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  • 301.
    Pan, Jinshan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Davoodi, A
    Leygraf, Christofer
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Norgren, S.
    Application of combined electrochemical AFM and SECM for in-situ study of localized corrosion of Al alloys in chloride solutions2005In: Proc. 16th International Corrosion Congress, Beijing, Sept. 19-24, 2005, 2005, p. 9-31Conference paper (Other academic)
  • 302.
    Pan, Jinshan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Leygraf, Christofer
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Rosborg, Bo
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Tafel slopes used in monitoring of copper corrosion in a bentonite/groundwater environment2005In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 47, no 12, p. 3267-3279Article in journal (Refereed)
    Abstract [en]

    The harmonic analysis, the polarization resistance, and the noise resistance methods have been applied in an effort to monitor corrosion of pure copper in a bentonite/groundwater environment with commercially available equipment. Without the need to use a reference electrode, the first method supplies not only an estimate of the corrosion rate, but also estimates of Tafel slopes required by the other methods. The recorded corrosion rate is overestimated but to a varying degree. While the recorded corrosion rates for the first two methods give quite similar values far below 3 lm/year, the electrochemical noise resistance method gives considerably higher values.

  • 303.
    Pan, Jinshan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Norlin, Anna
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Leygraf, Christofer
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Investigation of electrochemical behavior of stimulation/sensing electrode materials for pacemaker applications2005In: Proc. 16th International Corrosion Congress, Beijing, Sept. 19-24, 2005, 2005, p. 14-33Conference paper (Other academic)
  • 304. Panigrahi, P.
    et al.
    Naqvi, S. R.
    Hankel, M.
    Ahuja, Rajeev
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Uppsala University, Sweden.
    Hussain, T.
    Enriching the hydrogen storage capacity of carbon nanotube doped with polylithiated molecules2018In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 444, p. 467-473Article in journal (Refereed)
    Abstract [en]

    In a quest to find optimum materials for efficient storage of clean energy, we have performed first principles calculations to study the structural and energy storage properties of one-dimensional carbon nanotubes (CNTs) functionalized with polylithiated molecules (PLMs). Van der Waals corrected calculations disclosed that various PLMs like CLi, CLi2, CLi3, OLi, OLi2, OLi3, bind strongly to CNTs even at high doping concentrations ensuring a uniform distribution of dopants without forming clusters. Bader charge analysis reveals that each Li in all the PLMs attains a partial positive charge and transform into Li+ cations. This situation allows multiple H2 molecules adsorbed with each Li+ through the polarization of incident H2 molecules via electrostatic and van der Waals type of interaction. With a maximum doping concentration, that is 3CLi2/3CLi3 and 3OLi2/3OLi3 a maximum of 36 H2 molecules could be adsorbed that corresponds to a reasonably high H2 storage capacity with the adsorption energies in the range of −0.33 to −0.15 eV/H2. This suits the ambient condition applications.

  • 305. Partanen, Riitta
    et al.
    Forssell, Pirkko
    Mackie, Alan
    Blomberg, Eva
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Interfacial cross-linking of beta-casein changes the structure of the adsorbed layer2013In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 32, no 2, p. 271-277Article in journal (Refereed)
    Abstract [en]

    The mechanism of transglutaminase-induced cross-linking of interfacial beta-casein layer was investigated in tetradecane/buffer system. Monolayer studies were carried out in a Langmuir trough, where incubation with the enzyme mostly affected the compression of the film through adsorption of transglutaminase to the interface. Interfacial shear rheology was used to follow the kinetics of formation of a visco-elastic film upon cross-linking. Substrate concentration affected the rate of the interfacial cross-linking, when enzyme was dosed per protein concentration. This was most likely due to the saturated substrate layer at the interface in all cases. SDS-PAGE revealed that most of the beta-casein at the interface was not cross-linked by intermolecular links, but rather, intramolecular links were formed. Finally, studies of adsorbed beta-casein layers on polystyrene beads revealed that cross-linking reduced the thickness of the adsorption layer from 11-12 nm to 8-9 nm. These results suggest that it may be mainly intra-molecular cross-linking which modifies the physical interactions of beta-caseins at the interface resulting in a higher layer density and thus, formation of a visco-elastic network.

  • 306. Pasti, Igor A.
    et al.
    Skorodumova, Natalia V.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling. Uppsala University, Sweden.
    Mentus, Slavko V.
    Theoretical studies in catalysis and electrocatalysis: from fundamental knowledge to catalyst design2015In: Reaction Kinetics, Mechanisms and Catalysis, ISSN 1878-5190, E-ISSN 1878-5204, Vol. 115, no 1, p. 5-32Article in journal (Refereed)
    Abstract [en]

    Catalytic processes are an indispensable part of a large number of contemporary technologies that stimulate a constant research and development effort in the field. Computational methods represent a valuable tool to investigate crucial steps of catalytic cycles able to reveal the main characteristics of a catalyst and provide a basis for the design of materials with superior catalytic activity. This review is focused on the recent advances in density functional theory studies of the interactions of reactive species and intermediates with solid surfaces. As examples, we discuss the catalysts for the CO oxidation and electrocatalysis of H-2 and O-2 electrode reactions. We demonstrate how the theoretical modelling can contribute to the understanding of catalytic processes and help to design new catalysts and electrocatalysts.

  • 307.
    Pavankumar, Asalapuram Ramachandran
    et al.
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Norén, Johan
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Singh, Lakhvinder
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Gowda, Naveen Kumar Chandappa
    Scaling-up the production of recombinant Moringa oleifera coagulant protein for large-scale water treatment applications2014In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 4, no 14, p. 7136-7141Article in journal (Refereed)
    Abstract [en]

    Provision of safe drinking water, devoid of aetiologies is an all-time challenge due to the usage of unsafe chemicals in most of the water treatment processes. In this regard, proteins of Moringa oleifera (MO) provide most promising solutions, as its crude seed extracts are being used as natural 'water clarifiers' in drinking and wastewater treatments. Among MO seed proteins, a 6.5 kDa coagulant protein (MO coagulant protein; MOCP) has gained importance because of its antimicrobial and water clarification properties. Considering the biomedical and commercial values of the MO plant, in this study, the cDNA coding for MOCP was cloned and over expressed in E. coli BL21 (DE3). After bench-scale experiments, for the first time, the recombinant protein production was scaled up to 7 L bioreactors in Luria Broth supplemented with 1% glucose. About 42 mg of Moringa oleifera coagulating recombinant protein (MOCRP; 6.5 kDa) was purified using superparamagnetic iron oxide nanoparticles (SPION) from 1 litre of the over expressed E. coli cell cultures. The purified MOCRP revealed an efficient coagulation activity (similar to 66%) even with 0.1 mg L-1; while very good antimicrobial response was recorded against a set of Gram-negative and Gram-positive microorganisms at as low as 10 mg L-1. Thus, we report the over expression and purification of this dual-function protein (MOCRP) from moringa for the first time, using bioreactors with an economical and user-friendly approach for large-scale applications.

