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  • 1. Abdala, Paula M
    et al.
    Safonova, Olga V
    Wiker, Geir
    van Beek, Wouter
    Emerich, Herman
    van Bokhoven, Jeroen A
    Sá, Jacinto
    Szlachetko, Jakub
    Nachtegaal, Maarten
    Scientific opportunities for heterogeneous catalysis research at the SuperXAS and SNBL beam lines.2012Ingår i: Chimia (Basel), ISSN 0009-4293, Vol. 66, nr 9, s. 699-705Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this short review, we describe the complementary experimental capabilities for catalysis research at two beam lines available to the Swiss community, SuperXAS at SLS (Swiss Light Source, Villigen) and SNBL (Swiss Norwegian Beam lines) at ESRF (European Synchrotron Radiation Facility, Grenoble). Over the years, these two facilities have been developed to provide powerful techniques for structural studies under in situ and operando conditions. These techniques, X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), and X-ray emission spectroscopy (XES) in combination with Raman or infrared spectroscopy provide new avenues for structure-performance studies of catalysts. Several exemplary studies are used to demonstrate the capability of these facilities.

  • 2.
    Abdellah, Mohamed
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi. South Valley Univ, Qena Fac Sci, Dept Chem, Qena 83523, Egypt.
    Zhang, Shihuai
    Dalian Univ Technol, DUT KTH Joint Educ & Res Ctr Mol Devices, State Key Lab Fine Chem, Dalian 116024, Peoples R China..
    Wang, Mei
    Dalian Univ Technol, DUT KTH Joint Educ & Res Ctr Mol Devices, State Key Lab Fine Chem, Dalian 116024, Peoples R China..
    Hammarström, Leif
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Competitive Hole Transfer from CdSe Quantum Dots to Thiol Ligands in CdSe-Cobaloxime Sensitized NiO Films Used as Photocathodes for H-2 Evolution2017Ingår i: ACS Energy Letters, ISSN 2380-8195, Vol. 2, nr 11, s. 2576-2580Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Quantum dot (QD) sensitized NiO photocathodes rely on efficient photoinduced hole injection into the NiO valence band. A system of a mesoporous NiO film co-sensitized with CdSe QDs and a molecular proton reduction catalyst was studied. While successful electron transfer from the excited QDs to the catalyst is observed, most of the photogenerated holes are instead quenched very rapidly (ps) by hole trapping at the surface thiols of the capping agent used as linker molecules. We confirmed our conclusion by first using a thiol free capping agent and second varying the thiol concentration on the QD's surface. The later resulted in faster hole trapping as the thiol concentration increased. We suggest that this hole trapping by the linker limits the H-2 yield for this photocathode in a device.

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  • 3.
    Abrahamsson, Malin L. A.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen.
    Berglund Baudin, Helena
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen.
    Tran, A.
    Philouze, C.
    Berg, K.
    Raymond-Johansson, Mary Katherine
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen.
    Sun, L.
    Åkermark, B.
    Styring, S.
    Hammarström, Leif
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen.
    Ruthenium-Manganese Complexes for Artificial Photosynthesis: Factors Controlling Intramolecular Electron Transfer and Excited State Quenching Reactions2002Ingår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 41, nr 6, s. 1534-1544Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Continuing our work toward a system mimicking the electron-transfer steps from manganese to P(680)(+) in photosystem II (PS II), we report a series of ruthenium(II)-manganese(II) complexes that display intramolecular electron transfer from manganese(II) to photooxidized ruthenium(III). The electron-transfer rate constant (k(ET)) values span a large range, 1 x 10(5)-2 x 10(7) s(-1), and we have investigated different factors that are responsible for the variation. The reorganization energies determined experimentally (lambda = 1.5-2.0 eV) are larger than expected for solvent reorganization in complexes of similar size in polar solvents (typically lambda approximately 1.0 eV). This result indicates that the inner reorganization energy is relatively large and, consequently, that at moderate driving force values manganese complexes are not fast donors. Both the type of manganese ligand and the link between the two metals are shown to be of great importance to the electron-transfer rate. In contrast, we show that the quenching of the excited state of the ruthenium(II) moiety by manganese(II) in this series of complexes mainly depends on the distance between the metals. However, by synthetically modifying the sensitizer so that the lowest metal-to-ligand charge transfer state was localized on the nonbridging ruthenium(II) ligands, we could reduce the quenching rate constant in one complex by a factor of 700 without changing the bridging ligand. Still, the manganese(II)-ruthenium(III) electron-transfer rate constant was not reduced. Consequently, the modification resulted in a complex with very favorable properties.

  • 4.
    Abramavicius, V.
    et al.
    Vilnius University, Lithuania; Centre Phys Science and Technology, Lithuania.
    Pranculis, V.
    Centre Phys Science and Technology, Lithuania.
    Melianas, Armantas
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Inganäs, Olle
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Gulbinas, V.
    Centre Phys Science and Technology, Lithuania.
    Abramavicius, D.
    Vilnius University, Lithuania.
    Role of coherence and delocalization in photo-induced electron transfer at organic interfaces2016Ingår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, nr 32914Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Photo-induced charge transfer at molecular heterojunctions has gained particular interest due to the development of organic solar cells (OSC) based on blends of electron donating and accepting materials. While charge transfer between donor and acceptor molecules can be described by Marcus theory, additional carrier delocalization and coherent propagation might play the dominant role. Here, we describe ultrafast charge separation at the interface of a conjugated polymer and an aggregate of the fullerene derivative PCBM using the stochastic Schrodinger equation (SSE) and reveal the complex time evolution of electron transfer, mediated by electronic coherence and delocalization. By fitting the model to ultrafast charge separation experiments, we estimate the extent of electron delocalization and establish the transition from coherent electron propagation to incoherent hopping. Our results indicate that even a relatively weak coupling between PCBM molecules is sufficient to facilitate electron delocalization and efficient charge separation at organic interfaces.

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  • 5.
    Abreu, Barbara
    et al.
    Univ Porto, Fac Sci, Dept Chem & Biochem, CIQUP, Rua Campo Alegre, P-4169007 Porto, Portugal..
    Rocha, Jessica
    Univ Porto, Fac Sci, Dept Chem & Biochem, CIQUP, Rua Campo Alegre, P-4169007 Porto, Portugal..
    Ferreira Fernandes, Ricardo Manuel
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Tillämpad fysikalisk kemi.
    Regev, Oren
    Ben Gurion Univ Negev, Dept Chem Engn, IL-84105 Beer Sheva, Israel.;Ben Gurion Univ Negev, Ilse Katz Inst Nanotechnol, IL-84105 Beer Sheva, Israel..
    Furo, Istvan
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Tillämpad fysikalisk kemi.
    Marques, Eduardo F.
    Univ Porto, Fac Sci, Dept Chem & Biochem, CIQUP, Rua Campo Alegre, P-4169007 Porto, Portugal..
    Gemini surfactants as efficient dispersants of multiwalled carbon nanotubes: Interplay of molecular parameters on nanotube dispersibility and debundling2019Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 547, s. 69-77Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Surfactants have been widely employed to debundle, disperse and stabilize carbon nanotubes in aqueous solvents. Yet, a thorough understanding of the dispersing mechanisms at molecular level is still warranted. Herein, we investigated the influence of the molecular structure of gemini surfactants on the dispersibility of multiwalled carbon nanotubes (MWNTs). We used dicationic n-s-n gemini surfactants, varying n and s, the number of alkyl tail and alkyl spacer carbons, respectively; for comparisons, single-tailed surfactant homologues were also studied. Detailed curves of dispersed MWNT concentration vs. surfactant concentration were obtained through a stringently controlled experimental procedure, allowing for molecular insight. The gemini are found to be much more efficient dispersants than their single-tailed homologues, i.e. lower surfactant concentration is needed to attain the maximum dispersed MWNT concentration. In general, the spacer length has a comparatively higher influence on the dispersing efficiency than the tail length. Further, scanning electron microscopy imaging shows a sizeable degree of MWNT debundling by the gemini surfactants in the obtained dispersions. Our observations also point to an adsorption process that does not entail the formation of micelle-like aggregates on the nanotube surface, but rather coverage by individual molecules, among which the ones that seem to be able to adapt best to the nanotube surface provide the highest efficiency. These studies are relevant for the rational design and choice of optimal dispersants for carbon nanomaterials and other similarly water-insoluble materials.

