3 eV. The thickness of the gold oxide was deduced to be approximately 4 A at 1.3 V versus a saturated calomel reference electrode (SCE).
Electrochemical detection of copper(II) at a gold electrode modified with a self-assembled monolayer of penicillamine
A penicillamine (PCA) self-assembled monolayer (SAM) was prepared on a gold electrode. It has been found that the modified electrode exhibited a selective response to copper ions. As demonstrated by cyclic voltammetric experiments, the SAM-based electrode showed an attractive ability to preconcentrate efficiently traces of copper(II) from solutions. Under optimum conditions, the anodic peak current was proportional to the concentration of Cu(II) in the range from 8.0 × 10−7 to 1.0 × 10−4 M with a detection limit of 4.0 × 10−7 M. Moreover, this modified gold electrode is also characterized by excellent repeatability, showing a relative standard deviation of 3.2% for nine successive measurements of 1.0 × 10−5 M Cu(II). The PCA/Au SAM gold electrode was used for the determination of Cu(II) in a tap water sample and the results showed a good agreement with the data obtained by atomic emission spectrometry.