  • 308.
    Pei, Aihua
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Berglund, Lars A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Zhou, Qi
    KTH, School of Biotechnology (BIO), Glycoscience. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Surface-modification of nanocelluloses and their applications in poly(lactic acid)/nanocellulose biocomposites2014In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 247, p. 163-CELL-Article in journal (Other academic)
  • 309.
    Pei, Aihua
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Butchosa, Nuria
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Berglund, Lars A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Zhou, Qi
    KTH, School of Biotechnology (BIO), Glycoscience. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Surface quaternized cellulose nanofibrils with high water absorbency and adsorption capacity for anionic dyes2013In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 9, no 6, p. 2047-2055Article in journal (Refereed)
    Abstract [en]

    Surface quaternized cellulose nanofibrils were mechanically disintegrated from wood pulp that was pretreated through a reaction with glycidyltrimethylammonium chloride. The resulting quaternized cellulose nanofibrils (Q-NFC) with trimethylammonium chloride contents of 0.59-2.31 mmol g(-1) were characterized by conductometric titration, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), and atomic force microscopy (AFM). When the trimethylammonium chloride content on cellulose reached approximately 0.79 mmol g(-1) corresponding to a degree of substitution of 0.13 per bulk anhydroglucose unit, highly viscous and transparent aqueous dispersions of cellulose nanofibrils were obtained by mechanical homogenization of the chemically pretreated cellulose/water slurries. AFM observation showed that the dispersions consisted of individualized cellulose I nanofibrils 1.6-2.1 nm in width and 1.3-2.0 mu m in length. Cellulose nanopapers prepared from the Q-NFC aqueous dispersions exhibited high tensile strength (ca. 200 MPa) and Young's modulus (ca. 10 GPa) despite high porosity (37-48%). The nanopapers also demonstrated ultrahigh water absorbency (750 g g(-1)) with high surface cationic charge density. Stable hydrogels were obtained after swelling the nanopaper in water. The Q-NFC nanofibrils also possessed high anionic dye adsorption capability. The adsorption capacity increased with increasing trimethylammonium chloride content on cellulose.

  • 310.
    Perumal, Sathya
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Minaev, Boris
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Triplet State Phosphorescence in Tris(8-hydroxyquinoline) Aluminum Light Emitting Diode Materials2013In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, no 7, p. 3446-3455Article in journal (Refereed)
    Abstract [en]

    Time-dependent density functional theory (TD-DFT) with the quadratic response technique is applied to the tris(8-hydroxyquinoline) aluminum complex (Alq(3)) to calculate spin orbit coupling (SOC) effects and the main mechanism of the Alq(3) phosphorescence. This compound exhibits weak phosphorescence which provides additional emission in organic light emitting diodes (OLEDs) besides the main fluorescence band. The phosphorescence affords to overcome the efficiency limit imposed by the formation of triplet excitons in the emissive layer of OLEDs. The zero-field splitting (ZFS) parameters are also calculated taking into account the spin spin coupling in the first-order perturbation theory and the SOC in the second order. On the basis of the results obtained, we propose that an efficient spin-polarized injection and transport in long channels of Alq(3), which have been recently achieved with new hybrid organic inorganic interfaces, can proceed with the triplet electronic state admixture to the charge carriers. Our results also indicate that weak spin orbit coupling may be responsible for the room-temperature magneto-resistance at the ferromagnetic-Alq(3) interfaces and the spin-dependent charge transport.

  • 311.
    Pettersson, Torbjörn
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Nugroho, Robertus Wahyu N.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Odelius, Karin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Höglund, Anders
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Albertsson, Ann-Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Designing nonagglomerating polylactide particles with various interaction forces by covalent photografting2014In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 247, p. 768-COLL-Article in journal (Other academic)
  • 312.
    Pevere, Federico
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Sychugov, Ilya
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Sangghaleh, Fatemeh
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Fucikova, Anna
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Linnros, Jan
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Biexciton Emission as a Probe of Auger Recombination in Individual Silicon Nanocrystals2015In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, no 13, p. 7499-7505Article in journal (Refereed)
    Abstract [en]

    Biexciton emission from individual silicon nanocrystals was detected at room temperature by time-resolved, single-particle luminescence measurements. The efficiency of this process, however, was found to be very low, about 10-20 times less than the single exciton emission efficiency. It decreases even further at low temperature, explaining the lack of biexciton emission line observations in silicon nanocrystal single-dot spectroscopy under high excitation. The poor efficiency of the biexciton emission is attributed to the dominant nonradiative Auger process. Corresponding measured biexciton decay times then represent Auger lifetimes, and the values obtained here, from tens to hundreds of nanoseconds, reveal strong dot-to-dot variations, while the range compares well with recent calculations taking into account the resonant nature of the Auger process in semiconductor nanocrystals.

  • 313. Pietra, M. D.
    et al.
    Rexed, Ivan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Lagergren, Carina
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    McPhail, S.
    Paoletti, C.
    Moreno, A.
    Experimental procedures for accelerated aging tests using MCFC button cells2013In: EFC 2013 - Proceedings of the 5th European Fuel Cell Piero Lunghi Conference, 2013, p. 363-364Conference paper (Refereed)
    Abstract [en]

    The aim of this work is to study whether the effects of electrolyte evaporation in long term operation of MCFCs can be accelerated at button cell level due to the increased rate of evaporation in the open-chamber configuration. This study is being carried out with several trials: the first trial aims to generate a benchmark of performance at button cell level, i.e. with accelerated electrolyte evaporation, at reference operating conditions, carrying out regular polarization curves and EIS until the performance degrades below a predefined level. The second trial aims to compensate the evaporation of electrolyte from the button cell by periodically adding carbonate and maintain a constant performance for the length of time that the first button cell (without carbonate addition) achieved. Once the isolated effect of electrolyte evaporation has been thus quantified, successive trials can be set up to superimpose other degradation and evaluate their interaction with the mechanism of electrolyte evaporation.

  • 314.
    Pilkington, Georgia A.
    et al.
    School of Chemistry, University of Bristol.
    Thormann, Esben
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Fuge, Gareth M.
    School of Chemistry, University of Bristol.
    Fox, Oliver J. L.
    School of Chemistry, University of Bristol.
    Ashfold, Michael N. R.
    School of Chemistry, University of Bristol.
    Leese, Hannah
    Dept of Chemical Engineering, University of Bath, UK.
    Mattia, Davide
    Dept of Chemical Engineering, University of Bath, UK.
    Briscoe, Wuge H.
    School of Chemistry, University of Bristol.
    Amontonian frictional behaviour of nanostructured surfaces2011In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 13, p. 9318-9326Article in journal (Refereed)
    Abstract [en]

    With nanotextured surfaces and interfaces increasingly being encountered in technological and biomedical applications, there is a need for a better understanding of frictional properties involving such surfaces. Here we report friction measurements of several nanostructured surfaces using an Atomic Force Microscope (AFM). These nanostructured surfaces provide well defined model systems on which we have tested the applicability of Amontons' laws of friction. Our results show that Amontonian behaviour is observed with each of the surfaces studied. However, no correlation has been found between measured friction and various surface roughness parameters such as average surface roughness (Ra) and root mean squared (rms) roughness. Instead, we propose that the friction coefficient may be decomposed into two contributions, i.e., μ = μ0 + μg, with the intrinsic friction coefficient μ0 accounting for the chemical nature of the surfaces and the geometric friction coefficient μg for the presence of nanotextures. We have found a possible correlation between μg and the average local slope of the surface nanotextures.