  • 6.
    Adam, Stefan
    et al.
    Leibniz Institute Polymerforsch eV, Germany; Technical University of Dresden, Germany.
    Koenig, Meike
    Leibniz Institute Polymerforsch eV, Germany; Technical University of Dresden, Germany; Karlsruhe Institute Technology, Germany.
    Rodenhausen, Keith Brian
    University of Nebraska, NE 68588 USA; Biolin Science Inc, NJ 07652 USA.
    Eichhorn, Klaus-Jochen
    Leibniz Institute Polymerforsch eV, Germany.
    Oertel, Ulrich
    Leibniz Institute Polymerforsch eV, Germany.
    Schubert, Mathias
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten. Leibniz Institute Polymerforsch eV, Germany; University of Nebraska, NE 68588 USA; University of Nebraska, NE 68588 USA.
    Stamm, Manfred
    Leibniz Institute Polymerforsch eV, Germany; Technical University of Dresden, Germany.
    Uhlmann, Petra
    Leibniz Institute Polymerforsch eV, Germany; University of Nebraska, NE 68588 USA.
    Quartz crystal microbalance with coupled Spectroscopic Ellipsometry-study of temperature-responsive polymer brush systems2017Ingår i: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 421, s. 843-851Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Using a combined setup of quartz crystal microbalance with dissipation monitoring together with spectroscopic ellipsometry, the thermo-responsive behavior of two different brush systems (poly(N-isopropyl acrylamide) and poly(2-oxazoline)s) was investigated and compared to the behavior of the free polymer in solution. Poly(2-oxazoline)s with three different hydrophilicities were prepared by changing the content of a hydrophilic comonomer. While both polymer types exhibit a sharp, discontinuous thermal transition in solution, in the brush state the transition gets broader in the case of poly(N-isopropyl acrylamide) and is transformed into a continuous transition for poly(2-oxazoline)s. The position of the transition in solution is influenced by the degree of hydrophilicity of the poly(2-oxazoline). The difference in areal mass detected by quartz crystal microbalance and by spectroscopic ellipsometry, has been attributed to the chain segment density profile of the polymer brushes. Applying this density profile information, for poly(N-isopropyl acrylamide) two different swelling stages could be identified, while for poly(2-oxazoline) the transition between a parabolic and more step-wise profile is found continuous. The different swelling characteristics were attributed to the different miscibility behavior types, with the brush state acting similar to a crosslinked system. (C) 2017 Elsevier B.V. All rights reserved.

  • 7. Adamska-Venkatesh, Agnieszka
    et al.
    Mirmohades, Mohammad
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Sommer, Constanze
    Reijerse, Edward
    Lubitz, Wolfgang
    Lomoth, Reiner
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Hammarström, Leif
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Following [FeFe] Hydrogenase Active Site Intermediates by Flash Photolysis/Mid-IR ProbingManuskript (preprint) (Övrigt vetenskapligt)
  • 8.
    Adhikari, Arindam
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Claesson, Per M.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Pani, Jinshan
    KTH, Skolan för kemivetenskap (CHE), Kemi, Korrosionslära.
    Leygraf, Christofer
    KTH, Skolan för kemivetenskap (CHE), Kemi, Korrosionslära.
    Deidinaitei, Andra
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Blomberg, Eva
    KTH, Skolan för kemivetenskap (CHE), Kemi, Ytkemi.
    Electrochemical behavior and anticorrosion properties of modified polyaniline dispersed in polyvinylacetate coating on carbon steel2008Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 53, nr 12, s. 4239-4247Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Conducting polyaniline (Pani) was prepared in the presence of methane sulfonic acid (MeSA) as dopant by chemical oxidative polymerization. The Pani-MeSA polymer was characterized by FT-IR, UV-vis, X-ray diffraction (XRD) and impedance spectroscopy. The polyrner was dispersed in polyvinylacetate and coated oil carbon steel samples by a dipping method. The electrochemical behavior and anticorrosion properties of the coating, oil carbon steel in 3% NaCl were investigated using Open-circuit Potential (OCP) versus time of exposure, and electrochemical techniques including electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and cyclic voltammetry (CV). During initial exposure, the OCP dropped about 0.35 V and the interfacial resistance increased several times, indicating I certain reduction of the polymer and oxidation of the steel surface. Later the OCP shifted to the noble direction and remained at a stable value during the exposure up to 60 days. The EIS monitoring also revealed the initial change and later stabilization of the coating. The stable high OCP and low coating impedance Suggest that the conducting polymer maintains its oxidative state and provides corrosion protection for carbon steel through out the investigated period. The polarization curves and CV show that the conducting polymer coating induces a passive-like behavior and greatly reduces the corrosion of carbon steel.

  • 9.
    Aghbolagh, Mahdi Shahmohammadi
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Meynaq, Mohammad Yaser Khani
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Shimizu, Kenichi
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Lindholm-Sethson, Britta
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Aspects on mediated glucose oxidation at a supported cubic phase2017Ingår i: Bioelectrochemistry, ISSN 1567-5394, E-ISSN 1878-562X, Vol. 118, s. 8-13Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A supported liquid crystalline cubic phase housing glucose oxidase on an electrode surface has been suggested as bio-anode in a biofuel. The purpose of this investigation is to clarify some aspect on the mediated enzymatic oxidation of glucose in such a bio-anode where the mediator ferrocene-carboxylic acid and glucose were dissolved in the solution. The enzyme glucose oxidase was housed in the water channels of the mono-olein cubic phase. The system was investigated with cyclic voltammetry at different scan rates and the temperature was varied between 15 degrees C and 30 degrees C. The diffusion coefficient of the mediator and also the film resistance was estimated showing a large decrease in the mass-transport properties as the temperature was decreased. The current from mediated oxidation of glucose at the electrode surface increased with decreasing film thickness. The transport of the mediator in the cubic phase was the rate-limiting step in the overall reaction, where the oxidation of glucose took place at the outer surface of the cubic phase.

  • 10.
    Agmo Hernandez, Victor
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi, Fysikalisk kemi.
    Hermes, Michael
    Milchev, Alexander
    Scholz, Fritz
    The overall adhesion-spreading process of liposomes on a mercury electrode is controlled by a mixed diffusion and reaction kinetics mechanism2009Ingår i: Journal of Solid State Electrochemistry, ISSN 1432-8488, E-ISSN 1433-0768, Vol. 13, nr 4, s. 639-649Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Using high-resolution chronoamperometric measurements, with sampling each 1.333 micro s, the initial step of the adhesion-spreading of liposomes on a mercury electrode was studied. These measurements allow getting a deeper insight into the first interaction of the liposomes with the mercury electrode, and they show that the overall adhesion-spreading process at different potentials is partially controlled by a fast but weak interaction equilibrium resulting in a mixed diffusion- and reaction-kinetics-controlled mechanism of the overall reaction.

