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  • 6951.
    Zou, Haiyuan
    et al.
    Harbin Inst Technol, Sch Chem & Chem Engn, 92 West Da Zhi St, Harbin 150001, Heilongjiang, Peoples R China.;Southern Univ Sci & Technol, Dept Chem, Shenzhen 518055, Peoples R China.;Southern Univ Sci & Technol, Shenzhen Grubbs Inst, Shenzhen 518055, Peoples R China..
    Li, Ge
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Duan, Lele
    Southern Univ Sci & Technol, Dept Chem, Shenzhen 518055, Peoples R China.;Southern Univ Sci & Technol, Shenzhen Grubbs Inst, Shenzhen 518055, Peoples R China..
    Kou, Zongkui
    Harbin Inst Technol, Sch Chem & Chem Engn, 92 West Da Zhi St, Harbin 150001, Heilongjiang, Peoples R China.;Natl Univ Singapore, Dept Mat Sci & Engn, Singapore 117574, Singapore..
    Wang, John
    Natl Univ Singapore, Dept Mat Sci & Engn, Singapore 117574, Singapore..
    In situ coupled amorphous cobalt nitride with nitrogen-doped graphene aerogel as a trifunctional electrocatalyst towards Zn-air battery deriven full water splitting2019In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 259, article id UNSP 118100Article in journal (Refereed)
    Abstract [en]

    Herein, we report a new type of efficient trifunctional electrocatalyst by in situ coupling amorphous cobalt nitride (CoNx) nanoparticles within three-dimensional (3D) nitrogen-doped graphene aerogel (NGA). The CoNx/NGA nanohybrid with hierarchical porous strucuture guarantees the superior activities toward ORR, OER and HER, due to abundant dual active CoNx. and NxC sites. Impressively, it also exhibits a long lifetime and exceptionally high electrochemical performances as a cathode and an anode in a two-electrode overall water splitting electrolyzer, and also as an air-cathode in a rechargeable Zn-air battery. In addition, the CoNx/NGA-based water splitting electrolyzer and two Zn-air batteries can be integrated together to effectively self-drive electrochemical water splitting device with high gas evolution rates of 186 and 372 mu mol h(-1) for O-2 and H-2, respectively. This work paves a way for designing advanced non-noble multifunctional catalysts, aiming for the real application of energy storage and conversion devices.

  • 6952. Zou, Qi
    et al.
    Li, Xin
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Xu, Qunjie
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Zhao, Wandong
    Qu, Yi
    A near-infrared "on-off" fluorescent and colourimetric cyanide chemodosimeter based on phenothiazine with applications in living cell imaging2014In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 4, no 104, p. 59809-59816Article in journal (Refereed)
    Abstract [en]

    A great deal of effort has been devoted to developing easy-to-use near-infrared probes for detecting analytes due to their advantages in the field of biosensing. Herein, a near-infrared "on-off" fluorescent chemodosimeter PTZ based on dicyano-vinyl-functionalised phenothiazine was designed and synthesised. The PTZ compound was shown to efficiently recognise cyanide ions in aqueous media by virtue of the special nucleophilicity of cyanide ions, which affects the intramolecular charge transfer efficiency in the molecule. Furthermore, it was found that it exhibited a rapid colourimetric and quenchable near-infrared (NIR) fluorescent response to cyanide ions with a detection limit as low as 67 nM, and that other anions showed almost no interference even at high concentrations. Optical spectroscopic measurements, H-1 NMR and mass spectrometry titrations, and theoretical simulations were carried out to elucidate the sensing mechanism of compound PTZ. Moreover, potential applications of this compound for biosensing have been exemplified by the successful fluorescent microscopic imaging for the detection of cyanide ions in HeLa cells.

  • 6953. Zou, Qi
    et al.
    Li, Xin
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Configurable photochromism of an unsymmetrical dithienylethene derivative by Cu2+ ions or water2014In: Dyes and pigments, ISSN 0143-7208, E-ISSN 1873-3743, Vol. 111, p. 1-7Article in journal (Refereed)
    Abstract [en]

    We describe a gated photochromic behavior of an unsymmetrical dithienylethene derivative, which is intrinsically inert to photoisomerization in organic solvents and which is activated by addition of Cu2+ ions or water. The mechanism behind the gated photochromic property is interpreted by theoretical simulations, suggesting that the energy levels of frontier molecular orbitals are altered by the interaction of the Schiff base moiety with Cu2+ ions or water molecules. Potential applications of such gated photochromic materials have been exemplified not only by the reversible interchange between the photoactive and photoinactive states triggered by Cu2+ ions and EDTA, but also by the construction of a keypad with sequence-dependent input signals at the molecular level.

  • 6954. Zou, Yidong
    et al.
    Wang, Xiangxue
    Ai, Yuejie
    Liu, Yunhai
    Ji, Yongfei
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Wang, Hongqing
    Hayat, Tasawar
    Alsaedi, Ahmed
    Hu, Wenping
    Wang, Xiangke
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    beta-Cyclodextrin modified graphitic carbon nitride for the removal of pollutants from aqueous solution: experimental and theoretical calculation study2016In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 4, no 37, p. 14170-14179Article in journal (Refereed)
    Abstract [en]

    A novel beta-cyclodextrin modified, multifunctional, layer-by-layer graphitic carbon nitride (g-C3N4/beta-CD) was successfully synthesized and applied as an effective adsorbent for the removal of methyl orange (MO) and Pb(II) from aqueous solutions under various environmental conditions (e.g., solution pH, solid content, contact time and temperature). The kinetic results indicated that the adsorption was dominated by chemisorption, and the higher adsorption capacity of g-C3N4/beta-CD was attributed to it having more oxygen-containing functional groups than g-C3N4. The Langmuir, Freundlich and Sips models were applied to simulate the adsorption isotherms of MO and Pb(II), and the results demonstrated that the adsorption of MO was attributed to multilayer adsorption, while the coverage adsorption of Pb(II) on the g-C3N4/beta-CD was monolayer adsorption. The thermodynamic parameters showed that the adsorption of both MO and Pb(II) was spontaneous and endothermic. The DFT calculations further evidenced the surface complexation and electrostatic interaction of Pb(II) on the g-C3N4 and g-C3N4/beta-CD, whereas, the interaction of MO with g-C3N4 and g-C3N4/beta-CD was mainly attributed to hydrogen bonds and strong pi-pi interactions. The results demonstrated that g-C3N4/beta-CD is a promising material for the efficient removal of organic and inorganic pollutants in environmental pollution remediation.

  • 6955.
    Zuleta, Marcelo
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Björnbom, Pehr
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Lundblad, Anders
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Effects of pore surface oxidation on electrochemical and mass-transport properties of nanoporous carbon2005In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 152, no 2, p. A270-A276Article in journal (Refereed)
    Abstract [en]

    A new nanoporous (NP) carbon material with a high surface area and a narrow pore size distribution, around 8 A, has been used to investigate the effects that electrochemical oxidation at positive potentials exerts on the capacitance values and effective diffusion coefficients of ions inside the nanopores. An electroanalytical method, based on the single-particle microelectrode technique with micromanipulator, was applied to calculate the diffusion coefficients of 6 M KOH ions in NP carbon. The results were analyzed for short times using the Cottrell model and for long times using the spherical diffusion model. Using cyclic voltammetry, was found that different stages of oxidation took place between 0 and 0.5 V vs. Hg\HgO. After repeated cycling in the first region of oxidation (0-0.3 V), an activation leading to higher capacitance was observed, but the diffusion coefficients decreased from approximately 2 x 10(-9) to 0.5 x 10(-10) cm(2) s(-1). In the second region of oxidation (0.3-0.5 V), where CO2 and 02 evolution can occur, both the capacitance and the diffusion coefficients decreased more dramatically. The effective diffusion coefficients of ions of an activated carbon particle were dependent on the operation potential; decreasing by an order of magnitude when going from -0.3 to +0.3 V. The results are discussed in terms of chemisorption of small oxygen functional groups (-OH or C=O) and ionic interaction with the pore wall.

  • 6956.
    Zuleta, Marcelo
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Bursell, Martin
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Björnbom, Pehr
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Lundblad, Anders
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Determination of the effective diffusion coefficient of nanoporous carbon by means of a single particle microelectrode technique2003In: Journal of Electroanalytical Chemistry, ISSN 0022-0728, E-ISSN 1873-2569, Vol. 549, p. 101-108Article in journal (Refereed)
    Abstract [en]

    A single particle microelectrode technique with a micromanipulator was applied and adapted for characterisation of mass transport properties of ionic species in a high surface area nanoporous carbon, with uniform pore size of 8 Angstrom. The effective diffusivity of 6 M KOH in this material was determined by means of potential step experiments on nanoporous carbon particles of different sizes. The results were analysed for short times (Cottrell model) and for long times (spherical diffusion model). The average effective diffusion coefficient for short and long times was 1.5x10(-9) and 1.2x10(-9) cm(2) s(-1), respectively. The relatively small diffusivity values are discussed in terms of interaction between the ion hydration shell and water molecules adsorbed on the pore wall.