  • 315.
    Pink, David A.
    et al.
    Department of Physics, St. Francis Xavier University, Antigonish, Nova Scotia B2G 2W5, Canada.
    Hanna, Charles B.
    Advanced Foods and Materials Network of Centres of Excellence (AFMNet-NCE), Canada.
    Sandt, Christophe
    Department of Chemistry, St. Francis Xavier University, Antigonish, Nova Scotia B2G 2W5, Canada.
    MacDonald, Adam J.
    Advanced Foods and Materials Network of Centres of Excellence (AFMNet-NCE), Canada.
    MacEachern, Ronald
    Advanced Foods and Materials Network of Centres of Excellence (AFMNet-NCE), Canada.
    Corkery, Robert W.
    YKI, Institute for Surface Chemistry, Stockholm, Sweden.
    Rousseau, Derick.
    Advanced Foods and Materials Network of Centres of Excellence (AFMNet-NCE), Canada.
    Modeling the solid-liquid phase transition in saturated triglycerides2010In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 132, no 5, p. 054502/1-054502/11Article in journal (Refereed)
    Abstract [en]

    We investigated theor. two competing published scenarios for the melting transition of the triglyceride trilaurin (TL): those of (1) Corkery et al., in which the av. state of each TL mol. in the liq. phase is a discotic "Y" conformer whose three chains are dynamically twisted, with an av. angle of ∌120° between them, and those of (2) Cebula et al., in which the liq.-state conformation of the TL mol. in the liq. phase is a nematic h*-conformer whose three chains are in a modified "chair" conformation. We developed two competing models for the two scenarios, in which TL mols. are in a nematic compact-chair (or "h") conformation, with extended, possibly all-trans, chains at low-temps., and in either a Y conformation or an h* conformation in the liq. state at temps. higher than the phase-transition temp., T* = 319 K. We defined an h-Y model as a realization of the proposal of R. Corkery et al. (2007), and explored its predictions by mapping it onto an Ising model in a temp.-dependent field, performing a mean-field approxn., and calcg. the transition enthalpy ΔH. We found that the most plausible realization of the h-Y model, as applied to the solid-liq. phase transition in TL, and likely to all satd. triglycerides, gave a value of ΔH in reasonable agreement with the expt. We then defined an alternative h-h* model as a realization of the proposal of D. J. Cebula et al. (1992), in which the liq. phase exhibits an av. symmetry breaking similar to an h conformation, but with twisted chains, to see whether it could describe the TL phase transition. The h-h* model gave a value of ΔH that was too small by a factor of ∌3-4. We also predicted the temp. dependence of the 1132 cm-1 Raman band for both models, and performed measurements of the ratios of three TL Raman bands in the temp. range of -20° ≀ T ≀ 90°. The exptl. results were in accord with the predictions of the h-Y model and support the proposal of that the liq. state is made up of mols. that are each, on av., in a Y conformation. Finally, we carried out computer simulations of minimal-model TLs in the liq. phase, and concluded that although the individual TL mols. are, on av., Y conformers, long-range discotic order is unlikely to exist.

  • 316.
    Porsch, Christian
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Zhang, Yuning
    Ducani, Cosimo
    Vilaplana, Francisco
    KTH, School of Biotechnology (BIO), Glycoscience. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Nordstierna, Lars
    Nyström, Andreas M.
    Malmström, Eva
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Toward Unimolecular Micelles with Tunable Dimensions Using Hyperbranched Dendritic-Linear Polymers2014In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 15, no 6, p. 2235-2245Article in journal (Refereed)
    Abstract [en]

    A library of amphiphilic, hyperbranched dendritic-linear polymers (HBDLPs) are successfully synthesized, and evaluated as potential unimolecular micelles. Hyperbranched macroinitiators (HBMI), extended with poly(ethylene glycol) methacrylate (P(OEGMA)), are afforded via a combination of self-condensing vinyl (co)polymerization (SCV(C)P) and atom transfer radical polymerization (ATRP), providing a versatile two-step synthetic route. The HBDLP architecture and chain lengths are varied, and the effect on the nanoparticle (NP) stability and properties are evaluated. The HBDLPs form predominantly stable and spherical NPs, and the NP dimensions could be tailored by the HBDLP characteristics. The NPs formed are of high molecular weight, and their stability varies with the properties of the corresponding HBDLP. Too small dendritic segment, or too low degree of PEGylation, results to some extent in NP aggregation, while higher molecular weight HBDLPs, with a high amount of hydrophilic segments, appears to form discrete unimolecular micelles. The versatility of the platform is further demonstrated by the convenience of forming a HBDLP. with a more complex, linear copolymer extension instead of P(OEGMA).

  • 317.
    Porsch, Christian
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Zhang, Yuning
    Östlund, Åsa
    Damberg, Peter
    Ducani, Cosimo
    Malmström, Eva
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Nyström, Andreas M.
    In Vitro Evaluation of Non-Protein Adsorbing Breast Cancer Theranostics Based on 19F-Polymer Containing Nanoparticles2013In: Particle & particle systems characterization, ISSN 0934-0866, E-ISSN 1521-4117, Vol. 30, no 4, p. 381-390Article in journal (Refereed)
    Abstract [en]

    Eight fluorinated nanoparticles (NPs) are synthesized, loaded with doxorubicin (DOX), and evaluated as theranostic delivery platforms to breast cancer cells. The multifunctional NPs are formed by self-assembly of either linear or star-shaped amphiphilic block copolymers, with fluorinated segments incorporated in the hydrophilic corona of the carrier. The sizes of the NPs confirm that small circular NPs are formed. The release kinetics data of the particles reveals clear hydrophobic core dependence, with longer sustained release from particles with larger hydrophobic cores, suggesting that the DOX release from these carriers can be tailored. Viability assays and flow cytometry evaluation of the ratios of apoptosis/necrosis indicate that the materials are non-toxic to breast cancer cells before DOX loading; however, they are very efficient, similar to free DOX, at killing cancer cells after drug encapsulation. Both flow cytometry and confocal microscopy confirm the cellular uptake of NPs and DOX-NPs into breast cancer cells, and in vitro 19F-MRI measurement shows that the fluorinated NPs have strong imaging signals, qualifying them as a potential in vivo contrast agent for 19F-MRI.

  • 318.
    Prakobna, Kasinee
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Berthold, Fredrik
    Berglund, Lars A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Architecture of ultra-high porous honeycombs prepared from core-shell nanocellulose: Structure and mechanical performance2014In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 247, p. 160-CELL-Article in journal (Other academic)
  • 319.
    Prideaux, Sonja
    KTH, School of Chemical Science and Engineering (CHE).
    Speciation and bioavailability of chromium and nickel in Swedish freshwater: For improved assessments in life-cycle analysis (LCA)2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Metals are used in every part of our modern society. As population and wealth increases, so does the demand for metals and metal products. This inherently leads to metal emissions, from the process of mining and producing to usage and disposal. Emissions that may possess a threat to human health and the environment. One method to assess possible impacts over the entire chain ‘from cradle to grave’ is life-cycle assessment (LCA). This method is used today by regulatory instances as well as industry to evaluate total environmental impact of a certain product or process. Toxicity impact of chemical emissions is one part of the LCA analysis, calculated as the product of the fate of the chemical, the exposure routes of the chemical and the effect of the exposure. When it comes to metal emissions, evaluating exposure is not trivial, since it depends on the speciation of the metal whether or not an organism will be exposed. In freshwater ecosystems, the sum of all the metal species that are available for biological uptake are referred to as the bioavailable fraction. The speciation pattern, and thus the size of the bioavailable fraction of a metal, is largely dependent on ambient water chemistry, so that regional differences will be observed. Recent improvements in the LCA methodology have incorporated calculations of the bioavailable fraction of metal emissions, as well as regional variability by the use of seven European water types. However, Swedish freshwater is normally softer, with a lower pH and a higher concentration of metals than the European water types. There is therefore a need to evaluate whether the existing system is applicable to Swedish water chemistry, or if there is a need for further implementations.

    To this background, the aim of this project has been to evaluate the speciation and bioavailability of chromium and nickel, in a case study of emissions into a freshwater relevant for the Swedish steel industry. Specifically, bioavailability factors (BFs) for the two metals were sought, for implementation in the LCA methodology. To accomplish this, computer modelling using Visual MINTEQ and WHAM has been performed, as well as laboratory experiments. In addition, metal release from slag particles has been investigated.