  • 11.
    Agmo Hernández, Víctor
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Analytisk kemi.
    The theory of metal electronucleation applied to the study of fundamental properties of liposomes2013Ingår i: Journal of Solid State Electrochemistry, ISSN 1432-8488, E-ISSN 1433-0768, Vol. 17, nr 2 (SI), s. 299-305Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    This short review describes how the theory of electrochemical metal nucleation considering non-stationary effects due to the activation of latent nucleation sites has been successfully translated and applied to describe phenomena observed on lipid membranes. This rather unexpected connection is merely formal, but has resulted in a completely new approach in liposome research. It has been proposed that hydrophobic active sites spontaneously and constantly appear and disappear on lipid membranes. These sites control the affinity of liposomes for hydrophobic surfaces and determine the permeability of the lipid membrane to small hydrophilic molecules. Thus, the kinetic models for liposome adhesion on hydrophobic substrates and for the spontaneous leakage of liposomal content are identical to that of non-stationary nucleation mentioned above. Therefore, the broad scope of the available work on metal nucleation has facilitated the interpretation of the data obtained in liposome research. Future applications of the nucleation model in the realm of liposomes are also discussed.

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  • 12.
    Agmo Hernández, Víctor
    et al.
    Institut für Biochemie, Universität Greifswald, Felix-Hausdorff-Str. 4, 17487 Greifswald, Germany.
    Scholz, Fritz
    Universität Greifswald .
    The lipid composition determines the kinetics of adhesion and spreading of liposomes on mercury electrodes2008Ingår i: Bioelectrochemistry, ISSN 1567-5394, E-ISSN 1878-562X, Vol. 74, nr 1, s. 149-156Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The dependence of membrane properties on their composition was studied by following the adhesion and spreading of unilamellar and multilamellar liposomes on static mercury electrodes with the help of chronoamperometry. The analysis of the peak-shaped signals allows determining the kinetic parameters of the three-step adhesion-spreading process. The presence of cholesterol in the membrane stabilizes the bilayer in the liquid-crystal line phase, and destabilizes the gel phase. The kinetic parameters also show the effect of superlattice formation in the DMPC-cholesterol system. The detergent triton X-100 is only incorporated in the liquid-crystalline DMPC membranes, and it is expelled to the solution when the membrane is transformed to the gel phase. In the liquid-crystalline membrane, it enhances the adhesion-spreading of liposomes on mercury. The lyric peptides mastoparan X and melittin affect the adhesion-spreading in a similar manner. For the rupture-spreading step, their effect is explained by pore formation. The results obtained with lecithins of different length suggest that the bilayer opening process has much in common with flip-flop translocations. For this process the activation energies were found to be independent of the chain length of the lecithin molecules, while the preexponential factor in the Arthenius equation decreases drastically for longer chains.

  • 13.
    Agosta, Lorenzo
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Atomistic simulations of structural and dynamical properties of liquids under geometric constraints2019Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The statistical-mechanical description of liquids represents a formidable problem in physic due to the absence of the analytical theory of the liquid state. Atomistic simulations represent a unique source of information in this respect and can be implemented in order address macroscopically measurable liquid properties, including its structure and dynamics, based on the information of the interactions between its constituent molecules. A particularly intriguing challenge is represented by the problem of studying liquids under geometric constraints like surfaces, or where the dimensionality is strongly suppressed like for liquids in 2 dimensions. Experimental measurements cannot access to these regions due to the resolution limitations. In this thesis the study of confined liquids is achieved by particle-based simulations at different level of theory. In particular 3 study cases are considered: the first is the characterization of solid-liquid interfaces. The problem of adsorbing surfaces is treated as a specific case of inorganic surfaces in contact with liquid water. TiO2, chosen as reference material, is studied in its polymorphic structures in aqueous conditions. The surface reactivity and its influence on the liquid structure is solved considering the quantum nature of the system. The mechanism of a solute adsorbing at the interface, considering the interfacial liquid properties, is also addressed. New advanced analysis tools for determining the structural and dynamical properties of water under a surface confinement and the thermodynamic associated to relative adsorption processes are developed. We are confident that this study will represent a mile stone for a systematic study of complex environments as bio-inorganic interfaces. As second case a liquid confined in a 2D surface is studied. Simple liquids having spherically symmetric interaction are very powerful in order to understand the relevant degrees of freedom that governs a certain physical process. Here we expand the definition of 2D hexatic phases to smectic systems in 3D. Finally the self-assembly of a triply periodic mesophase having a Fddd space symmetry group is fully characterized for a simple liquid. This phase can be thought as a geometrical reduction to a two-dimensional separation surface. The possibility of generating such complex network with simple particles, like in colloids, opens the frontiers for the exploration of new materials and applications.

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    Atomistic simulations of structural and dynamical properties of liquids under geometric constraints
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  • 14.
    Agosta, Lorenzo
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Thermodynamic and electronic characterization of Glycine adsorbing on TiO2 anatase (101) surface from first principles simulationsManuskript (preprint) (Övrigt vetenskapligt)
  • 15.
    Agosta, Lorenzo
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Brandt, Erik G.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Lyubartsev, Alexander P.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Improved Sampling in Ab Initio-Based Free Energy Calculations of Amino Acids at Solid-Liquid Interfaces: A Tight-Binding Assessment on TiO2 Anatase (101)Manuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    Atomistic simulations are powerful for probing molecules at bioinorganic interfaces and excellent complements to scarcely available experimental techniques. The free energy controls the adsorption behavior of molecules on nanosurfaces, and is therefore a quantity of particular importance. Advanced sampling techniques can efficiently explore the adsorption free energy landscape, but molecular simulations with classical (Newtownian) dynamics fail to capture charge transfer and polarization at the solid-liquid interface. First principle simulations do not suffer from this limitation but come with a heavy computational load. Here, we introduce an efficient protocol to explore the free energy of adsorption in the ab initio framework. This approach accurately models the complex phenomena at bio-inorganic surfaces on the nanoscale and properly samples the relevant thermodynamic properties. We present a case study of adsorption of the Lysine and Aspartate amino acids on the anatase (101) TiO2 surface with the tight binding method. The high values of the calculated adsorption free energies highlight the importance of a proper description of the electronic state for surface binding processes.

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  • 16.
    Agosta, Lorenzo
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Metere, Alfredo
    Oleynikov, Peter
    Dzugutov, Mikhail
    Self-assembly of orthorhombic Fddd network in simple one-component liquidsManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    Triply periodic continuous morphologies arising a result of the microphase separation in block copolymer melts have so far never been observed self-assembled in systems of particles with spherically symmetric interaction. We report a molecular dynamics simulation of two simple one-component liquids which self-assemble upon cooling into equilibrium orthorhombic continuous network morphologies with the Fddd space group symmetry reproducing the structure of those observed in block copolymers. The finding that the geometry of constituent molecules isn't relevant for the formation of triply periodic networks indicates the generic nature of this class of phase transition.

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  • 17. Ahlgren, Sara
    et al.
    Reijmar, Karin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Analytisk kemi.
    Edwards, Katarina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Analytisk kemi.
    EGF-targeting lipodisks for specific delivery of cationic amphiphilic peptides to tumour cellsManuskript (preprint) (Övrigt vetenskapligt)
  • 18.
    Ahlgren, Sara
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Analytisk kemi.
    Reijmar, Karin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Analytisk kemi.
    Edwards, Katarina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Analytisk kemi.
    Targeting lipodisks enable selective delivery of anticancer peptides to tumor cells2017Ingår i: Nanomedicine: Nanotechnology, Biology and Medicine, ISSN 1549-9634, E-ISSN 1549-9642, Vol. 13, nr 7, s. 2325-2328Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Issues concerning non-specificity, degradation and hemolysis severely hamper the development of membranolytic amphiphilic peptides into safe and efficient anticancer agents. To increase the therapeutic potential, we have previously developed a strategy based on formulation of the peptides in biocompatible nanosized lipodisks. Studies using melittin as model peptide show that the proteolytic degradation and hemolytic effect of the peptide are substantially reduced upon loading in lipodisks. Here, we explored the possibilities to increase the specificity and boost the cytotoxicity of melittin to tumor cells by use of targeting lipodisk. We demonstrate that small (~20 nm) EGF-targeted lipodisks can be produced and loaded with substantial amounts of peptide (lipid/peptide molar ratio >7) by means of a simple and straightforward preparation protocol. In vitro cell studies confirm specific binding of the peptide-loaded disks to tumor cells and suggest that cellular internalization of the disks results in a significantly improved cell-killing effect.