  • 6957.
    Zuleta, Marcelo
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Edvinsson, Tomas
    Yu, Shun
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Ahmadi, Sareh
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Boschloo, Gerrit
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Hagfeldt, Anders
    Light-induced rearrangements of chemisorbed dyes on anatase(101)2012In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 14, no 30, p. 10780-10788Article in journal (Refereed)
    Abstract [en]

    Photoinduced molecular rearrangements are important in daily events essential for life such as visual perception and photo-protection of light harvesting complexes in plants. In this study we demonstrate that similar photoarrangements appear in an analogous technological application where the device performance is controlled by chromophores in sensitized anatase TiO2, one of the main components for light-harvesting in dye-sensitized solar cells (DSC). STM reveals that illumination leads to distortions of organic dyes containing conjugated backbones and of cis-bis(isothiocyanate)-bis-(2,2'-bipyridyl-4,4'-dicarboxylate)ruthenium(II)-bis(tetrabutylammonium), known as N719. The dyes were adsorbed in a closed-packed mode on an anatase(101) single crystal surface and imaged in the dark and under white light illumination in an ultra-high vacuum (UHV). STM images of N719 clearly suggest rearrangements caused by rotation of the dye. Conversely, organic dyes rearrange by photoisomerization depending on the number of double bonds, their position in the molecular structure and on the ligand modifications.

  • 6958.
    Zuleta, Marcelo
    et al.
    KTH, School of Information and Communication Technology (ICT).
    Yu, Shun
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Ahmadi, Sareh
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Boschloo, Gerrit
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Hagfeldt, Anders
    Monitoring N719 Dye Configurations on (1 x n)-Reconstructed Anatase (100) by Means of STM: Reversible Configurational Changes upon Illumination2010In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, no 16, p. 13236-13244Article in journal (Refereed)
    Abstract [en]

    We report experimental results concerning the STM imaging of cis-bis (isothiocyanate)-bis-(2,2'-bipyridyl-4,4'dicarboxylate)ruthenium(II)bis( tetrabutylammonium) dye (known as N719) adsorbed on a single crystal of anatase TiO2(100). The cleaning pretreatment, by sputtering and annealing, of TiO2(100) yields a reproducible (1 x n) surface reconstruction. Previous to dye deposition, TiO2 was covered with one monolayer of 4-tert-butylpyridine (4-TBP) in ultrahigh vacuum (UHV) in order to protect the surface against air contamination. N719 was subsequently deposited by dipping the crystal into the dye solution. 4-TBP was removed partially in the solution and totally by heating the sample to around 285-300 degrees C in UHV. The images of the deposited 4-TBP on TiO2(100) revealed a complete surface coverage showing three modes of adsorption on TiO2. The relatively uncomplicated desorption of 4-TBP enables the accommodation and chemisorption of most N719 molecules directly onto the TiO2 surface. The STM imaging of N719 was affected, in a reversible way, by illumination, because the quality of the image changed after a few hours in the dark or under illumination conditions. The results presented herein are discussed in terms of changes in molecular configurations and in open circuit potentials.

  • 6959.
    Zyuzin, Alexander
    et al.
    KTH, School of Engineering Sciences (SCI), Physics.
    Garaud, Julien
    KTH, School of Engineering Sciences (SCI), Physics.
    Babaev, Egor
    KTH, School of Engineering Sciences (SCI), Physics.
    Nematic Skyrmions in Odd-Parity Superconductors2017In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 119, no 16, article id 167001Article in journal (Refereed)
    Abstract [en]

    We study topological excitations in two-component nematic superconductors, with a particular focus on CuxBi2Se3 as a candidate material. We find that the lowest-energy topological excitations are coreless vortices: a bound state of two spatially separated half-quantum vortices. These objects are nematic Skyrmions, since they are characterized by an additional topological charge. The inter-Skyrmion forces are dipolar in this model, i.e., attractive for certain relative orientations of the Skyrmions, hence forming multi-Skyrmion bound states.

  • 6960.
    Álvarez Asencio, Rubén
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Bettini, Eleonora
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Pan, Jinshan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Thormann, Esben
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Rutland, Mark
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Technical Research Institute of Sweden, Sweden .
    Friction Coefficient Mapping (FCM) and Contact Adhesion Mapping (CAM): Surface Microstructure and Function2013In: 5th World Tribology Congress, WTC 2013, 2013, Vol. 4, p. 3120-3121Conference paper (Refereed)
  • 6961.
    Álvarez Asencio, Rubén
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Cranston, Emily
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Wakeham, Deborah
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Niga, Petru
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Werzer, O.
    Sweeney, J.
    Hausen, F.
    Hayes, R.
    Webber, G. B.
    Endres, F.
    Bennewitz, R.
    Hjalmarsson, Nicklas
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Glavatskih, Sergei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Atkin, R.
    Rutland, Mark
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Nanotribology: Tribotronics, ionic liquids and control of surface interactions2013In: 5th World Tribology Congress, WTC 2013, 2013, Vol. 4, p. 3106-3108Conference paper (Refereed)
    Abstract [en]

    The interfacial ordering of Ionic liquids leads to interesting nanotribological properties as revealed by colloid probe studies. The first of these is the clear correlation between the number of ion pairs trapped in the tribological contact and the friction coefficient displayed. The second is the fact that the surface electrical potential can be used to control the composition of the boundary layer and thus tune the friction. Thirdly, the interfacial ordering appears to significantly affect the fluid dynamics over large distances.

  • 6962.
    Álvarez-Asencio, Rubén
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. Institute for Advanced Studies, IMDEA Nanoscience, C/Faraday 9, Spain.
    Wallqvist, V.
    Kjellin, M.
    Rutland, Mark
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Technical Research Institute of Sweden, SP Chemistry, Materials and Surfaces, Sweden.
    Camacho, A.
    Nordgren, N.
    Luengo, G. S.
    Nanomechanical properties of human skin and introduction of a novel hair indenter2016In: Journal of The Mechanical Behavior of Biomedical Materials, ISSN 1751-6161, E-ISSN 1878-0180, Vol. 54, p. 185-193Article in journal (Refereed)
    Abstract [en]

    The mechanical resistance of the stratum corneum, the outermost layer of skin, to deformation has been evaluated at different length scales using Atomic Force Microscopy. Nanomechanical surface mapping was first conducted using a sharp silicon tip and revealed that Young’s modulus of the stratum corneum varied over the surface with a mean value of about 0.4 GPa. Force indentation measurements showed permanent deformation of the skin surface only at high applied loads (above 4 μN). The latter effect was further demonstrated using nanomechanical imaging in which the obtained depth profiles clearly illustrate the effects of increased normal force on the elastic/plastic surface deformation. Force measurements utilizing the single hair fiber probe supported the nanoindentation results of the stratum corneum being highly elastic at the nanoscale, but revealed that the lateral scale of the deformation determines the effective elastic modulus.This result resolves the fact that the reported values in the literature vary greatly and will help to understand the biophysics of the interaction of razor cut hairs that curl back during growth and interact with the skin.

  • 6963. Ågren, H.
    et al.
    Norman, P.
    Jonsson, D.
    Liegener, C.
    On the vibrational and orientational probing of surface-adsorbates by direct and resonance photoemission1994In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 311, no 3, p. 375-384Article in journal (Refereed)
    Abstract [en]

    Vibrationally resolved direct photoemission spectra of physisorbed molecules separated from the substrate by spacer layers, show remarkable splittings of vibronic progressions. The corresponding resonant photoemission spectra have recently confirmed these splittings and also revealed their strong dependence on the polarization of the exciting radiation. We apply a self-consistent mirror image model on the physisorbed nitrogen and oxygen molecules to explore the origin of these shifts and their dependence on the orientation of the adsorbate molecule with respect to the surface. The symmetry character and orientational probing of autoionization is analyzed for the resonant cases by a decomposition of the interacting matrix elements.

  • 6964.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Modeling of multi-photon-induced photoluminescence from organic fluorophores and metal-coated semiconductor nanoparticles2006In: Proceedings of International Symposium on Biophotonics, Nanophotonics and Metamaterials, 2006, p. 26-26Conference paper (Refereed)
    Abstract [en]

    In this talk I will describe some applications of multiphysics modeling of molecular and nano-particle materials that have been carried out at our department. Among the various multiphysics approaches, those that combine quantum mechanics with wave mechanics and quantum mechanics with statistical mechanics have turned out to be particularly powerful for predicting optical properties of organic fluorophores, respectively, nanoparticles. The first type of combined approach allows to estimate the optical transmission from cross sections of multi-photon absorption processes and from considerations of propagation and saturation effects. The other type of combined approach, quantum mechanics with statistical mechanics, allows to account for the spontaneous photon emission of two-photon excited quantum dots including the nonradiative energy dissipation process of phonon scattering. Multi-photon quantum dots offer the combined advantage of brilliance and photo-resistance of normal quantum dots with the 3-dimensional confocality and penetration of multi-photon excitation, something that can have a broad ramification on fluorescence based experiments in biology. We have in particular investigated multiphoton-induced photoluminescence from metal-coated coated quantum dots under the influence of electromagnetic field enhancement associated with surface plasmon resonances. It is argued that up-conversion luminescence of coated quantum dots is a promising approach for bio-imaging as it can generate the multiphoton excitation at reduced laser intensities.

