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  • 1.
    Agrios, Alexander George
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry (closed 20110630). KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Cesar, I.
    Comte, P.
    Nazeeruddin, M. K.
    Grätzel, M.
    Nanostructured composite films for dye-sensitized solar cells by electrostatic layer-by-layer deposition2006In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 18, no 23, p. 5395-5397Article in journal (Refereed)
    Abstract [en]

    The possibilities for making nanocomposite semiconductor films for DSC using the ELBL method was investigated. Coated slides were cut in half vertically giving two strips that can be subjected to different treatments for comparison. The electrode was heated to 450 °C for 30 min and then Cooled to 80 °C. Scanning electron microscopy of a sintered film with 5 cycles of TiO2 nanoparticles shows that the particles are well distributed and completely cover the transparent conducting oxide substrate. Spectroscopic measurements of a dye-coated film in acetonitrile found a dye concentration within the film of 0.15 mM based on an extinction coefficient. The solar cell including a scattering layer had more than double the current of the transparent layer-only cell. It was observed that ELBL method can produce TiO2 films for DSC with high efficiencies at low thickness.

  • 2. Alarcon, H.
    et al.
    Boschloo, Gerrit
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Mendoza, P.
    Solis, J. L.
    Hagfeldt, Anders
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Dye-sensitized solar cells based on nanocrystalline TiO2 films surface treated with Al3+ ions: Photovoltage and electron transport studies2005In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 109, no 39, p. 18483-18490Article in journal (Refereed)
    Abstract [en]

    Nanocrystalline TiO2 films, surface modified with Al3+, were manufactured by depositing a TiO2 suspension containing small amounts of aluminum nitrate or aluminum chloride onto conducting glass substrates, followed by drying, compression, and finally heating to 530 degrees C. Electrodes prepared with TiO2 nanoparticles coated with less than 0.3 wt % aluminum oxide with respect to TiO2 improved the efficiency of the dye sensitized solar cell. This amount corresponds to less than a monolayer of aluminum oxide. Thus, the Al ions terminate the TiO2 surface rather than form a distinct aluminum oxide layer. The aluminum ion surface treatment affects the solar cell in different ways: the potential of the conduction band is shifted, the electron lifetime is increased, and the electron transport is slower when aluminum ions are present between interconnected TiO2 particles.

  • 3. Alarcon, Hugo
    et al.
    Hedlund, Maria
    Johansson, Erik M. J.
    Rensmo, Hakan
    Hagfeldt, Anders
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Boschloo, Gerrit
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Modification of nanostructured TiO2 electrodes by electrochemical Al3+ insertion: Effects on dye-sensitized solar cell performance2007In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 111, no 35, p. 13267-13274Article in journal (Refereed)
    Abstract [en]

    Nanostructured TiO2 films were modified by insertion with aluminum ions using an electrochemical process. After heat treatment these films were found suitable as electrodes in dye-sensitized solar cells. By means of a catechol adsorption test, as well as photoelectron spectroscopy (PES), it was demonstrated that the density of Ti atoms at the metal oxide/electrolyte interface is reduced after Al modification. There is, however, not a complete coverage of aluminum oxide onto the TiO2, but the results rather suggest either the formation of a mixed Al-Ti oxide surface layer or formation of a partial aluminum oxide coating. No new phase could, however, be detected. In solar cells incorporating Al-modified TiO2 electrodes, both electron lifetimes and electron transport times were increased. At high concentrations of inserted aluminum ions, the quantum efficiency for electron injection was significantly decreased. Results are discussed at the hand of different models: A multiple trapping model, which can explain slower kinetics by the creation of additional traps during Al insertion, and a surface layer model, which can explain the reduced recombination rate, as well as the reduced injection efficiency, by the formation of a blocking layer.

  • 4. Alberius, Peter Carl Anders
    et al.
    Corkery, Robert W.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry (closed 20110630).
    Spray-drying process for the manufacture of dye-loaded particles.2007Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    According to a first aspect of the invention, a process is provided for the prepn. of amorphous particles comprising a homogeneous distribution of one or more dyes encapsulated by an amorphous, siliceous encapsulating agent, the process comprising: (a) providing a precursor of the encapsulating agent in liq. form; (b) providing the one or more dyes in liq. form; (c) mixing the liq. forms; (d) spraying the mixt. to form droplets comprising the one or more dyes and encapsulating agent; and (e) heating the droplets to form the particles comprising the one or more dyes encapsulated by the siliceous encapsulating agent; wherein at least one of the liq. forms provided is aq. and the or each aq. liq. form is acidic. According to a second aspect of the invention, encapsulated dyes made by the process of the first aspect of the invention are provided. [on SciFinder(R)]

  • 5. Andrae, Johan C. G.
    et al.
    Brinck, Tore
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry (closed 20110630).
    Kalghatgi, G. T.
    HCCI experiments with toluene reference fuels modeled by a semidetailed chemical kinetic model2008In: Combustion and Flame, ISSN 0010-2180, E-ISSN 1556-2921, Vol. 155, no 4, p. 696-712Article in journal (Refereed)
    Abstract [en]

    A semidetailed mechanism (137 species and 633 reactions) and new experiments in a homogeneous charge conic pression ignition (HCCI) engine on the autoignition of toluene reference fuels are presented. Skeletal mechanisms for isooctane and n-heptane were added to a detailed toluene submechanism. The model shows generally good agreement with ignition delay times measured in a shock tube and a rapid compression machine and is sensitive to changes in temperature, pressure, and mixture strength. The addition of reactions involving the formation and destruction of benzylperoxide radical was crucial to modeling toluene shock tube data. Laminar burning velocities for benzene and toluene were well predicted by the model after some revision of the high-temperature chemistry. Moreover, laminar burning velocities of a real gasoline at 353 and 500 K Could be predicted by the model using a toluene reference fuel as a surrogate. The model also captures the experimentally observed differences in combustion phasing of toluene/n-heptane mixtures, compared to a primary reference fuel of the same research octane number, in HCCI engines as the intake pressure and temperature are changed. For high intake pressures and low intake temperatures, a sensitivity analysis at the moment of maximum heat release rate shows that the consumption of phenoxy radicals is rate-limiting when a toluene/n-heptane fuel is used, which makes this fuel more resistant to autoignition than the primary reference fuel. Typical CPU times encountered in zero-dimensional calculations were on the order of seconds and minutes in laminar flame speed calculations. Cross reactions between benzylperoxy radicals and n-heptane improved the model prediction,,; of shock tube experiments for phi = 1.0 and temperatures lower than 800 K for an n-heptane/toluene fuel mixture, but cross reactions had no influence on HCCI Simulations.

