The Experts below are selected from a list of 144 Experts worldwide ranked by ideXlab platform

Daniel A. Scherson - One of the best experts on this subject based on the ideXlab platform.

  • XPS studies of the chemical and electrochemical behavior of copper in Anhydrous hydrogen fluoride
    Journal of Electroanalytical Chemistry, 2002
    Co-Authors: George G. Totir, Gary S. Chottiner, Christopher L. Gross, Daniel A. Scherson
    Abstract:

    Abstract The reactivity of copper toward liquid Anhydrous Hydrofluoric Acid (AHF) has been examined using ex situ X-ray photoelectron spectroscopy (XPS). Exposure of either oxide-free or air-oxidized Cu surfaces to AHF yielded XPS spectra consistent with the presence of a CuF2 layer devoid of oxygen. Cyclic voltammetric experiments involving oxide-free Cu electrodes in hexafluorobutanol (HFB)+AHF displayed a prominent oxidation peak during the first few cycles. XPS analysis of Cu electrodes emersed at potentials positive to this feature provided evidence for the presence of a CuF2 layer much thicker than that found by simple immersion in AHF. Furthermore, the onset potential for both oxidation and subsequent reduction of the film was 0.0 V versus a Cu electrode in the same solution, which suggests that the Cu/CuF2 redox couple controls the potential of the reference electrode.

  • Electrofluorination of Hexafluorobutanol in Anhydrous Hydrofluoric Acid Quasi On Line Mass Spectrometry and X-Ray Photoelectron Spectroscopy Studies
    Journal of The Electrochemical Society, 2001
    Co-Authors: George G. Totir, Gary S. Chottiner, Christopher L. Gross, Daniel A. Scherson
    Abstract:

    Certain aspects of the electrochemical fluorination (ECF) of hexafluorobutanol (HFB) in Anhydrous HF (AHF) on Ni electrodes have been examined by mass spectrometry (MS) and X-ray photoelectron spectroscopy (XPS). Measurements were performed using a portable ultrahigh vacuum compatible chamber that allows for the transfer and characterization of specimens without exposure to the ambient atmosphere. Quasi on line MS analysis of the gases released during ECF of HFB/AHF solutions revealed features attributable to perfluorobutyryl fluoride [PBF - CF 3 CF 2 CF 2 C(O)F] with no evidence of the presence of other reaction products. Ex situ XPS analysis of Ni electrodes following ECF yielded spectra consistent with the formation of a rather thick. irregular layer of NiF 2 of average thickness of about 150-200 monolayers, with small contributions due to O (6%) and C (7%) localized primarily in the surface region.

  • X‐Ray Photoelectron Spectroscopy and Morphological Studies of Polycrystalline Nickel Surfaces Exposed to Anhydrous HF
    Journal of The Electrochemical Society, 2000
    Co-Authors: George G. Totir, Gary S. Chottiner, Christopher L. Gross, W. Ves Childs, Daniel A. Scherson
    Abstract:

    The reactivity of nominally clean polycrystalline Ni toward gas-phase and liquid Anhydrous Hydrofluoric Acid (AHF) has been examined by X-ray photoelectron spectroscopy (XPS). To avoid contamination with atmospheric components, experiments were carried out using a portable ultrahigh vacuum (UHV)-compatible chamber to transfer Ni specimens between a UHV system that houses the XPS spectrometer and an additional UHV-compatible chamber where the actual exposures were performed. For exposures of ca. 10 min, the extent of surface oxidation of clean Ni to form NiF 2 , as calculated from Ni 2p and F Is XPS spectra, was found to be significantly higher for gas-, compared to liquid-phase AHF. Thin (ca. 100 nm), mirror-like Ni films sputtered onto the surface of a sapphire disk yielded upon exposure to gas-phase AHF (after contact with the laboratory atmosphere) scanning electron microscope images displaying a coherent, patchy structure with raised junctures. This behavior was ascribed to internal compressive stresses induced by the formation of a nickel(II) fluoride layer on the metal surface.

George G. Totir - One of the best experts on this subject based on the ideXlab platform.