  • 6965.
    Ågren, Hans
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Harczuk, Ignat
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Vahtras, Olav
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Decomposition of molecular properties2019In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 21, no 5, p. 2251-2270Article in journal (Refereed)
    Abstract [en]

    We review recent work on property decomposition techniques using quantum emical methods and discuss some topical applications in terms of antum mechanics-molecular mechanics calculations and the constructing properties of large molecules and clusters. Starting out from the -called LoProp decomposition scheme [Gagliardi et al., J. Chem. Phys., 04, 121, 4994] for extracting atomic and inter-atomic contributions to lecular properties we show how this method can be generalized to calized frequency-dependent polarizabilities, to localized perpolarizabilities and to localized dispersion coefficients. Some plications of the generalized decomposition technique are reviewed - lculations of frequency-dependent polarizabilities, Rayleigh attering of large clusters, and calculations of hyperpolarizabilities proteins.

  • 6966.
    Ågren, Hans
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Tu, Yaoquan
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Modeling of Non-linear Optic Properties of Guest-Host Systems2006In: Nonlinear Optics, Quantum Optics: concepts in modern optics, ISSN 1543-0537, Vol. 35, no 1-3, p. 39-55Article in journal (Refereed)
    Abstract [en]

    In this paper we summarize our recent work in computer modeling of nonlinear optical (NLO) properties of guest-host systems. The modeling involves quantum chemistry calculations to predict the NLO properties of a single chromophore molecule and molecular dynamics simulations to estimate the macroscopic NLO properties of the corresponding guest-host systems and to find the microscopic origin behind the macroscopic properties. The systems studied cover solutions solvated with NLO chromophores and amorphous polymers doped with dipolar chromophore molecules. Some gained insight and conclusions obtained from the combined modeling approaches are presented.

  • 6967.
    Ågren, Hans
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Tu, Yaoquan
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Luo, Yi
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Modelling nonlinear optical effects in guest-host systems2005In: Chinese Optics Letters (COL), ISSN 1671-7694, Vol. 3, no Suppl., p. S17-S22Article in journal (Refereed)
    Abstract [en]

    We briefly outline a modelling strategy, combining quantum chemistry and molecular dynamics simulations, for obtaining macroscopic nonlinear optical coefficients in guest-host systems like chromophores in solutions or in polymer matrices. The parameters required for the calculation of the macroscopic nonlinear optical property, like the chromophore number density, local field factors, and the order parameter of the chromophore molecules, are derived. These parameters, together with the molecular first hyperpolarizabilities, obtained from quantum chemistry calculations, are used to estimate the macroscopic electro-optic coefficients. The combined approach leads to some new conclusions about the relation of the chromophore property and its solvent interactions in order to optimize the nonlinear optical coefficient. For instance, from the simulation results a totally different notion is derived about the collective properties of octupolar molecules. We find that such molecules receive a solvent induced dipole moment that makes it possible to pole them by an external electric field, but also that they can aggregate as an effect of this solvent interaction.

  • 6968.
    Åhlund, John
    et al.
    Department of Physics, Uppsala University.
    Nilson, Katharina
    Department of Physics, Uppsala University.
    Schiessling, Joachim
    Department of Physics, Uppsala University.
    Kjeldgaard, Lisbeth
    MAX-lab., University of Lund.
    Berner, Simon
    Department for Surface Biotechnology, BMC, Uppsala.
    Mårtensson, Nils
    Department of Physics, Uppsala University.
    Puglia, Carla
    Department of Physics, Uppsala University.
    Brena, Barbara
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Nyberg, Mats
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Luo, Yi
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    The electronic structure of iron phthalocyanine probed by photoelectron and x-ray absorption spectroscopies and density functional theory calculations2006In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 125, no 3, p. 034709-1-034709-7Article in journal (Refereed)
    Abstract [en]

    A joint experimental and theoretical work to explain the electronic and geometrical structure of an in situ prepared film of iron phthalocyanine (FePc) on silicon (100) is presented. FePc molecular films have been characterized by core and valence photoemission spectroscopy (PES) and x-ray absorption spectroscopy (XAS), and the results have been interpreted and simulated by density functional theory (DFT) calculations. C1s and N1s PE spectra have been analyzed by taking into account all chemically nonequivalent C and N atoms in the molecule. In the Fe2p(3/2) spectra it has been possible to resolve two components that can be related to the open shell structure of the molecule. By valence PES and N1s XAS data, the geometrical orientation of the FePc molecules in the film could be determined. Our results indicate that for the FePc on Si(100), the molecules within the film are mainly standing on the surface. The experimental N1s XAS spectra are very well reproduced by the theoretical calculations, which are both angle and atomic resolved, giving a detailed description of the electronic and geometric structure of the FePc film. Furthermore, the asymmetry and the intensity angle variation of the first N1s XAS threshold feature could be explained by the presented DFT calculations as due to the chemical nonequivalence of the N atoms and the symmetry character of the lowest unoccupied molecular orbital.

  • 6969.
    Åkerstedt, Josefin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Subvalent Cluster Compounds and Synthesis in Alternative Reaction Media2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    With the aim of finding alternative reaction media for the synthesis of subvalent main group and transition metal cluster compounds, traditionally made through solid state reactions or in superacidic media, different alternative reaction media have been explored in this work. Room-temperature ionic liquids are amongst the more unconventional reaction media used. The syntheses performed have been aimed at both anionic and cationic cluster and the main tools used for characterization have been different X-ray diffraction and spectroscopic techniques.

    Selected ionic liquids have along with dichloromethane been shown to work as alternative reaction media for room temperature synthesis of the Bi5[GaCl4]3 salt. The salt containing the subvalent naked bismuth polycation Bi5 3+ was isolated from reduction reactions of BiCl3 in Ga/GaCl3-dichloromethane respectively Ga/GaCl3-ioinc liquid media. Three different classes of ionic liquids based on phosphonium-, imidazolium- and pyrrolidinium- salts have been used in synthesis. Homopolyatomic clusters from the lighter Group 15 element arsenic have also been studied. Solutions from the oxidative and reductive reaction routes of arsenic and AsCl3 in Lewis acidic toluene media were studied by EXAFS spectroscopy. The results were evaluated using molecular dynamics simulations of arsenic clusters. A discussion on how the calculated As4 cluster model relates to the experimental data resulted from this study.

    In terms of homopolyatomic anionic clusters the [K+(2,2,2-crypt)]2Ge9 2- compound containing the naked Ge9 2- anionic cluster has been isolated. The crystallographic investigation of [K+(2,2,2-crypt)]2Ge9 2- shows Zintl cluster anion Ge9 2- to be tricapped trigonal-prismatic with a symmetry very close to D3h. A chemical bonding analysis reveals two local minima of D3h symmetry and the cluster interaction scheme to be based on highly delocalised bonding.

    Ligand supported transition metal clusters from tungsten and palladium have also been prepared. Reduction of WCl6 in a reaction mixture of ionic liquid and co-solvent toluene resulted in tritungsten decachloride; W3Cl10(MeCN)3, being formed. Furthermore, palladium sandwich compounds; [Pd2(Ga2Cl7)(C7H8)2], [Pd2(GaCl4)(C9H12)2]∙C9H12 and [Pd2(Ga2Cl7)(C6H5Cl)2] have been prepared using GaCl3-arene reaction media.

  • 6970.
    Åkerstedt, Josefin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Inorganic Chemistry (closed 20110630).
    Gorlov, Mikhail
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Fischer, Andreas
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Inorganic Chemistry (closed 20110630).
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Inorganic Chemistry (closed 20110630).
    Synthesis and characterization of binuclear palladium(I) compounds and the influence of competing arenes2010In: Journal of Organometallic Chemistry, ISSN 0022-328X, E-ISSN 1872-8561, Vol. 695, no 10-11, p. 1513-1517Article in journal (Refereed)
    Abstract [en]

    The binuclear palladium(I) compounds, [Pd-2(Ga2Cl7)(2)(C7H8)(2)] (1), [Pd-2(GaCl4)(2)(C9H12)(2)]center dot C9H12 (2) and [Pd-2(Ga2Cl7)(2)(C6H5Cl)(2)] (3), have been prepared from palladium(II) chloride in gallium(III) chloride-arene reaction media. All isolated crystalline solids (1, 2 and 3) have been structurally characterized by single crystal X-ray diffraction and Raman spectroscopy. The results form quantum chemical calculations on the interaction energies of the arenes and the dipalladium unit of these compounds is also presented.

