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  • 51.
    Rutland, Mark W.
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. SP Tech Res Inst, Sweden.
    Liljeblad, Jonathan D. F.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Tyrode, Eric
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Thormann, Esben
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Dublanchet, Ann-Claude
    Luengo, Gustavo
    Johnson, C. Magnus
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Long chained fatty acid monolayers: Influence of methyl branching2014Ingår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 247, s. 61-COLL-Artikel i tidskrift (Övrigt vetenskapligt)
  • 52. Salter, M. E.
    et al.
    Hamacher-Barth, E.
    Leck, C.
    Werner, J.
    Johnson, C. Magnus
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Riipinen, I.
    Nilsson, E. D.
    Zieger, P.
    Calcium enrichment in sea spray aerosol particles2016Ingår i: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 43, nr 15, s. 8277-8285Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Sea spray aerosol particles are an integral part of the Earth's radiation budget. To date, the inorganic composition of nascent sea spray aerosol particles has widely been assumed to be equivalent to the inorganic composition of seawater. Here we challenge this assumption using a laboratory sea spray chamber containing both natural and artificial seawater, as well as with ambient aerosol samples collected over the central Arctic Ocean during summer. We observe significant enrichment of calcium in submicrometer (<1m in diameter) sea spray aerosol particles when particles are generated from both seawater sources in the laboratory as well as in the ambient aerosols samples. We also observe a tendency for increasing calcium enrichment with decreasing particle size. Our results suggest that calcium enrichment in sea spray aerosol particles may be environmentally significant with implications for our understanding of sea spray aerosol, its impact on Earth's climate, as well as the chemistry of the marine atmosphere.

  • 53. Schwind, Markus
    et al.
    Hosseinpour, Saman
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Johnson, C. Magnus
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Langhammer, Christoph
    Zoric, Igor
    Leygraf, Christofer
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Kasemo, Bengt
    Combined in Situ Quartz Crystal Microbalance with Dissipation Monitoring, Indirect Nanoplasmonic Sensing, and Vibrational Sum Frequency Spectroscopic Monitoring of Alkanethiol-Protected Copper Corrosion2013Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 29, nr 23, s. 7151-7161Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study, we have applied three techniques to simultaneously and in situ study the initial stage of corrosion of copper protected by a self-assembled monolayer of octadecanethiol (ODT). We combined quartz crystal microbalance with dissipation monitoring (QCM-D), indirect nanoplasmonic sensing (INPS), and vibrational sum frequency spectroscopy (VSFS) and obtained complementary information about mass uptake and optical and spectroscopic changes taking place during the initial corrosion phase. All three techniques are very sensitive to the formation of a corrosion film (thickness in the range 0-0.41 nm) under mildly corrosive conditions (dry air, <0.5% relative humidity). The three techniques yield information about the viscoelasticity of the corrosion film (QCM-D), the homogeneity of the corrosion reaction on the surface (INPS), and the stability of the ODT. protection layer (VSFS). Furthermore, by also studying the corrosion process in humid air (ca. 70% relative humidity), we illustrate how the combination of these techniques can be used to differentiate between simultaneously occurring processes, such as water adsorption and corrosion product formation.

  • 54. Sugiharto, A. B.
    et al.
    Johnson, Claes Magnus
    De Aguiar, H. B.
    Alloatti, L.
    Roke, S.
    Generation and application of high power femtosecond pulses in the vibrational fingerprint region2008Ingår i: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 91, nr 2, s. 315-318Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present a novel high power femtosecond infrared laser source, based on a three-stage chirped-pulse amplification scheme. Owing to the high power output of the Ti:sapphire amplifiers, it becomes routinely possible to produce femtosecond infrared laser pulses in the wavelength region of 2.6-20 mu m with minimum pulse energies of 15 mu J, to our knowledge roughly an improvement of an order of magnitude. With such pulses we have performed femtosecond second-order nonlinear optical surface spectroscopy in the fingerprint region. We have probed the skeletal modes of the first few monolayers of a polymer/air interface in a femtosecond vibrational sum frequency generation experiment. This development opens up new possibilities to investigate surface structures and dynamics of, e.g., organo-metallic compounds, proteins, and peptides.

  • 55. Sugiharto, A. B.
    et al.
    Johnson, Claes Magnus
    Dunlop, I. E.
    Roke, S.
    Delocalized surface modes reveal three-dimensional structures of complex biomolecules2008Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 112, nr 20, s. 7531-7534Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Interfaces are important for many processes in chemistry, physics, and biology. Crucial to their properties are the details of the three-dimensional structure of the participating (macro) molecules. Vibrational Sum Frequency Generation (VSFG) is a tool specifically suited to probing the first few atomic layers of an interface. Traditionally, interfaces are probed by mapping localized vibrational modes. Here, we show that the three-dimensional structure of large interfacial biomolecules can be probed by measuring delocalized vibrational backbone modes, which appear to be extremely sensitive to changes in the skeletal structure. We demonstrate that for three different films of chemically identical poly(lactic acid) polymer, we can observe dramatic changes in the three-dimensional arrangement of the surface molecular backbones. This type of information could not be obtained from probing only localized group modes.

