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  • 1.
    Baber, Ashleigh E.
    et al.
    Brookhaven National Laboratory, USA.
    Xu, Fang
    Brookhaven National Laboratory, USA.
    Dvorak, Filip
    Charles University, Czech Republic.
    Mudiyanselage, Kumudu
    Brookhaven National Laboratory, USA.
    Soldemo, Markus
    KTH.
    Weissenrieder, Jonas
    KTH.
    Senanayake, Sanjaya D.
    Brookhaven National Laboratory, USA.
    Sadowski, Jerzy T.
    Rodriguez, José A.
    Brookhaven National Laboratory, USA.
    Matolín, Vladimír
    Charles University, Czech Republic.
    White, Michael G.
    Brookhaven National Laboratory, USA; Brookhaven National Laboratory, USA.
    Stacchiola, Darío J.
    Brookhaven National Laboratory, USA.
    In Situ Imaging of Cu2O under Reducing Conditions: Formation of Metallic Fronts by Mass Transfer2013In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 135, no 45, p. 16781-16784Article in journal (Refereed)
    Abstract [en]

    Active catalytic sites have traditionally been analyzed based on static representations of surface structures and characterization of materials before or after reactions. We show here by a combination of in situ microscopy and spectroscopy techniques that, in the presence of reactants, an oxide catalyst's chemical state and morphology are dynamically modified. The reduction of Cu2O films is studied under ambient pressures (AP) of CO. The use of complementary techniques allows us to identify intermediate surface oxide phases and determine how reaction fronts propagate across the surface by massive mass transfer of Cu atoms released during the reduction of the oxide phase in the presence of CO. High resolution in situ imaging by AP scanning tunneling microscopy (AP-STM) shows that the reduction of the oxide films is initiated at defects both on step edges and the center of oxide terraces.

  • 2.
    Besharat, Zahra
    et al.
    KTH .
    Halldin Stenlid, Joakim
    KTH.
    Soldemo, Markus
    KTH.
    Marks, Kess
    Stockholm University.
    Önsten, Anneli
    KTH.
    Johnson, Magnus
    KTH.
    Öström, Henrik
    Stockholm University.
    Weissenrieder, Jonas
    KTH.
    Brinck, Tore
    KTH.
    Göthelid, Mats
    KTH.
    Dehydrogenation of methanol on Cu2O(100) and (111)2017In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 146, no 24Article in journal (Refereed)
    Abstract [en]

    Adsorption and desorption of methanol on the (111) and (100) surfaces of  Cu2O have been studied using high-resolution photoelectron spectroscopy in the temperature range 120–620 K, in combination with density functional theorycalculations and sum frequency generation spectroscopy. The bare (100) surfaceexhibits a (3,0; 1,1) reconstruction but restructures during the adsorption process into a Cu-dimer geometry stabilized by methoxy and hydrogen binding in Cu-bridge sites. During the restructuring process, oxygen atoms from the bulk that can host hydrogen appear on the surface. Heating transforms methoxy to formaldehyde, but further dehydrogenation is limited by the stability of the surface and the limited access to surface oxygen. The (√3 × √3)R30°-reconstructed (111) surface is based on ordered surface oxygen and copper ions and vacancies, which offers a palette of adsorption and reaction sites. Already at 140 K, a mixed layer of methoxy, formaldehyde, and CHxOy is formed. Heating to room temperature leaves OCH and CHx. Thus both CH-bond breaking and CO-scission are active on this  surface at low temperature. The higher ability to dehydrogenate methanol on (111) compared to (100) is explained by the multitude of adsorption sites and, in particular, the availability of surfaceoxygen.

  • 3.
    Briscoe, Wuge H.
    et al.
    University of Bristol, England.
    Speranza, Francesca
    University of Bristol, England.
    Li, Peixun
    University of Oxford, England.
    Konovalov, Oleg
    ESRF, France.
    Bouchenoire, Laurence
    University of Liverpool, England.
    van Stam, Jan
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Klein, Jacob
    Weizmann institute of science, Israel.
    Jacobs, Robert M.J.
    University of Oxford, England.
    Thomas, Robert K.
    University of Oxford, England.
    Synchtrotron XRR study of soft nanofilms at the mica-water interface2012In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 8, no 18, p. 5055-5068Article in journal (Refereed)
  • 4.
    Carlsson, Gunilla
    Karlstad University, Division for Chemistry.
    Latex Colloid Dynamics in Complex Dispersions: Fluorescence Microscopy Applied to Coating Color Model Systems2004Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Coating colors are applied to the base paper in order to maximize the performance of the end product. Coating colors are complex colloidal systems, mainly consisting of water, binders, and pigments. To understand the behavior of colloidal suspensions, an understanding of the interactions between its components is essential.