    The results show that the bioavailability of chromium is dominated by the oxidation state of the metal. In the form of Cr(III), it will mainly form insoluble complexes, and the BF is as low as 5·10-5. In the form of Cr(VI) the BF is 0.64. Hence a large amount will be in the largely mobile and bioavailable fraction. This is also the most toxic form of chromium. It is thus very important when assessing chromium emissions to know the oxidation state of the metal. Nickel will mainly be removed from the bioavailable fraction by formation of strong complexes with organic matter. The BF of Ni was established as 0.37 for this case study. Modelling in WHAM gave results in accordance with laboratory results, while Visual MINTEQ seemed to underestimate the BF. Metal content was low in the slag, and the release hardly detectable. However, the results suggest that a large fraction of the released Cr, although low, is in the form of Cr(VI).

  • 320. Qian, Z.
    et al.
    Raghubanshi, H.
    Sterlin Leo Hudson, M.
    Srivastava, O. N.
    Liu, X.
    Ahuja, Rajeev
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Uppsala University, Sweden.
    Ab initio insight into graphene nanofibers to destabilize hydrazine borane for hydrogen release2017In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 669, p. 404-411Article in journal (Refereed)
    Abstract [en]

    We report the potential destabilizing effects of graphene nanofibers on the hydrogen release property of hydrazine borane via state-of-the-art ab initio calculations for the first time. Interactions of a hydrazine borane cluster with two types of graphene patch edges which exist abundantly in our synthesized graphene nanofibers have been investigated. It is found that both zigzag and armchair edges can greatly weaken the H-host bonds (especially the middle N[sbnd]H bond) of hydrazine borane. The dramatic decrease in hydrogen removal energy is caused by the strong interaction between hydrazine borane and the graphene patch edges concerning the electronic charge density redistribution.

  • 321. Qu, Jishuang
    et al.
    Jiang, Xiaoqing
    Yu, Ze
    Lai, Jianbo
    Zhao, Yawei
    Hu, Maowei
    Yang, Xichuan
    Sun, Licheng
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Improved performance and air stability of perovskite solar cells based on low-cost organic hole-transporting material X60 by incorporating its dicationic salt2018In: Science in China Series B: Chemistry, ISSN 1674-7291, E-ISSN 1869-1870, Vol. 61, no 2, p. 172-179Article in journal (Refereed)
    Abstract [en]

    The development of an efficient, stable, and low-cost hole-transporting material (HTM) is of great significance for perovskite solar cells (PSCs) from future commercialization point of view. Herein, we specifically synthesize a dicationic salt of X60 termed X60(TFSI)(2), and adopt it as an effective and stable "doping" agent to replace the previously used lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) for the low-cost organic HTM X60 in PSCs. The incorporation of this dicationic salt significantly increases the hole conductivity of X60 by two orders of magnitude from 10(-6) to 10(-4) S cm(-1). The dramatic enhancement of the conductivity leads to an impressive power conversion efficiency (PCE) of 19.0% measured at 1 sun illumination (100 mW cm(-2), AM 1.5 G), which is comparable to that of the device doped with LiTFSI (19.3%) under an identical condition. More strikingly, by replacing LiTFSI, the PSC devices incorporating X60(TFSI)(2) also show an excellent long-term durability under ambient atmosphere for 30 days, mainly due to the hydrophobic nature of the X60(TFSI)(2) doped HTM layer, which can effectively prevent the moisture destroying the perovskite layer. The present work paves the way for the development of highly efficient, stable, and low-cost HTM for potential commercialization of PSCs.

  • 322. Quignon, Benoit
    et al.
    Pilkington, Georgia A.
    Thormann, Esben
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Claesson, Per M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Ashfold, Michael N. R.
    Mattia, Davide
    Leese, Hannah
    Davis, Sean A.
    Briscoe, Wuge H.
    Sustained Frictional Instabilities on Nanodomed Surfaces: Stick Slip Amplitude Coefficient2013In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 7, no 12, p. 10850-10862Article in journal (Refereed)
    Abstract [en]

    Understanding the frictional properties of nanostructured surfaces is important because of their increasing application in modem minlaturized devices. In this work, lateral force microscopy was used to study the frictional properties between AFM nanotip and surfaces bearing well-defined ranging from tens to hundreds of nanometers. Our results show that the average lateral force varied linearly with applied load, as described by Amontons' first law of friction, although no direct correlation between the sample topographic properties and their measured friction coeffidents was identified. Furthermore, all the nanodomed textures exhibited pronounced osdllations in the shear traces, similar to the dassic stick slip behavior, under all the shear velocities and load regimes studied. That is, the nanotextured topography led to sustained frictional instabilities, effectively with no contact frictional sliding. The amplitude of the stick slip oscillations, ab was found to correlate with the topographic properties of the surfaces and scale linearly with the applied load. In line with the friction coefficient, we define the slope of this linear plot as the stick slip amplitude coeffident (SSAC). We suggest that such stick slip behaviors are characteristics of surfaces with nanotextures and that such local frictional instabilities have important implications to surface damage and wear. We thus propose that the shear characteristics of the nanodomed surfaces cannot be fully described by the framework of Amontons' laws of friction and that additional parameters (e.g., a, and SSAQ are required, when their friction, lubrication, and wear properties are important considerations in related nanodevices.

  • 323. Rasheed, Faiza
    et al.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Kuktaite, Ramune
    Plivelic, Tomas S.
    Gallstedt, Mikael
    Johansson, Eva
    Mild gluten separation - A non-destructive approach to fine tune structure and mechanical behavior of wheat gluten films2015In: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 73, p. 90-98Article in journal (Refereed)
    Abstract [en]

    Despite the increasing production of wheat gluten (WG) for industrial use, minor attention has been given to the impact of the separation procedure on the gluten quality. The purpose of the present study was to probe the effect of the separation treatments (harsh vs mild) on gluten structure, morphology, and performance in bio-based films. The harshly separated industrial WG showed aggregated and pre-cross linked structure in the starting material most likely due to shear forces during gluten separation from flour and heat effect during the drying procedures. Further, when the harshly separated WG was processed into films the pre-crosslinked starting material restricted new crosslinks formation and structural rearrangements at nano-scale. The mechanical integrity of the film was also affected resulting in films with low Young's modulus and strength. WG (from cultivars Diskette, Puntari, and Sleipner) recovered from mild separation showed relatively "native" non-destructed crosslinking pattern and not previously observed structural morphology at nano-scale. When processed into films the mildly separated WG showed well polymerized intimately crosslinked proteins both with disulfide and other covalent crosslinks. The nano-scale morphology showed lamellar and hexagonal arrangements, not reported so far in any study. The structural rearrangements among films from mildly separated WG resulted in materials with improved mechanical integrity as compared to films from harshly separated WG. The present study showed that the quality of WG is significantly affected by the separation procedure which also affects protein polymerization, nano-scale morphology, and tensile properties of films.

  • 324. Rasheed, Faiza
    et al.
    Newson, William R.
    Plivelic, Tomas S.
    Kuktaite, Ramune
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Gällstedt, Mikael
    Johansson, Eva
    Structural architecture and solubility of native and modified gliadin and glutenin proteins: non-crystalline molecular and atomic organization2014In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 4, no 4, p. 2051-2060Article in journal (Refereed)
    Abstract [en]

    Wheat gluten (WG) and its components, gliadin and glutenin proteins, form the largest polymers in nature, which complicates the structural architecture of these proteins. Wheat gluten, gliadin and glutenin proteins in unmodified form showed few secondary structural features. Structural modification of these proteins using heat, pressure and the chemical chaperone glycerol resulted in a shift to organized structure. In modified gliadin, nano-structural molecular arrangements in the form of hexagonal closed packed (HCP) assemblies with lattice parameter of (58 angstrom) were obvious together with development of intermolecular disulphide bonds. Modification of glutenin resulted in highly polymerized structure with proteins linked not only by disulphide bonds, but also with other covalent and irreversible bonds, as well as the highest proportion of beta-sheets. From a combination of experimental evidence and protein algorithms, we have proposed tertiary structure models of unmodified and modified gliadin and glutenin proteins. An increased understanding of gliadin and glutenin proteins structure and behavior are of utmost importance to understand the applicability of these proteins for various applications including plastic materials, foams, adhesives, films and coatings.