  • 56.
    Tyrode, Eric
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi.
    Johnson, C. Magnus
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Yt- och korrosionsvetenskap.
    Claesson, Per M.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi.
    Rutland, Mark W.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi.
    COLL 153-Molecular ordering at the liquid/air interface and hydration of surfactants2006Ingår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 232Artikel i tidskrift (Övrigt vetenskapligt)
  • 57.
    Tyrode, Eric
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Johnson, Claes Magnus
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Rutland, Mark W
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Claesson, Per M
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Structure and hydration of poly(ethylene oxide) surfactants at the air/liquid interface. A vibrational sum frequency spectroscopy study2007Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 111, nr 31, s. 11642-11652Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Adsorption layers of penta(ethylene oxide) n-dodecyl ether (C12E5) at the air/liquid interface have been studied using the surface-sensitive technique vibrational sum frequency spectroscopy (VSFS). The CH and COC stretching vibrations of the surfactant molecule, as well as the OH stretching vibrations of the surface water molecules, have been targeted to obtain a comprehensive picture of the adsorption process. The concentration range studied comprises different adsorption regimes, starting from the neat water surface until attaining the saturated liquid expanded monolayer when approaching the critical micellar concentration (cmc). The surfactant molecules were found to first adsorb to the air-liquid interface with their hydrocarbon tails preferentially orientated close to the surface plane, surrounded by patches of unperturbed surface water. These patches were only seen to disappear at areas per molecule close to 65 A(2), coinciding with a sudden change in the orientation of the surfactant alkyl chains, which adopted a more upright configuration. Nonetheless, gauche defects in the hydrocarbon tails were observed along the whole concentration range, even above the cmc. Moreover, the poly(ethylene oxide) headgroup was seen to induce a significant structuring of the water molecules in direct proximity to the surfactant monolayer, despite being themselves substantially disordered. Comparison of the hydration fingerprint region is made with another non-ionic surfactant with a sugar-based headgroup. The temperature effect in the VSFS spectra of C12E4 and C12E8 solutions has also been considered, and the results are discussed in terms of the different models proposed to explain the peculiar temperature dependence of ethylene oxide-based surfactants and polymers in water.

  • 58.
    Tyrode, Eric
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Johnson, Magnus
    KTH, Skolan för kemivetenskap (CHE), Kemi, Korrosionslära.
    Baldelli, Steve
    Leygraf, Christofer
    KTH, Skolan för kemivetenskap (CHE), Kemi, Korrosionslära.
    Rutland, Mark
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    A vibrational sum frequency spectroscopy study of the liquid-gas interface of acetic acid-water mixtures: 2: orientation analysis2005Ingår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 109, nr 1, s. 329-341Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Vibrational sum frequency spectroscopy has been used to investigate the surface of aqueous acetic acid solutions. By studying the methyl and carbonyl vibrations with different polarization combinations, an orientation analysis of the acetic acid molecules has been performed in the concentration range 0-100%. The surface tension of acetic acid solutions was also measured in order to obtain the surface concentration. The orientation of the interfacial acetic acid molecules was found to remain essentially constant in an upright position with the methyl group directed toward the gas phase in the whole concentration range. The tilt angle (theta(CH3)) of the symmetry axis of the methyl group with respect to the surface normal was found to be lower than 15degrees when considering a delta distribution of angles or as narrow as 0 +/- 11degrees when assuming a Gaussian distribution. Further investigations showed that the C=O bond tilt (theta(C=O)) of the acetic acid hydrated monomer was constant and close to 55degrees in the concentration range where it was detected. Finally, the orientation information is discussed in terms of different species of acetic acid, where the formation of a surface layer of acetic acid cyclic dimers is proposed at high acid concentrations.