  • 5.
    Carlsson, Gunilla
    et al.
    Karlstad University, Division for Chemistry.
    Järnström, Lars
    Karlstad University, Division for Chemistry.
    van Stam, Jan
    Karlstad University, Division for Chemistry.
    Latex Diffusion at High Volume Fractions Studied by Fluorescence Microscopy2006In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 298, no 1, p. 162-171Article in journal (Refereed)
  • 6.
    Carlsson, Gunilla
    et al.
    Karlstad University, Division for Chemistry.
    van Stam, Jan
    Karlstad University, Division for Chemistry.
    Interactions between Charged Latex Colloids and Starch Polyelectrolytes Studied with Fluorescence  Microscopy with Image Analysis2005In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 20, no 2, p. 192-199Article in journal (Refereed)
    Abstract [en]

    The interactions between carboxylated polystyrene latex probe particles and ionically substituted starches have been investi-gated by fluorescence microscopy with image analysis. The degree of substitution of the starches was varied, as was also thepolyelectrolyte molecular weight and the probe size. 

  • 7.
    Christophliemk, Hanna
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Jokela, Jukka
    Christophliemk, Mika
    Kuokkanen, Toivo
    Study of Organic Coagulants and Flocculants in the Waste Water Treatment2007Conference paper (Other academic)
  • 8.
    Dou, Yangpeng
    et al.
    China.
    Peng, Junjun
    China.
    Li, Wei
    China.
    Li, Ming
    China.
    Liu, Huihong
    China.
    Zhang, Hanmin
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Effects of reducibility of graphene oxide nanosheets on preparation of AgNPs/GO nanocomposites and their electrocatalytic performance2015In: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 17, no 12, p. 1-10, article id 489Article in journal (Refereed)
    Abstract [en]

    Silver nanoparticles/graphene oxide (AgNPs/GO) nanocomposites were prepared in a solution of AgNO3 and GO. The GO serves not only as a reductant but also as a substrate to support the as-reduced silver nanoparticles. The reducibility of GO was investigated by analyzing the influence factors such as pH, duration, the reaction temperature, and the weight ratio of AgNO3 and GO in the AgNP/GO nanocomposite mixture, which were evaluated by the UV–vis absorption spectroscopy. The results demonstrated that Ag nanoparticles with an average diameter of 5–10 nm were uniformly dispersed on the surface of GO nanosheets under the optimum synthesis conditions of pH between 8 and 11, weight ratio of AgNO3 and GO between 55 % and 60 %, and at 80 °C for 6 h. Moreover, the obtained AgNPs/GO nanocomposites exhibit good electrocatalytic activity for the reduction of p-nitrophenol to 4-(hydroxyamino) phenol.

  • 9.
    Drechsler, Michal
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Van Driel, Jan
    ICLON, Leiden University, Graduate School of Teaching, The Netherlands.
    Teachers’ knowledge and beliefs about the teaching of acids and bases in Swedish upper secondary schoolsManuscript (preprint) (Other academic)
  • 10.
    Enmark, Martin
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Forssén, Patrik
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Samuelsson, Jörgen
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Fornstedt, Torgny
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Determination of adsorption isotherms in supercritical fluid chromatography2013In: Journal of Chromatography A, ISSN 0021-9673, E-ISSN 1873-3778, Vol. 1312, p. 124-133Article in journal (Refereed)
    Abstract [en]

    Abstract In this study we will demonstrate the potential of modern integrated commercial analytical SFC-systems for rapid and reliable acquisition of thermodynamic data. This will be done by transferring the following adsorption isotherm determination methods from liquid chromatography (LC) to supercritical fluid chromatography (SFC): Elution by Characteristic Points (ECP), the Retention Time Method (RTM), the Inverse Method (IM) and the Perturbation Peak (PP) method. In order to transfer these methods to SFC in a reliable, reproducible way we will demonstrate that careful system verification using external sensors of mass flow, temperature and pressure are needed first. The adsorption isotherm data generated by the different methods were analyzed and compared and the adsorption isotherms ability to predict new experimental elution profiles was verified by comparing experiments with simulations. It was found that adsorption isotherm data determined based on elution profiles, i.e., ECP, IM and RTM, were able to accurately predict overloaded experimental elution profiles while the more tedious and time-consuming PP method, based on small injections on concentration plateaus, failed in doing so.