  • 325.
    Rehn, Dirk Robert
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Dreuw, Andreas
    Norman, Patrick
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Resonant Inelastic X-ray Scattering Amplitudes and Cross Sections in the Algebraic Diagrammatic Construction/Intermediate State Representation (ADC/ISR) Approach2017In: Journal of Chemical Theory and Computation, ISSN 1549-9618, E-ISSN 1549-9626, Vol. 13, no 11, p. 5552-5559Article in journal (Refereed)
    Abstract [en]

    A scheme has been derived and implemented to gain computational access to the full electronic part of the Kramers-Heisenberg-Dirac (KHD) expression for resonant and nonresonant inelastic scattering amplitudes. Our implementation of this scheme is based on the complex polarization propagator in the algebraic diagrammatic construction (ADC) framework and within its intermediate state representation (ISR). The hierarchy of the second- and third-order ADC/ISR computational schemes known as ADC(2), ADC(2)-x, and ADC(3/2) is considered, and the calculated resonant inelastic X-ray scattering (RIXS) amplitudes and transition strengths for water are in excellent agreement with recent experimental data.

  • 326.
    Renberg, Björn
    et al.
    KTH, School of Biotechnology (BIO), Proteomics and Nanobiotechnology.
    Andersson-Svahn, Helene
    KTH, School of Biotechnology (BIO), Proteomics and Nanobiotechnology.
    Hedhammar, My
    Mimicking silk spinning in a microchip2014In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 195, p. 404-408Article in journal (Refereed)
    Abstract [en]

    Nature's high performance material, spider silk, is formed during the passage of a protein solution through a spinning duct. Herein we present a microfluidic device with dual laminar mobile phases where silk formation can be mimicked and investigated. Recombinant miniature spidroins, with or without the pH-switching N-terminal domain, were used to investigate spinning conditions into silk-like fibers using this setup.

  • 327.
    Rexed, Ivan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    della Pietra, Massimiliano
    University of Perugia.
    McPhail, Stephen
    ENEA.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lagergren, Carina
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Molten carbonate fuel cells for CO2 separation and segregation by retrofitting existing plants - An analysis of feasible operating windows and first experimental findings2015In: International Journal of Greenhouse Gas Control, ISSN 1750-5836, E-ISSN 1878-0148, Vol. 35, p. 120-130Article in journal (Refereed)
    Abstract [en]

    Molten carbonate fuel cells (MCFC) used as active carbon dioxide concentrator units are a promising solution to reduce greenhouse gas (GHG) emissions from traditional combustion plants. The cell reaction transfers carbonate ions from the cathode to the anode and allows the fuel cell to simultaneously produce power and separate CO2 from a stream of flue gas. Carbon dioxide separation is of high interest for use in natural gas combined cycles and coal gas combustion plants, as a large part of anthropogenic CO2 worldwide originates from such installations. The flue gas from these types of combustion technologies typically contains 3-15% CO2, which is in the lower operational range of the MCFC. The aim of this work was to investigate the possibility to retrofit existing power plants with MCFC to reduce the total release of CO2 without necessarily reducing the power output, and to understand which kind of power plant could have the major benefits with an MCFC retrofitting. The performance of lab scale MCFC fed with simulated flue gas was evaluated, and a number of operational parameters, such as utilization factor and cathode humidification were varied to study the effect on fuel cell performance. The results show that it is feasible to operate the MCFC as a CO2 separator for simulated gas turbine flue gas; however, the voltage drop due to low CO2 concentration may restrict the operating window depending on various operating conditions.

  • 328.
    Rexed, Ivan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lagergren, Carina
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Performance degradation of Molten Carbonate Fuel Cells caused by SO2 in simulated flue gasManuscript (preprint) (Other academic)
    Abstract [en]

    The effect on MCFC performance degradation SO2 contaminant at the cathode, in combination with operating the fuel cell with CO2 lean oxidant gas, simulating combustion flue gas, was evaluated. Of special focus was the effect of electrolyte degradation.

     Measurements were performed to test the effect of SO2 in the oxidant gas stream, followed by regeneration with clean gas. A 3cm2 button cell MCFC allowing active electrolyte management by refilling was for 1500h to benchmark the performance degradation without contaminants. In order to study the poisoning effect of SO2 entering the fuel cell gas, the MCFC was operated for 250h with the addition of 18ppm SO2 in the oxidant gas. Electrolyte was added after 1500h of benchmark operation and after 250h of contaminant operation. The addition of 18ppm SO2 greatly accelerated the performance degradation of the fuel cell. Measurements showed that the internal resistance was the single factor which was most affected by the SO2 poisoning, and that the performance degradation after 250h was not reversed by regeneration with clean gas, but with the addition of fresh electrolyte. This led us to conclude that SO2 in oxidant gas leads to an accelerated loss of electrolyte and subsequent decrease in conductivity of the electrolyte, causing loss of performance and meeting end of life criteria after relatively short operational time. Other factors, such as poisoning of the anode and corrosion of cathode side current collectors, were also detected. 

  • 329. Riedlinger, Michael D.
    et al.
    Corkery, Robert W.
    Naturalnano Inc.
    Cosmetic skincare applications employing mineral-derived tubules for controlled release2005Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    Compositions and methods pertaining to the topical treatment of skin are disclosed. The present invention relates to topical compositions for regulating the condition of skin, especially for regulating visible and/or tactile discontinuities in skin associated with skin aging, environmental affects and the like. One embodiment of the present invention relates to improving skin with compositions containing one or more non-volatile, slowly absorbed, liquid or semi-liquid organic substances (active agents) via controlled release of active agents associated with mineral-derived tubules such as halloysite nanotubules. For example, the active agents, in the form of organic substances may include vitamin compounds and glycerin, among others.

  • 330. Ringholm, Magnus
    et al.
    Bast, Radovan
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. KTH, School of Computer Science and Communication (CSC), Centres, Centre for High Performance Computing, PDC.
    Oggioni, Luca
    Ekstrom, Ulf
    Ruud, Kenneth
    Analytic calculations of hyper-Raman spectra from density functional theory hyperpolarizability gradients2014In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 141, no 13, p. 134107-Article in journal (Refereed)
    Abstract [en]

    We present the first analytic calculations of the geometrical gradients of the first hyperpolarizability tensors at the density-functional theory (DFT) level. We use the analytically calculated hyperpolarizability gradients to explore the importance of electron correlation effects, as described by DFT, on hyper-Raman spectra. In particular, we calculate the hyper-Raman spectra of the all-trans and 11-cis isomers of retinal at the Hartree-Fock (HF) and density-functional levels of theory, also allowing us to explore the sensitivity of the hyper-Raman spectra on the geometrical characteristics of these structurally related molecules. We show that the HF results, using B3LYP-calculated vibrational frequencies and force fields, reproduce the experimental data for all-trans-retinal well, and that electron correlation effects are of minor importance for the hyper-Raman intensities.