  • 19.
    Ahlstrand, Emma
    et al.
    Linnus Univ, Dept Chem & Biomed Sci, S-39182 Kalmar, Sweden.;Linnus Univ, Ctr Biomat Chem, S-39182 Kalmar, Sweden..
    Hermansson, Kersti
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Friedman, Ran
    Linnus Univ, Dept Chem & Biomed Sci, S-39182 Kalmar, Sweden.;Linnus Univ, Ctr Biomat Chem, S-39182 Kalmar, Sweden..
    Interaction Energies in Complexes of Zn and Amino Acids: A Comparison of Ab Initio and Force Field Based Calculations2017Ingår i: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 121, nr 13, s. 2643-2654Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Zinc plays important roles in structural stabilization of proteins, eniyine catalysis, and signal transduction. Many Zn binding sites are located at the interface between the protein and the cellular fluid. In aqueous solutions, Zn ions adopt an octahedral coordination, while in proteins zinc can have different coordinations, with a tetrahedral conformation found most frequently. The dynainics of Zn binding to proteins and the formation of complexes that involve Zn are dictated by interactions between Zn and its binding partners. We calculated the interaction energies between Zn and its ligands in complexes that mimic protein binding sites and in Zn complexes of water and one or two amino acid moieties, using quantum mechanics (QM) and molecular mechanics (MM). It was found that MM calculations that neglect or only approximate polarizability did not reproduce even the relative order of the QM interaction energies in these complexes. Interaction energies calculated with the CHARMM-Diode polarizable force field agreed better with the ab initio results,:although the deviations between QM and MM were still rather large (40-96 kcallmol). In order to gain further insight into Zn ligand interactions, the free energies of interaction were estimated by QM calculations with continuum solvent representation, and we performed energy decomposition analysis calculations to examine the characteristics of the different complexes. The ligand-types were found to have high impact on the relative strength of polarization and electrostatic interactions. Interestingly, ligand ligand interactions did not play a significant role in the binding of Zn. Finally) analysis of ligand exchange energies suggests that carboxylates could be exchanged with water molecules, which explains the flexibility in Zn:binding dynamics. An exchange between earboxylate (Asp/Glii) and imidazole (His) is less likely.

  • 20.
    Ahlstrand, Emma
    et al.
    Linnéuniversitetet, Fakulteten för Hälso- och livsvetenskap (FHL), Institutionen för kemi och biomedicin (KOB).
    Hermansson, Kersti
    Uppsala University.
    Friedman, Ran
    Linnéuniversitetet, Fakulteten för Hälso- och livsvetenskap (FHL), Institutionen för kemi och biomedicin (KOB).
    Interaction Energies in Complexes of Zn and Amino Acids: A Comparison of Ab Initio and Force Field Based Calculations2017Ingår i: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 121, nr 13, s. 2643-2654Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Zinc plays important roles in structural stabilization of proteins, eniyine catalysis, and signal transduction. Many Zn binding sites are located at the interface between the protein and the cellular fluid. In aqueous solutions, Zn ions adopt an octahedral coordination, while in proteins zinc can have different coordinations, with a tetrahedral conformation found most frequently. The dynainics of Zn binding to proteins and the formation of complexes that involve Zn are dictated by interactions between Zn and its binding partners. We calculated the interaction energies between Zn and its ligands in complexes that mimic protein binding sites and in Zn complexes of water and one or two amino acid moieties, using quantum mechanics (QM) and molecular mechanics (MM). It was found that MM calculations that neglect or only approximate polarizability did not reproduce even the relative order of the QM interaction energies in these complexes. Interaction energies calculated with the CHARMM-Diode polarizable force field agreed better with the ab initio results,:although the deviations between QM and MM were still rather large (40-96 kcallmol). In order to gain further insight into Zn ligand interactions, the free energies of interaction were estimated by QM calculations with continuum solvent representation, and we performed energy decomposition analysis calculations to examine the characteristics of the different complexes. The ligand-types were found to have high impact on the relative strength of polarization and electrostatic interactions. Interestingly, ligand ligand interactions did not play a significant role in the binding of Zn. Finally) analysis of ligand exchange energies suggests that carboxylates could be exchanged with water molecules, which explains the flexibility in Zn:binding dynamics. An exchange between earboxylate (Asp/Glii) and imidazole (His) is less likely.

  • 21.
    Ahlstrand, Emma
    et al.
    Linnéuniversitetet, Fakulteten för Hälso- och livsvetenskap (FHL), Institutionen för kemi och biomedicin (KOB).
    Zukerman Schpector, Julio
    Universidade Federal de São Carlos, Brazil.
    Friedman, Ran
    Linnéuniversitetet, Fakulteten för Hälso- och livsvetenskap (FHL), Institutionen för kemi och biomedicin (KOB).
    Computer simulations of alkali-acetate solutions: Accuracy of the forcefields in difference concentrations2017Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 147, s. 1-10, artikel-id 194102Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    When proteins are solvated in electrolyte solutions that contain alkali ions, the ions interact mostlywith carboxylates on the protein surface. Correctly accounting for alkali-carboxylate interactionsis thus important for realistic simulations of proteins. Acetates are the simplest carboxylates thatare amphipathic, and experimental data for alkali acetate solutions are available and can be comparedwith observables obtained from simulations. We carried out molecular dynamics simulations of alkali acetate solutions using polarizable and non-polarizable forcefields and examined the ionacetateinteractions. In particular, activity coefficients and association constants were studied in a range of concentrations (0.03, 0.1, and 1M). In addition, quantum-mechanics (QM) based energy decomposition analysis was performed in order to estimate the contribution of polarization, electrostatics, dispersion, and QM (non-classical) effects on the cation-acetate and cation-water interactions. Simulations of Li-acetate solutions in general overestimated the binding of Li+ and acetates. In lower concentrations, the activity coefficients of alkali-acetate solutions were too high, which is suggested to be due to the simulation protocol and not the forcefields. Energy decomposition analysis suggested that improvement of the forcefield parameters to enable accurate simulations of Li-acetate solution scan be achieved but may require the use of a polarizable forcefield. Importantly, simulations with some ion parameters could not reproduce the correct ion-oxygen distances, which calls for caution in thechoice of ion parameters when protein simulations are performed in electrolyte solutions.