  • 6.
    Bastardo Zambrano, Luis Alejandro
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Iruthayaraj, Joseph
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Lundin, Maria
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Dédinaité, Andra
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Vareikis, Aušvydas
    Department of Polymer Chemistry, Vilnius University.
    Makuška, Ričardas
    Department of Polymer Chemistry, Vilnius University.
    van der Wal, Albert
    Lever Faberage Europe Global Technology Centre, Unilever R and D.
    Furó, István
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Garamus, Vasil M.
    GKSS Research Centre.
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface Chemistry.
    Soluble complexes in aqueous mixtures of low charge density comb polyelectrolyte and oppositely charged surfactant probed by scattering and NMR2007In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 312, no 1, p. 21-33Article in journal (Refereed)
    Abstract [en]

    A low charge density polyelectrolyte with a high graft density of 45 units long poly(ethylene oxide) side-chains has been synthesized. In this comb polymer, denoted PEO(45)MEMA:METAC-2, 2 mol% of the repeating methacrylate units in the polymer backbone carry a permanent positive charge and the remaining 98 mol% a 45 unit long PEO side-chain. Here we describe the solution conformation of this polymer and its association with an anionic surfactant, sodium dodecylsulfate, SDS. It will be shown that the polymer can be viewed as a stiff rod with a cross-section radius of gyration of 29 A. The cross section of the rod contracts with increasing temperature due to decreased solvency of the PEO side-chains. The anionic surfactant associates to a significant degree with PE045MEMA:METAC-2 to form soluble complexes at all stoichiometries. A cooperative association is observed as the free SDS concentration approaches 7 mM. At saturation the number of SDS molecules associated with the polymer amounts to 10 for each PEO side-chain. Two distinct populations of associated surfactants are observed, one is suggested to be molecularly distributed over the comb polymer and the other constitutes small micellar-like structures at the periphery of the aggregate. These conclusions are reached based on results from small-angle neutron scattering, static light scattering, NMR, and surface tension measurements.

  • 7.
    Berglund, Per
    et al.
    KTH, Superseded Departments, Biotechnology.
    Branneby, Cecilia
    Svedendahl Humble, Maria
    KTH, School of Biotechnology (BIO), Biochemistry (closed 20130101).
    Carlqvist, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry (closed 20110630).
    Magnusson, Anders
    Hult, Karl
    KTH, School of Biotechnology (BIO), Biochemistry (closed 20130101).
    Brinck, Tore
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry (closed 20110630).
    Aldol and Michael additions catalyzed by a rationally redesigned hydrolytic enzyme2003In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 226, no 2, p. U155-U156Article in journal (Refereed)
  • 8. Borgstrom, M.
    et al.
    Blart, E.
    Boschloo, Gerrit
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Mukhtar, E.
    Hagfeldt, Anders
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Hammarstrom, L.
    Odobel, F.
    Sensitized hole injection of phosphorus porphyrin into NiO: Toward new photovoltaic devices2005In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 109, no 48, p. 22928-22934Article in journal (Refereed)
    Abstract [en]

    This paper describes the preparation and the characterization of a photovoltaic cell based on the sensitization of a wide band gap p-type semiconductor (NiO) with a phosphorus porphyrin. A photophysical study with femtosecond transient absorption spectroscopy showed that light excitation of the phosphorus porphyrin chemisorbed on NiO particles induces a very rapid interfacial hole injection into the valence band of NiO, occurring mainly on the 2-20 ps time scale. This is followed by a recombination in which ca. 80% of the ground-state reactants are regenerated within 1 ns. A photoelectrochernical device, prepared with a nanocrystalline NiO electrode coated with the phosphorus porphyrin, yields a cathodic photocurrent indicating that electrons indeed flow from the NiO electrode toward the solution. The low incident-to-photocurrent efficiency (IPCE) can be rationalized by the rapid back recombination reaction between the reduced sensitizer and the injected hole which prevents an efficient regeneration of the sensitizer ground state from the iodide/triiodide redox mediator. To the best of our knowledge, this work represents the first example of a photovoltaic cell in which a mechanism of hole photoinjection has been characterized.

  • 9.
    Boschloo, Gerrit
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Hagfeldt, Anders
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Activation energy of electron transport in dye-sensitized TiO2 solar cells2005In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 109, no 24, p. 12093-12098Article in journal (Refereed)
    Abstract [en]

    Various characteristics of dye-sensitized nanostructured TiO2 solar cells, such as electron transport and electron lifetime, were studied in detail using monochromatic illumination conditions. The electron transport was found to be a thermally activated process with activation energies in the range of 0.10-0.15 eV for light intensities that varied 2 orders of magnitude. Electron lifetimes were determined using a new method and found to be significantly larger (> 1 s) than previously determined. An average potential was determined for electrons in the nanostructured TiO2 under illumination in short-circuit conditions. This potential is about 0.2 V lower than the open-circuit potential at the same light intensity. The electron transport time varies exponentially with the internal potential at short-circuit conditions, indicating that the gradient in the electrochemical potential is the driving force for electron transport in the nanostructured TiO2 film. The applicability of the conventionally used trapping/detrapping model is critically analyzed. Although experimental results can be fitted using a trapping/detrapping model with an exponential distribution of traps, the distribution parameters differ significantly between different types of experiment. Furthermore, the experimental activation energies for electron transport are smaller than those expected in a trapping/detrapping model.

  • 10.
    Boschloo, Gerrit
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Hagfeldt, Anders
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Photoinduced absorption spectroscopy as a tool in the study of dye-sensitized solar cells2008In: Inorganica Chimica Acta, ISSN 0020-1693, E-ISSN 1873-3255, Vol. 361, no 3, p. 729-734Article in journal (Refereed)
    Abstract [en]

    Photoinduced absorption (PIA) spectroscopy, where the excitation is provided by a square-wave modulated (on/off) monochromatic light source, is a versatile tool in the study of dye-sensitized solar cells. Spectra of transient species, such as the oxidized dye, can easily be obtained and their kinetics can be explored using frequency or time-resolved techniques. Experimental PIA conditions can be kept close to typical solar cell operating conditions, allowing extraction of relevant time constants. PIA is also a suitable method to study the quality of pore filling in case of solid hole conductors. Dye molecules that are not in direct contact with the hole conductor will have long lifetimes in their oxidized state and appear clearly in the PIA spectrum. The basic principles of PIA are explained using the example of electron injection and recombination in dye-sensitized TiO2 in the absence of redox electrolyte.

  • 11.
    Boschloo, Gerrit
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Haggman, L.
    Hagfeldt, Anders
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Quantification of the effect of 4-tert-butylpyridine addition to I-/I-3(-) redox electrolytes in dye-sensitized nanostructured TiO2 solar cells2006In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 110, no 26, p. 13144-13150Article in journal (Refereed)
    Abstract [en]

    Addition of 4-tert-butylpyridine (4TBP) to redox electrolytes used in dye- sensitized TiO2 solar cells has a large effect on their performance. In an electrolyte containing 0.7 M LiI and 0.05 M I-2 in 3-methoxypropionitrile, addition of 0.5 M 4TBP gave an increase of the open-circuit potential of 260 mV. Using charge extraction and electron lifetime measurements, this increases could be attributed to a shift of the TiO2 band edge toward negative potentials (responsible for 60% of the voltage increase) and to an increase of the electron lifetime (40%). At a lower 4TBP concentration the shift of the band edge was similar, but the effect on the electron lifetime was less pronounced. The working mechanism of 4TBP can be summarized as follows: (1) 4TBP affects the surface charge of TiO2 by decreasing the amount of adsorbed protons and/or Li+ ions. ( 2) It decreases the recombination of electrons in TiO2 with triiodide in the electrolyte by preventing triiodide access to the TiO2 surface and/or by complexation with iodine in the electrolyte.