  • 59.
    Tyrode, Eric
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Johnson, Magnus
    KTH, Skolan för kemivetenskap (CHE), Kemi, Korrosionslära.
    Kumpulainen, Atte
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Rutland, Mark
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Claesson, Per
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Hydration State of Non-ionic Surfactant Monolayers at the Liquid/Vapor Interface:  Structure Determination by Vibrational Sum Frequency Spectroscopy2005Ingår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 127, nr 48, s. 16848-16859Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The OH stretching region of water molecules in the vicinity of nonionic surfactant monolayers has been investigated using vibrational sum frequency spectroscopy (VSFS) under the polarization combinations ssp, ppp, and sps. The surface sensitivity of the VSFS technique has allowed targeting the few water molecules present at the surface with a net orientation and, in particular, the hydration shell around alcohol, sugar, and poly(ethylene oxide) headgroups. Dramatic differences in the hydration shell of the uncharged headgroups were observed, both in comparison to each another and in comparison to the pure water surface. The water molecules around the rigid glucoside and maltoside sugar rings were found to form strong hydrogen bonds, similar to those observed in tetrahedrally coordinated water in ice. In the case of the poly(ethylene oxide) surfactant monolayer a significant ordering of both strongly and weakly hydrogen bonded water was observed. Moreover, a band common to all the surfactants studied, clearly detected at relatively high frequencies in the polarization combinations ppp and sps, was assigned to water species located in proximity to the surfactant hydrocarbon tail phase, with both hydrogen atoms free from hydrogen bonds. An orientational analysis provided additional information on the water species responsible for this band.

  • 60.
    Tyrode, Eric
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Johnson, Magnus
    KTH, Skolan för kemivetenskap (CHE), Kemi, Korrosionslära.
    Rutland, Mark
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Day, James P. R.
    Bain, Colin D.
    A study of the adsorption of ammonium perfluorononanoate at the air-liquid interface by vibrational sum-frequency spectroscopy2007Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 111, nr 1, s. 316-329Artikel i tidskrift (Refereegranskat)
    Abstract [en]

     Vibrational sum frequency spectroscopy (VSFS) has been used to study the adsorption of ammonium perfluorononanoate (APFN) at the air-liquid interface, specifically targeting the C-F and carboxylate stretches. In the spectral region extending from 1050 to 1850 cm(-1), three major peaks situated at 1369, 1408, and similar to 1665 cm(-1) were detected under the polarization combinations ssp, ppp, and sps. The first of these peaks was assigned to CF3 stretching vibrations after a detailed comparison with other surfactant molecules with different degrees of fluorination, while the last two resonant features were assigned to symmetric and antisymmetric carboxylate stretching vibrations. From the combined analysis of the VSFS, ellipsometry, and previous FTIR measurements, a consistent physical model for the adsorption of APFN to the liquid surface is proposed. At low surface coverages the APFN molecules lie essentially flat on the surface. At concentrations from 1 mM to the critical micellar concentration (molecular areas < 70 angstrom(2)) the mean orientation of both the surfactant head group and terminal CF3 group remained constant. The formation of surface micelles at higher concentrations is consistent with the experimental data.

  • 61.
    Tyrode, Eric
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Niga, Petru
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Johnson, Magnus
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Rutland, Mark W.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Molecular Structure upon Compression and Stability toward Oxidation of Langmuir Films of Unsaturated Fatty Acids: A Vibrational Sum Frequency Spectroscopy Study2010Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, nr 17, s. 14024-14031Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Vibrational sum frequency spectroscopy (VSFS) has been used to determine the stability toward oxidation in air of a series of unsaturated fatty acids, measuring as a function of time the changes in the chemical structure and conformational order of films spread on a Langmuir trough. The fatty acids studied consisted of a 20-carbon backbone with increasing numbers of cis double bonds in the chain: 11c-eicosenoic acid (20:1 EA, omega-9), 11c,14c-eicosadienoic acid (20:2 EA, omega-6), and 11c, 14c, 17c-eicosatrienoic acid (20:3 EA, omega-3). Measurements at constant surface pressure show that double bonds are lost from the surface region and that drops in intensity of the vinyl CH stretch are detectable within a few minutes of spreading the monolayer. The results are consistent with the fatty acid peroxidation free radical mechanism. The sum frequency spectra also reveal that what remains on the surface is conformationally more disordered with a larger number of gauche defects. The oxidation kinetics are found to be strongly dependent on the packing density of the monolayer, being more stable at higher pressures. Oxidation can be avoided by purging the system in an inert atmosphere. Finally, the molecular structure upon compression was tracked in unoxidized monolayers. The results suggest that the packing and orientation of the double bond sections of all three unsaturated fatty acids show remarkable similarities, with the direction of the double bonds approximately parallel to each other irrespective of the number of unsaturations in the chain, with the 20:3 EA probably forming "iron-angle" structures. The possibility of unsaturated chains in a "hairpin" configuration is discarded for area per molecules smaller than similar to 50 angstrom(2), which corresponds to the lowest surface pressure measured with VSFS.

  • 62.
    Tyrode, Eric
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Niga, Petru
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Johnson, Magnus
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Rutland, Mark W.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Molecular Structure upon Compression and Stability towards Oxidation of Langmuir Films of Unsaturated Fatty Acids: a Vibrational Sum Frequency Spectroscopy StudyArtikel i tidskrift (Övrigt vetenskapligt)
12 51 - 62 av 62
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  • en-GB
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