  • XPS studies of the chemical and electrochemical behavior of copper in Anhydrous hydrogen fluoride
    Journal of Electroanalytical Chemistry, 2002
    Co-Authors: George G. Totir, Gary S. Chottiner, Christopher L. Gross, Daniel A. Scherson
    Abstract:

    Abstract The reactivity of copper toward liquid Anhydrous Hydrofluoric Acid (AHF) has been examined using ex situ X-ray photoelectron spectroscopy (XPS). Exposure of either oxide-free or air-oxidized Cu surfaces to AHF yielded XPS spectra consistent with the presence of a CuF2 layer devoid of oxygen. Cyclic voltammetric experiments involving oxide-free Cu electrodes in hexafluorobutanol (HFB)+AHF displayed a prominent oxidation peak during the first few cycles. XPS analysis of Cu electrodes emersed at potentials positive to this feature provided evidence for the presence of a CuF2 layer much thicker than that found by simple immersion in AHF. Furthermore, the onset potential for both oxidation and subsequent reduction of the film was 0.0 V versus a Cu electrode in the same solution, which suggests that the Cu/CuF2 redox couple controls the potential of the reference electrode.

  • Electrofluorination of Hexafluorobutanol in Anhydrous Hydrofluoric Acid Quasi On Line Mass Spectrometry and X-Ray Photoelectron Spectroscopy Studies
    Journal of The Electrochemical Society, 2001
    Co-Authors: George G. Totir, Gary S. Chottiner, Christopher L. Gross, Daniel A. Scherson
    Abstract:

    Certain aspects of the electrochemical fluorination (ECF) of hexafluorobutanol (HFB) in Anhydrous HF (AHF) on Ni electrodes have been examined by mass spectrometry (MS) and X-ray photoelectron spectroscopy (XPS). Measurements were performed using a portable ultrahigh vacuum compatible chamber that allows for the transfer and characterization of specimens without exposure to the ambient atmosphere. Quasi on line MS analysis of the gases released during ECF of HFB/AHF solutions revealed features attributable to perfluorobutyryl fluoride [PBF - CF 3 CF 2 CF 2 C(O)F] with no evidence of the presence of other reaction products. Ex situ XPS analysis of Ni electrodes following ECF yielded spectra consistent with the formation of a rather thick. irregular layer of NiF 2 of average thickness of about 150-200 monolayers, with small contributions due to O (6%) and C (7%) localized primarily in the surface region.

  • X‐Ray Photoelectron Spectroscopy and Morphological Studies of Polycrystalline Nickel Surfaces Exposed to Anhydrous HF
    Journal of The Electrochemical Society, 2000
    Co-Authors: George G. Totir, Gary S. Chottiner, Christopher L. Gross, W. Ves Childs, Daniel A. Scherson
    Abstract:

    The reactivity of nominally clean polycrystalline Ni toward gas-phase and liquid Anhydrous Hydrofluoric Acid (AHF) has been examined by X-ray photoelectron spectroscopy (XPS). To avoid contamination with atmospheric components, experiments were carried out using a portable ultrahigh vacuum (UHV)-compatible chamber to transfer Ni specimens between a UHV system that houses the XPS spectrometer and an additional UHV-compatible chamber where the actual exposures were performed. For exposures of ca. 10 min, the extent of surface oxidation of clean Ni to form NiF 2 , as calculated from Ni 2p and F Is XPS spectra, was found to be significantly higher for gas-, compared to liquid-phase AHF. Thin (ca. 100 nm), mirror-like Ni films sputtered onto the surface of a sapphire disk yielded upon exposure to gas-phase AHF (after contact with the laboratory atmosphere) scanning electron microscope images displaying a coherent, patchy structure with raised junctures. This behavior was ascribed to internal compressive stresses induced by the formation of a nickel(II) fluoride layer on the metal surface.

Christopher L. Gross - One of the best experts on this subject based on the ideXlab platform.

  • XPS studies of the chemical and electrochemical behavior of copper in Anhydrous hydrogen fluoride
    Journal of Electroanalytical Chemistry, 2002
    Co-Authors: George G. Totir, Gary S. Chottiner, Christopher L. Gross, Daniel A. Scherson
    Abstract:

    Abstract The reactivity of copper toward liquid Anhydrous Hydrofluoric Acid (AHF) has been examined using ex situ X-ray photoelectron spectroscopy (XPS). Exposure of either oxide-free or air-oxidized Cu surfaces to AHF yielded XPS spectra consistent with the presence of a CuF2 layer devoid of oxygen. Cyclic voltammetric experiments involving oxide-free Cu electrodes in hexafluorobutanol (HFB)+AHF displayed a prominent oxidation peak during the first few cycles. XPS analysis of Cu electrodes emersed at potentials positive to this feature provided evidence for the presence of a CuF2 layer much thicker than that found by simple immersion in AHF. Furthermore, the onset potential for both oxidation and subsequent reduction of the film was 0.0 V versus a Cu electrode in the same solution, which suggests that the Cu/CuF2 redox couple controls the potential of the reference electrode.