  • 12.
    Boschloo, Gerrit K.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry (closed 20110630). KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Edvinsson, Tomas
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry (closed 20110630). KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Hagfeldt, Anders
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry (closed 20110630). KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Dye-Sensitized Nanostructured ZnO Electrodes for Solar Cell Applications2006In: Nanostructured Materials for Solar Energy Conversion, Elsevier, 2006, p. 227-254Chapter in book (Other academic)
    Abstract [en]

    This chapter describes dye-sensitized nanostructured ZnO electrodes for solar cell applications. Dye-sensitized nanostructured solar cells (DNSCs) based on nanostructured metal oxide films have attracted much attention in recent years. This chapter explains the schematic representation of the DNSC. The performance of dye-sensitized ZnO solar cells in terms of solar-to-electrical energy conversion efficiencies is so far significantly lower than that of TiO2, reaching currently about 4-5%. An analysis of the energetics and kinetics of ZnO-based DNSCs suggests that this is mainly because of the lesser degree of optimization in case of ZnO compared to TiO2-based DNSCs. A large potential exists to improve on the performance of dye-sensitized ZnO solar cells by learning how to use new types of anchoring groups and controlling the chemistry at the oxide/dye/electrolyte interface. This, in combination with the possibilities to tailor-make ZnO materials, manifests the opportunities for future research and development of these devices.

  • 13.
    Brandt, Erik G.
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Hellgren, Mikko
    Brinck, Tore
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Bergman, Tomas
    Edholm, Olle
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Molecular dynamics study of zinc binding to cysteines in a peptide mimic of the alcohol dehydrogenase structural zinc site2009In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 11, no 6, p. 975-983Article in journal (Refereed)
    Abstract [en]

    The binding of zinc (Zn) ions to proteins is important for many cellular events. The theoretical and computational description of this binding (as well as that of other transition metals) is a challenging task. In this paper the binding of the Zn ion to four cysteine residues in the structural site of horse liver alcohol dehydrogenase (HLADH) is studied using a synthetic peptide mimic of this site. The study includes experimental measurements of binding constants, classical free energy calculations from molecular dynamics (MD) simulations and quantum mechanical (QM) electron structure calculations. The classical MD results account for interactions at the molecular level and reproduce the absolute binding energy and the hydration free energy of the Zn ion with an accuracy of about 10%. This is insufficient to obtain correct free energy differences. QM correction terms were calculated from density functional theory (DFT) on small clusters of atoms to include electronic polarisation of the closest waters and covalent contributions to the Zn-S coordination bond. This results in reasonably good agreement with the experimentally measured binding constants and Zn ion hydration free energies in agreement with published experimental values. The study also includes the replacement of one cysteine residue to an alanine. Simulations as well as experiments showed only a small effect of this upon the binding free energy. A detailed analysis indicate that the sulfur is replaced by three water molecules, thereby changing the coordination number of Zn from four (as in the original peptide) to six (as in water).

  • 14. Branneby, Cecilia
    et al.
    Carlqvist, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry (closed 20110630).
    Hult, Karl
    KTH, School of Biotechnology (BIO), Biochemistry (closed 20130101).
    Brinck, Tore
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry (closed 20110630).
    Berglund, Per
    KTH, Superseded Departments, Biotechnology.
    Rational redesign of a lipase to an aldolase2003In: Biochemistry, ISSN 0006-2960, E-ISSN 1520-4995, Vol. 42, no 28, p. 8633-8633Article in journal (Refereed)
  • 15.
    Brinck, Tore
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Haeberlein, Markus
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Jonsson, Mats
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    A Computational Analysis of Substituent Effects on the O-H Bond Dissociation Energy in Phenols: Polar Versus Radical Effects1997In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 119, no 18, p. 4239-4244Article in journal (Refereed)
  • 16.
    Brinck, Tore
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Lee, Hau-Nan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Jonsson, Mats
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Quantum Chemical Studies on the Thermochemistry of Alkyl and Peroxyl Radicals.1999In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 103, p. 7094-7104-Article in journal (Refereed)
  • 17. Bulat, Felipe A.
    et al.
    Toro-Labbé, Alejandro
    Brinck, Tore
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Murray, Jane S.
    Politzer, Peter
    Quantitative analysis of molecular surfaces: areas, volumes, electrostatic potentials and average local ionization energies2010In: Journal of Molecular Modeling, ISSN 1610-2940, E-ISSN 0948-5023, Vol. 16, no 11, p. 1679-1691Article in journal (Refereed)
    Abstract [en]

    We describe a procedure for performing quantitative analyses of fields f(r) on molecular surfaces, including statistical quantities and locating and evaluating their local extrema. Our approach avoids the need for explicit mathematical representation of the surface and can be implemented easily in existing graphical software, as it is based on the very popular representation of a surface as collection of polygons. We discuss applications involving the volumes, surface areas and molecular surface electrostatic potentials, and local ionization energies of a group of 11 molecules.

  • 18.
    Caraballo, Rémi
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Deng, Lingquan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Amorim, Luis
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Brinck, Tore
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Ramström, Olof
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    pH-Dependent Mutarotation of 1-Thioaldoses in Water. Unexpected Behavior of (2S)-D-Aldopyranoses2010In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 75, no 18, p. 6115-6121Article in journal (Refereed)
    Abstract [en]

    The pH-dependent mutarotation of 1-thioaldopyranoses in aqueous media has been investigated. Anomerization readily occurred at lower and neutral pH for all aldopyranoses studied, whereas mainly for (2S)-D-aldopyranoses at higher pH. 1-Thio-D-mannopyranose and 1-thio-D-altropyranose showed very strong pH dependence where the anomeric equilibrium ratios changed dramatically from a preference for the beta-anomer at lower pH to the alpha-anomer at higher pH.

  • 19.
    Carlqvist, Peter
    et al.
    KTH, Superseded Departments, Chemistry.
    Ostmark, H.
    Brinck, Tore
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry (closed 20110630).
    The stability of arylpentazoles2004In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 108, no 36, p. 7463-7467Article in journal (Refereed)
    Abstract [en]

    The stability of phenylpentazole along with para-substituted and ortho,para-substituted arylpentazoles have been studied using high-level density functional theory (DFT). The decomposition of arylpentazoles to N-2 and the corresponding azide is a first-order reaction, where the breaking of the N1-N2 bond is concomitant with cleavage of the N3-N4 bond. Calculations confirm that the stability of arylpentazoles increases with electron-donating groups and decreases with electron-withdrawing groups, in the para position, as found in experiments. The stabilizing effect of the electron-donating groups is shown to be due to a resonance interaction with the electron-withdrawing pentazole ring. Addition of solvation effects, using the polarizable continuum model to simulate the polar solvent methanol, increases the stability of arylpentazoles. This is due to a more polar ground state than transition state. The calculated free energies of activation for the arylpentazoles agree well with experimental results. From the calculations, the electron-withdrawing effect of the pentazole group is found to be similar to that of cyanide (-CN). Some new arylpentazoles with hydroxyl groups in the ortho position are proposed. These are predicted to be more stable than all previously synthesized neutral arylpentazoles.