  • 11.
    Forshult, Stig E.
    Karlstad University, Division for Chemistry.
    Quantitative analysis with pulsed NMR and the CONTIN computer program2004Report (Other academic)
    Abstract [en]

    Various substances have been analyzed by pulsed NMR at 0.47 T in order to extract quantitative information from the CPMG spin-echo signal. This signal can be considered to show the true T2 relaxation of the analyte/s. In most cases the relaxation is a first order process and the FID will be a sum of several exponentially decreasing signals. This can be resolved into its components by an inverse Laplace transform. To achieve this the CONTIN computer program has been our tool. The result is a spectrum-like graph with the peaks of the individual FIDs as functions of the time constants T2. By calculating the peak areas and divide them with the T2 of the peaks one can find the total number of protons relaxing in a T2-range. This may also bee done by drawing the graph with a logarithmic abscissa. Then the peak areas, now integrals of f(T2) with respect to lg T2, will directly show the relative amounts of protons at each T2 The spectrum will also be better resolved over a broader range of various relaxation times. However, as the peaks are assumed to have Gaussian shapes, they will be slightly distorted on a logarithmic abscissa.

    Thus, with an inverse Laplace transform it is possible to make calculations of the relative amount of protons in a sample without any chemical pretreatment. The result is not a full analysis of the sample but can be regarded as a characterization of its main components.

  • 12.
    Fredriksson, Lars
    Karlstad University, Division for Chemistry.
    A Brief Survey of Lévy Walks: with applications to probe diffusion2010Independent thesis Basic level (degree of Bachelor), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    Lévy flights and Lévy walks are two mathematical models used to describe anomalous diffusion(i.e. those having mean square displacements nonlinearly related to time (as opposed to Brownian motion)). Lévy flights follow probability distributions p(|r|) yielding infinite mean square displacements since some rare steps are very long. Lévy walks, however, have coupled space-time probability distributions penalising very long steps. Both Lévy flights and Lévy walks are dominated by a few long steps, but most steps are much, much smaller. The semi-experimental part ofthis work dealt with how fluorescent probes moved in systems of cationic starch and latex/solutions of dodecyl trimethyl ammonium bromide, respectively. Visually, no Lévy walks couldbe detected. However, mathematical regression suggested enhanced diffusion and subdiffusion. Moreover, time-dependent diffusion coefficients were calculated. Also examined was how Microsoft Excel could be used to generate normal diffusion as well as anomalous diffusion.

  • 13.
    Heidkamp, Hannah
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Rogowski, Rafal
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Dzwilewski, Andrzej
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    van Stam, Jan
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Carlsson, Gunilla
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Morphology of polymer blends in films made by dip-coating2011Conference paper (Refereed)
    Abstract [en]

    Thin spincoated polymer films are used in various applications and there has been anincreasing demand to understand and get precise control over the film formation process. One of the most exciting applications is organic solar cells which have an active layer made of a polymer based blend. The film morphology has a strong effect on the efficiency of solar cells and therefore it is crucial to understand the film formation process in order to tailor thedesired morphology [1].

    In this study we are combining and comparing results from three different deposition processes: drop-casting, sphere-on-flat arrangement and dip-coating. We are using dip-coating to produce thin films of polymer blends with different morphologies under controlled conditions. The main goal is to gain a deeper insight into the processes that occur while solvent evaporates and to understand why certain structures are formed.

    Drop-casting allows for little control of the structure formation. In the sphere-on-flat arrangement a droplet of a solution is constrained between a half-sphere and the substrate, which provides more controllable conditions for the deposition process. For more precise control, dip-coating can be used, where a substrate is withdrawn from a solution at a constant speed.

    In this study we have used the polymer poly(3-hexylthiophene) (P3HT) and the fullerene derivative [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) dissolved in toluene. These components are the model system for studies on organic solar cells [1]. The dip-coated films show a wide variety of morphologies depending on the coating speed. This dependence can be rationalized by the different mechanisms occurring at low and high speeds: At low speeds, evaporation is dominant, [2] resulting in well ordered patterns. At high speeds, viscous forces become dominant, [2] yielding optically homogeneous films.

    [1] G. Dennler, M. C. Scharber, C. J. Brabec, Adv. Mat. 21, 1323-1338 (2009)

    [2] R. Z. Rogowski and A. A. Darhuber, Langmuir 26, 11485-93 (2010)