  • 6971.
    Åkerstedt, Josefin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Inorganic Chemistry.
    Ponou, Simeon
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Inorganic Chemistry.
    Lidin, Sven
    Structural Investigation of a Fully Ordered closo-Ge(9)(2-) Cluster in the Compound [K(+)(2,2,2-crypt)](2)Ge(9)(2-)2011In: European Journal of Inorganic Chemistry, ISSN 1434-1948, E-ISSN 1099-1948, no 26, p. 3999-4005Article in journal (Refereed)
    Abstract [en]

    [K(+)(2,2,2-crypt)] (2)Ge(9)(2-) containing the deltahedral Zintl anion Ge(9)(2-) has been isolated from a solution of K(4)Ge(9) in ethylenediamine in the presence of 2,2,2-crypt, intended as an intermediate in mixed-cluster synthesis. The subsequent crystallographic characterisation shows the closo-Ge(9)(2-) cluster unit to be tricapped trigonal-prismatic with a symmetry very close to D(3h). Each Ge(9)(2-) unit is surrounded by two 2,2,2-crypt units, each with a chelated K(+) cation, viz. [K(+)(2,2,2-crypt)]. The structure characterisation of this ordered Ge(9)(2-) cluster is surprisingly enough the first one reported. A chemical bonding analysis reveals two local minima of D(3h) symmetry, with that of lowest energy being highly similar to that resulting from the crystallographic analysis of low-temperature data. The cluster interaction scheme is based on highly delocalised bonding.

  • 6972.
    Åkerstedt, Josefin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Inorganic Chemistry.
    Zaffaroni, Riccardo
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Inorganic Chemistry.
    Dichloromethane as solvent for the synthesis of polycationic clusters at room temperature: a link to standard organometallic chemistry2010In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 39, no 35, p. 8132-8134Article in journal (Refereed)
    Abstract [en]

    Dichloromethane (DCM), CH2Cl2 has been identified as an alternative reaction medium for room-temperature synthesis of subvalent homopolyatomic clusters of the group 15 element bismuth.

  • 6973.
    Ålander, Eva Marie
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Rasmuson, Åke C.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Mechanisms of agglomeration of molecular crystals in organic solvents2005In: 16th International Symposium on Industrial Crystallization, September, 11 - 14, International Congress Center, Dresden, Germany, 2005, no 1901 I, p. 511-516Conference paper (Refereed)
    Abstract [en]

    The agglomeration of paracetamol has been investigated by fully seeded isothermal crystallization experiments operated at constant supersaturation. The particles from crystallization in ethanol, methyl ethyl ketone, water and acetone-water mixtures are characterized by image analysis and multivariate data evaluation. The number of crystals in each agglomerated particle is characterized and used as a measure of the degree of agglomeration. Surfaces of large, well grown paracetamol crystals have been characterised by contact angle measurements and the Lifshitz-van der Waals acid-base theory to determine the crystal-crystal adhesion energy. It is found that, beyond the effect of differences in liquid viscosity and crystal growth rate, there is a dependence of the degree of agglomeration on the solvent composition that can be correlated to the free energy of adhesion.

  • 6974.
    Öberg Hed, Kim
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Advanced polymeric scaffolds for functional materials in biomedical applications2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Advancements in the biomedical field are driven by the design of novel materials with controlled physical and bio-interactive properties. To develop such materials, researchers rely on the use of highly efficient reactions for the assembly of advanced polymeric scaffolds that meet the demands of a functional biomaterial. In this thesis two main strategies for such materials have been explored; these include the use of off-stoichiometric thiol-ene networks and dendritic polymer scaffolds. In the first case, the highly efficient UV-induced thiol-ene coupling (TEC) reaction was used to create crosslinked polymeric networks with a predetermined and tunable excess of thiol or ene functionality. These materials rely on the use of readily available commercial monomers. By adopting standard molding techniques and simple TEC surface modifications, patterned surfaces with tunable hydrophobicity could be obtained. Moreover, these materials are shown to have great potential for rapid prototyping of microfluidic devices. In the second case, dendritic polymer scaffolds were evaluated for their ability to increase surface interactions and produce functional 3D networks. More specifically, a self-assembled dendritic monolayer approach was explored for producing highly functional dendronized surfaces with specific interactions towards pathogenic E. coli bacteria. Furthermore, a library of heterofunctional dendritic scaffolds, with a controllable and exact number of dual-purpose azide and ene functional groups, has been synthesized. These scaffolds were explored for the production of cell interactive hydrogels and primers for bone adhesive implants. Dendritic hydrogels decorated with a selection of bio-relevant moieties and with Young’s moduli in the same range as several body tissues could be produced by facile UV-induced TEC crosslinking. These gels showed low cytotoxic response and relatively rapid rates of degradation when cultured with normal human dermal fibroblast cells. When used as primers for bone adhesive patches, heterofunctional dendrimers with high azide-group content led to a significant increase in the adhesion between a UV-cured hydrophobic matrix and the wet bone surface (compared to patches without primers).

  • 6975.
    Öberg, Helena
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Brinck, Tore
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Fragment molecular orbital study of the cAMP-dependent protein kinase catalyzed phosphoryl transfer: a comparison with the differential transition state stabilization method2016In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 18, no 22, p. 15153-15161Article in journal (Refereed)
    Abstract [en]

    The importance of key residues to the activity of the cAMP-dependent protein kinase catalyzed phosphoryl transfer and to the stabilization of the transition state of the reaction has been investigated by means of the fragment molecular orbital (FMO) method. To evaluate the accuracy of the method and its capability of fragmenting covalent bonds, we have compared stabilization energies due to the interactions between individual residues and the reaction center to results obtained with the differential transition state stabilization method (Szarek, et al., J. Phys. Chem. B, 2008, 112, 11819-11826) and observe, despite a size difference in the fragment describing the reaction center, near-quantitative agreement. We have also computed deletion energies to investigate the effect of virtual deletion of key residues on the activation energy. These results are consistent with the stabilization energies and yield additional information as they clearly capture the effect of secondary interactions, i. e. interactions in the second coordination layer of the reaction center. We find that using FMO to calculate deletion energies is a powerful and time efficient approach to analyze the importance of key residues to the activity of an enzyme catalyzed reaction.

  • 6976.
    Öberg, Kim
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Hed, Yvonne
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Joelsson Rahmn, Isabella
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Kelly, Jonathan
    Löwenhielm, Peter
    Malkoch, Michael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Dual-purpose PEG scaffolds for the preparation of soft and biofunctional hydrogels: the convergence between CuAAC and thiol-ene reactions2013In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 49, no 62, p. 6938-6940Article in journal (Refereed)
    Abstract [en]

    Orthogonally functionalized PEGs displaying alkenes and azides have been prepared and their dual-purpose scaffolding potential was exploited via click chemistry for controlled insertion of bio-relevant moieties as well as facile fabrication of soft, non-toxic and degradable hydrogels.

  • 6977.
    Öberg, Kim
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Ropponen, Jarmo
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Kelly, Jonathan
    Löwenhielm, Peter
    Berglin, Mattias
    Malkoch, Michael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Templating Gold Surfaces with Function: A Self-Assembled Dendritic Monolayer Methodology Based on Monodisperse Polyester Scaffolds2013In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 29, no 1, p. 456-465Article in journal (Refereed)
    Abstract [en]

    The antibiotic resistance developed among several pathogenic bacterial strains has spurred interest in understanding bacterial adhesion down to a molecular level. Consequently, analytical methods that rely on bioactive and multivalent sensor surfaces are sought to detect and suppress infections. To deliver functional sensor surfaces with an optimized degree of molecular packaging, we explore a library of compact and monodisperse dendritic scaffolds based on the nontoxic 2,2-bis(methylol)propionic acid (bis-MPA). A self-assembled dendritic monolayer (SADM) methodology to gold surfaces capitalizes on the design of aqueous soluble dendritic structures that bear sulfur-containing core functionalities. The nature of sulfur (either disulfide or thiol), the size of the dendritic framework (generation 1-3), the distance between the sulfur and the dendritic wedge (4 or 14 angstrom), and the type of functional end group (hydroxyl or mannose) were key structural elements that were identified to affect the packaging densities assembled on the surfaces. Both surface plasmon resonance (SPR) and resonance-enhanced surface impedance (RESI) experiments revealed rapid formation of homogenously covered SADMs on gold surfaces. The array of dendritic structures enabled the fabrication of functional gold surfaces displaying molecular covering densities of 0.33-2.2 molecules.nm(-2) and functional availability of 0.95-5.5 groups.nm(-2). The cell scavenging ability of these sensor surfaces for Escherichia coli MS7fim+ bacteria revealed 2.5 times enhanced recognition for G3-mannosylated surfaces when compared to G3-hydroxylated SADM surfaces. This promising methodology delivers functional gold sensor surfaces and represents a facile route for probing surface interactions between multivalently presented motifs and cells in a controlled surface setting.

