Gold electrodes, adsorption

Kolics A, Thomas A E and Wieckowski A 1996 CI-labelled and electrochemical study of chloride adsorption on a gold electrode from perchloric acid media J. Chem. See. Faraday Trans. 92 3727-36... 

Rodes A, Feliu JM, Aldaz A, Claviher J. 1988. Irreversible tin adsorption on polyoriented gold electrodes. J Electroanal Chem 256 455-462. 

Uchida H, Ikeda N, Watanahe M. 1997. Electrochemical quartz crystal microhalance study of copper ad-atoms on gold electrodes. Part II. Further discussion on the specific adsorption of anions from the solutions. J Electroanal Chem 424 5-12. 

Corrigan DS, Krauskopf EK, RiceLM, Wieckowski A, Weaver MJ. 1988. Adsorption of acetic acid at platinum and gold electrodes— A combined infrared spectroscopic and radiotracer study. J Phys Chem 92 1596-1601. 

Cuesta A, Lopez N, Gutierrez C. 2003. Electrolyte electroreflectance study of carbon monoxide adsorption on polycrystalline silver and gold electrodes. Electrochim Acta 48 2949-2956. Date M, Hamta M. 2001. Moisture effect on CO oxidation over Au/Ti02 catalyst. J Catal 201 221-224. 

The second most widely used noble metal for preparation of electrodes is gold. Similar to Pt, the gold electrode, contacted with aqueous electrolyte, is covered in a broad range of anodic potentials with an oxide film. On the other hand, the hydrogen adsorption/desorption peaks are absent on the cyclic voltammogram of a gold electrode in aqueous electrolytes, and the electrocatalytic activity for most charge transfer reactions is considerably lower in comparison with that of platinum. 

Although identifying the major criteria for a successful promoter, the work of Hill and colleagues (1987) did raise a fundamental question concerning the mode of adsorption of SSBipy. This was addressed directly by Taniguchi et at (1985) who employed SERS to study the adsorption of both SSBipy and PySH at a gold electrode in aqueous buffer at pH 7. 

Figure 3 shows the cyclic voltammograms of cytochrome c recorded in aqueous solution either when the protein is adsorbed (or immobilized) on the electrode (Sn02) surface (a), or when it diffuses to a gold electrode pretreated by adsorption of 4,4 -bipyridyl (b). 

A large number of examples of redox polyelectrolyte monolayers have been reported [42[. Anson described the adsorption of poly(acrylic acid) onto glassy carbon with electrostatic binding of Ru(NH3)6 and Co(NH3)6 ions from solution [43]. Finklea [44] adsorbed poly(4-vinyl-I-methyl-pyridinium methylsulfate) on self-assembled mercapto-undecanoic self-assembled monolayer (SAM) on gold electrodes to... 

Immobilization strategies for electrochemical detection may involve physical adsorption, thiol-finking chemistries to gold electrodes, and organosilane finking chemistries to oxidized silicon or glass substrates. Immobilization... 

In the oxide region of gold electrodes, residual lead can be present, resulting from irreversible adsorption, and presence of hydroxide species has been postulated ]265]. Pb UPD on Au(lll) has also been studied in selected organic solvents, mainly propylene carbonate [284]. Results similar to those in aqueous solutions have been obtained. Deposition of Pb on Au electrodes coated by silver has also been studied [285]. Depending on the silver layer thickness, results typical for Pb deposited on Au or Ag have been obtained. 

Some attention has also been paid to the simultaneous adsorption of sulfate anions and organic compounds. Futamata [44] has detected coadsorption of water molecules and sulfate species with uracil on polycrystalline gold electrode, applying attenuated total reflection-infrared spectroscopy. The adsorbed sulfate species appeared either as S04 or HS04, depending on the pH of the electrolyte solution. Skoluda... 