    Ladda ner fulltext (pdf)
    Accepted_Manuscript
  • 22.
    Ahlström, Peter
    et al.
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    Aim, Karel
    Dohrn, Ralf
    Elliott, J. Richard
    Jackson, George
    Jaubert, Jean-Noel
    Rebello de A. Macedo, Maria Eugénia
    Pokki, Juha-Pekka
    Reczey, Kati
    Victorov, Alexey
    Fele Zilnik, Ljudmila
    Economou, Ioannis
    A Survey of Thermodynamics and Transport Properties in Chemical Engineering Education in Europe and the USA2008Ingår i: Proceedings of the 100th Annual Meeting of the American Institute for Chemical Engineering, 2008Konferensbidrag (Refereegranskat)
    Ladda ner fulltext (pdf)
    FULLTEXT01
  • 23.
    Ahlström, Peter
    et al.
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    Moodley, Suren
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    Bolton, Kim
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    Ramjugernath, D.
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    Computer Simulations of Vapor-Liquid-Liquid Equilibria Involving Hydrocarbons and Water2008Ingår i: Proceedings of the 100th Annual Meeting of the American Institute for Chemical Engineering, 2008, CHPC National Meeting, Durban, South Africa, December 9-10, 2008, AlChe Annual Meeting, Philadelphia, November 15-21, 2008, 2008Konferensbidrag (Övrigt vetenskapligt)
    Ladda ner fulltext (pdf)
    FULLTEXT01
  • 24.
    Ahmed, Hamzah
    et al.
    Luleå tekniska universitet, Institutionen för hälsovetenskap, Medicinsk vetenskap.
    Shimpi, Manishkumar R.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Kemiteknik.
    Velaga, Sitaram P.
    Luleå tekniska universitet, Institutionen för hälsovetenskap, Medicinsk vetenskap.
    Relationship between mechanical properties and crystal structure in cocrystals and salt of paracetamol2017Ingår i: Drug Development and Industrial Pharmacy, ISSN 0363-9045, E-ISSN 1520-5762, Vol. 43, nr 1, s. 89-97Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Objectives were to study mechanical properties of various solid forms of paracetamol and relate to their crystal structures. Paracetamol Form I (PRA), its cocrystals with oxalic acid (PRA-OXA) and 4,4-bipyridine (PRA-BPY) and hydrochloride salt (PRA-HCL) were selected. Cocrystals and salt were scaled-up using rational crystallization methods. The resulting materials were subjected to differential scanning solid-state characterization. The powders were sieved and 90-360 µm sieve fraction was considered. These powders were examined by scanning electron microscopy (SEM) and densities were determined. Tablets were made at applied pressures of 35-180 MPa under controlled conditions and the tablet height, diameter and hardness were measured. Tensile strength and porosity of the tablets were estimated using well known models. Crystal structures of these systems were visualized and slips planed were identified. Cocrystal and salt of PRA were physically pure. Sieved powders had comparable morphologies and particle size. The apparent and theoretical densities of powders were similar but no clear trends were observed. The tensile strengths of these compacts were increased with increasing pressure whereas tabletability decreased in the order oxalic acid > PRA-HCL ≈ PRA-OXA > BPY > PRA-BPY. Tablet tensile strength decreases exponentially with increasing porosity with the exception of PRY-BPY and BPY. Slip plane prediction based on attachment energies may not be independently considered. However, it was possible to explain the improved mechanical properties of powders based on the crystal structure. Cocrystallization and salt formation have introduced structural features that are responsible for improved tableting properties of PRA.

  • 25.
    Ahmed, Taha
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Edvinsson, Tomas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för materialvetenskap, Fasta tillståndets fysik.
    Optical Quantum Confinement in Ultrasmall ZnO and the Effect of Size on Their Photocatalytic Activity2020Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 124, nr 11, s. 6395-6404Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Zinc oxide is a well-known metal oxide semiconductor with a wide direct band gap that offers a promising alternative to titanium oxide in photocatalytic applications. ZnO is studied here as quantum dots (QDs) in colloidal suspensions, where ultrasmall nanoparticles of ZnO show optical quantum confinement with a band gap opening for particles below 9 nm in diameter from the shift of the band edge energies. The optical properties of growing ZnO QDs are determined with Tauc analysis, and a system of QDs for the treatment and degradation of distributed threats is analyzed using an organic probe molecule, methylene blue, whose UV/vis spectrum is analyzed in some detail. The effect of optical properties of the QDs and the kinetics of dye degradation are quantified for low-dimensional ZnO materials in the range of 3-8 nm and show a substantial increase in photocatalytic activity compared to larger ZnO particles. This is attributed to a combined effect from the increased surface area as well as a quantum confinement effect that goes beyond the increased surface area. The results show a significantly higher photocatalytic activity for the QDs between 3 and 6 nm with a complete decolorization of the organic probe molecule, while QDs from 6 nm and upward in diameter show signs of competing reduction reactions. Our study shows that ultrasmall ZnO particles have a reactivity beyond that which is expected because of their increased surface area and also demonstrates size-dependent reaction pathways, which introduces the possibility for size-selective catalysis.

  • 26. Ahmed, Towfiq
    et al.
    Haraldsen, Jason T.
    Zhu, Jian-Xin
    Balatsky, Alexander V.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. Institute for Materials Science, Los Alamos National Laboratory, United States.
    Next-Generation Epigenetic Detection Technique: Identifying Methylated Cytosine Using Graphene Nanopore2014Ingår i: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 5, nr 15, s. 2601-2607Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    DNA methylation plays a pivotal role in the genetic evolution of both embryonic and adult cells. For adult somatic cells, the location and dynamics of methylation have been very precisely pinned down with the 5-cytosine markers on cytosine-phosphate-guanine (CpG) units. Unusual methylation on CpG islands is identified as one of the prime causes for silencing the tumor suppressant genes. Early detection of methylation changes can diagnose the potentially harmful oncogenic evolution of cells and provide promising guideline for cancer prevention. With this motivation, we propose a cytosine methylation detection technique. Our hypothesis is that electronic signatures of DNA acquired as a molecule translocates through a nanopore would be significantly different for methylated and nonmethylated bases. This difference in electronic fingerprints would allow for reliable real-time differentiation of methylated DNA. We calculate transport currents through a punctured graphene membrane while the cytosine and methylated cytosine translocate through the nanopore. We also calculate the transport properties for uracil and cyanocytosine for comparison. Our calculations of transmission, current, and tunneling conductance show distinct signatures in their spectrum for each molecular type. Thus, in this work, we provide a theoretical analysis that points to a viability of our hypothesis.

  • 27.
    Ahnfelt, Emelie
    et al.
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för farmaci.
    Degerstedt, Oliver
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för farmaci.
    Lilienberg, Elsa
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för farmaci.
    Sjögren, Erik
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för farmaci.
    Hansson, Per
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för farmaci.
    Lennernäs, Hans
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för farmaci.
    Lipiodol-based emulsions used for transarterial chemoembolization and drug delivery: Effects of composition on stability and product quality2019Ingår i: Journal of Drug Delivery Science and Technology, ISSN 1773-2247, Vol. 53, artikel-id UNSP 101143Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Transarterial chemoembolization with emulsion-based formulations using doxorubicin hydrochloride (DOX) and Lipiodol (R) is the golden standard for the loco-regional treatment of unresectable hepatocellular carcinoma (HCC). However, from a pharmaceutical quality perspective these emulsions are poorly characterized. In this study, clinically relevant Lipiodol (R)-based emulsions were characterized in terms of emulsion stability, continuous phase classification and droplet-size distribution. Also, the solubility of DOX in the different emulsion components and the distribution of DOX to the lipid phase were investigated. These are key features to investigate due to the claimed tumor-seeking properties of Lipiodol (R). The in vitro release of DOX was studied in a miniaturized dialysis method and an empirical release model was applied to adjust for the passage of DOX across the dialysis membrane. The most stable emulsion ( > 72 h) was classified as water-in-oil (w/o), had the highest distribution of DOX to the lipid phase (20%) and an aqueous-to-lipid phase ratio of 1:4. The composition of the aqueous phase was a mixture (v/v) of iohexol (85%) and water (15%). Emulsions containing iohexol and a high aqueousto-lipid phase ratio (1:2-1:4) displayed prolonged in vitro release profiles of DOX. This study further emphasizes the medical need to standardize these emulsion-based drug delivery systems.