  • 6978.
    Öhman, Maria
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    An in situ spectro-electrochemical study of aluminium/polymer interfaces: development of ATR-FTIR and its integration with EIS for corrosion studies2006Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    In order to extend the applications of aluminium, organic coatings may be applied on sheet materials, for instance for corrosion protection or aesthetic surface finish purposes in the automotive and construction industries, or on foil materials in the flexible packaging industry.

    The most common mechanisms for deterioration and structural failure of organically coated aluminium structures are triggered by exposures to the surrounding environment. Despite the great importance to elucidate the influence of exposure parameters on a buried aluminium/polymer interface, there is still a lack of knowledge regarding the mechanisms that destabilise the structure. It is generally believed that a detailed in situ analysis of the transport of corroding species to the buried interface, or of surface processes occurring therein, is most difficult to perform at relevant climatic and real-time conditions.

    In this work, Attenuated Total Reflection Fourier Transform Infrared Spectroscopy (ATR-FTIR) in the Kretschmann-ATR configuration was successfully applied to in situ studies of the transport of water and ionic species through polymer films to the aluminium/polymer interface upon exposure to ultra pure deionised water and to a 1 M sodium thiocyanate (NaSCN) model electrolyte. Other main processes distinguished were the formation of corrosion products on the aluminium surface and swelling of the surface-near polymer network. Hence, in situ ATR-FTIR was capable to separate deterioration-related processes from each other.

    To perform more unambiguous interpretations, a spectro-electrochemical method was also developed for in situ studies of the buried aluminium/polymer interface by integrating the ATR-FTIR technique with a complementary acting technique, Electrical Impedance Spectroscopy (EIS). While transport of water and electrolyte through the polymer film to the aluminium/polymer interface and subsequent oxidation/corrosion of aluminium could be followed by ATR-FTIR, the protective properties of the polymer as well as of processes at the aluminium surface were simultaneously studied by EIS. The integrated set-up provided complementary information of the aluminium/polymer sample investigated, with ATR-FTIR being sensitive to the surface-near region and EIS being sensitive to the whole system. While oxidation/corrosion and delamination are difficult to distinguish by EIS, oxide formation could be confirmed by ATR-FTIR. Additionally, while delamination and polymer swelling may be difficult to separate with ATR-FTIR, EIS distinguished swelling of the polymer network and also identified ultimate failure as a result of delamination.

    The capability of the integrated ATR-FTIR / EIS in situ technique was explored by studying aluminium/polymer systems of varying characteristics. Differences in water and electrolyte ingress could be monitored, as well as metal corrosion, polymer swelling and delamination.

  • 6979.
    Öhman, Maria
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science.
    Development of ATR-FTIR Kretschmann Spectroscopy for In situ Studies of Metal / Polymer Interfaces: and its Intergration with EIS for Exposure to Corrosive Conditions2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The environmental stability of a metal / polymer interface is essential for the durability and mechanical stability of constructions in several important areas such as the automotive, offshore, building and aerospace industries. The protective capability of a polymer film is strongly connected to its barrier properties, but the transport of water and corrosive constituents through the polymer and the subsequent processes at the metal surface are complicated to analyse in detail. The surface to be analysed is confined between two media that are impermeable to most probing particles used in conventional analytical techniques. Several methods exist to describe separate parts of the system, but few techniques work atambient pressure and have the capacity to conduct real-time analysis at relevant exposure conditions. In this work, attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) in the Kretschmann geometry was successfully employed for systematic studies of metal / polymer interfaces. This technique requires the use of thin metal films deposited on an internal reflection element (IRE). Most studies were performed on aluminium, which is an important structural light-weight material, but also zinc was analysed, being frequently used for corrosion protection of steel. Upon exposure to water and electrolytes, the ATR-FTIR Kretschmann technique was found capable to monitor and to separate early deterioration related processes at the aluminium / polymer interface, including water sorption and transport of ionic species through the polymer film. Other main processes identified were the formation of corrosion products and swelling of the surface-near polymer network. To perform more comprehensive interpretations, a spectro-electrochemical method was further developed for in situ studies of the hidden metal / polymer interfaces. The ATR-FTIR Kretschmann technique was here combined with the complementary acting technique, Electrical Impedance Spectroscopy (EIS). The integrated set-up was able to provide complementary information, with ATR-FTIR Kretschmann being sensitive to the surface-near region and EIS to the whole system. For instance, metal oxidation and delamination processes can be difficult to distinguish by EIS, while on the other hand oxidation and hydration reactions on aluminiumcan be confirmed as IR bands at distinct positions. Delamination and swelling of a polymer both result in negative bands in an IR spectrum, but these processes may be distinguished by EIS as alterations in different frequency regions. While traditional chemical pre-treatments for enhanced hydrolytic stability perform excellent, they are being phased out from industrial applications due to environmental concerns and work health issues. Today there is an intense ongoing research regarding the mechanisms and performance of environmentally friendly pretreatments to develop systems of similar performance, and the analysis of the confined metal / polymer interface is crucial for this development. The capability of the integrated in situ ATR-FTIR Kretschmann and EIS set-up was therefore further applied to systems where a surface pre-treatment had been applied to the metal prior to the organic coating. Studies were first performed on vacuum-evaporated films of zinc treated with a titanium-based conversion coating and further coated with a UV-curing polymer. Alterations of the conversion layer could be detected upon exposure to the electrolyte. Also alkaline-cleaned aluminium coated with an amino-functional silane film and a thermo-curing epoxy top-coat was thoroughlycharacterized by both ATR-FTIR and IRRAS and further investigated upon exposure toelectrolyte and humid air. Changes at the hidden interface were detected upon thermal curingof the epoxy film and during exposure in electrolyte, and the in situ ATR-FTIR Kretschm annanalysis showed a high sensitivity towards alterations in the interfacial region. Complementary studies in the absence of metal could confirm a water uptake within the silane film and water-induced alterations of the siloxane network.

  • 6980.
    Öhman, Maria
    et al.
    Kimab.
    Persson, Dan
    Kimab.
    Leygraf, Christofer
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    In situ ATF-FTIR studies of the aluminium/polymer interface upon exposure to water and electrolyte2006In: Progress in organic coatings, ISSN 0300-9440, E-ISSN 1873-331X, Vol. 57, no 1, p. 78-88Article in journal (Refereed)
    Abstract [en]

    Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) with the Kretschmann configuration was applied for in situ studies of the transport of water and ionic species through a polymer film to an aluminium/polymer interface. The time dependent intensity changes of the infrared bands of water were used to follow the transport of water to the aluminium/polymer interfacial region and a NaSCN solution was employed as model electrolyte to follow the transport and accumulation of thiocyanate ions. Apart from water sorption and ion transport, the main processes identified were corrosion/oxidation of the aluminium surface and swelling of the polymer film. The method proved to be useful for detailed in situ studies of changes at a polymer coated metal surface, such as oxidation and surface film formation on the metal. It should also be possible to study the effects of defects and pores in the polymer film on the transport properties of water and ions to the metal/polymer interface, as well as adsorption and other chemical reactions and physical interactions in the metal/polymer interfacial region.

  • 6981.
    Öijerholm, Johan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Ionic Transport in Metal Oxides Studied in situ by Impedance Spectroscopy and Cyclic Voltammetry2007Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Ionic transport in metal oxides is crucial for the functioning of a broad range of different components, such as heat resistant alloys designed for high temperature applications and oxide electrolytes in solid oxide fuel cells. This thesis presents results from in situ electrochemical studies of properties related to ionic transport in metal oxides that are important for their applications as protective oxides and ionic conductors.

    Heat resistant alloys of alumina-former type are known to form an adherent, slowly growing and protective aluminium oxide (Al2O3) scale that protects metals from chemical degradation at high temperature. In situ impedance spectroscopy was used to study highly pure and dense samples of a-alumina in the temperature range 400 – 1000 °C. It was shown that surface conduction on the sample could severely distort the measurement below 700 °C. The magnitude of the distortions appeared to be sensitive to the type of electrodes used. The use of a so-called guard electrode was shown to effectively block the surface conduction in the measurements. By varying the grain size of the sintered alpha-alumina samples, the influence of grain size on the overall conductivity of the a-alumina was studied. It was shown that the activation energy for conductivity increased as the grain size decreased. Molecular dynamics calculations were performed in order to elucidate whether Al- or O ions are dominant in the ionic conductivity of the alpha-alumina. Comparing the calculation and experimental results, the dominating charge carrier was suggested to be oxygen ions.