  • 331.
    Rinkevicius, Zilvinas
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Li, Xin
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Rosal Sandberg, Jaime Axel
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Non-linear optical properties of molecules in heterogeneous environments: a quadratic density functional/molecular mechanics response theory2014In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 16, no 19, p. 8981-8989Article in journal (Refereed)
    Abstract [en]

    We generalize a density functional theory/molecular mechanics approach for heterogeneous environments with an implementation of quadratic response theory. The updated methodology allows us to address a variety of non-linear optical, magnetic and mixed properties of molecular species in complex environments, such as combined metallic, solvent and confined organic environments. Illustrating calculations of para-nitroaniline on gold surfaces and in solution reveals a number of aspects that come into play when analyzing second harmonic generation of such systems - such as surface charge flow, coupled surface-solvent dynamics and induced geometric and electronic structure effects of the adsorbate. Some ramifications of the methodology for applied studies are discussed.

  • 332.
    Rokhas, Maria Khihon
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Mikkonen, Saara
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Beyer, J.
    Jacksén, Johan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Emmer, Åsa
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    CE analysis of single wood cells performing hydrolysis and preconcentration in open microchannels2014In: Electrophoresis, ISSN 0173-0835, E-ISSN 1522-2683, Vol. 35, no 2-3, p. 450-457Article in journal (Refereed)
    Abstract [en]

    In the present work, monosaccharides from pulp samples and single wood fibers were analyzed with CE, using indirect detection due to the lack of chromophores on the monosaccharides. The hydrolysis degradation of cellulose and hemicellulose into monosaccharides was performed using TFA, either in bulk scale or in microscale. In the microscale, one single wood fiber was hydrolyzed in an open microchannel manufactured on a silicon microchip with the dimensions 50 μm × 50 μm (length 1 or 3 cm). The low monosaccharide amounts derived from a single fiber implied that a preconcentration step was necessary to increase the detectability. Thus, an electromigration preconcentration of the hydrolyzed samples was performed within the microchannel, which resulted in a significantly enhanced signal intensity of the monosaccharides. In addition to the experimental study, computer simulations were performed regarding the preconcentration step of monosaccharides. The results from these simulations correlated well with the experimental results.

  • 333.
    Rosal Sandberg, Jaime Axel
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Rinkevicius, Zilvinas
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    New recurrence relations for analytic evaluationof two-electron repulsion integrals over highly contracted gaussian-type orbitalsManuscript (preprint) (Other academic)
  • 334.
    Rosal Sandberg, Jaime Axel
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Rinkevicius, Zilvinas
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Efficient time dependent density functional theory calculations using general contraction basis setsManuscript (preprint) (Other academic)
  • 335. Rubio-Magnieto, Jenifer
    et al.
    Gebremedhn Azene, Elias
    Knoops, Jeremie
    Knippenberg, Stefan
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. University of Mons, Belgium.
    Delcourt, Cecile
    Thomas, Amandine
    Richeter, Sebastien
    Mehdi, Ahmad
    Dubois, Philippe
    Lazzaroni, Roberto
    Beljonne, David
    Clement, Sebastien
    Surin, Mathieu
    Self-assembly and hybridization mechanisms of DNA with cationic polythiophene2015In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 11, no 2, p. 6460-6471Article in journal (Refereed)
    Abstract [en]

    The combination of DNA and pi-conjugated polyelectrolytes (CPEs) represents a promising approach to develop DNA hybridization biosensors, with potential applications for instance in the detection of DNA lesions and single-nucleotide polymorphisms. Here we exploit the remarkable optical properties of a cationic poly[3-(6'-(trimethylphosphonium)hexyl)thiophene-2,5-diyl] (CPT) to decipher the self-assembly of DNA and CPT. The ssDNA/ CPT complexes have chiroptical signatures in the CPT absorption region that are strongly dependent on the DNA sequence, which we relate to differences in supramolecular interactions between the thiophene monomers and the various nucleobases. By studying DNA-DNA hybridization and melting processes on preformed ssDNA/ CPT complexes, we observe sequence-dependent mechanisms that can yield DNA-condensed aggregates. Heating-cooling cycles show that non-equilibrium mixtures can form, noticeably depending on the working sequence of the hybridization experiment. These results are of high importance for the use of pi-conjugated polyelectrolytes in DNA hybridization biosensors and in polyplexes.

  • 336.
    Rutland, Mark W.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. SP Tech Res Inst, Sweden.
    Liljeblad, Jonathan D. F.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Tyrode, Eric
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Thormann, Esben
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Dublanchet, Ann-Claude
    Luengo, Gustavo
    Johnson, C. Magnus
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Long chained fatty acid monolayers: Influence of methyl branching2014In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 247, p. 61-COLL-Article in journal (Other academic)
  • 337. Sacui, Iulia A.
    et al.
    Nieuwendaal, Ryan C.
    Burnett, Daniel J.
    Stranick, Stephan J.
    Jorfi, Mehdi
    Weder, Christoph
    Foster, E. Johan
    Olsson, Richard T.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Gilman, Jeffery W.
    Comparison of the Properties of Cellulose Nanocrystals and Cellulose Nanofibrils Isolated from Bacteria, Tunicate, and Wood Processed Using Acid, Enzymatic, Mechanical, and Oxidative Methods2014In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 6, no 9, p. 6127-6138Article in journal (Refereed)
    Abstract [en]

    This work describes the measurement and comparison of several important properties of native cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs), such as crystallinity, morphology, aspect ratio, and surface chemistry. Measurement of the fundamental properties of seven different CNCs/CNFs, from raw material sources (bacterial, tunicate, and wood) using typical hydrolysis conditions (acid, enzymatic, mechanical, and 2,2,6,6-tetramethylpiperidiny1-1-oxyl (TEMPO)-mediated oxidation), was accomplished using a variety of measurement methods. Atomic force microscopy (AFM), transmission electron microscopy (TEM), and C-13 cross-polarization magic angle spinning (CPMAS) nuclear magnetic resonance (NMR) spectroscopy were used to conclude that CNCs, which are rodlike in appearance, have a higher crystallinity than CNFs, which are fibrillar in appearance. CNC aspect ratio distributions were measured and ranged from 148 +/- 147 for tunicate-CNCs to 23 +/- 12 for wood-CNCs. Hydrophobic interactions, measured using inverse gas chromatography (IGC), were found to be an important contribution to the total surface energy of both types of cellulose. In all cases, a trace amount of naturally occurring fluorescent compounds was observed after hydrolysis. Confocal and Raman microscopy were used to confirm that the fluorescent species were unique for each cellulose source, and demonstrated that such methods can be useful for monitoring purity during CNC/CNF processing. This study reveals the broad, tunable, multidimensional material space in which CNCs and CNFs exist.

  • 338. Saigal, Trishna
    et al.
    Riley, John K.
    Golas, Patricia Lynn
    Bodvik, Rasmus
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Claesson, Per Martin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Matyjaszewski, Krzysztof
    Tilton, Robert D.
    Poly(Ethylene Oxide) Star Polymer Adsorption at the Silica/Aqueous Interface and Displacement by Linear Poly(Ethylene Oxide)2013In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 29, no 12, p. 3999-4007Article in journal (Refereed)
    Abstract [en]

    Multiarm star copolymers with approximately 460 poly(ethylene oxide) (PEO) arms that have a degree of polymerization N = 45 were synthesized via atom transfer radical polymerization (ATRP) of PEO-methacrylate macro-monomers in the presence of divinyl benzene cross-linkers. These are an example of molecular or nanoparticulate brushes that are of interest as steric stabilizers or boundary lubrication agents when adsorbed from solution to a solid/aqueous interface. We use ellipsometry to measure adsorption isotherms at the silica/aqueous interface for PEO star polymers and linear PEO chains having molecular weights comparable either to the star polymer or to the individual arms. The compactness of the PEO star polymers (molecular weight 1.2 x 10(6)) yields a saturation surface excess concentration that is approximately 3.5 times greater than that of the high molecular weight (1 X 10(6)) linear PEO. Adsorption of low molecular weight (6000) linear PEO was below the detection limit. Competitive adsorption experiments were conducted with ellipsometry, complemented by independent quartz crystal microbalance with dissipation (QCM-D) measurements. Linear PEO (high molecular weight) displaced preadsorbed PEO star polymers over the course of approximately 1.5 h, to form a mixed adsorbed layer having not only a significantly lower overall polymer surface excess concentration, but also a significantly greater amount of hydrodynamically entrapped water. Challenging a preadsorbed linear PEO (high molecular weight) layer with PEO star polymers produced no measurable change in the overall polymer surface excess concentration, but changes in the QCM-D energy dissipation and resonance frequency suggested that the introduction of PEO star polymers caused a slight swelling of the layer with a correspondingly small increase in entrapped water content.

