| 1. |
- Oberg, K., et al.
(author)
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Comparison of monolayer films of stearic acid and methyl stearate on an Al2O3 surface
- 2001
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In: Thin Solid Films. - : Elsevier. - 0040-6090. ; 397:1-2, s. 102-8
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Journal article (peer-reviewed)abstract
- Both stearic acid and methyl stearate chemisorbs onto an oxide surface of aluminum with an asymmetric coordination of the carboxylate group as concluded from infrared (IR) spectroscopy data. Similarities in the IR spectra of the films from the two compounds suggest that the ester is bonded in the same way as the acid, and that the ester therefore undergoes hydrolysis during the surface reaction. X-Ray photoelectron spectroscopy (XPS) and IR data are interpreted in terms of self-assembled monolayer formation and a more dense film from the carboxylic acid in comparison with that from the ester. (C) 2001 Elsevier Science B.V. All rights reserved.
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| 2. |
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| 3. |
- Chernyschova, Irina V., et al.
(author)
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Mechanism of adsorption of long-chain alkylamines on silicates : a spectroscopic study. 2. Albite
- 2001
-
In: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 17:3, s. 775-785
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Journal article (peer-reviewed)abstract
- Using FTIR (DRIFTS and IRRAS) and XPS spectroscopy, ζ potential measurements, and Hallimond flotation tests, we confirmed that long-chain primary amines are adsorbed on silicates at pH 6-7 through the 2D-3D precipitation mechanism. The orientation and packing of dodecyl- and hexadecylammonium acetate and chloride adsorbed on albite in the different regions of the adsorption isotherm were determined. It was shown that these characteristics depend strongly on the substrate. Coadsorption of the counterion was not revealed, but the counterion was found to affect indirectly the adsorption at concentrations above the concentration of the bulk amine precipitation
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| 4. |
- Chernysova, Irina V., et al.
(author)
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Mechanism of adsorption of long-chain alkylamines on silicates. A spectroscopic study. 1. Quartz
- 2000
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In: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 16:21, s. 8071-8084
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Journal article (peer-reviewed)abstract
- The mechanism of adsorption of long-chain alkylamines at pH 6-7 onto quartz was studied using FTIR and XPS spectroscopy. The spectroscopic data were correlated with ζ potential and Hallimond flotation results. For the first time it was shown that (1) amine cation in the first monolayer is H-bonded with surface silanol group and this H-bond becomes stronger after the break in the adsorption characteristics (isotherm, ζ potential, floatability); (2) at the break the origin of the adsorbed amine species changes qualitatively, and along with alkylammonium ion attached to deprotonated silanol group, molecular amine appears at the surface and, as a result, monolayer thick patches of well-oriented and densely packed adsorbed amine species form rendering the surface highly hydrophobic; and (3) at higher amine concentration, bulk precipitation of molecular amine takes place. The counterion was found to influence both these steps. A model of successive two-dimensional and three-dimensional precipitation was suggested to explain amine adsorption on a silicate surface.
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| 5. |
- Eriksson, Johan, et al.
(author)
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Binding of 2,4,6-Trinitrotoluene, Aniline, and Nitrobenzene to Dissolved and Particulate Soil Organic Matter
- 2004
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In: Environmental Science & Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 38:11, s. 3074-80
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Journal article (peer-reviewed)abstract
- The distribution of TNT* (the sum of TNT and its degradation products), aniline, and nitrobenzene between particulate organic matter (POM), dissolved soil organic matter (DOM), and free compound was studied in controlled kinetic (with and without irradiation) and equilibrium experiments with mixtures of POM and DOM reflecting natural situations in organic rich soils. The binding of TNT* to POM was fast, independent of irradiation, and adsorption isotherms had a great linear contribution (as determined by a mixed model), indicative of a hydrophobic partitioning mechanism. The binding of TNT* to DOM was slower, strongly enhanced under nonirradiated conditions, and adsorption isotherms were highly nonlinear, indicative of a specific interaction between TNT derivatives and functional groups of DOM. Nitrobenzene was associated to both POM and DOM via hydrophobic partitioning, whereas aniline binding was dominated by specific binding to POM and DOM functional groups. On the basis of nitrobenzene and TNT* adsorption parameters determined by a mixed Langmuir + linear model, POM had 2-3 times greater density of hydrophobic moieties as compared to DOM. This difference was reflected by a greater (O + N)/C atomic ratio for DOM. The sum of C-C and C-H moieties, as determined by X-ray photoelectron spectroscopy (XPS), and the sum of aryl-C and alkyl-C, as determined by solid-state cross-polarization magic-angle spinning (CP-MAS) 13C NMR, could only qualitatively account for differences in adsorption parameters. Aliphatic C was found to be more important for the hydrophobic partitioning than aromatic C. On the basis of nonlinear adsorption parameters, the density of functional groups reactive with aniline and TNT derivatives was 1.3-1.4 times greater in DOM than in POM, which was in fair agreement with 13C NMR and XPS data for the sum of carboxyl and carbonyl groups as potential sites for electrostatic and covalent bonding. We conclude that in contaminated soils characterized by continuous leaching of DOM, formation of TNT derivatives (via biotic and abiotic reductive degradation) and their preference for specific functional groups in DOM may contribute to a significant transportation of potentially toxic TNT compounds into surface waters and groundwaters.