    Moreover, the ionic transport in thermally grown alumina-like oxide scales formed on a FeCrAl alloy was studied in situ by impedance spectroscopy between 600 and 1000 °C. It was shown that the properties of these scales differ largely from those of pure and dense alpha-alumina. Furthermore, the conductivity is mainly electronic, due to the multiphase/multilayer microstructure and substantial incorporation of species from the base metal. However, the diffusivity obtained from the ionic conductivity was in line with diffusion data in literature obtained by other methods such as thermogravimetry. Besides, the initial stage of oxidation of a number of Fe-, Ni- and Co-based alloys at temperatures between 500 and 800 °C was studied in situ by high temperature cyclic voltammetry, in which the oxygen activity was changed over a wide range. From the resulting voltammograms the redox reactions occurring on the alloy surface could be identified. It was concluded that the base metal oxidized readily on these alloys before a protective chromia- or alumina-like scale is formed. The base metal oxide is most likely incorporated into the more protective oxide.

    Further, the oxygen ionic conductivity of highly pure and fully dense yttria-stabilized zirconia produced by spark plasma sintering was studied by impedance spectroscopy. The aim was to evaluate intrinsic blocking effects on the ionic conduction associated with the space charge layer in the grain boundary region. It was observed that the ionic conductivity of the spark plasma sintered oxides is equal or slightly higher than what has been achieved by conventional sintering methods. In addition, it was shown that the specific grain boundary conductivity increases with decreasing grain size, which can be explained by a decreasing Schottky barrier height (i.e., decreasing blocking effect). The quantitative results from this work verify the space charge model describing the influence of grain size on the ionic conductivity of yttria-stabilized zirconia through dopant segregation and oxygen vacancy depletion along the grain boundaries.

  • 6982.
    Öijerholm, Johan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Fafilek, Günter
    Pan, Jinshan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Cyclic Voltammetry Study of the Early Stage of High Temperature Oxidation of Fe-, Co- and Ni-based alloysIn: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111Article in journal (Other academic)
  • 6983.
    Öijerholm, Johan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science.
    Fafilek, Günter
    Institute of Chemical Technology and Analytics, University of Technology of Vienna.
    Pan, Jinshan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science.
    Study of Initial Oxidation of Engineering Alloys by High Temperature Cyclic Voltammetry2007In: Electrochemical and solid-state letters, ISSN 1099-0062, E-ISSN 1944-8775, Vol. 10, no 6, p. 47-50Article in journal (Refereed)
    Abstract [en]

    The initial oxidation of Fe-, Co-, and Ni-based engineering alloys was studied in situ by high-temperature cyclic voltammetry. Measurements were performed at constant temperatures between 500 and 800 degrees C in an electrochemical cell utilizing oxygen ion-conducting yttria-stabilized zirconia as electrolyte and a reference electrode whose potential is determined by the oxygen activity in the ambient gas. The recorded voltammograms show clear current peaks that are associated with the oxidation of the base metal in the investigated alloys. For the Fe- based alloy, multiple peaks are observed, showing oxidation of Fe into different valence oxides. The results indicate that the base metal oxide is formed in the initial oxidation process of these engineering alloys, which may influence long-term high-temperature oxidation resistance of the alloys.

  • 6984.
    Öijerholm, Johan
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Pan, Jinshan
    KTH, Superseded Departments, Materials Science and Engineering.
    Jönsson, Bo
    Kanthal AB, Hallstahammar.
    Influence of Grain Size on Ionic Conductivity of Pure and Dense alpha-Al2O3 in the Temperature Range 400-1000 degrees C2004In: High Temperature Corrosion And Protection Of Materials 6, Prt 1 And 2, Proceedings, 2004, Vol. 461-464, no II, p. 865-872Conference paper (Refereed)
    Abstract [en]

    Ionic transport in alpha-Al2O3 at high temperatures is important for oxidation/corrosion resistance of Al2O3-forming heat resistant alloys. Whereas most of previous studies were performed at temperatures above 1000degreesC, this work concerns the temperature range 400 to 1000degreesC. Electrical proper-ties of polycrystalline and single crystal alpha-Al2O3 were measured in air by using impedance spectroscopy in order to study the ionic transport in Al2O3. The influence of grain size was investigated by measurements on a series of highly pure and dense samples with well-defined grain size ranging from 0.5 to 15 mum, produced by the spark plasma sintering technique. The results show that the grain size has a certain influence on the conductivity in the temperature range between 650 and 1000degreesC, where the activation energy for conductivity decrease from 2.4 to 1.6 eV with increasing grain size. At lower temperatures the activation energy is about 1.0 eV and independent of the grain size, indicating a different conduction mechanism.

  • 6985.
    Öijerholm, Johan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Pan, Jinshan
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Leygraf, Christofer
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    In-situ measurements by impedance spectroscopy of highly resistive alpha-alumina2006In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 48, no 1, p. 243-257Article in journal (Refereed)
    Abstract [en]

    In-situ impedance spectroscopy has been used for characterisation of oxides at elevated temperatures. However, for highly resistive oxides, the influence of electrode contact and leakage currents due to gas phase and surface conduction needs to be taken into account. In this study, IS measurements of pure and dense alpha-alumina (alpha-Al2O3) samples were performed in the temperature range 400-1000 degrees C with different types of electrode contact, in air and in nitrogen. The results show that above 700 degrees C the influence is negligible, whereas at lower temperatures the surface leakage current was substantial, and a so-called guard electrode recommendable.

  • 6986.
    Öijerholm, Johan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science (closed 20081231).
    Pan, Jinshan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science (closed 20081231).
    Lu, Q.
    Kanthal AB, Hallstahammar.
    Leygraf, Christofer
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science (closed 20081231).
    In-situ impedence spectroscopy study of electrical conductivity and ionic transport in thermally grown oxide scales on a commercial FeCrA1 alloy2007In: Oxidation of Metals, ISSN 0030-770X, E-ISSN 1573-4889, Vol. 68, no 5-6, p. 253-269Article in journal (Refereed)
    Abstract [en]

    In-situ impedance-spectroscopy measurements were performed at temperatures between 600 and 1,000 degrees C to investigate ionic transport in oxide scales formed on Kanthal AF alloy. The samples were pre-oxidized at 800, 900 and 1,000 degrees C in air. The impedance spectra of the oxide formed at 1,000 degrees C exhibited essentially one semicircle, whereas samples oxidized at lower temperatures showed an additional semicircle at high frequencies suggesting a more heterogeneous oxide. The ionic-transference number, derived by measuring the voltage across the oxide scale, indicates that the oxide is a predominant electronic conductor. Ionic diffusivity in the oxide scales formed at different pre-oxidizing temperatures was calculated, using the ionic-transference number. The ionic diffusivities obtained in this way are in reasonable agreement with literature data acquired by other methods. The oxide-formation temperature has a significant influence on the conductivity and ionic-transport properties of the oxide scale.

  • 6987. Öjekull, J.
    et al.
    Andersson, P. U.
    Någård, M. B.
    Pettersson, J. B. C.
    Neau, A.
    Rosén, S.
    Thomas, R. D.
    Larsson, M.
    Semaniak, J.
    Österdahl, Fabian
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Danared, H.
    Källberg, A.
    af Ugglas, M.
    Dissociative recombination of ammonia clusters studied by storage ring experiments2006In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 125, no 19, p. 194306-Article in journal (Refereed)
    Abstract [en]

    Dissociative recombination of ammonia cluster ions with free electrons has been studied at the heavy-ion storage ring CRYRING (Manne Siegbahn Laboratory, Stockholm University). The absolute cross sections for dissociative recombination of H+(NH3)(2), H+(NH3)(3), D+(ND3)(2), and D+(ND3)(3) in the collision energy range of 0.001-27 eV are reported, and thermal rate coefficients for the temperature interval from 10 to 1000 K are calculated from the experimental data and compared with earlier results. The fragmentation patterns for the two ions H+(NH3)(2) and D+(ND3)(2) show no clear isotope effect. Dissociative recombination of X+(NX3)(2) (X=H or D) is dominated by the product channels 2NX(3)+X [0.95 +/- 0.02 for H+(NH3)(2) and 1.00 +/- 0.02 for D+(ND3)(2)]. Dissociative recombination of D+(ND3)(3) is dominated by the channels yielding three N-containing fragments (0.95 +/- 0.05).