  • 20.
    Carlqvist, Peter
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Svedendahl, Maria
    KTH, School of Biotechnology (BIO), Biochemistry.
    Branneby, Cecilia
    KTH, School of Biotechnology (BIO), Biochemistry.
    Hult, Karl
    KTH, School of Biotechnology (BIO), Biochemistry.
    Brinck, Tore
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Berglund, Per
    KTH, School of Biotechnology (BIO), Biochemistry.
    Exploring the Active-Site of a Rationally Redesigned Lipase for Catalysis of Michael-Type Additions2005In: ChemBioChem (Print), ISSN 1439-4227, E-ISSN 1439-7633, Vol. 6, p. 331-336Article in journal (Refereed)
    Abstract [en]

    Michael-type additions of various thiols and alpha,beta-unsaturated carbonyl compounds were performed in organic solvent catalyzed by wild-type and a rationally redesigned mutant of Candida antarctica lipase B. The mutant locks the nucleophilic serine 105 in the active-site; this results in a changed catalytic mechanism of the enzyme. The possibility of utilizing this mutant for Michael-type additions was initially explored by quantum-chemical calculations on the reaction between acrolein and methanethiol in a model system. The model system was constructed on the basis of docking and molecular-dynamics simulations and was designed to simulate the catalytic properties of the active site. The catalytic system was explored experimentally with a range of different substrates. The k(cat) values were found to be in the range of 10(-3) to 4 min(-1), similar to the values obtained with aldolase antibodies. The enzyme proficiency was 10(7). Furthermore, the Michael-type reactions followed saturation kinetics and were confirmed to take place in the enzyme active site.

  • 21. Castro, Vasco
    et al.
    Stevensson, Baltzar
    Dvinskikh, Sergey V.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Hogberg, Carl-Johan
    Lyubartsev, Alexander P.
    Zimmermann, Herbert
    Sandstrom, Dick
    Maliniak, Arnold
    NMR investigations of interactions between anesthetics and lipid bilayers2008In: Biochimica et Biophysica Acta - Biomembranes, ISSN 0005-2736, E-ISSN 1879-2642, Vol. 1778, no 11, p. 2604-2611Article in journal (Refereed)
    Abstract [en]

    Interactions between anesthetics (lidocaine and short chain alcohols) and lipid membranes formed by dimyristoylphosphatidylcholine (DMPC) were studied using NMR spectroscopy. The orientational order of lidocaine was investigated using deuterium NMR on a selectively labelled compound whereas segmental ordering in the lipids was probed by two-dimensional H-1-C-13 separated local field experiments under magic-angle spinning conditions. In addition, trajectories generated in molecular dynamics (MD) computer simulations were used for interpretation of the experimental results. Separate simulations were carried out with charged and uncharged lidocame molecules. Reasonable agreement between experimental dipolar interactions and the calculated counterparts was observed. Our results clearly show that charged lidocaine affects significantly the lipid headgroup. In particular the ordering of the lipids is increased accompanied by drastic changes in the orientation of the P-N vector in the choline group.

  • 22. Cifelli, Mario
    et al.
    Domenici, Valentina
    Dvinskikh, Sergey V.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Glogarova, Milada
    Veracini, Carlo Alberto
    Translational self-diffusion in the synclinic to anticlinic phases of a ferroelectric liquid crystal2010In: SOFT MATTER, ISSN 1744-683X, Vol. 6, no 23, p. 5999-6003Article in journal (Refereed)
    Abstract [en]

    In this work, the first direct measurement of inter and intra-layer molecular self-diffusion in the smectic phases of a chiral smectogen (S)-2-methylbutyl-[4'-(4 ''-heptyloxyphenyl)-benzoyl-4-oxy-(S)-2-((S)-2')benzoyl)-propionyl)]-pro pionate (ZLL7/*) by means of pulsed field gradient NMR is reported. Self-diffusion coefficients as low as 10(-13) m(2) s(-1) have been measured by combining magic echo spin decoupling with a stimulated echo sequence. The transitions among synclinic-anticlinic smectic phases are associated with a change in the self-diffusion coefficients.

  • 23.
    Corkery, Robert W.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry (closed 20110630).
    Fleischer, Cathy
    Daly, Robert C.
    Polymeric composition, adhesive including nanoparticle filler and composite production.2006Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    Nanoparticle fillers, including a novel halloysite nanoparticle filler, are generally cylindrical or tubular nanoparticles (e.g. rolled scroll-like shape). The filler is effectively employed in a polymer nanoparticle adhesive composite, contg. the halloysite nanoparticle or other equiv. naturally occurring nanotubular filler, in which the advantages of the nanoparticle filler are provided (e.g., reinforcement, flame retardant, etc.) while maintaining or improving mech. performance of the adhesive composite (e.g., adhesive strength and tack). [on SciFinder(R)]

  • 24.
    Dahlberg, Carina
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Drugs and polymers in dissolving solid dispersions: NMR imaging and spectroscopy2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The number of poorly water-soluble drug substances in the pharmaceutical pipeline is increasing, and thereby also the need to design effective drug delivery systems providing high bioavailability. One favourable formulation approach is preparation of solid dispersions, where dispersing a poorly water-soluble drug in a water-soluble polymer matrix improves the dissolution behaviour and the bioavailability of the drug. However, in order to take full advantage of such formulations the impact of material properties on their performance needs to be investigated.

     

    An experimental toolbox has been designed, and applied, for analysing the processes which govern the behaviour of solid pharmaceutical formulations in general, and that of solid dispersions in particular. For the purpose of monitoring multifaceted phenomena in situ during tablet dissolution, nuclear magnetic resonance (NMR) spectroscopy and NMR imaging are superior to many other techniques, both on macroscopic and molecular levels. The versatility of NMR with its isotope and chemical selectivity allows one to follow the influence of the original tablet properties on polymer mobilisation, drug migration and water penetration selectively. Mapping these processes on relevant time scales in dissolving tablets highlighted the gel layer inhomogeneity below the originally dry tablet surface as a key factor for drug release kinetics.

     

    Furthermore, NMR relaxometry has been shown to provide novel information about the particle size of the drug and its recrystallisation behaviour within swelling solid dispersions. The NMR experiments have been complemented and supported by investigation of the crystalline state, the powder morphology and the surface composition of the dry solid dispersions. These experiments have been performed by X-ray photoelectron spectroscopy (XPS),  scanning electron microscopy (SEM), powder X-ray diffraction (pXRD), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and dynamic contact angle (DAT) measurements.

     

    The methods presented in this thesis provide a new avenue towards better understanding of the behaviour of solid dispersions, which in turn may result in more effective distribution of promising drug candidates despite their low water-solubility.