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| 6. |
- Ramstedt, Madeleine, et al.
(author)
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Characterization of hydrous manganite (-MnOOH) surfaces - an XPS study
- 2002
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In: Surface and Interface Analysis. - : Wiley. - 0142-2421. ; 34:1, s. 632-6
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Journal article (peer-reviewed)abstract
- Crystalline manganite (-MnOOH) has been synthesized and characterized using x-ray diffraction and high-resolution transmission electron microscopy techniques. The surface composition was studied with XPS between pH 0.4 and 11. Special pre-cooling procedures were developed to keep the manganite/water interface intact before and during XPS measurements. The O/OH group ratio differs between pH 6 and 11, in agreement with the acid/base characteristics of the surface. Below pH 6, on the other hand, drastic changes can be seen in the O 1s spectra due to dissolution of manganite. Possibly the interaction of OH groups with H+ in acidic suspensions is a first step leading to dissolution. The surface charge arising at high and low pH is compensated by the counter-ions Na+ and Cl-, respectively. The XPS spectra are presented and discussed in terms of the mechanisms for surface complexation and dissolution processes.
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| 7. |
- Ramstedt, Madeleine, et al.
(author)
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Chemical speciation of N-(phosphonomethyl)glycine in solution and at mineral interfaces
- 2004
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In: Surface and Interface Analysis. - : Wiley. - 0142-2421 .- 1096-9918. ; 36:8, s. 1074-7
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Journal article (peer-reviewed)abstract
- The chemical speciation of the zwitterionic compound N-(phosphonomethyl)glycine (PMG) was studied in solution and at the mineral/water interface at different pH. Results from vacuum techniques such as XPS were compared with previously published conventional batch experiments. It was shown that by keeping the samples frozen during XPS analyses it was possible to keep a water interface. The frozen interface enables studies of the protonation of the nitrogen group which has previously been difficult using XPS. The protonation in frozen solutions was compared with literature data and the differences discussed. Furthermore, the speciation of PMG at the surface of manganite (-MnOOH) and goethite (-FeOOH) was studied. It was found that at least one of the protonation constants for surface-bound PMG differs significantly from the protonation constants in a pure PMG solution. The formation of different surface complexes is discussed together with differences between the sorption capacities of PMG onto the minerals studied.
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| 8. |
- Ramstedt, Madeleine, et al.
(author)
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Surface Properties of Hydrous Manganite (γ-MnOOH) : A Potentiometric, Electroacoustic, and X-ray Photoelectron Spectroscopy Study
- 2004
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In: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 20:19, s. 8224-8229
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Journal article (peer-reviewed)abstract
- The acid-base characteristics of the manganite (-MnOOH) surface have been studied at pH above 6, where dissolution is negligible. Synthetic microcrystalline particles of manganite were used in the experiments. From potentiometric titrations, electrophoretic mobility measurements, and X-ray photoelectron spectroscopy (XPS), a one pKa model was constructed that describes the observed behavior. The data show no ionic strength effect at pH < 8.2, which is the pH at the isoelectric point (pHiep), but ionic strength effects were visible above this pH. To explain these observations, Na+ ions were suggested to form a surface complex. The following equilibria were established: =MnOH2+1/2 =MnOH-1/2 + H+, log 0 (intr.) = -8.20; =MnOH2+1/2 + Na+ =MnOHNa+1/2 + H+, log 0 (intr.) = -9.64. The excess of Na+ at the surface was supported by XPS measurements of manganite suspensions containing 10 mM NaCl. The dielectric constant of synthetic manganite powder was also determined in this study.
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| 9. |
- Shchukarev, Andrey, et al.
(author)
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XPS imaging of surface diffusion of alkylketene dimer on paper surfaces
- 2003
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In: Colloids and Surfaces A: Physicochemical and Engineering Aspects. ; 219:1-3, s. 35-43
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Journal article (peer-reviewed)abstract
- The alkylketene dimer (AKD) wax dispersion is introduced in the wet-end of a paper machine, and during drying it spreads and anchors to the fiber surface. Direct observation of the surface diffusion of the AKD wax at paper surfaces was obtained using X-ray photoelectron spectroscopy imaging technique. An AKD diffusion of approximately 400 μm was observed at a paper surface that was stored for 3 h at 80 °C. This gives a diffusion coefficient of approximately 10−11 m2 s−1. Storage for 1 week at room temperature also showed a remarkable spreading of AKD.