    Ladda ner fulltext (pdf)
    FULLTEXT01
  • 28. Ai, Yuejie
    et al.
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Ji, Yongfei
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Song, Wei-Guo
    Luo, Yi
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Hydrophobicity and Hydrophilicity Balance Determines Shape Selectivity of Suzuki Coupling Reactions Inside Pd@meso-SiO2 Nanoreactor2016Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, nr 19, s. 10244-10251Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Molecular sorting and catalysis directed by shape selectivity have been extensively applied in porous extended frameworks for a low-carbon, predictable, renewable component of modern industry. A comprehensive understanding of the underlying recognition mechanism toward different shapes is unfortunately still missing, owing to the lack of structural and dynamic information under operating conditions. We demonstrate here that such difficulties can be overcome by state-of-the-art molecular dynamics simulations which provide atomistic details that are not accessible experimentally, as exemplified by our interpretation for the experimentally observed aggregation induced shape selectivity for Suzuki C-C coupling reaction catalyzed by Pd particles in mesoporous silica. It is found that both aggregation ability and aggregating pattern of the reactants play the decisive role in controlling the shape selectivity, which are in turn determined by the balance between the hydrophobicity and hydrophilicity of the reactants, or in other words, by the balance between the noncovalent hydrogen bonding interaction and van der Waals forces. A general rule that allows prediction of the shape selectivity of a reactant has been proposed and verified against experiments. We show that molecular modeling is a powerful tool for rational design of new mesoporous systems and for the control of catalytic reactions that are important for the petrochemical industry.

  • 29. Ai, Yue-jie
    et al.
    Tian, Guangjun
    Liao, Rong-zhen
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Zhang, Qiong
    Fang, Wei-hai
    Luo, Yi
    Intrinsic Property of Flavin Mononucleotide Controls its Optical Spectra in Three Redox States2011Ingår i: ChemPhysChem, ISSN 1439-4235, E-ISSN 1439-7641, Vol. 12, nr 16, s. 2899-2902Artikel i tidskrift (Refereegranskat)
  • 30. Aidas, Kestutis
    et al.
    Agren, Hans
    Kongsted, Jacob
    Laaksonen, Aatto
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för tillämpad miljövetenskap (ITM).
    Mocci, Francesca
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    A quantum mechanics/molecular dynamics study of electric field gradient fluctuations in the liquid phase. the case of na+ in aqueous solution2013Ingår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 15, nr 5, s. 1621-1631Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Na-23 quadrupolar coupling constant of the Na+ ion in aqueous solution has been predicted using molecular dynamics simulations and hybrid quantum mechanics/molecular mechanics methods for the calculation of electric field gradients. The developed computational approach is generally expected to provide reliable estimates of the quadrupolar coupling constants of monoatomic species in condensed phases, and we show here that intermolecular polarization and non-electrostatic interactions are of crucial importance as they result in a 100% increased quadrupolar coupling constant of the ion as compared to a simpler pure electrostatic picture. These findings question the reliability of the commonly applied classical Sternheimer approximation for the calculations of the electric field gradient. As it can be expected from symmetry considerations, the quadrupolar coupling constants of the 5- and 6-coordinated Na+ ions in solution are found to differ significantly.

  • 31.
    Aidas, Kestutis
    et al.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Ågren, Hans
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Kongsted, Jacob
    Laaksonen, Aatto
    Mocci, Francesca
    A quantum mechanics/molecular dynamics study of electric field gradient fluctuations in the liquid phase. The case of Na+ in aqueous solution2013Ingår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 15, nr 5, s. 1621-1631Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Na-23 quadrupolar coupling constant of the Na+ ion in aqueous solution has been predicted using molecular dynamics simulations and hybrid quantum mechanics/molecular mechanics methods for the calculation of electric field gradients. The developed computational approach is generally expected to provide reliable estimates of the quadrupolar coupling constants of monoatomic species in condensed phases, and we show here that intermolecular polarization and non-electrostatic interactions are of crucial importance as they result in a 100% increased quadrupolar coupling constant of the ion as compared to a simpler pure electrostatic picture. These findings question the reliability of the commonly applied classical Sternheimer approximation for the calculations of the electric field gradient. As it can be expected from symmetry considerations, the quadrupolar coupling constants of the 5- and 6-coordinated Na+ ions in solution are found to differ significantly.

  • 32.
    Aisenbrey, Christopher
    et al.
    Institut de Chimie Universit0 Louis Pasteur Strasbourg—CNRS, UMR 7177 4, Rue Blaise Pascal, 67000 Strasbourg (France); Max-Planck-Institut f>r Biochemie Am Klopferspitz 18A, 82152 Martinsried (Germany).
    Cusan, Monica
    Lambotte, Stephan
    Jasperse, Pieter
    Georgescu, Julia
    Harzer, Ulrike
    Bechinger, Burkhard
    Specific Isotope Labeling of Colicin E1 and B Channel Domains For Membrane Topological Analysis by Oriented Solid-State NMR Spectroscopy2008Ingår i: ChemBioChem (Print), ISSN 1439-4227, E-ISSN 1439-7633, Vol. 9, nr 6, s. 944-951Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An approach is presented to selectively label the methionines of the colicin E1 and B channel domains, each about 200 residues in size, and use them for oriented solid-state NMR investigations. By combining site-directed mutagenesis, bacterial overexpression in a methionine auxotroph E. coli strain and biochemical purification, quantitative amounts of the proteins for NMR structural investigations were obtained. The proteins were selectively labeled with 15N at only one, or at a few, selected sites. Multidimensional heteronuclear correlation high-resolution NMR spectroscopy and mass spectrometry were used to monitor the quality of isotopic labeling. Thereafter the proteins were reconstituted into oriented phospholipid bilayers and investigated by proton-decoupled 15N solid-state NMR spectroscopy. The colicin E1 thermolytic fragment that carries a single 15N methionine within its hydrophobic helix 9 region exhibited 15N resonances that are characteristic of helices that are oriented predominantly parallel to the membrane surface at low temperature, and a variety of alignments and conformations at room temperature. This suggests that the protein can adopt both umbrella and pen-knife conformations.

  • 33.
    Aitola, Kerttu
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Domanski, Konrad
    Ecole Polytech Fed Lausanne, Inst Chem Sci & Engn, Lab Photon & Interfaces, CH-1015 Lausanne, Switzerland..
    Correa-Baena, Juan-Pablo
    MIT, 77 Massachusetts Ave, Cambridge, MA 02139 USA..
    Sveinbjörnsson, Kári
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Saliba, Michael
    Ecole Polytech Fed Lausanne, Inst Chem Sci & Engn, Lab Photon & Interfaces, CH-1015 Lausanne, Switzerland..
    Abate, Antonio
    Univ Fribourg, Adolphe Merkle Inst, CH-1700 Fribourg, Switzerland..
    Graetzel, Michael
    Ecole Polytech Fed Lausanne, Inst Chem Sci & Engn, Lab Photon & Interfaces, CH-1015 Lausanne, Switzerland..
    Kauppinen, Esko
    Aalto Univ, Dept Appl Phys, POB 15100, Aalto 00076, Finland..
    Johansson, Erik M.J.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Tress, Wolfgang
    Ecole Polytech Fed Lausanne, Inst Chem Sci & Engn, Lab Photon & Interfaces, CH-1015 Lausanne, Switzerland..
    Hagfeldt, Anders
    Ecole Polytech Fed Lausanne, Inst Chem Sci & Engn, Lab Photomol Sci, CH-1015 Lausanne, Switzerland..
    Boschloo, Gerrit
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    High Temperature-Stable Perovskite Solar Cell Based on Low-Cost Carbon Nanotube Hole Contact2017Ingår i: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 29, nr 17, artikel-id 1606398Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Mixed ion perovskite solar cells (PSC) are manufactured with a metal-free hole contact based on press-transferred single-walled carbon nanotube (SWCNT) film infiltrated with 2,2,7,-7-tetrakis(N, N-di-p-methoxyphenylamine)-9,90-spirobifluorene (Spiro-OMeTAD). By means of maximum power point tracking, their stabilities are compared with those of standard PSCs employing spin-coated Spiro-OMeTAD and a thermally evaporated Au back contact, under full 1 sun illumination, at 60 degrees C, and in a N-2 atmosphere. During the 140 h experiment, the solar cells with the Au electrode experience a dramatic, irreversible efficiency loss, rendering them effectively nonoperational, whereas the SWCNT-contacted devices show only a small linear efficiency loss with an extrapolated lifetime of 580 h.

