Studies of L-dopa and Related Compounds Adsorbed from Aqueous Solutions at pt(100) and pt(111): Electron Energy-Loss Spectroscopy, Auger Spectroscopy, and Electrochemistry

Donald A. Stern, Ghaleb N. Salaita, Frank Lu, James W. McCargar, Nikola Batina, Douglas G. Frank, Laarni Laguren-Davidson, Chiu-Hsun Lin, Nicholas Walton, John Y. Gui, Arthur T. Hubbard

研究成果: Article

47 引文 斯高帕斯(Scopus)

摘要

Adsorption of L-DOPA and a series of other amino acids and related compounds from aqueous solutionsat well-defined Pt(111) and Pt(100) single-crystal surfaces has been studied: 3-(3,4-dihydroxyphenyl)-Lalanine (DOPA), L-tyrosine (TYR), L-cysteine (CYS), L-phenylalanine (PHE), L-alanine (ALA), dopamine (DA), catechol (CT), and (3,4-dihydroxyphenyl)acetic acid (DOPAC). Packing densities (moles adsorbed per unit area) were measured for each compound by means of quantitative Auger spectroscopy; two independent Auger spectroscopic methods were employed: one based upon measurement of elemental Auger signals from the adsorbed layer and the other upon measurement of the attenuation of the Pt Auger signal by the adsorbed layer. Packing densities of DOPA, TYR, DA, CT, and DOPAC indicate adsorption with the aromatic ring attached parallel to the surface. In contrast, CYS is adsorbed through the sulfur atom, while ALA and PHE are attached to the surface through their amino acid moieties. Vibrational spectra of the adsorbed layer formed from each of these compounds were obtained by means of electron energy-loss spectroscopy (EELS) and were compared with the infrared spectra of the parent compounds in KBr. The EELS (adsorbed layer) and IR (solid compound) spectra are similar except that the hydroxyl hydrogens of DOPA, TYR, DA, CT, and DOPAC as well as the carboxyl hydrogens of PHE and DOPAC are removed as a result of the adsorption process. EELS bands of polar groups such as O-H are not broadened to the same extent as in the IR spectra of the solid compounds, evidently due to less intermolecular bonding among such groups at the surface. LEED experiments indicate that CT forms a (3X3) adlattice at Pt(111), while each of the other compounds forms an oriented but otherwise structurally disordered layer at Pt(111) and Pt(100). The packing density of DOPA, CYS, and DOPAC is higher at Pt(100) than at Pt(111) due to differences in molecular orientation. Single-crystal surface structure, adsorbate orientation, and mode of surface bonding exert a profound influence on the product distribution of electrocatalytic oxidation of these well-characterized adsorbed organic intermediates, on the basis of cyclic voltammetry and potential-step chronocoulometry experiments. This study has also revealed that evacuation does not alter the composition or electrochemical properties of the chemisorbed layer formed from solution.

原文English
頁(從 - 到)711-722
頁數12
期刊Langmuir
4
發行號3
DOIs
出版狀態Published - 1988 五月 1

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry

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  • 引用此

    Stern, D. A., Salaita, G. N., Lu, F., McCargar, J. W., Batina, N., Frank, D. G., Laguren-Davidson, L., Lin, C-H., Walton, N., Gui, J. Y., & Hubbard, A. T. (1988). Studies of L-dopa and Related Compounds Adsorbed from Aqueous Solutions at pt(100) and pt(111): Electron Energy-Loss Spectroscopy, Auger Spectroscopy, and Electrochemistry. Langmuir, 4(3), 711-722. https://doi.org/10.1021/la00081a037