  • 6988.
    Önsten, Anneli
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Stoltz, Dunja
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Palmgren, Pål
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Yu, Shun
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Water Adsorption on ZnO(0001): Transition from Triangular Surface Structures to a Disordered Hydroxyl Terminated phase2010In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 114, no 25, p. 11157-11161Article in journal (Refereed)
    Abstract [en]

    We present room temperature scanning tunneling microscopy and photoemission spectroscopy studies of water adsorption on the Zn-terminated ZnO(0001) surface. Data indicates that the initial adsorption is dissociative leaving hydroxyl groups on the surface. At low water coverage, the adsorption occurs next to the oxygen-terminated step edges, where water is believed to bind to zinc cations leaving off hydrogen atoms to under-coordinated oxygen anions. When increasing the water dose, triangular terraces grow in size and pits diminish until the surface is covered with wide irregular terraces and a large number of small pits. Higher water exposure (20 Langmuir) results in a much more irregular surface. Hydrogen, which is produced in the dissociation reaction is believed to have an important role in the changed surface structure at high exposures. The fact that adsorbed water completely changes the structure of ZnO(0001) is an important finding toward the understanding of this surface at atmospheric conditions.

  • 6989.
    Önsten, Anneli
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Weissenrieder, Jonas
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Stoltz, Dunja
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Yu, Shun
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Role of defects in surface chemistry on Cu2O(111)2013In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, no 38, p. 19357-19364Article in journal (Refereed)
    Abstract [en]

    High-resolution photoemission spectroscopy and scanning tunneling microscopy (STM) have been used to investigate defects on Cu2O(111) and their interaction with water and sulfur dioxide (SO2). Two types of point defects, i.e., oxygen and copper vacancies, are identified. Copper vacancies are believed to be the most important defects in both water and SO2 surface chemistry. Multiply coordinatively unsaturated oxygen anions (OMCUS) such as oxygen anions adjacent to copper vacancies are believed to be adsorption sites for both water and SO2 reaction products. Water adsorption at 150 K results in both molecular and dissociated water. Molecular water leaves the surface at 180 K. At 300 K and even more at 150 K, SO2 interacts with oxygen sites at the surface forming SO 3 species. However, thermal treatment up to 280 K of Cu 2O(111)/SO2 prepared at 150 K renders only SO4 on the surface.

  • 6990.
    Örnberg, Andreas
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science.
    Study of Electrochemical Behaviour and Corrosion Resistance of Materials for Pacemaker Lead Applications2007Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    For patients suffering bradycardia, i.e., too slow heart rhythm, the common treatment is having a pacemaker implanted. The pacemaker system consists of the pacemaker and a pacing lead. The pacing lead is connected to the pacemaker and at the other end there is a stimulation electrode. The most common conductor material is a cobalt-based super alloy (MP35N® or 35N LT®), with the main constituents Ni, Co, Cr and Mo. The pacemaker electrode is often made of a substrate material with a rough surface coating. The substrate materials are predominantly platinum/iridium alloy and titanium. The material choice is of great importance for the performance and stability during long-term service. Excellent corrosion resistance is required to minimize elution of metal ions in the human body.

    In this thesis, the electrochemical behaviour and corrosion resistance of the Co-based alloys and Ta (as electrode substrate), in a phosphate buffer saline (PBS) solution with and without addition of H2O2, was investigated by means of potentiodynamic polarization, cyclic voltammetry, electrochemical impedance spectroscopy and simulated pacemaker pulsing. The metal release from the Co-based alloy during the passivation treatment and exposure in the synthetic biological media was measured by using inductive coupled plasma - atomic emission spectroscopy (ICP-AES). Moreover, surface composition was analyzed by using x-ray photoelectron spectroscopy.

    The results show that the chemical passivation of Co-based alloy 35N LT® increased the corrosion resistance and reduced Co release significantly, even in more hostile environment, i.e. PBS with addition of H2O2. The increased corrosion resistance is due to the Cr enrichment in the surface layer. The reduced Co release is due to a preferential dissolution of Co from the surface oxide layer during the chemical passivation. The electrochemical investigation of uncoated and rough TiN coated Ta show that uncoated Ta is not suitable electrode material due to formation of a highly resistive surface oxide film. Whereas the rough TiN coated Ta exhibits desirable electrochemical performance for pacemaker electrodes. The addition of H2O2 in the PBS has a large influence on the electrochemical behaviour of Ta, but the influence is small on the rough TiN coated Ta.

  • 6991.
    Örnberg, Andreas
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Pan, Jinshan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science.
    Herstedt, M.
    Leygraf, Christofer
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science.
    Corrosion resistance, chemical passivation and metal release of 35N LT and MP35N for biomedical material application2007In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 154, no 9, p. C546-C551Article in journal (Refereed)
    Abstract [en]

    The Co-based special wire alloys 35N LT and MP35N are used for biomedical applications. The corrosion resistance of the two alloys, chemical passivation, and metal release of 35N LT were studied by electrochemical measurements, surface analysis, and solution analysis. The results show no significant difference in the corrosion resistance between 35N LT and MP35N. Preferential dissolution of Co and Ni occurs during chemical passivation of 35N LT in an HNO3 solution, which results in enrichment of oxidized Cr and depletion of oxidized Co in the passive film. The passivation treatment leads to an increased corrosion resistance in a phosphate-buffered saline solution, even with addition of 100 mM H2O2 simulating an inflammatory response. A further effect of the passivation treatment is a significantly reduced metal release, especially Co, from 35N LT during exposure to the synthetic biological medium.

  • 6992.
    Örnek, Cem
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Leygraf, Christofer
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Pan, Jinshan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    On the Volta potential measured by SKPFM - fundamental and practical pects with relevance to corrosion science2019In: Corrosion Engineering, Science and Technology, ISSN 1478-422X, E-ISSN 1743-2782, Vol. 54, no 3, p. 185-198Article, review/survey (Refereed)
    Abstract [en]

    The Volta potential is an electron-sensitive parameter and describes the ermodynamic propensity of a metal to take part in electrochemical actions. It has found widespread acceptance among corrosion searchers due to its connection to the corrosion potential and its sy measurability in local scale, being often used to study localised rrosion phenomena and micro-galvanic activities. The principle object this paper is to provide a comprehensive, fundamental insight into e meaning of the Volta potential and to define a polarity convention measured potentials by the scanning Kelvin probe force microscopy KPFM) in order to assess local nobilities in microstructures. nditions to relate the Volta potential with the mixed-potential theory e discussed and a possible connection to corrosion phenomena plained. The limitations of the Volta potential as well as the SKPFM chnique are also aimed to be explained, with some practical formation to maximise the output of high quality data.

  • 6993.
    Örnek, Cem
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Långberg, Marie
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. Swerim, SE-16407 Kista, Sweden..
    Evertsson, Jonas
    Lund Univ, Div Synchrotron Radiat Res, SE-22100 Lund, Sweden.;Deutsch Elektronen Synchrotron DESY, D-22607 Hamburg, Germany.;Justus Liebig Univ Giessen, Phys Chem Dept, D-35392 Giessen, Germany..
    Harlow, Gary
    Lund Univ, Div Synchrotron Radiat Res, SE-22100 Lund, Sweden..
    Linpe, Weronica
    Lund Univ, Div Synchrotron Radiat Res, SE-22100 Lund, Sweden..
    Rullik, Lisa
    Lund Univ, Div Synchrotron Radiat Res, SE-22100 Lund, Sweden..
    Carla, Francesco
    Diamond Light Source, Didcot OX11 0DE, Oxon, England..
    Felici, Roberto
    SPINCNR, Area Ric Roma 2 Tor Vergata, I-00133 Rome, Italy..
    Kivisakk, Ulf
    Sandvik Mat Technol, SE-81181 Sandviken, Sweden..
    Lundgren, Edvin
    Lund Univ, Div Synchrotron Radiat Res, SE-22100 Lund, Sweden..
    Pan, Jinshan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Influence of Surface Strain on Passive Film Formation of Duplex Stainless Steel and Its Degradation in Corrosive Environment2019In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 166, no 11, p. C3071-C3080Article in journal (Refereed)
    Abstract [en]

    The effect of surface strain on the passive film evolution of SAF 2507 super duplex stainless steel exposed to ambient air and 0.1 M NaCl solution with varying anodic polarization at room temperature has been investigated using in-situ grazing incidence X-ray diffraction (GIXRD) in combination with electrochemical measurements. Surface strain affected the crystallinity of the passive film as such that the surface oxides/hydroxides were predominantly amorphous, with some minor crystalline CrOOH and FeOOH present in the film. Crystalline CrOOH was seen to diminish in volume upon immersion in the NaCl solution, well-possibly becoming amorphous during anodic polarization, whereas crystalline FeOOH was seen to increase in volume during polarization to the passive potential regime. Strain relaxation, associated with metal dissolution, occurred in both austenitic and ferritic grains during immersion in the electrolyte. Anodic polarization to the transpassive regime led to maximum strain relaxation, occurring more on the austenite than the ferrite. The selective transpassive dissolution nature of the ferrite was significantly reduced due to large strains in the austenite. Passive film breakdown was reflected by enhanced dissolution of Fe, Cr, Mo and Ni occurring simultaneously around 1300 mV vs. Ag/AgCl. 