  • 25.
    Dahlberg, Carina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Dvinskikh, Sergey V.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Furó, István
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Polymer mobilization and drug release during tablet swelling: A 1H NMR and NMR microimaging study2007In: Journal of Controlled Release, ISSN 0168-3659, E-ISSN 1873-4995, Vol. 122, p. 199-205Article in journal (Refereed)
    Abstract [en]

    The objective of this study was to investigate the swelling characteristics of a hydroxypropyl methylcellulose (HPMC) matrix incorporating the hydrophilic drug antipyrine. We have used this matrix to introduce a novel analytical method, which allows us to obtain within one experimental setup information about the molecular processes of the polymer carrier and its impact on drug release. Nuclear magnetic resonance (NMR) imaging revealed in situ the swelling behavior of tablets when exposed to water. By using deuterated water, the spatial distribution and molecular dynamics of HPMC and their kinetics during swelling could be observed selectively. In parallel, NMR spectroscopy provided the concentration of the drug released into the aqueous phase. We find that both swelling and release are diffusion controlled. The ability of monitoring those two processes using the same experimental setup enables mapping their interconnection, which points on the importance and potential of this analytical technique for further application in other drug delivery forms.

  • 26.
    Dahlberg, Carina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Dvinskikh, Sergey V.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Schuleit, Michael
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Polymer Swelling, Drug Mobilization and Drug Recrystallization in Hydrating Solid Dispersion Tablets Studied by Multinuclear NMR Microimaging and Spectroscopy2011In: Molecular Pharmaceutics, ISSN 1543-8384, E-ISSN 1543-8392, Vol. 8, no 4, p. 1247-1256Article in journal (Refereed)
    Abstract [en]

    Despite the advantages offered by solid dispersions, the marketed products based on this technology are few. The most frequent concern is the stability of the amorphous drug. The state of the drug in solid dispersions is, in general, poorly characterized as the number of characterization techniques available to monitor nanometer-sized drug particles embedded in a matrix are limited. Here we present a combination of localized NMR spectroscopic and NMR imaging techniques which allow in situ monitoring of the state of the drug during tablet disintegration and dissolution. (19)F NMR relaxation is shown to be sensitive to both the crystalline/amorphous state and the size of the model nanoparticles made of the drug substance flutamide. The time course of drug mobilization and recrystallization is detected with spatial resolution within swelling solid dispersion tablets. Comparing results from spatially resolved (19)F, (2)H and (1)H NMR experiments, recrystallization is related to its enabling factors such as local hydration level and local mobility of the polymer matrix. The initially amorphous drug may recrystallize either by nanoparticle coalescence or by ripening of crystalline grains.

  • 27.
    Dahlberg, Carina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Dvinskikh, Sergey V.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Schuleit, Michael
    Furó, István
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Recrystallization of drug nanoparticles in solid dispersion tablets by multinuclear NMR spectroscopy and NMR microimagingManuscript (preprint) (Other academic)
  • 28.
    Dahlberg, Carina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Millqvist-Fureby, Anna
    Schuleit, Michael
    Surface composition and contact angle relationships for differently prepared solid dispersions2008In: European journal of pharmaceutics and biopharmaceutics, ISSN 0939-6411, E-ISSN 1873-3441, Vol. 70, p. 478-485Article in journal (Refereed)
    Abstract [en]

    Solid dispersions are promising drug delivery forms which offer the possibility to disperse a hydrophobic drug in a hydrophilic matrix and thereby improve the dissolution behavior and the bioavailability of the drug. One important aspect and a prerequisite in understanding the drug dissolution mechanism from solid dispersions is a better analytical monitoring of the solid dispersion surface properties, such as powder surface composition and water adsorption properties. In this paper, we have considered chemical and structural surface analysis data for solid dispersions processed by spray drying or roto-evaporation and compared these data with information obtained by contact angle measurements. Firstly, we establish the usefulness and suitability of X-ray photoelectron spectroscopy (XPS) for determination of surface chemical composition and scanning electron microscopy (SEM) for determining the structure of solid dispersions composed of different types of carriers, drugs and drug concentrations. Secondly, we measure contact angles of solid dispersions to describe wettability, to finally establish a link between the surface chemical composition, the powder structure and the wetting behavior. These experimental methods offer a rapid screening tool for the selection of carrier, drug concentration and/or process in early development. In addition, they provide a useful tool for investigating structural aspects of solid dispersions which have intrinsic relevance for drug dissolution and stability.

  • 29.
    Dahlberg, Carina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Millqvist-Fureby, Anna
    Schuleit, Michael
    Furó, István
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Polymer–drug interactions and wetting of solid dispersions2009In: European Journal of Pharmaceutical Sciences, ISSN 0928-0987, E-ISSN 1879-0720, Vol. 39, no 1-3, p. 125-133Article in journal (Refereed)
    Abstract [en]

    We demonstrate the ability of drugs to influence the wetting of solid dispersion tablets in unexpected ways. Five model drugs of different water solubility and ability to interact with the involved polymers were incorporated in hydrophilic polymer matrices, made of either hydroxypropyl methylcellulose (HPMC) or polyvinyl pyrrolidone (PVP). The physical mixtures of all combinations of drug and polymer presented surface hydrophobicities, as measured by the equilibrium advancing contact angle of water, which are expected for materials that do not influence the interactions of each other with water. However, the solid dispersions containing HPMC deviated from this regular behaviour and displayed contact angles below those of the pure compounds involved, either drug or polymer. This behaviour is explained by changed surface exposure of HPMC side groups, as a result of changes in intermolecular hydrogen bonds. In addition to water contact angle measurements, we employed NMR imaging to monitor the time course of water ingress and swelling.

  • 30.
    Dahlberg, Carina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Millqvist-Fureby, Anna
    Schuleit, Michael
    Furó, István
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Relationships between solid dispersion preparation process, particle size and drug release: an NMR and NMR microimaging study2010In: European journal of pharmaceutics and biopharmaceutics, ISSN 0939-6411, E-ISSN 1873-3441, Vol. 76, no 2, p. 311-319Article in journal (Refereed)
    Abstract [en]

    Solid dispersion tablets prepared by either spray drying or rotoevaporation and exhibiting different grain and pore sizes were investigated under the process of hydration-swelling-gelation. H-2 and H-1 NMR microimaging experiments were used to selectively follow water penetration and polymer mobilization kinetics, respectively, while the drug release kinetics was followed by H-1 NMR spectroscopy. The obtained data, in combination with morphological information by scanning electron microscopy (SEM), reveal a complex process that ultimately leads to release of the drug into the aqueous phase. We find that the rate of water ingress has no direct influence on release kinetics, which also renders air in the tablets a secondary factor. On the other hand, drug release is directly correlated with the polymer mobilization kinetics. Water diffusion into the originally dry polymer grains determines the rate of grain swelling and the hydration within the grains varies strongly with grain size. We propose that this sets the stage for creating homogeneous gels for small grain sizes and heterogeneous gels for large grain sizes. Fast diffusion through water-rich sections of the inhomogeneous gels that exhibit a large mesh size is the factor which yields a faster drug release from tablets prepared by rotoevaporation.