  • 34.
    Aitola, Kerttu
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Sveinbjörnsson, Kári
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Correa-Baena, Juan-Pablo
    Ecole Polytech Fed Lausanne, Lab Photomol Sci, EPFL SB ISIC LSPM, CH G1 523,Chemin Alamb,Stn 6, CH-1015 Lausanne, Switzerland..
    Kaskela, Antti
    Aalto Univ, Sch Sci, Dept Appl Phys, POB 15100, FI-00076 Aalto, Finland..
    Abate, Antonio
    Ecole Polytech Fed Lausanne, Lab Photon & Interfaces, Inst Chem Sci & Engn, EPFL SB ISIC LPI, CH G1 526,Stn 6, CH-1015 Lausanne, Switzerland..
    Tian, Ying
    Aalto Univ, Sch Sci, Dept Appl Phys, POB 15100, FI-00076 Aalto, Finland..
    Johansson, Erik M. J.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Graetzel, Michael
    Ecole Polytech Fed Lausanne, Lab Photon & Interfaces, Inst Chem Sci & Engn, EPFL SB ISIC LPI, CH G1 526,Stn 6, CH-1015 Lausanne, Switzerland..
    Kauppinen, Esko I.
    Aalto Univ, Sch Sci, Dept Appl Phys, POB 15100, FI-00076 Aalto, Finland..
    Hagfeldt, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi. Ecole Polytech Fed Lausanne, Lab Photomol Sci, EPFL SB ISIC LSPM, CH G1 523,Chemin Alamb,Stn 6, CH-1015 Lausanne, Switzerland..
    Boschloo, Gerrit
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Carbon nanotube-based hybrid hole-transporting material and selective contact for high efficiency perovskite solar cells2016Ingår i: Energy & Environmental Science, ISSN 1754-5692, E-ISSN 1754-5706, Vol. 9, nr 2, s. 461-466Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We demonstrate a high efficiency perovskite solar cell with a hybrid hole-transporting material-counter electrode based on a thin single-walled carbon nanotube (SWCNT) film and a drop-cast 2,2,7,-7-tetrakis(N, N-di-p-methoxyphenylamine)-9,90-spirobifluorene (Spiro-OMeTAD) hole-transporting material (HTM). The average efficiency of the solar cells was 13.6%, with the record cell yielding 15.5% efficiency. The efficiency of the reference solar cells with spin-coated Spiro-OMeTAD hole-transportingmaterials (HTMs) and an evaporated gold counter electrode was 17.7% (record 18.8%), that of the cells with only a SWCNT counter electrode (CE) without additional HTM was 9.1% (record 11%) and that of the cells with gold deposited directly on the perovskite layer was 5% (record 6.3%). Our results show that it is possible to manufacture high efficiency perovskite solar cells with thin film (thickness less than 1 mu m) completely carbon-based HTMCEs using industrially upscalable manufacturing methods, such as press-transferred CEs and drop-cast HTMs.

  • 35.
    Aitola, Kerttu
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Zhang, Jinbao
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Vlachopoulos, Nick
    Ecole Polytech Fed Lausanne, Inst Chem Sci & Engn, SB ISIC LSPM, CH-1015 Lausanne, Switzerland..
    Halme, Janne
    Aalto Univ, Sch Sci, Dept Appl Phys, Aalto 00076, Finland..
    Kaskela, Antti
    Aalto Univ, Sch Sci, Dept Appl Phys, Aalto 00076, Finland..
    Nasibulin, Albert G.
    Aalto Univ, Sch Sci, Dept Appl Phys, Aalto 00076, Finland.;Skolkovo Inst Sci & Technol, Skolkovo, Russia..
    Kauppinen, Esko I.
    Aalto Univ, Sch Sci, Dept Appl Phys, Aalto 00076, Finland..
    Boschloo, Gerrit
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Hagfeldt, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Carbon nanotube film replacing silver in high-efficiency solid-state dye solar cells employing polymer hole conductor2015Ingår i: Journal of Solid State Electrochemistry, ISSN 1432-8488, E-ISSN 1433-0768, Vol. 19, nr 10, s. 3139-3144Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A semitransparent, flexible single-walled carbon nanotube (SWCNT) film was efficiently used in place of evaporated silver as the counter electrode of a poly(3,4-ethylenedioxythiophene) polymer-based solid-state dye solar cell (SSDSC): the solar-to-electrical energy conversion efficiency of the SWCNT-SSDSC was 4.8 % when it was 5.2 % for the Ag-SSDSC. The efficiency difference stemmed from a 0.1-V difference in the open-circuit voltage, whose reason was speculated to be related to the different recombination processes in the two types of SSDSCs.

  • 36. Aitola, Kerttu
    et al.
    Zhang, Jinbao
    Vlachopoulos, Nick
    Halme, Janne
    Kaskela, Antti
    Nasibulin, Albert
    Kauppinen, Esko
    Boschloo, Gerrit
    Hagfeldt, Anders
    Carbon nanotube film replacing silver in high-efficiency solid-state dye solar cells employing polymer hole conductor2015Ingår i: Journal of Solid State ElectrochemistryArtikel i tidskrift (Refereegranskat)
    Abstract [en]

    A semitransparent, flexible single-walled carbon nanotube (SWCNT) film was efficiently used in place of evaporated silver as the counter electrode of a poly(3,4-ethylenedioxythiophene) polymer-based solid-state dye solar cell (SSDSC): the solar-to-electrical energy conversion efficiency of the SWCNT-SSDSC was 4.8 % when it was 5.2 % for the Ag-SSDSC. The efficiency difference stemmed from a 0.1-V difference in the open-circuit voltage, whose reason was speculated to be related to the different recombination processes in the two types of SSDSCs.

  • 37. Ai-Xi, Chen
    et al.
    Hong, Wang
    Duan, Sai
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Hai-Ming, Zhang
    Xin, Xu
    Li-Feng, Chi
    Potential-Induced Phase Transition of N-Isobutyryl-L-cysteine Monolayers on Au(111) Surfaces2017Ingår i: Wuli huaxue xuebao, ISSN 1000-6818, Vol. 33, nr 5, s. 1010-1016Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Functional solid substrates modified by self-assembled monolayers (SAMs) have potential applications in biosensors, chromatography, and biocompatible materials. The potential-induced phase transition of N-isobutyryl-L-cysteine (L-NIBC) SAMs on Au(111) surfaces was investigated by in-situ electrochemical scanning tunneling microscopy (EC-STM) in 0.1 mol.L-1 H2SO4 solution. The NIBC SAMs with two distinct structures (alpha phase and beta phase) can be prepared by immersing the Au(111) substrate in pure NIBC aqueous solution and NIBC solution controlled by phosphate buffer at pH 7, respectively. The as-prepared a phase and beta phase of NIBC SAMs show various structural changes under the control of electrochemical potentials of the Au(111) in H2SO4 solution. The a phase NIBC SAMs exhibit structural changes from ordered to disordered structures with potential changes from 0.7 V (vs saturated calomel electrode, SCE) to 0.2 V. However, the beta phase NIBC SAMs undergo structural changes from disordered structures (E < 0.3 V) to y phase (0.4 V < E < 0.5 V) and finally to the beta phase (0.5 V < E < 0.7 V). EC-STM images also indicate that the phase transition from the alpha phase NIBC SAMs to the a phase occurs at positive potential. Combined with density functional theory (DFT) calculations, the phase transition from the beta phase to the a phase is explained by the potential-induced break of bonding interactions between -COO- and the negatively charged gold surfaces.