  • 6994.
    Österdahl, Kerstin
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena.
    Crystallization of iron fluoride trihydrate from mixed acid solutions2005Licentiate thesis, comprehensive summary (Other scientific)
  • 6995.
    Östlund, Jenny A.
    et al.
    KTH, Superseded Departments, Chemistry.
    Nydén, M.
    Stilbs, Peter
    KTH, Superseded Departments, Chemistry.
    Component-resolved diffusion in multicomponent mixtures. A case study of high-field PGSE-NMR self-diffusion measurements in asphaltene/naphthenic acid/solvent systems2004In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 18, no 2, p. 531-538Article in journal (Refereed)
    Abstract [en]

    The diffusion of a multitude of different-sized molecules in various asphaltene mixtures has been measured by means of the pulsed gradient spin-echo nuclear magnetic resonance (PGSE-NMR) self-diffusion technique. The multicomponent mixtures studied contained mixtures of polydisperse asphaltenes and monodisperse naphthenic acid in solvent. Spectra obtained from a high-field PGSE-NMR self-diffusion experiment on these systems showed that the peaks from all components were almost completely overlapping, making a standard least-squares fit approach for evaluating individual self-diffusion coefficients from the decrease in signal intensity quite difficult. However, to study the details of the molecular interactions that occur between asphaltenes and naphthenic acids, the experimental data must be such that component-resolved information is obtained. Hence, with the purpose to obtain a robust evaluation procedure, with regard to obtaining component-resolved diffusion coefficients, a standard least-squares fit approach was tested against a global least-squares approach. The global least-squares evaluation was performed using a program called CORE (component-resolved spectroscopy). CORE not only fits predetermined functions to specific peak intensities or areas obtained from the diffusion experiments, but also considers the full information in the spectra. That is, the intensity at each frequency in the spectra is considered and the band shapes for all components in the mixture can be calculated. The calculated band shapes are thus a good test of the validity of the results for the diffusion coefficients. In this work, the band shapes were calculated and the diffusion for each individual component in the samples was extracted. The band shapes were observed to be in close agreement with the spectra obtained for the pure components. In addition, the diffusion coefficients, as obtained from CORE and from the least-squares fit method, were in close agreement, although some discrepancies were noted.

  • 6996.
    Östmark, E
    et al.
    KTH, Superseded Departments (pre-2005), Fibre and Polymer Technology.
    Harrisson, S
    Hult, Anders
    KTH, Superseded Departments (pre-2005), Polymer Technology.
    Wooley, K L
    Hawker, C J
    Malmström, Eva
    KTH, Superseded Departments (pre-2005), Polymer Technology.
    Modification of hydroxyethyl cellulose using dendrons or ATRP. Template for molecular rods?2004In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 228, p. U437-U437Article in journal (Other academic)
  • 6997.
    Östmark, Emma
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Tuning Properties of Surfaces and Nanoscopic Objects using Dendronization and Controlled Polymerizations2007Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    In this study, dendronization and grafting via controlled polymerization techniques, atom transfer radical polymerization (ATRP) and ring-opening polymerization (ROP), have been explored. Modification of surfaces and cellulose using these techniques, which enable grafting of well-defined polymer architectures, has been investigated. The interest in using cellulose stems from its renewability, biocompatibility, high molecular weight, and versatile functionalization possibilities.

    Dendronization was performed using disulfide-cored didendrons of 2,2-bis(methylol)propionic acid (bis-MPA) on gold surfaces, for the formation of self-assembled monolayers. It was found that the height of the monolayer increased with increasing dendron generation and that the end-group functionality controlled the wettability of the modified surface.

    Superhydrophobic cellulose surfaces could be obtained when a ‘graft-on-graft’ architecture was obtained using ATRP from filter paper after subsequent post-functionalized using a perfluorinated compound. The low wettability could be explained by a combination of a high surface roughness and the chemical composition.

    Biobased dendronized polymers were synthesized through the ‘attach to’ route employing dendronization of soluble cellulose, in the form of hydroxypropyl cellulose (HPC). The dendronized polymers were studied as nanosized objects using atomic force microscopy (AFM) and it was found that the dendron end-group functionality had a large effect on the molecular conformation on surfaces of spun cast molecules.

    ATRP of vinyl monomers was conducted from an initiator-functionalized HPC and an initiator-functionalized first generation dendron, which was attached to HPC. The produced comb polymers showed high molecular weight and their sizes could be estimated via AFM of spun cast molecules on mica and from dynamic light scattering in solution, to around 100-200 nm. The comb polymers formed isoporous membranes, exhibiting pores of a few micrometers, when drop cast from a volatile solvent in a humid environment. HPC was also used to initiate ROP of ε-caprolactone, which was chain extended using ATRP to achieve amphiphilic comb block copolymers. These polymers could be suspended in water, cross-linked and were able to solubilize a hydrophobic compound.

  • 6998.
    Östmark, Emma
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Harrisson, Simon
    Center for Materials Innovation, Department of Chemistry, Washington University in Saint Louis.
    Wooley, Karen L.
    Center for Materials Innovation, Department of Chemistry, Washington University in Saint Louis.
    Malmström, Eva
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Comb Polymers Prepared by ATRP from Hydroxypropyl Cellulose2007In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 8, no 4, p. 1138-1148Article in journal (Refereed)
    Abstract [en]

    Hydroxypropyl cellulose (HPC) was used as a core molecule for controlled grafting of monomers by ATRP, the aim being to produce densely grafted comb polymers. HPC was either allowed to react with an ATRP initiator or the first generation initiator-functionalized 2,2-bis(methylol)propionic acid dendron to create macroinitiators having high degrees of functionality. The macroinitiators were then "grafted from" using ATRP of methyl methacrylate (MMA) or hexadecyl methacrylate. Block copolymers were obtained by chain extending PMMA-grafted HPCs via the ATRP of tert-butyl acrylate. Subsequent selective acidolysis of the tert-butyl ester moieties was performed to form a block of poly(acrylic acid) resulting in amphiphilic block copolymer grafts. The graft copolymers were characterized by H-1 NMR and FT-IR spectroscopies, DSC, TGA, rheological measurements, DLS, and tapping mode AFM on samples spin coated upon mica. It was found that the comb (co)polymers were in the nanometer size range and that the dendronization had an interesting effect on the rheological properties.

  • 6999.
    Östmark, Emma
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Lindqvist, Josefina
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Nyström, Daniel
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Malmström, Eva
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Dendronized Hydroxypropyl Cellulose: Synthesis and Characterization of Biobased Nanoobjects2007In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 8, no 12, p. 3815-3822Article in journal (Refereed)
    Abstract [en]

    Dendronized polymers containing a cellulose backbone have been synthesized with the aim of producing complex molecules with versatile functionalization possibilites and high molecular weight from biobased starting materials. The dendronized polymers were built by attaching premade acetonide-protected 2,2-bis(methylol)propionic acid functional dendrons of generation one to three to a hydroxypropyl cellulose backbone. Deprotection or functionalization of the end groups of the first generation dendronized polymer to hydroxyl groups and long alkyl chains was performed, respectively. The chemical structures of the dendronized polymers were confirmed through analysis using H-1 NMR and FT-IR spectroscopies. From SEC analysis, the dendronized polymers were found to have an increasing polystyrene-equivalent molecular weight up to the second generation (M-n = 50 kg mol(-1)), whereas the polystyrene-equivalent molecular weight for the third generation was lower than for the second, although the same grafting density was obtained from H-1 NMR spectroscopy for the second and third generations. Tapping-mode atomic force microscopy was used to characterize the properties of the dendronized polymers in the dry state, exploring both the effect of the polar substrate mica and the less polar substrate highly oriented pyrolytic graphite (HOPG). It was found that the molecules were in the size range of tens of nanometers and that they were apt to undertake a more elongated conformation on the HOPG surfaces when long alkyl chains were attached as the dendron end-groups.

  • 7000.
    Östmark, Emma
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Macakova, Lubica
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Auletta, Tommaso
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Malkoch, Michael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Malmström, Eva
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Blomberg, Eva
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Dendritic Structures Based on Bis(hydroxymethyl)propionic Acid as Platforms for Surface Reactions2005In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 21, no 10, p. 4512-4519Article in journal (Refereed)
    Abstract [en]

    In this paper we present results related to the self-assembly of different generations of disulfide-cored 2,2-bis(hydroxymethyl)propionic acid-based dendritic structures onto gold surfaces. These molecular architectures, ranging from generation 1 to generation 3, contain removable acetonide protecting groups at their periphery that are accessible for hydrolysis with subsequent formation of OH-terminated surface-attached dendrons. The deprotection has been investigated in detail as a versatile approach to accomplish reactive surface platforms. A special focus has been devoted to the comparison of the properties of the layers formed by hydrolysis of the acetonide moieties directly on the surface and in solution, prior to the layer formation.

137138139140141 6951 - 7000 of 7005
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