  • 14.
    Heidkamp, Hannah
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    van Stam, Jan
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Carlsson, Gunilla
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Rogowski, Rafal
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Morphology of PCBM and P3HT blends in films made by dip-coating on homogeneous and chemically patterned surfaces,2011Conference paper (Refereed)
  • 15.
    Hillerström, Anna
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Andersson, Martin
    YKI, Institute of Surface Chemistry, Stockholm.
    Jan, Skov Pedersen
    University of Aarhus.
    Altskär, Annika
    SIK, The Swedish Institute for Food and Biotechnology, Göteborg.
    Langton, Maud
    SIK, The Swedish Institute for Food and Biotechnology, Göteborg.
    van Stam, Jan
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Kronberg, Bengt
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Transparency and Wettability of PVD/PDMS-IPN Synthesized in Different Organic Solvents2009In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 114, no 3, p. 1828-1839Article in journal (Refereed)
  • 16.
    Hillerström, Anna
    et al.
    Technical Research Institute of Sweden, Box 5607, SE-114 86 Stockholm, Sweden.
    Andersson, Martin
    Technical Research Institute of Sweden, Box 5607, SE-114 86 Stockholm, Sweden.
    Samuelsson, Jörgen
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    van Stam, Jan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Solvent strategies for loading and release in mesoporous silica2014In: Colloid and Interface Science Communications, ISSN 2215-0382, Vol. 3, p. 5-8Article in journal (Refereed)
    Abstract [en]

    A model molecule, ibuprofen, was loaded in the pores of mesoporous silica by adsorption from nonpolar solvents (liquid carbon dioxide and cyclohexane) and from a polar solvent (methanol). It was sufficient with a very low concentration of ibuprofen in the nonpolar solvents to achieve maximum loading of ibuprofen in the mesoporous particles. When using liquid carbon dioxide, the pores of the mesoporous silica particles were filled completely with ibuprofen at a lower ibuprofen concentration than similar experiments performed with cyclohexane. When methanol was used, the maximum amount of loaded ibuprofen was never achieved. Furthermore, x-ray scattering showed that all ibuprofen loaded into the mesoporous particles were in an amorphous state. Ibuprofen was released from the mesoporous particles to water within a couple of minutes, regardless of solvent used for loading. It was found that the release of ibuprofen from mesoporous silica was much faster than that of crystalline ibuprofen.

  • 17.
    Hillerström, Anna
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Kronberg, Bengt
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    A Two-Step method for the Synthesis of a Hydrophilic PDMS Interpenetrating Polymer Network2008In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 110, no 5, p. 3059-3067Article in journal (Refereed)
    Abstract [en]

    A hydrophilic PDMS (polydimethylsiloxane) surface was formed by the synthesis of an interpenetrating polymer network (IPN) in a two-step process. In the first step, PDMS was loaded with crosslinker and initiator using a solvent that swells the PDMS. In the second step, the PDMS sample was submerged into a solution containing the hydrophilic monomer followed by a UV-polymerization step. The choice of solvent in the second step is critical to obtain a hydrophilic surface. It can be concluded that the solubility parameter of the solvent should be above a threshold value. Hence, in the second step only sufficiently polar solvents will result in hydrophilic PDMS-IPNs. These principles are illustrated by using N-vinyl-2-pyrrolidone as the hydrophilic monomer forming PVP/PDMS-IPNs.

  • 18.
    Hussain, Arif
    Karlstad University, Faculty of Technology and Science.
    Adsorption of Polyvinyl Alcohol on Nano-Cellulose Fibers2010Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Nano-cellulose fibers/suspension has very high viscosity, its viscosity has to be lower before it can be applied in the paper coating recipe. For this purpose the adsorption behaviour of polyvinyl alcohol on nano-cellulose fibers were investigated using method developed by Zwick in 1960, based on the formation of PVA-iodide blue complex in the presence of boric acid. The experiments showed that the maximum adsorbed amount i.e. 0.13 g PVA/g NFC was obtained in a dispersion with 0.2 % PVA concentration. It should be possible to further increase the PVA adsorption as the adsorbed amount didn’t reach a saturation point where the PVA adsorption attained a constant value. It was also found that adsorption of PVA on NFC is time dependent. The absorbance measurement after four days of mixing PVA/NFC suspension showed only partially adsorption of PVA on nano-cellulose surface.  An equilibrium time of 10-13 days was needed for PVA to fully adsorb on nano-cellulose fibers surface. Another important observation was that PVA adsorption also depends on the concentration of nano-cellulose fibers. A lower concentration of NFC easily allows PVA to adsorb on its surface, as compared to higher NFC concentration. An important finding during the methodology development was the method to get rid of formation of flocs in the blue iodide complex solution; by slowly addition of reactants, especially the KI/I2 solution under continuous stirring around 60oC the tendency to flocs formation was suppressed.

  • 19.
    Jansson Rådberg, Weronica
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    A model system for understanding the distribution of fines in a paper structure using fluorescence microscopy2015Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Fines have a very important role in paper chemistry and are a determinant in retention,

    drainage and the properties of paper. The purpose of this project was to be able to label the

    fines with fluorophores and study their Brownian motion with fluorescence microscopy.