  • 339.
    Saito, Tsuguyuki
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Kuramae, R.
    Wohlert, Jakob
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Berglund, Lars A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Isogai, A.
    An ultrastrong nanofibrillar biomaterial: The strength of single cellulose nanofibrils revealed via sonication-induced fragmentation2013In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 14, no 1, p. 248-253Article in journal (Refereed)
    Abstract [en]

    We report the mechanical strength of native cellulose nanofibrils. Native cellulose nanofibrils, purified from wood and sea tunicate, were fully dispersed in water via a topochemical modification of cellulose nanofibrils using 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO) as a catalyst. The strength of individual nanofibrils was estimated based on a model for the sonication-induced fragmentation of filamentous nanostructures. The resulting strength parameters were then analyzed based on fracture statistics. The mean strength of the wood cellulose nanofibrils ranged from 1.6 to 3 GPa, depending on the method used to measure the nanofibril width. The highly crystalline, thick tunicate cellulose nanofibrils exhibited higher mean strength of 3-6 GPa. The strength values estimated for the cellulose nanofibrils in the present study are comparable with those of commercially available multiwalled carbon nanotubes.

  • 340.
    Sandberg, Jan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science (closed 20081231).
    Odnevall Wallinder, Inger
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science (closed 20081231).
    Leygraf, Christofer
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Corrosion Science (closed 20081231).
    Le Bozec, N.
    Frensh Corrosion Insitute, Brest, France.
    Corrosion-induced copper runoff from naturally and pre-patinated copper, with and without surface treatments, in a marine environment2005In: Proc. 16th International Corrosion Congress, 2005Conference paper (Other academic)
  • 341.
    Sauge, Sebastien
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Antiprotonic helium atomcules2012In: From Quantum Chemistry To Astrophysics: A Tribute To Pierre Valiron, EDP Sciences, 2012, p. 03002-Conference paper (Refereed)
    Abstract [en]

    About 3% of antiprotons (p̄) stopped in helium are long-lived with microsecond lifetimes, against picoseconds in all other materials. This unusual longevity has been ascribed to the trapping of p̄ on metastable bound states in p̄He+ helium atom-molecules thus named atomcules. Apart from their unique dual structure investigated by laser spec-troscopy - a near-circular quasi-classical Rydberg atom with l ∼ n - 1 ∼ 37 or a special diatomic molecule with a negatively charged p̄ nucleus in high rotational state with J = l - the chemical physics aspects of their interaction with other atoms or molecules constitute an interesting topic for molecular physics. While atomcules may resist to million collisions in helium, molecular contaminants such as H2 are likely to destroy them in a single one, down to very low temperatures. In the Born-Oppenheimer framework, we interpret the molecular interaction obtained by ab initio quantum chemical calculations in terms of classical reactive channels, with activation barriers accounting for the experiments carried out in He and H2. From classical trajectory Monte Carlo simulations, we show that the thermalization stage strongly quenches initial populations, thus reduced to a recovered 3 % trapping fraction. This work illustrates the pertinence of chemical physics concepts to the study of exotic processes involving antimatter. New insights into the physico-chemistry of cold interstellar radicals are anticipated.

  • 342.
    Schaefer, A.
    et al.
    Lund Univ, Dept Synchrotron Radiat Res, POB 118, SE-22100 Lund, Sweden.;Chalmers Univ Technol, Competence Ctr Catalysis, S-41296 Gothenburg, Sweden..
    Lanzilotto, V.
    Uppsala Univ, Dept Phys & Astron, POB 516, SE-75120 Uppsala, Sweden..
    Cappel, Ute
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry. Uppsala Univ, Dept Phys & Astron, POB 516, SE-75120 Uppsala, Sweden.
    Uvdal, P.
    Lund Univ, Dept Chem, Chem Phys, POB 124, SE-22100 Lund, Sweden..
    Borg, A.
    NTNU Norwegian Univ Sci & Technol, Dept Phys, NO-07491 Trondheim, Norway..
    Sandell, A.
    Uppsala Univ, Dept Phys & Astron, POB 516, SE-75120 Uppsala, Sweden..
    First layer water phases on anatase TiO2(101)2018In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 674, p. 25-31Article in journal (Refereed)
    Abstract [en]

    The anatase TiO2(101) surface and its interaction with water is an important topic in oxide surface chemistry. Firstly, it benchmarks the properties of the majority facet of TiO2 nanoparticles and, secondly, there is a controversy as to whether the water molecule adsorbs intact or deprotonates. We have addressed the adsorption of water on anatase TiO2(101) by synchrotron radiation photoelectron spectroscopy. Three two-dimensional water structures are found during growth at different temperatures: at 100 K, a metastable structure forms with no hydrogen bonding between the water molecules. In accord with prior literature, we assign this phase to chains of disordered molecules. Growth 160 K results in a metastable structure with expressed hydrogen bonding between the water molecules. At 190 K, the water molecules become disordered as the thermal energy is too high and hence the hydrogen bonds break. The result is a structure with isolated monomers. Partial dissociation is observed for all three growths, with the molecular state only slightly favored in energy (20-40 meV) over the dissociated state. Heating of a thick film leads to more dissociation compared to a bilayer, when formed at 100 K. Thus, extending the water network facilitates proton transport and hence dissociation. The results reconcile apparent conflicting experimental results previously obtained by scanning tunneling microscopy (STM) and core level photoelectron spectroscopy.

  • 343. Schwind, Markus
    et al.
    Hosseinpour, Saman
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Johnson, C. Magnus
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Langhammer, Christoph
    Zoric, Igor
    Leygraf, Christofer
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Kasemo, Bengt
    Combined in Situ Quartz Crystal Microbalance with Dissipation Monitoring, Indirect Nanoplasmonic Sensing, and Vibrational Sum Frequency Spectroscopic Monitoring of Alkanethiol-Protected Copper Corrosion2013In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 29, no 23, p. 7151-7161Article in journal (Refereed)
    Abstract [en]

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

  • 344.
    Schütz, Christina
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Sort, Jordi
    Bacsik, Zoltan
    Oliynyk, Vitaliy
    Pellicer, Eva
    Fall, Andreas
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Berglund, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Bergström, Lennart
    Salazar-Alvarez, German
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Hard and Transparent Films Formed by Nanocellulose-TiO2 Nanoparticle Hybrids2012In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 7, no 10, p. e45828-Article in journal (Refereed)
    Abstract [en]

    The formation of hybrids of nanofibrillated cellulose and titania nanoparticles in aqueous media has been studied. Their transparency and mechanical behavior have been assessed by spectrophotometry and nanoindentation. The results show that limiting the titania nanoparticle concentration below 16 vol% yields homogeneous hybrids with a very high Young's modulus and hardness, of up to 44 GPa and 3.4 GPa, respectively, and an optical transmittance above 80%. Electron microscopy shows that higher nanoparticle contents result in agglomeration and an inhomogeneous hybrid nanostructure with a concomitant reduction of hardness and optical transmittance. Infrared spectroscopy suggests that the nanostructure of the hybrids is controlled by electrostatic adsorption of the titania nanoparticles on the negatively charged nanocellulose surfaces.