Hexacyanoferrates were immobilized on Au covered with SAM of 3,3 -thiodipropionic acid [86]. It has been found from voltammetric studies that the surface coverage of hexacyanoferrate is close to one monolayer and such an electrode exhibits very good surface redox behavior. Cheng et al. [87] have described the formation of an extremely thin multilayer film of polybasic lanthanide heteropolytungstate-molybdate complex and cationic polymer of quaternary poly(4-vinylpyridine), partially complexed with osmium bis(2,2 -bipyridine) on a gold electrode precoated with a cysteamine SAM. Consequently, adsorption of inorganic species might also be related to the properties of SAMs. This problem will be discussed in detail in a separate section later. 

Adsorption of Disulfides and Related Compounds Adsorption and further electrode reactions of different disulfides at gold electrodes depend on chemical properties of the adsorbates. It has been evidenced in some papers that at least for some disulfides, adsorption process involves the cleavage of the S—S bond. Adsorption of diphenyl disulfide on a polycrystalline gold electrode has been studied in detail by Borsari etal. [166]. They have proposed the mechanism of adsorption shown in Scheme 1 ... 

Similar behavior of other aromatic disulfides and thiols on gold electrodes has been described based on the SERS experiments [167]. Adsorption of benzenethiol, benzenemethanethiol, p-cyanobenzenemethanethiol, diphenyl sulfide, and dibenzyl sulfide was studied on the roughened gold electrode. All these species adsorb dissociatively as the corresponding thiolates. Monolayers formed from symmetric disulfides were exactly like those formed from the corresponding thiols. These monolayers were stable in a wide potential window from -1-800 to —1000 mV (versus SCE), which was limited by the oxidation of the Au surface from the positive side and hydrogen evolution at —1000 to —1200 mV at the negative side. 

Other Sulfur Compounds and Complex Adsorption Layers Adsorption of 5-(octyldithio)-2-nitrobenzoic acid on a gold electrode has been investigated using a quartz crystal microbalance [177]. 

On a pc-Au electrode in 1 M NaF vertically oriented pyridine molecules have been observed at 0.7 V (versus Ag/AgCl), applying in situ IR. In contrast, they have not been detected at this potential in electrochemical method [240]. Considering the fact that adsorption of pyridine on gold electrodes is a replacement reaction and taking into account the results obtained from quartz crystal microbalance experiments, the conclusion has been made that adsorption of one pyridine molecule is accompanied by the removal of 10-12 water molecules [241]. 

Using reflectometry, Barten etal. [259] have investigated adsorption of quater-nized poly-2-vinyl pyridine, of a fixed charge per monomer, on a gold electrode. The total adsorbed amount of the compound decreased linearly with the double-layer potential of gold. Adsorption proceeded up to a relatively high doublelayer potential and was accompanied by a relatively high contribution of nonelectro-static interactions. 

Xiao and Sun [267] have investigated adsorption of p-nitrobenzoic acid at a gold electrode in 0.1 M HCIO4, using various methods. At potentials more positive than 0.3 V, the molecules tended to adsorb in a vertical orientation via their carboxylic group directed toward the Au surface. 

Surface-enhanced near-infrared Raman spectroscopy has been utilized to study the behavior of nicotinamide adenine dinucleotide on a gold electrode [303]. It has been found that either adenine or nicotinamide moiety changes its adsorption states during potential scanning. 

Adsorption of putidaredoxin on gold electrodes has been studied using dynamic spectroscopic ellipsometry and differential capacitance measurements [307]. In Ref. 307, a method for the measurement of metal surface optical perturbation during protein adsorption at a constant potential has been described. The method is based on the concept that the charged transition layer develops between the electrode substrate and the adsorbate. 

Adsorption of glutathione on a gold electrode has been studied [310] using electrochemical quartz crystal impedance, electrochemical impedance spectroscopy, and CV. 

Structural differences between the monolayers of anthraquinone derivatives self-assembled on silver and gold electrodes have been investigated using CV and in situ SERS spectroscopy [323]. Neves etal. ]324] have described Monte Carlo simulations of phenol adsorption on gold electrodes. 

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