    When succeeded this could then be used to study fines, fibers and other additives in a

    suspension thus giving the fundamental knowledge of why fines have this important role. Due

    to aggregation of the fines no Brownian motion could be detected. Instead the fines were

    handled as a network system and small fluorescence labeled latex particles were then studied

    in this system. This approach yields information about the fines when the obstacle with

    sedimentation of the network is resolved.

  • 20.
    Magnusson, Hans
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    From recovery boiler to integration of a textile fiber plant: Combination of mass balance analysis and chemical engineering2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Modern chemical technology is an efficient tool for solving problems, particularly within the complex environment of the pulp and paper industry, and the combination of experimental studies, mill data and mass balance calculations are of fundamental importance to the development of the industry. In this study various examples are presented, whereby chemical technology is of fundamental importance.

    It is well documented that under normal conditions the molten salt mixture from the kraft recovery boiler flows down into the dissolving tank without problems. However, in the case of  alternatives to the kraft recovery boiler, knowledge of more precise data of the molten salts is required for the design calculations. In this study the viscosity for the case of sodium carbonate and 30 mole% sulphide has been measured and is of the magnitude 2 – 3 cP at temperatures relevant for a recovery boiler, i.e. similar to water at room temperature.

    The presence of non-process elements (NPE) in a typical pulp mill has been investigated. The main input is with regards to the wood, and anticipated problems include; deposits in evaporators, high dead-load in liquor streams, plugging of the upper part of the recovery boiler and decreasing efficiency in the causticization department. Efficient green liquor clarification is of the greatest importance as an efficient kidney for many NPE. Mill data and calculations show that the magnesium added in the oxygen delignification does not form a closed loop.

    Integration of a prehydrolysis kraft pulp mill producing dissolving pulp with a plant producing viscose textile fiber could be highly beneficial. The prehydrolysis liquor will contain both sugars and acetic acid. It is however not possible to fully replace the sulphuric acid of the viscose spinning bath with acetic acid of own production. The sulphuric chemicals from the viscose plant can be partly taken care of in the kraft recovery area as well as the viscose plant which can be supplied with alkali and sulphuric acid. Zinc-containing effluents from the viscose plant can be treated with green liquor to precipitate zinc sulphide.

  • 21.
    Martynova, Y.
    et al.
    Max-Planck-Gesellschaft, Berlin, Germany.
    Soldemo, Markus
    KTH.
    Weissenrieder, Jonas
    KTH.
    Sachert, S.
    Martin-Luther-Universität, Germany.
    Polzin, S.
    Martin-Luther-Universität, Germany.
    Widdra, W.
    Martin-Luther-Universität, Germany; Max-Planck-Institut für Mikrostrukturphysik, Germany.
    Shaikhutdinov, S.
    Fritz-Haber-Institut der Max-Planck-Gesellschaft, Germany.
    Freund, H. -J
    Fritz-Haber-Institut der Max-Planck-Gesellschaft, Germany.
    CO Oxidation Over Monolayer Manganese Oxide Films on Pt(111)2013In: Catalysis Letters, ISSN 1011-372X, E-ISSN 1572-879X, Vol. 143, no 11, p. 1108-1115Article in journal (Refereed)
    Abstract [en]

    Ultrathin manganese oxide films grown on Pt(111) were examined in the low temperature CO oxidation reaction at near atmospheric pressures. Structural characterization was performed by X-ray photoelectron spectroscopy, Auger electron spectroscopy, high-resolution electron energy loss spectroscopy, and temperature programmed desorption. The results show that the reactivity of MnOx ultrathin films is governed by a weakly bonded oxygen species, which may even be formed at low oxygen pressures (similar to 10(-6) mbar). For stable catalytic performance at realistic conditions the films required highly oxidizing conditions (CO:O-2 < 1:10), otherwise the films dewetted, ultimately resulting in the catalyst deactivation. Comparison with other thin films on Pt(111) shows, that the desorption temperature of weakly bonded oxygen species can be used as a benchmark for its activity in this reaction.

  • 22.
    Meier, S. A.
    et al.
    University of Bremen.
    Peter, M. A.
    University of Bremen.
    Muntean, Adrian
    University of Bremen.
    Böhm, M.
    University of Bremen.
    Dynamics of the internal reaction layer arising during carbonation of concrete2007In: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405, Vol. 62, no 4, p. 1125-1137Article in journal (Refereed)
    Abstract [en]

    Carbonation is the reaction of environmental carbon dioxide with alkaline species in concrete. It is one of the major degradation mechanisms affecting the durability of reinforced concrete structures. In this paper, a mathematical model of the carbonation process is formulated and simulated using the finite-element method. Nonlinear reaction rates, Robin boundary conditions and a decrease of the concrete porosity in time are taken into account. A dimensional analysis based on a nondimensionalisation of the entire model is introduced to identify the key parameters and the different characteristic time and length scales of the whole process. Numerical simulations show the occurrence of an internal reaction layer travelling through the material. The speed and the width of the layer are rigorously defined via dimensionless quantities. A parameter study shows that the speed and the width are strongly related to the size of the Thiele modulus which is typically large. The relevance of other parameters is also investigated. The model is validated for accelerated and natural carbonation settings.