  • 345. Segerie, Audrey
    et al.
    Lin, Li-Li
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Liegeois, Vincent
    Luo, Yi
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Champagne, Benoit
    Effects of the basis set and of the exchange-correlation functional on the Inelastic Electron Tunneling signatures of 1,4-benzenedithiol2014In: Spectrochimica Acta Part A - Molecular and Biomolecular Spectroscopy, ISSN 1386-1425, E-ISSN 1873-3557, Vol. 119, p. 34-41Article in journal (Refereed)
    Abstract [en]

    The effects of the atomic basis set and of the exchange-correlation (XC). functional on the Inelastic Electron Tunneling (LET) spectra have been investigated by considering the prototypical 1,4-benzenedithiol molecule. These studies have been completed by tackling the reliability of the same methods for predicting the IR absorption spectrum of the same molecule. The main conclusions are (i) the B3LYP XC functional is suitable to predict the relative vibrational frequencies, (ii) provided a scaling factor is used, the root mean square error on the vibrational frequencies goes down to 18 cm(-1), (iii) triple-zeta basis sets and in particular the cc-pVTZ basis set is a good compromise between accuracy and computational needs, (iv) basis set effects on the IET intensities are larger than those of the XC functional, and (v) the cc-pVTZ, cc-pVQZ, and aug-cc-pVDZ basis sets provide consistent IET intensities.

  • 346. Shen, J.
    et al.
    Wang, M.
    Gao, J.
    Han, H.
    Liu, H.
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Improvement of Electrochemical Water Oxidation by Fine-Tuning the Structure of Tetradentate N4 Ligands of Molecular Copper Catalysts2017In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 10, no 22, p. 4581-4588Article in journal (Refereed)
    Abstract [en]

    Two copper complexes, [(L1)Cu(OH2)](BF4)2 [1; L1=N,N′-dimethyl-N,N′-bis(pyridin-2-ylmethyl)-1,2-diaminoethane] and [(L2)Cu(OH2)](BF4)2 [2, L2=2,7-bis(2-pyridyl)-3,6-diaza-2,6-octadiene], were prepared as molecular water oxidation catalysts. Complex 1 displayed an overpotential (η) of 1.07 V at 1 mA cm−2 and an observed rate constant (kobs) of 13.5 s−1 at η 1.0 V in pH 9.0 phosphate buffer solution, whereas 2 exhibited a significantly smaller η (0.70 V) to reach 1 mA cm−2 and a higher kobs (50.4 s−1) than 1 under identical test conditions. Additionally, 2 displayed better stability than 1 in controlled potential electrolysis experiments with a faradaic efficiency of 94 % for O2 evolution at 1.58 V, when a casing tube was used for the Pt cathode. A possible mechanism for 1- and 2-catalyzed O2 evolution reactions is discussed based on the experimental evidence. These comparative results indicate that fine-tuning the structures of tetradentate N4 ligands can bring about significant change in the performance of copper complexes for electrochemical water oxidation.

  • 347. Shi, Changchun
    et al.
    Zhe, Kong
    Sun, Tianyang
    Liang, Lijun
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. Zhejiang University, China.
    Shen, Jiawei
    Zhao, Zhengyan
    Wang, Qi
    Kang, Zhengzhong
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Tu, Yaoquan
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Sequence dependence on DNA translocation time by graphene nanoporeManuscript (preprint) (Other academic)
  • 348. Shi, J.
    et al.
    Hedberg, Yolanda
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Lundin, Maria
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Odnevall Wallinder, Inger
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Karlsson, H. L.
    Möller, L.
    Hemolytic properties of synthetic nano- and porous silica particles: The effect of surface properties and the protection by the plasma corona2012In: Acta Biomaterialia, ISSN 1742-7061, E-ISSN 1878-7568, Vol. 8, no 9, p. 3478-3490Article in journal (Refereed)
    Abstract [en]

    Novel silica materials incorporating nanotechnology are promising materials for biomedical applications, but their novel properties may also bring unforeseen behavior in biological systems. Micro-size silica is well documented to induce hemolysis, but little is known about the hemolytic activities of nanostructured silica materials. In this study, the hemolytic properties of synthetic amorphous silica nanoparticles with primary sizes of 7-14 nm (hydrophilic vs. hydrophobic), 5-15 nm, 20 nm and 50 nm, and model meso/macroporous silica particles with pore diameters of 40 nm and 170 nm are investigated. A crystalline silica sample (0.5-10 ÎŒm) is included for benchmarking purposes. Special emphasis is given to investigations of how the temperature and solution complexity (solvent, plasma), as well as the physicochemical properties (such as size, surface charge, hydrophobicity and other surface properties), link to the hemolytic activities of these particles. Results suggests the potential importance of small size and large external surface area, as well as surface charge/structure, in the hemolysis of silica particles. Furthermore, a significant correlation is observed between the hemolytic profile of red blood cells and the cytotoxicity profile of human promyelocytic leukemia cells (HL-60) induced by nano- and porous silica particles, suggesting a potential universal mechanism of action. Importantly, the results generated suggest that the protective effect of plasma towards silica nanoparticle-induced hemolysis as well as cytotoxicity is primarily due to the protein/lipid layer shielding the silica particle surface. These results will assist the rational design of hemocompatible silica particles for biomedical applications.

  • 349.
    Shovskyy, Oleksandr
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Varga, Imre
    YKI, Institute of Surface Chemistry.
    Makuska, Ricardas
    Dept of Polymer Chemistry, Vilnius University, Lithania.
    Claesson, Per
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Formation and Stability of Water-Soluble Molecular Polyelectrolyte Complexes: Effects of Charge Density, Mixing Ratio and Polyelectrolyte Concentration2009In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, no 11, p. 6113-6121Article in journal (Refereed)
    Abstract [en]

    The formation of complexes with stoichiometric (1:1) as well as nonstoichiometric (2:1) and (1:2) compositions between oppositely charged synthetic polyelectrolytes carrying strong ionic groups and significantly different molecular weights is reported in this contribution. Poly(sodium styrenesulfonate) (NaPSS) was used as polyanion, and a range of copolymers with various molar ratios of the poly(methacryloxyethyltrimethylammonium) chloride, poly(METAC), and the nonionic poly(ethylene oxide) ether methacrylate, poly(PEO45MEMA), were used as polycations. Formation and stability of PECs have been investigated by dynamic and static light scattering (LS), turbidity, and electrophoretic mobility measurements as a function of polyelectrolyte solution concentration, charge density of the cationic polyelectrolyte, and mixing ratio. The data obtained demonstrate that in the absence of PEO45 side chains the 100% charged polymer (polyMETAC) formed insoluble PECs with PSS that precipitate from solution when exact stoichiometry is achieved. In nonstoichiometric complexes (1:2) and (2:1) large colloidally stable aggregates were formed. The presence of even a relatively small amount of PEO45 side chains (25%) in the cationic copolymer was sufficient for preventing precipitation of the formed stoichiometric and nonstoichiometric complexes. These PEC’s are sterically stabilized by the PEO45 chains. By further increasing the PEO45 side-chain content (50 and 75%) of the cationic copolymer, small, water-soluble molecular complexes could be formed. The data suggest that PSS molecules and the charged backbone of the cationic brush form a compact core, and with sufficiently high PEO45 chain density (above 25%) molecular complexes are formed that are stable over prolonged times.

  • 350.
    Sjöstedt, Anna
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Larsson, Per Tomas
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Innventia AB, Sweden.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Structural changes during swelling of highly charged cellulose fibres2014In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 247, p. 45-CELL-Article in journal (Other academic)
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