  • 31.
    Dahlberg, Carina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Schuleit, Michael
    Furó, István
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Estimating the size range of drug nanoparticles in solid dispersions by NMR spectroscopyManuscript (preprint) (Other academic)
  • 32. Dvinskikh, S. V.
    et al.
    Furó, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry (closed 20110630).
    Nuclear magnetic resonance studies of translational diffusion in thermotropic liquid crystals2006In: Russian Chemical Reviews, ISSN 0036-021X, E-ISSN 1468-4837, Vol. 75, no 6, p. 497-506Article in journal (Refereed)
    Abstract [en]

    The experimental NMR techniques for studies of translational diffusion in anisotropic systems and the results of their applications to thermotropic liquid crystals arc reviewed. The main approaches to the theoretical description and computer simulations of diffusion are discussed. The experimental results are compared with computations. The bibliography includes 194 references.

  • 33.
    Dvinskikh, Sergey
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Furó, István
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Sandberg, Dick
    Linnæus University, School of Engineering.
    Söderström, Ove
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology.
    Moisture content profiles and uptake kinetics in wood cladding materials evaluated by a portable nuclear magnetic resonance spectrometer2011In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 6, no 3, p. 119-127Article in journal (Refereed)
    Abstract [en]

    This study evaluated the capability of nuclear magnetic resonance (NMR) technology based on small portable magnets for in situ studies of the local moisture content in wood. Low-field and low-resolution [1H]NMR with a unilateral permanent magnet was used to monitor and map the moisture content of wood cladding materials of various types in a spatially resolved manner. The results show that portable NMR equipment based on small open-access permanent magnets can be successfully used for non-invasive monitoring of the moisture content in various extended wood specimens. The moisture content was measured with a depth resolution of 0.2 mm and a maximum penetration depth of 3 mm. This makes the technique suitable for in situ local moisture content measurements beneath a coating layer in the cladding, for example, and it is also possible to relate the moisture level to specific properties of the wood material.

  • 34. Dvinskikh, Sergey V.
    et al.
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Nuclear magnetic resonance studies of translational diffusion in thermotropic liquid crystals2006In: Uspehi himii, ISSN 0042-1308, E-ISSN 1817-5651, Vol. 75, no 6, p. 557-568Article, review/survey (Refereed)
  • 35.
    Dvinskikh, Sergey V.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Furó, István
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Magnetic resonance imaging and nuclear magnetic resonance investigations of bentonite systems2009Report (Refereed)
  • 36.
    Dvinskikh, Sergey V.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Henriksson, Marielle
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites.
    Berglund, Lars A.
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites.
    Furó, István
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    A multinuclear magnetic resonance imaging (MRI) study of wood with adsorbed water: Estimating bound water concentration and local wood density2011In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 65, no 1, p. 103-107Article in journal (Refereed)
    Abstract [en]

    The interaction between moisture and the macromolecular wood tissue is of critical importance to wood properties. In this context, magnetic resonance imaging (MRI) is very promising as this method could deliver molecular information on the submillimeter scale (i.e., along concentration gradients) about both free and adsorbed water and the cell wall polymers. In the present study, it is demonstrated for the first time that wood containing adsorbed heavy water ((H2O)-H-2) can be studied by MRI based on separated images due to water (H-2 MRI) and cell wall polymers (H-1 MRI). Data confirm that in specimens equilibrated at controlled humidity there is a direct correlation between bound water content and relative density of the polymers in wood tissue; there is a strong variation across annual rings.

  • 37.
    Dvinskikh, Sergey V.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre. KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Henriksson, Marielle
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Mendicino, Antonio Lorenzo
    Fortino, Stefania
    Toratti, Tomi
    NMR imaging study and multi-Fickian numerical simulation of moisture transfer in Norway spruce samples2011In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 33, no 11, p. 3079-3086Article in journal (Refereed)
    Abstract [en]

    Wood has potential as a renewable material for a large variety of applications that often call for improved properties such as dimensional stability, moisture insensitivity, and durability. Moisture migration in wood is a particularly important factor in determining the cost-effective service life of wooden construction. Within the present research, proton NMR imaging was applied for recording the moisture spatial distribution of various samples of Norway Spruce. Moisture distribution along the radial, tangential and longitudinal directions in wood was monitored at different times upon three consecutive changes of relative humidity: (1) from 65% to 94%; (2) from 94% to 33%; (3) from 33% to 65%. Uncoated samples and specimens treated with different types of surface coatings were studied. The experiments were numerically simulated by using the multi-Fickian model. The model describes the moisture transport process in wood which is characterized by three phenomena: (a) bound water diffusion, (b) water vapor diffusion and (c) coupling between the two phases through sorption. The model is implemented into the Abaqus FEM code. The numerical results are found to be in agreement with the experimental data.

  • 38.
    Dvinskikh, Sergey V.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Szutkowski, Kosma
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    MRI profiles over very wide concentration ranges: Application to swelling of a bentonite clay2009In: Journal of magnetic resonance, ISSN 1090-7807, E-ISSN 1096-0856, Vol. 198, no 2, p. 146-150Article in journal (Refereed)
    Abstract [en]

    In MRI investigation of soils, clays, and rocks, mainly mobile water is detected, similarly to that in biological and medical samples. However, the spin relaxation properties of water in these materials and/or low water concentration may make it difficult to use standard MRI approaches. Despite these limitations, one can combine MRI techniques developed for solid and liquid states and use independent information on relaxation properties of water, interacting with the material of interest, to obtain true images of both water and material content. We present procedures for obtaining such true density maps and demonstrate their use for studying the swelling of bentonite clay by water. A constant time imaging protocol provides 1D mapping of the clay distribution in regions with clay concentration above 10 vol%. T-1 relaxation time imaging is employed to monitor the clay content down to 10(-3) vol%. Data provided by those two approaches are in good agreement in the overlapping range of concentrations. Covering five orders of magnitude of clay concentration, swelling of sodium-exchanged bentonite clays from pre-compacted pellets into a gel phase is followed in detail.

  • 39.
    Dvinskikh, Sergey V.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Yamamoto, Kazutoshi
    Scanu, David
    Deschenaux, Robert
    Ramamoorthy, Ayyalusamy
    High-resolution characterization of liquid-crystalline 60 fullerenes using solid-state nuclear magnetic resonance spectroscopy2008In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 112, no 39, p. 12347-12353Article in journal (Refereed)
    Abstract [en]

    Liquid-crystalline materials containing fullerenes are valuable in the development of supramolecular switches and in solar cell technology. In this study, we characterize the liquid-crystalline and dynamic properties of fullerene-containing thermotropic compounds using solid-state natural abundance C-13 NMR experiments under stationary and magic angle spinning sample conditions. Chemical shifts spectra were measured in isotropic, liquid-crystalline nematic and smectic A and crystalline phases using one-dimensional 13C experiments, while two-dimensional separated local-field experiments were used to measure the H-1-C-13 dipolar couplings in mesophases. Chemical shift and dipolar coupling parameters were used to characterize the structure and dynamics of the liquid-crystalline dyads. NMR data of fullerene-containing thermotropic liquid crystals are compared to that of basic mesogenic unit and mesomorphic promoter compounds. Our NMR results suggest that the fullerene-ferrocene dyads form highly dynamic liquid-crystalline phases in which molecules rotate fast around the symmetry axis on the characteristic NMR time scale of similar to 10(-1) s.