  • Electrofluorination of Hexafluorobutanol in Anhydrous Hydrofluoric Acid Quasi On Line Mass Spectrometry and X-Ray Photoelectron Spectroscopy Studies
    Journal of The Electrochemical Society, 2001
    Co-Authors: George G. Totir, Gary S. Chottiner, Christopher L. Gross, Daniel A. Scherson
    Abstract:

    Certain aspects of the electrochemical fluorination (ECF) of hexafluorobutanol (HFB) in Anhydrous HF (AHF) on Ni electrodes have been examined by mass spectrometry (MS) and X-ray photoelectron spectroscopy (XPS). Measurements were performed using a portable ultrahigh vacuum compatible chamber that allows for the transfer and characterization of specimens without exposure to the ambient atmosphere. Quasi on line MS analysis of the gases released during ECF of HFB/AHF solutions revealed features attributable to perfluorobutyryl fluoride [PBF - CF 3 CF 2 CF 2 C(O)F] with no evidence of the presence of other reaction products. Ex situ XPS analysis of Ni electrodes following ECF yielded spectra consistent with the formation of a rather thick. irregular layer of NiF 2 of average thickness of about 150-200 monolayers, with small contributions due to O (6%) and C (7%) localized primarily in the surface region.

  • X‐Ray Photoelectron Spectroscopy and Morphological Studies of Polycrystalline Nickel Surfaces Exposed to Anhydrous HF
    Journal of The Electrochemical Society, 2000
    Co-Authors: George G. Totir, Gary S. Chottiner, Christopher L. Gross, W. Ves Childs, Daniel A. Scherson
    Abstract:

    The reactivity of nominally clean polycrystalline Ni toward gas-phase and liquid Anhydrous Hydrofluoric Acid (AHF) has been examined by X-ray photoelectron spectroscopy (XPS). To avoid contamination with atmospheric components, experiments were carried out using a portable ultrahigh vacuum (UHV)-compatible chamber to transfer Ni specimens between a UHV system that houses the XPS spectrometer and an additional UHV-compatible chamber where the actual exposures were performed. For exposures of ca. 10 min, the extent of surface oxidation of clean Ni to form NiF 2 , as calculated from Ni 2p and F Is XPS spectra, was found to be significantly higher for gas-, compared to liquid-phase AHF. Thin (ca. 100 nm), mirror-like Ni films sputtered onto the surface of a sapphire disk yielded upon exposure to gas-phase AHF (after contact with the laboratory atmosphere) scanning electron microscope images displaying a coherent, patchy structure with raised junctures. This behavior was ascribed to internal compressive stresses induced by the formation of a nickel(II) fluoride layer on the metal surface.

Gary S. Chottiner - One of the best experts on this subject based on the ideXlab platform.

  • XPS studies of the chemical and electrochemical behavior of copper in Anhydrous hydrogen fluoride
    Journal of Electroanalytical Chemistry, 2002
    Co-Authors: George G. Totir, Gary S. Chottiner, Christopher L. Gross, Daniel A. Scherson
    Abstract:

    Abstract The reactivity of copper toward liquid Anhydrous Hydrofluoric Acid (AHF) has been examined using ex situ X-ray photoelectron spectroscopy (XPS). Exposure of either oxide-free or air-oxidized Cu surfaces to AHF yielded XPS spectra consistent with the presence of a CuF2 layer devoid of oxygen. Cyclic voltammetric experiments involving oxide-free Cu electrodes in hexafluorobutanol (HFB)+AHF displayed a prominent oxidation peak during the first few cycles. XPS analysis of Cu electrodes emersed at potentials positive to this feature provided evidence for the presence of a CuF2 layer much thicker than that found by simple immersion in AHF. Furthermore, the onset potential for both oxidation and subsequent reduction of the film was 0.0 V versus a Cu electrode in the same solution, which suggests that the Cu/CuF2 redox couple controls the potential of the reference electrode.