  • 23.
    Michels, Jasper J.
    et al.
    Holst Centre/TNO, Eindhoven, The Netherlands.
    Moons, Ellen
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Simulation of Surface-Directed Phase Separation in a Solution- Processed Polymer/PCBM Blend2013In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 46, no 21, p. 8693-8701Article in journal (Refereed)
    Abstract [en]

    The formation of the surface-induced stratified lamellar composition profile experimentally evidenced in spincoated layers of the photovoltaic donor–acceptor blend consisting of poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole]/phenyl-C61-butyric acid methyl ester (APFO-3/PCBM), as processed from chloroform, is simulated using square gradient theory extended with terms describing the interaction of the blend components with the air and substrate interfaces. The surface energy contributions have been formulated based on an enthalpic nearest-neighbor model which allows integration of common surface tension theory and experimentally accessible surface energies of the fluid phase constituents with a mean field description of a multicomponent blend confined by substrate and air interfaces. Using estimates for the quench depth and transport properties of the blend components as a function of polymer concentration, the time-resolved numerical simulations yield results that compare favorably with experimental observations, both in terms of the number of lamellae as a function of the blend layer thickness and their compositional order. The effect of blend ratio is reproduced as well, the lamellar pattern becoming more pronounced if the amount of PCBM increases relative to APFO-3.

  • 24.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Polymer solar cells – Visualising spontaneous organisation in solution-based thin films of Polymer:fullerene blends2011In: Soft and hard materials: A symposium on surface and materials chemistry / [ed] Swedish Chemical Society, division for surface and materials chemistry, 2011Conference paper (Refereed)
    Abstract [en]

    The performance and recent improvements of polymer-based solar cells can be traced back

    to two main factors: the chemical design of new conjugated polymers and the control and

    improved understanding of morphology in these solution-processed thin films. When a thin

    film is prepared from a blend of a conjugated polymer and the fullerene-based material,

    PCBM, demixing determines the final nanostructure, which in turn is influenced by the

    polymer-fullerene interactions, the molecules’ tendency to self-organise, and the kinetics of

    the film formation. During spincoating, characterized of rapid solvent evaporation, the

    kinetics of nucleation and of two-phase separation compete. The resulting film morphology

    is important for the performance of photovoltaic devices, because, first of all, excitons need

    to diffuse to the donor/acceptor interface to separate into mobile charges, and, secondly,

    these mobile charges need to travel to the electrodes. Characterization of the structure,

    composition and molecular orientation at these interfaces and in the thin film has been one

    major challenge, because of the critical requirements of chemical contrast combined with

    lateral or depth resolution. We have used a combination of Atomic Force Microscopy

    (AFM), dynamic Secondary Ion Mass Spectrometry (d-SIMS), Near-Edge Absorption Fine

    Structure (NEXAFS) spectroscopy, and recently Neutron Reflectometry (NR), to probe the

    surface and bulk composition of polymer:fullerene blends. Differences in composition

    between surface and sub-surface are observed, and form strong evidence for vertical phase

    separation.

     