  • 40. Edvinsson, Tomas
    et al.
    Li, Chen
    Pschirer, Neil
    Schoeneboom, Jan
    Eickemeyer, Felix
    Sens, Ruediger
    Boschloo, Gerrit
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Herrmann, Andreas
    Muellen, Klaus
    Hagfeldt, Anders
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Intramolecular charge-transfer tuning of perylenes: Spectroscopic features and performance in Dye-sensitized solar cells2007In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 111, no 42, p. 15137-15140Article in journal (Refereed)
    Abstract [en]

    Five novel perylene molecules with different intramolecular charge-transfer (ICT) characters have been synthesized. The relation between the ICT character for different donating groups and the results for their electro- and photochemical properties as well as their performance in nanostructured dye-sensitized solar cells (nDSC) are reported. With the stronger donors, we obtain a shift of the lowest unoccupied molecular orbital (LUMO) to more negative potential versus normal hydrogen electrode (NHE) as well as an increase the charge separation in the dye upon excitation. Ab initio calculations were used to analyze the effects on orbital energies and electron distribution with the different donors. Incorporating the dyes in nDSCs, we see a drastical improvement in the performance for the more polar dyes. In particular, we find a much improved photovoltage because of higher LUMO levels, allowing conduction band tuning in the TiO2 as well as a contribution from the permanent dipoles in the dyes. The photocurrent improves remarkably with increasing ICT character of the dyes. The external quantum efficiency reached over 70%, and the overall solar-to-electrical energy conversion efficiency was improved to almost 4% for the dye with highest ICT character, which can be compared with devices with the standard N719 dye (Ru(dcbPY)(2)(NCS)(2)) showing 6% under similar conditions. The performance is a significant improvement compared to previous reports for perylenes and lifts the performance from modest to promising. Initial stability tests show that the dye with the highest performance was spectrally stable after more than 2000 h of irradiation in a solar-cell device.

  • 41. Edvinsson, Tomas
    et al.
    Pschirer, Neil
    Schoneboom, Jan
    Eickemeyer, Felix
    Boschloo, Gerrit
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Hagfeldt, Anders
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Photoinduced electron transfer from a terrylene dye to TiO2: Quantification of band edge shift effects2009In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 357, no 1-3, p. 124-131Article in journal (Refereed)
    Abstract [en]

    A terrylene chromophore exhibiting a high extinction coefficient has been developed as a sensitizer for photovoltaic applications. The photophysical and photochemical properties of the dye were analyzed both experimentally and theoretically. Terrylene-sensitized nanocrystalline TiO2 solar cells yielded good photocurrents providing more than 60% in external quantum efficiency. The photoinduced electron transfer from the dye to TiO2 was found to be very sensitive to conduction band edge shifts in TiO2 induced, either by changes in the composition of the redox electrolyte or by UV-illumination. This sensitivity was observed in quantum efficiencies for photocurrent generation of terrylene-sensitized solar cells and in photoinduced absorption experiments. The conduction band shifts were quantified using charge extraction methods. The observed sensitivity of the injection efficiency suggests that photoinduced electron transfer occurs from the relaxed excited state, possibly due to poor electronic coupling between TMIMA excited states and TiO2 conduction band states.

  • 42. Eitelberger, J.
    et al.
    Hofstetter, K.
    Dvinskikh, Sergey V.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    A multi-scale approach for simulation of transient moisture transport processes in wood below the fiber saturation point2011In: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 71, no 15, p. 1727-1738Article in journal (Refereed)
    Abstract [en]

    This paper presents a new, physically-based model for transport processes in wood for conditions below the fiber saturation point. The macroscopic mathematical description of these processes involves three coupled differential equations: two mass balance laws for the bound water and the water vapor phase, and an energy balance equation. These governing equations and the corresponding boundary conditions are expressed in terms of the state variables bound water concentration, water vapor concentration, and temperature. Macroscopic material properties are estimated based on a multiscale approach in the framework of continuum micromechanics. The phase change between the two water phases and the thus resulting coupling between the differential equations cannot be suitably captured in a purely macroscopic description, therefore a microscale sub-model is presented. Numerical solutions of the model equations are derived by means of the Finite Element Method. Finally, the model is applied to prediction of moisture profiles in a wood sample under transient environmental conditions. Comparing these results with corresponding profiles obtained non-destructively by proton magnetic resonance imaging (MRI) validates the model and confirms suitability of the underlying physical assumptions.

  • 43. Eriksson, Jan Christer
    et al.
    Henriksson, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry (closed 20110630).
    Bridging-cluster model for hydrophobic attraction2007In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 23, no 20, p. 10026-10033Article in journal (Refereed)
    Abstract [en]

    A new model is proposed to account for the long-range hydrophobic attraction repeatedly observed for thin water films between two stable (solid) hydrophobic surfaces. The model is based on the notion of structurally organized, elongated water clusters that span the gap between the hydrophobic surfaces. Two features are noted: (i) Mixing entropy due to the mixing of the clusters and the remainder of the water in the thin film is explicitly taken into account. (ii) A term is invoked that depends inversely on the film thickness, which accounts for the free-energy change associated with reorganizing the film as the film thickness varies. Fitting to experimental surface force data resulted in parameter values of reasonable magnitudes. The model developed covers film thicknesses from about 2 nm and above. On this basis, the amazingly long range of the hydrophobic attraction can be attributed to the formation of bridging, quasi-cylindrical clusters having a radius on the order of 1 to 2 nm.

  • 44.
    Eriksson, Jan Christer
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Henriksson, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Thermodynamic surface properties of single crystal faces of xenon calculated by employing the Einstein model of crystalline solids2012In: Colloid Journal of the Russian Academy of Science, ISSN 1061-933X, E-ISSN 1608-3067, Vol. 74, no 2, p. 186-193Article in journal (Refereed)
    Abstract [en]

    By broadening the scope of the Einstein statistical-mechanical treatment of a crystalline solid to cover also low-index faces, and using the Lennard-Jones interaction potential and, in addition, adopting an approximate monolayer-nearest-neighbor model, we have calculated the thermodynamic properties of (100) and (111) single crystal faces of Xe(s) in the temperature range 20-80 K. The reversible cleavage work (that corresponds to the Gibbs sigma-quantity of interfaces) was found to be on the order of 20-30 mJ m(-2) and is largely due to reduction of the pair-wise dispersion interactions for monolayer atoms as compared with the atoms in the bulk of the crystal. For an unstrained crystal, sigma diminishes slightly with temperature for both energetic as well as entropic reasons. On the other hand, the differential work of stretching a solid interface, gamma, is a negative quantity (-5 to -30 mN m(-1)), corresponding to surface pressure, the main reason being that upon (elastic, homogeneous) stretching, the vibration energy levels of the top monolayer are shifted upward, at the same time becoming more closely spaced. It is shown that such a stretching operation causes the T x surface excess entropy term to increase at a faster rate than the corresponding surface energy term, which accounts for the negative sign found for gamma. On the same basis, we can also verify that the general, though sometimes questioned, Shuttleworth relation, is necessarily fulfilled for an ideally terminated (metastable) Xe crystal face with a filled monolayer of immobile Xe atoms. As a matter of fact, this equation merely represents an alternative mathematical disguise of the basic energy differential expression for the monolayer.