  • Electrofluorination of Hexafluorobutanol in Anhydrous Hydrofluoric Acid Quasi On Line Mass Spectrometry and X-Ray Photoelectron Spectroscopy Studies
    Journal of The Electrochemical Society, 2001
    Co-Authors: George G. Totir, Gary S. Chottiner, Christopher L. Gross, Daniel A. Scherson
    Abstract:

    Certain aspects of the electrochemical fluorination (ECF) of hexafluorobutanol (HFB) in Anhydrous HF (AHF) on Ni electrodes have been examined by mass spectrometry (MS) and X-ray photoelectron spectroscopy (XPS). Measurements were performed using a portable ultrahigh vacuum compatible chamber that allows for the transfer and characterization of specimens without exposure to the ambient atmosphere. Quasi on line MS analysis of the gases released during ECF of HFB/AHF solutions revealed features attributable to perfluorobutyryl fluoride [PBF - CF 3 CF 2 CF 2 C(O)F] with no evidence of the presence of other reaction products. Ex situ XPS analysis of Ni electrodes following ECF yielded spectra consistent with the formation of a rather thick. irregular layer of NiF 2 of average thickness of about 150-200 monolayers, with small contributions due to O (6%) and C (7%) localized primarily in the surface region.

  • X‐Ray Photoelectron Spectroscopy and Morphological Studies of Polycrystalline Nickel Surfaces Exposed to Anhydrous HF
    Journal of The Electrochemical Society, 2000
    Co-Authors: George G. Totir, Gary S. Chottiner, Christopher L. Gross, W. Ves Childs, Daniel A. Scherson
    Abstract:

    The reactivity of nominally clean polycrystalline Ni toward gas-phase and liquid Anhydrous Hydrofluoric Acid (AHF) has been examined by X-ray photoelectron spectroscopy (XPS). To avoid contamination with atmospheric components, experiments were carried out using a portable ultrahigh vacuum (UHV)-compatible chamber to transfer Ni specimens between a UHV system that houses the XPS spectrometer and an additional UHV-compatible chamber where the actual exposures were performed. For exposures of ca. 10 min, the extent of surface oxidation of clean Ni to form NiF 2 , as calculated from Ni 2p and F Is XPS spectra, was found to be significantly higher for gas-, compared to liquid-phase AHF. Thin (ca. 100 nm), mirror-like Ni films sputtered onto the surface of a sapphire disk yielded upon exposure to gas-phase AHF (after contact with the laboratory atmosphere) scanning electron microscope images displaying a coherent, patchy structure with raised junctures. This behavior was ascribed to internal compressive stresses induced by the formation of a nickel(II) fluoride layer on the metal surface.

Garland R. Marshall - One of the best experts on this subject based on the ideXlab platform.

  • Electrochemical Cyclization of Dipeptides To Form Novel Bicyclic, Reverse-Turn Peptidomimetics. 2. Synthesis and Conformational Analysis of 6,5-Bicyclic Systems
    The Journal of Organic Chemistry, 1996
    Co-Authors: Urszula Slomczynska, David K. Chalmers, Fabrice Cornille, Mark L. Smythe, Denise D. Beusen, And Kevin D. Moeller, Garland R. Marshall
    Abstract:

    Novel, highly constrained, 6,5-bicyclic dipeptides (1-aza-5-oxa-2-oxobicyclo[4.3.0]nonane ring skeletons, 2) have been synthesized by a one-step electrochemical cyclization from the dipeptides Boc-(S)-serine-(S)-proline-OMe (Boc-(S)-Ser-(S)-Pro-OMe, 3) and Boc-(R,S)-α-methylserine-(S)-proline-OMe (Boc-(R,S)-α-MeS-(S)-Pro-OMe, 12) in yields of 10−25% and 41%, respectively. The one-pot reaction uses selective anodic amide oxidation to generate an N-acyliminium cation which is trapped by an intramolecular hydroxyl group. The cyclization of Boc-(S)-Ser-(S)-Pro-OMe (3) to the 6,5-bicyclic skeleton 4 was highly diastereoselective, generating a new chiral center with an S configuration. This bicyclic compound was sufficiently stable to trifluoroacetic Acid and Anhydrous Hydrofluoric Acid for use in standard solid phase peptide synthesis methodologies. Oxidation of Boc-(R,S)-MeS-(S)-Pro-OMe (12) gave different results for each diastereoisomer. Cyclization only occurred for the S,S-diastereoisomer with very low st...