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| 10. |
- Shchukarev, Andrey, et al.
(author)
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XPS study of living tree : Per Persson
- 2002
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In: Surface and Interface Analysis. - : Wiley. - 0142-2421 .- 1096-9918. ; 34:1, s. 284-8
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Journal article (peer-reviewed)abstract
- X-ray photoelectron spectroscopy (XPS) was used to study the distribution of elements and main wood components (cellulose and lignin) within the wood and at the bark/wood interface of a living hybrid aspen stem. The hybrid aspen was grown upright in a greenhouse and then tilted at 45° to induce tension wood formation and upright bending of the stem. The wood between the pith and the bark on the upper side of the tilted stem was analysed. Changes in the middle lamella/S1 layer chemical composition, which corresponded to the transition from normal wood produced during upright stem growth to tension wood produced upon stem tilting, were observed. Such changes were related to the lower lignin and higher cellulose/hemicellulose contents in the tension wood. A non-uniform radial distribution of nitrogen (amino acids, proteins) within the stem was also noted. At the bark/wood interface the presence of inorganic elements (Ca, K and P) and a significant increase in nitrogen were found. The opposite wood side of the tree was enriched in lignin and fatty acids. It was shown that application of XPS imaging to a very rough surface of wood split allows the inhomogeneous lateral lignin distribution to be visualized. Copyright © 2002 John Wiley & Sons, Ltd.
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| 11. |
- Shchukarev, Andrey, et al.
(author)
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XPS study of the silica–water interface
- 2004
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In: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048. ; 137-140, s. 171-6
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Journal article (peer-reviewed)abstract
- XPS was applied to study the silica–water interface formed in NaCl solution at variable pH (2–9) and ionic strength (10–600 mM).To prevent alteration of the interface, the wet silica pastes were precooled with liquid nitrogen. After measurements under liquid nitrogen, XPS spectra were collected the next day at room temperature to follow changes at the silica surface caused by water loss.XPS data show that, at low ionic strength (<20 mM), Cl− ions could not be detected at the surface even at the lowest pH. Changes of the Na/Si atomic ratio with pH are in close agreement with the adsorption curve of OH− ions. At higher ionic strength (>100 mM), the silica surface’s point of zero charge can be determined from the Na/Cl atomic ratio. At pH 9 the amount of “free” Na+ at the surface is independent of NaCl concentration reflecting the formation of SiO---Na bonds, confirmed by O 1s spectra.Removing water from the sample surface allows determination of a “built-in” potential at the interface. Si 2p and O 1s spectra of the matrix shift to lower BE values whereas Na 1s and Cl 2p lines of the counter-ions shift to higher BE. At higher ionic strength and pH<2, shifts of Si 2p and O 1s spectra change sign, reflecting the formation of positively charged silica surfaces. The absolute value of the photoelectron line shifts for the matrix elements does not exceed 0.25 eV at any pH, whereas the shifts for counter-ions can reach 0.6 eV. The shifts decrease with increasing ionic strength, implying the formation of a more compact interface.
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| 12. |
- Öberg, Kjell, et al.
(author)
-
Comparison of monolayer films of stearic acid and methyl stearate on an Al2O3 surface
- 2001
-
In: Thin Solid Films. ; 397:1-2, s. 102-8
-
Journal article (peer-reviewed)abstract
- Both stearic acid and methyl stearate chemisorbs onto an oxide surface of aluminum with an asymmetric coordination of the carboxylate group as concluded from infrared (IR) spectroscopy data. Similarities in the IR spectra of the films from the two compounds suggest that the ester is bonded in the same way as the acid, and that the ester therefore undergoes hydrolysis during the surface reaction. X-Ray photoelectron spectroscopy (XPS) and IR data are interpreted in terms of self-assembled monolayer formation and a more dense film from the carboxylic acid in comparison with that from the ester.
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| 13. |
- Öberg, Kjell, et al.
(author)
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Spectroscopic Characterization of the Bonding, Orientation, and Coverage of Copper Tetraazaphthalocyanine Monolayer Films on SiO2 Surfaces
- 2000
-
In: The Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 104:45, s. 10627-34
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Journal article (peer-reviewed)abstract
- Self-assembled monolayer films of a metallotetraazaphthalocyanine were prepared using two different reaction conditions. The films were characterized by ellipsometry, AFM, electronic absorption spectroscopy, semiempirical MO calculations, core-level XPS, and projection of a calculated structure of the chromophore onto a surface to obtain its silhouette area for comparison with surface concentration from absorption spectroscopy. A denser packing of the chromophores is found in the SAM film prepared with bromonaphthalene at 250 C as compared with the film from the more polar solvent DMF at 120 C. Data is consistent with an almost vertical orientation of the chromophores in the former film. A different number of bonds connecting the chromophore with the coupling molecule is suggested as an explanation to differences in the absorption bands for the two films.
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