  • 25.
    Moons, Ellen
    et al.
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Anselmo, Ana Sofia
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Dzwilewski, Andrzej
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    van Stam, Jan
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Vertical Phase Separation in Polymer:Fullerene Films for Photovoltaics2012In: Hybrid and Organics Photovoltaics Conference 2012: Uppsala, Sweden, 6th to 9th May 2012 / [ed] Anders Hagfeldt, Castelló, Spain: Society for Nanomolecular Photovoltaics (SEFIN) , 2012, p. 53-53Conference paper (Refereed)
  • 26.
    Muntean, Adrian
    et al.
    Tech Univ Eindhoven, CASA Ctr Anal Sci Comp & Applicat.
    Böhm, M. A.
    Univ Bremen, ZeTeM Ctr Ind Math, Bremen, Germany.
    Kropp, J.
    Univ Appl Sci, Lab Baustofftechnol, Bremen, Germany.
    Moving carbonation fronts in concrete: A moving-sharp-interface approach2011In: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405, Vol. 66, no 3, p. 538-547Article in journal (Refereed)
  • 27.
    Müller, Christian
    et al.
    Department of Physics, Chemistry and Biology, Linköpings universitet, Sweden.
    Bergqvist, Jonas
    Department of Physics, Chemistry and Biology, Linköpings universitet, Sweden.
    Vandewal, Koen
    Department of Physics, Chemistry and Biology, Linköpings universitet, Sweden.
    Tvingstedt, Kristoffer
    Department of Physics, Chemistry and Biology, Linköpings universitet, Sweden.
    Anselmo, Ana Sofia
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Magnusson, Roger
    Department of Physics, Chemistry and Biology, Linköpings universitet, Sweden.
    Alonso, M. Isabel
    Institut de Ciencia de Materials de Barcelona (ICMAB-CSIC), Esfera UAB, ES-08193 Bellaterra, Spain.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Arwin, Hans
    Department of Physics, Chemistry and Biology, Linköpings universitet, Sweden.
    Campoy-Quiles, Mariano
    Institut de Ciencia de Materials de Barcelona (ICMAB-CSIC), Esfera UAB, ES-08193 Bellaterra, Spain.
    Inganäs, Olle
    Department of Physics, Chemistry and Biology, Linköpings universitet, Sweden.
    Phase behaviour of liquid-crystalline polymer/fullerene organic photovoltaic blends: thermal stability and miscibility2011In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 21, p. 10676-10684Article in journal (Refereed)
    Abstract [en]

    The thermal behaviour of an organic photovoltaic (OPV) binary system comprised of a liquidcrystalline fluorene-based polymer and a fullerene derivative is investigated. We employ variabletemperature ellipsometry complemented by photo- and electroluminescence spectroscopy as well as optical microscopy and scanning force nanoscopy to explore phase transitions of blend thin films. The high glass transition temperature correlates with the good thermal stability of solar cells based on these materials. Furthermore, we observe partial miscibility of the donor and acceptor together with the tendency of excess fullerene derivative to segregate into exceedingly large domains. Thus, for charge generation less adequate bulk-heterojunction nanostructures are poised to develop if this mixture is exposed to more elevated temperatures. Gratifyingly, the solubility of the fullerene derivative in the polymer phase is found to decrease if a higher molecular-weight polymer fraction is employed, which offers routes towards improving the photovoltaic performance of non-crystalline OPV blends.

  • 28.
    Nilsson, Svante
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Bernasik, Andrzej
    Faculty of Physics and Applied Computer Science, AGH-University of Science and Technology, Al. Mickiewicza 30, Krakow 30–059, Poland.
    Budkowski, Andrzej
    M. Smoluchowski Insitute of Physics, Jagiellonian University, Reymonta 4, Krakow 30–059, Poland.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Morphology and phase segregation of spin-casted films of polyfluorene/PCBM blends2007In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 40, no 23, p. 8291-8301Article in journal (Refereed)
    Abstract [en]

    In this study the morphology of spin-casted films of polymers blended with [6,6]-phenyl C61-butyric acid methyl ester (PCBM) has been studied. It was found that the lateral structure formation in the films is favored by rapid solvent evaporation and strong polymer−PCBM repulsion. The formation of homogeneous films is favored by slow evaporation and weak polymer−PCBM repulsion. The effect of solvent evaporation rate is the opposite of what is found for spin-casting polymer−polymer blends. The results can be explained by the kinetics of phase separation and the phase behavior involving limited solubility and crystallization of PCBM.

  • 29.
    Paakkonen, Johan
    Karlstads Universitet, Avdelningen för kemi och biomedicinsk vetenskap.
    Surfactants in anionic latex films2010Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 30.
    Rådberg, Weronica
    Karlstad University, Division for Chemistry.
    Determination of Distribution of Fines in a Paper Structure using Fluorescence Microscopy- an introduction2010Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    When making paper, fibers and additives are suspended in water to a fiber suspension. The sheet is formed by draining a specific amount of suspension through a wire-cloth. The procedure is well known, but the underlying mechanisms are not fully understood. To understand how the different particles such as fines, fibers, retention aids and other additives interact with each other, further research is needed. This knowledge is important because in the production of paper, the retention and the distribution of fines and additives within a paper structure are vital parameters for the properties and also for the profitability of the final product. In this study fluorescence microscopy was used to study fines from bleached kraft pulp which were labeled with fluorophores. When the fines exhibit fluorescence we can study their individual trajectories and understand more about the interactions between fibers, fines and additives in different chemical environments. Fines from bleached kraft pulp have no fluorescent properties and therefore it is necessary to bind a fluorophore to the material. It was difficult to find a suitable fluorophore which binds covalently to the cellulose, the dominating part of fines. The result from this study was that the labeled fines did exhibited fluorescence. As the fines were aggregated no individual trajectories could be analyzed with fluorescence microscopy. Further development of the technique for labeling fines must be carried out to avoid aggregation of fines.

