Oriented adsorption at well-defined electrode surfaces studied by Auger, LEED, and EELS spectroscopy

Batina, Nikola; Frank, Douglas G.; Gui, John Y.; Kahn, Bruce E.; Lin, Chun-Ping; Lu, Frank K.; McCargar, James W.; Salaita, Ghaleb N.; Stern, Donald A.; Zapien, Donald C.; Hubbard, Arthur T.

doi:10.1016/0013-4686(89)87136-1

Cited by 33 publications

(25 citation statements)

References 17 publications

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“…Conventionally, the attenuation of electrons emitted from a surface due to the presence of an adsorbed monolayer can be described by a simple exponential function . If the monolayer is adsorbed uniformly across the surface, an effective film thickness can be calculated using known values of the electron mean free path.…”

Section: Resultsmentioning

confidence: 99%

Electrochemistry of Surface-Confined Mixed Monolayers of 4-Aminothiophenol and Thiophenol on Au

1996

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We report the electrochemistry of surface-confined monolayers of 4-aminothiophenol (4-ATP) and mixed monolayers of 4-ATP and thiophenol (TP) on Au surfaces. Cyclic voltammograms of the 4-ATP monolayer in acidic aqueous perchlorate solutions are characterized by an irreversible oxidative wave at 0.730 V vs Ag/AgCl on the first scan and, upon scan reversal, by a persistent, reversible, surface-confined wave centered at approximately 0.500 V and a transient peak at about 0.300 V. We propose an ECE mechanism to account for this electrochemistry: 4-ATP is first oxidized to the cation radical, followed by chemical coupling to form an adsorbed dimer. The dimer is subsequently hydrolyzed in the presence of H2O to yield an adsorbed quinone species that is reversibly electroactive. Grazing angle FTIR spectroscopy was used to identify the product. The transient peak is due to the coupling of desorbed molecules and is consistent with the formation of a phenazine species. We then show that mixed monolayers of 4-ATP and TP can be used to study the coverage dependence of surface-confined reactions. The chemical composition of the mixed systems was determined using two independent Auger electron spectroscopic techniques and grazing angle FTIR spectroscopy. Using 20 min assembly times, we find that the surface concentration of 4-ATP is directly proportional to its mole fraction in solution. Interestingly, TP does not participate in the 4-ATP electrochemistry and functions only to dilute the surface concentration of 4-ATP. We find that the efficiency of the conversion of 4-ATP to product is somewhat higher at low mole fractions of 4-ATP.

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Section: Resultsmentioning

confidence: 99%

Electrochemistry of Surface-Confined Mixed Monolayers of 4-Aminothiophenol and Thiophenol on Au

1996

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“…Hydroquinone (HQ) is a well-studied molecule, which undergoes electrochemical oxidation/reduction reactions in solution. , Hubbard and co-workers extensively studied the HQ adlayer on Pt electrodes. ,− They measured the surface packing density of HQ on both polycrystalline and single crystalline Pt electrodes employing a thin-layer cell. ,− Earlier studies reported that HQ could exist in horizontal and vertical orientational states at polycrystalline Pt surfaces: the horizontal orientation gave packing densities close to the expected value of 0.309 nmol cm -2 , while those for the vertical orientation were also close to the expected value, 0.581 nmol cm -2 . , The horizontal form was reported to reorient itself irreversibly to the vertical form when the surface containing the horizontally adsorbed HQ molecules was exposed to a solution of a higher HQ concentration. , On the other hand, Ren and Hubbard reported little variation in the packing density on Pt(111) (0.3 nmol cm -2 ), stating that HQ is predominantly adsorbed in a horizontal orientation on the Pt(111) single crystalline surface irrespective of the concentration of HQ in solution ,− They reported the adlayer structure of HQ on Pt(111) to be (3 × 3), using the low-energy electron diffraction (LEED) technique after transferring the sample into a vacuum, , which led to the packing density of 0.276 nmol cm -2 . Results of packing density measurements performed by Auger electron spectroscopy (AES) on Pt(111) 20-22 were in agreement with those obtained by using the thin-layer cell .…”

Section: Introductionmentioning

confidence: 99%

Adlayer of Hydroquinone on Pt(111) in Solution and in a Vacuum Studied by STM and LEED

et al. 2004

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Hydroquinone (HQ) adlayers were formed on Pt(111) in HF solution and in a vacuum. By using scanning tunneling microscopy (STM) in solution, it was revealed that HQ formed an ordered structure on Pt(111) with a strong attractive interaction between two adjacent hydroxyl groups in neighboring HQ molecules. After the sample was transferred into a vacuum, low-energy electron diffraction (LEED) measurement was performed, which showed that the (2.56 x 2.56)R16 degrees incommensurate structure of the HQ adlayer was formed in solution. The HQ adlayer on Pt(111) was formed also by vapor deposition, and the identical (2.56 x 2.56)R16 degrees adlayer structure was found by LEED and STM in a vacuum.

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“…The AFM images suggest that the surface roughness of ORC Ag has the size of approximately 20-100 nm, whereas the Au surface presents not explicitly defined forms in the 100-500 nm diameter. Table 1 summarizes the wavenumbers of the bands observed in these spectra together with the proposed bands assignment [31,[40][41][42][43][44][45][46][47][48][49][50]. The SERS spectra comparison show changes in the acetyl-[Leu 28,31 ]-NPY(24-36) SERS spectral patterns upon substrate change.…”

Section: Resultsmentioning

confidence: 98%

Characterization of the surface geometry of acetyl-[Leu 28,31 ]-NPY(24-36), a selective Y 2 receptor agonist, onto the Ag and Au surfaces

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Piergies

et al. 2016

Vibrational Spectroscopy

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Oriented adsorption at well-defined electrode surfaces studied by Auger, LEED, and EELS spectroscopy

Cited by 33 publications

References 17 publications

Electrochemistry of Surface-Confined Mixed Monolayers of 4-Aminothiophenol and Thiophenol on Au

Electrochemistry of Surface-Confined Mixed Monolayers of 4-Aminothiophenol and Thiophenol on Au

Adlayer of Hydroquinone on Pt(111) in Solution and in a Vacuum Studied by STM and LEED

Characterization of the surface geometry of acetyl-[Leu 28,31 ]-NPY(24-36), a selective Y 2 receptor agonist, onto the Ag and Au surfaces

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