  • 45. Eriksson, Jan Christer
    et al.
    Henriksson, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Kumpulainen, Atte
    Hydrophobic attraction forces in asymmetric aqueous films between hydrophobized mica/bare mica surfaces2006In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 282, p. 79-83Article in journal (Refereed)
    Abstract [en]

    The water-structure-based, quasi-thermodynamic theory published several years ago of hydrophobic interaction forces in symmetric aqueous films [J.C. Eriksson, S. Ljunggren, P.M. Claesson, J. Chem. Sec., Faraday Trans. 2 (85) (1989) 1631 has been generalized to encompass asymmetric films between, e.g. a hydrophobized mica surface and a bare mica surface. The interaction pressures derived on this basis are in good agreement with the experimental data recorded by Claesson et al. [P.M. Claesson, P.C. Herder. C.E. Blom, B.W. Ninham. J. Colloid Interface Sci. 118 (1987) 68]. Hence, additional support is gathered for the original claim that the hydrophobic attraction is related with hydrogen-bond-dependent cluster formation processes in water contacted with a hydrophobic solid Surface.

  • 46. Fabregat-Santiago, F.
    et al.
    Bisquert, J.
    Garcia-Belmonte, G.
    Boschloo, Gerrit
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Hagfeldt, Anders
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Influence of electrolyte in transport and recombination in dye-sensitized solar cells studied by impedance spectroscopy2005In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 87, no 04-jan, p. 117-131Article in journal (Refereed)
    Abstract [en]

    The main features of the characteristic impedance spectra of dye-sensitized solar cells are described in a wide range of potential conditions: from open to short circuit. An equivalent circuit model has been proposed to describe the parameters of electron transport, recombination, accumulation and other interfacial effects separately. These parameters were determined in the presence of three different electrolytes, both in the dark and under illumination. Shift in the conduction band edge due to the electrolyte composition was monitored in terms of the changes in transport resistance and charge accumulation in TiO2. The interpretation of the current-potential curve characteristics, fill factor, open-circuit photopotential and efficiency in the different conditions, was correlated with this shift and the features of the recombination resistance.

  • 47.
    Fischer, Andreas
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Inorganic Chemistry.
    Pettersson, Henrik
    Hagfeldt, Anders
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Boschloo, Gerrit
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Kloo, Lars A.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Inorganic Chemistry.
    Gorlov, Mikhail
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Inorganic Chemistry.
    Crystal formation involving 1-methylbenzimidazole in iodide/triiodide electrolytes for dye-sensitized solar cells2007In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 91, no 12, p. 1062-1065Article in journal (Refereed)
    Abstract [en]

    Nitrogen heterocyclic compounds, such as N-methylbenzimidazole (MBI), are commonly used as additives to electrolytes for dye-sensitized solar cells (DSCs), but the chemical transformation of additives in electrolyte solutions remains poorly understood. Solid crystalline compound (MBI)(6)(MBI-H+)(2)(I-)(I-3(-)) (1) was isolated from different electrolytes for DSCs containing MBI as additive. The crystal structure of I was determined by single-crystal X-ray diffraction. In the crystal structure, 1 contains neutral and protonated MBI fragments; iodide and triiodide anions form infinite chains along the crystallographic a-axis. The role of the solvent and additives in the crystallization process in electrolytes is discussed.

  • 48.
    Fredin, Kristofer
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Rühle, S.
    Condensed Matter and Interfaces, Debye Institute, Utrecht University.
    Grasso, C.
    Electronics and Information Systems (ELIS), Gent.
    Hagfeldt, Anders
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Studies of coupled charge transport in dye-sensitized solar cells using a numerical simulation tool2006In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 90, no 13, p. 1915-1927Article in journal (Refereed)
    Abstract [en]

    In this paper, we present a simulation platform designed to study coupled charge transport in dye-sensitized solar cell (DSC) devices. The platform, SLICE, is used to study the influence of ions in the electrolyte on electron transport in the nanoporous medium. The simulations indicate that both cationic and anionic properties should be considered when modelling DSCs and similar systems. Additionally, it was found that the effective permittivity coefficient, epsilon, has no influence on the electron transport when the ionic concentration is sufficiently high due to the strong coupling between the respective charged species.

  • 49.
    Frise, Anton
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Nano-segregated soft materials observed by NMR spectroscopy2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis is about using nuclear magnetic resonance (NMR) spectroscopy for studying soft materials. Soft materials may be encountered everyday by most readers of this thesis, for example when taking a shower or watching TV. The usefulness of these materials originates from them being soft yet, at the same time, having some kind of a structure. The characteristic length scale of those structures is often on the order of nanometers (10-9 m) and the structure can respond to various external stimuli such as temperature, electric and magnetic fields, or the presence of interfaces.

    NMR spectroscopy excels when studying soft materials because it is a non-invasive technique with a large spectral resolution. Moreover, different NMR methods allow us to study local molecular dynamics or longer-range translational diffusion. Understanding those latter aspects is very important for the development of dynamic and responsive materials.

    Papers I-III present our work on assessing molecular adsorption on interfaces in colloidal dispersions. Here, carbon nanotubes (CNTs) or silica particles were the colloidal substrates to which proteins, polymers or surfactants adsorbed. Papers IV-VI concern ionic mobility in liquid crystals (LCs). The influence of material structure on, for example, the anisotropy of diffusion or on the association/dissociation of ions was studied in several LC phases.

  • 50.
    Frise, Anton
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry (closed 20110630). KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Dvinskikh, Sergey V.
    Ichikawa, Takahiro
    Yoshio, Masafumi
    Ohno, Hiroyuki
    Kato, Takashi
    Furó, István
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry (closed 20110630). KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Anisotropic Ion Mobility in an Ionic Liquid Crystal Complex of a Rodlike Mesogen Containing an Oxyethylene Moiety and Lithium TriflateManuscript (preprint) (Other academic)
    Abstract [en]

    A liquid-crystalline (LC) complex of a rodlike mesogen containing an oxyethylene moiety and lithium triflate has been synthesized and its mesophases have been characterized by differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD) and polarized optical microscopy (POM). The ion conductive behaviour was investigated in isotropic and LC phases and related to the ionic mobility, as observed by 7Li and 19F NMR diffusometry. The observed two-dimensional ion mobilities show that planes conducting both lithium and triflate ions are formed in the smectic mesophases. The conductivity of the lithium ions is large in the smectic C phase where conductive planes rich in ethylene oxide chains exist.

1234 1 - 50 of 178
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