  • 31.
    Van fraeyenhoven, Paulien
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Comparing morphology in dip-coated and spin-coated polyfluorene:fullerene films2016Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Unsustainable energy sources are running out and global warming is getting worse. Therefore the need for renewable energy sources is growing. Solar cells are a popular options used as an energy source. Most popular are the inorganic photovoltaic cells. With their high efficiency and long lifetime, they make a very good energy source. Unfortunately the costs for inorganic solar cells are rather high. Organic solar cells can make a good replacement for inorganic photovoltaic. They are easy to make, light and rather cheap.

    In this thesis, the morphology of a model system of the active layer of organic solar cells will be discussed, using dip coating as well as spin coating as a technique to prepare the films. The films consist of a blend of poly(9,9-dioctylfluorenyl-2,7-diyl) and [6,6]-phenyl C61-butyric acid methyl ester in different ratios and different solvents. The films that were made were prepared by spin coating or dip coating a glass substrate. After analysing the samples using atomic force microscopy, fluorescence spectroscopy and absorption spectroscopy it was clear that the morphology, as well as the position of the polymer chains can be influenced by using different dipping speeds, ratios or solvents.

  • 32.
    van Pelt, Thomas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Thin films of [6,6]-phenyl-C61-butyric acid methyl ester for application in organic solar cells: preparation and effects of exposure to light and heat2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 33.
    van Stam, Jan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Hansson, Rickard
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Lindqvist, Camilla
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Ericsson, Leif
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Fluorescence spectroscopy studies on polymer blend solutions and films for photovoltaics2015In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 483, p. 292-296Article in journal (Refereed)
  • 34.
    van Stam, Jan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Lindqvist, Camilla
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Hansson, Rickard
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Ericsson, Leif
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Moons, Ellen
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Fluorescence and UV/VIS absorption spectroscopy studies on polymer blend films for photovoltaics2015In: Proceedings of SPIE: Physical Chemistry of Interfaces and Nanomaterials XIV / [ed] Hayes, SC; Bittner, ER, SPIE - International Society for Optical Engineering, 2015, Vol. 9549, p. 95490L1-95490L9Conference paper (Refereed)
  • 35.
    van Stam, Jan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Van fraeyenhoven, Petra
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences. UC Leuven Limburg, Leuven, Belgium.
    Andersén, Mikael
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences.
    Moons, Ellen
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Comparing Morphology in Dip-Coated and Spin-Coated Polyfluorene:Fullerene Films2016In: Proceedings of SPIE: Organic Photovoltaics XVII / [ed] Zakya H. Kafafi, Paul A. Lane, Ifor D.W. Samuel, SPIE - International Society for Optical Engineering, 2016, Vol. 9942, p. 99420D-1-99420D-10, article id UNSP 99420DConference paper (Refereed)
  • 36.
    Watcharinyanon, Somsakul
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Johansson, Lars S.O.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Mixed Self-Assembled Monolayers of Ferrocene-Terminated and Unsubstituted Alkanethiols on Gold: Surface Structure and Work Function2009In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 113, no 5, p. 1972-1979Article in journal (Refereed)
    Abstract [en]

    Mixed self-assembled monolayers of 11-ferrocene-1-undecanethiol (FcC11) and decanethiol (C10) were prepared by two different methods: from a mixed solution and by subsequent immersion. These preparations result in self-assembled monolayers (SAMs) with different portions of FcC11 molecules, orientations, and degrees of order in the SAM. The structure of these layers was studied by high-resolution X-ray photoelectron spectroscopy (HRXPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, and their effect on the surface electronic properties was investigated by Kelvin probe. The fraction of FcC11 in C10 thiol could be estimated from the intensity of the HRXPS Fe 2p3/2 peaks. The SAM prepared from the mixed solution was of high quality, and the portion of FcC11 molecules in this film was about 60%. The interaction of neighboring ferrocene moieties indicated phase separation between FcC11 and C10 species in the film. For the SAMs prepared by subsequent immersion in C10 and FcC11 solutions, the portion of FcC11 molecules varied from 35% to 55% dependent on the immersion times in the C10 solution. The degree of orientational order of the alkyl chains increased with increasing immersion time in C10. In addition, the adsorption of C10 decreased the work function of the gold surface while the adsorption of FcC11 increased this value. By varying the fraction of FcC11 in the SAMs with different preparation schemes, the work function of the gold surface could be varied in a controllable way

1 - 36 of 36
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