  • 38.
    Ajaikumar, Samikannu
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Ahlkvist, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Larsson, William
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Kordas, K
    Mikkola, Jyri-Pekka
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Laboratory of Industrial Chemistry and Reaction Engineering, Process Chemistry Centre, Åbo Akademi University, Piispankatu 8, FIN-20500, Turku/Åbo, Finland.
    Oxidation of α-pinene over gold containing bimetallic nanoparticles supported on reducible TiO2 by DPU method2011Ingår i: Applied Catalysis A: General, ISSN 0926-860X, E-ISSN 1873-3875, Vol. 392, nr 1-2, s. 11-18Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A series of bimetallic catalysts Au–M (where M = Cu, Co and Ru) were supported on a reducible TiO2 oxide via deposition-precipitation (DP) method with a slow decomposition of urea as the precipitating agent. The characteristic structural features of the prepared materials were characterized by various physico-chemical techniques such as X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). XPS results indicated the formation of alloyed bimetallic particles on the TiO2 support. TEM results confirmed the fine dispersion of metal nanoparticles on the support with an average particle size in the range of 3–5 nm. An industrially important process, oxy-functionalization of α-pinene was carried out over the prepared bimetallic heterogeneous catalysts under liquid phase conditions. Reaction parameters such as the reaction time, temperature, and the effect of solvent were studied for optimal conversion of α-pinene into verbenone. The major products obtained were verbenone, verbenol, α-pinene oxide and alkyl-pinene peroxide. The activity of the catalysts followed the order; AuCu/TiO2 > AuCo/TiO2 > Cu/TiO2 > Au/TiO2 > AuRu/TiO2. Upon comparison of the various catalysts, AuCu/TiO2 was found to be an active and selective catalyst towards the formation of verbenone. The temperature, nature of the catalysts and the choice of solvents greatly influenced the reaction rate.

  • 39.
    Ajjan, Fátima
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Laboratoriet för organisk elektronik. Linköpings universitet, Tekniska fakulteten.
    Mecerreyes, David
    Univ Basque Country UPV EHU, Spain.
    Inganäs, Olle
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska fakulteten.
    Enhancing Energy Storage Devices with Biomacromolecules in Hybrid Electrodes2019Ingår i: Biotechnology Journal, ISSN 1860-6768, E-ISSN 1860-7314, artikel-id 1900062Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    The development of energy storage devices with higher energy and power outputs, and long cycling stability is urgently required in the pursuit of the expanding challenges of electrical energy storage. The utilization of biologically renewable redox compounds holds a great potential in designing sustainable energy storage systems and contributes in reducing the dependence on fossil fuels for energy materials. Quinones are the principal redox centers in natural organic materials and play a key role as charge storage electrode materials because of their abundance, multiple forms and integration into the materials flow through the biosphere. Electrical energy storage devices and systems can be significantly improved by the combination of scalable quinone-based biomaterials with good electronic conductors. This review uses recent examples to show how biopolymers are providing new directions in the development of renewable biohybrid electrodes for energy storage devices.

  • 40.
    Akpe, Victor
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Cellens fysik.
    Brismar, Hjalmar
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Cellens fysik.
    Nyokong, Tebello
    Osadebe, P. O.
    Photophysical and photochemical parameters of octakis (benzylthio) phthalocyaninato zinc, aluminium and tin: Red shift index concept in solvent effect on the ground state absorption of zinc phthalocyanine derivatives2010Ingår i: Journal of Molecular Structure, ISSN 0022-2860, E-ISSN 1872-8014, Vol. 984, nr 1-3, s. 1-14Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper addresses the synthesis of octa-substituted benzylthio metallophthalocyanines (OBTMPcs) that contain the central metal ions of Zn2+, Al3+ and Sn4+. The ground state absorption of ZnPc(SR)(8) (OBTZnPc) along with the ZnPc derivatives, well documented in literature were used to study a new concept called the red shift index (RsI). The concept is based on the empirical values of RsI of the different complexes in solvent media. Unequivocally, parameters used in this paper show strong correlations that are consistent with the results obtained. For instance, 12,1 of the complexes tend to increase as the refractive index, n(D), and solvent donor, DN, of solvent increases. Photodegradation (photobleaching) quantum yield, phi(d) measurements of these compounds show that they are highly photostable, phi(d) (0.03-0.33 x 10(-5)). The triplet quantum yield, phi(T) (0.40-0.53) and the triplet lifetime, tau(T) (610-810 mu s) are within the typical range for metallophthalocyanines in DMSO. The photosensitisation efficiency. S-Delta, is relatively high for all the molecules (0.74-0.90). (C) 2010 Elsevier B.V. All rights reserved.

  • 41.
    Al Soubaihi, Rola Mohammad
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Saoud, Khaled Mohammad
    Virginia Commonwealth Univ Qatar, Liberal Arts & Sci Program, POB 8095, Doha, Qatar..
    Dutta, Joydeep
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Critical Review of Low-Temperature CO Oxidation and Hysteresis Phenomenon on Heterogeneous Catalysts2018Ingår i: Catalysts, ISSN 2073-4344, Vol. 8, nr 12, artikel-id 660Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    There is a growing demand for new heterogeneous catalysts for cost-effective catalysis. Currently, the hysteresis phenomenon during low-temperature CO oxidation is an important topic in heterogeneous catalysis. Hysteresis provides important information about fluctuating reaction conditions that affect the regeneration of active sites and indicate the restoration of catalyst activity. Understanding its dynamic behavior, such as hysteresis and self-sustained kinetic oscillations, during CO oxidation, is crucial for the development of cost-effective, stable and long-lasting catalysts. Hysteresis during CO oxidation has a direct influence on many industrial processes and its understanding can be beneficial to a broad range of applications, including long-life CO2 lasers, gas masks, catalytic converters, sensors, indoor air quality, etc. This review considers the most recent reported advancements in the field of hysteresis behavior during CO oxidation which shed light on the origin of this phenomenon and the parameters that influence the type, shape, and width of the conversion of the hysteresis curves.

  • 42.
    Alaei, Zahra
    KTH, Skolan för kemivetenskap (CHE).
    Release of Solubilizate from Micelle Triggered by Core Freezing2016Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    I denna avhandling har frisläppningen av hexametyldisiloxan (HMDSO) från micellära system som initierats via kärnfrysning studerats med hjälp av 1H-NMR spektroskopi. Den studerade surfaktanten, den nonjoniska BrijTM S20 bildar miceller vid 1 vikt% i vatten. Den underliggande mekanismen för frisläppning härrör ifrån att micellens kärna fryser vid sänkt temperatur. Förutom de uppmätta 1H-NMR spektra så mätts även temperatur beroendet av självdiffusionkoefficienter och longitudinella relaxationstider                         . Den temperaturberoende andelen av HMDSO i micellen bestämdes tillsammans med relevanta egenskaper hos micellen, såsom temperatur för kärnfrysning, interna dynamik och storlek. Dessa jämfördes med motsvarande data från systemet utan HMDSO.

  • 43.
    Alami, E
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen.
    Almgren, Mats
    Brown, Wyn
    Francois, Jeanette
    Aggregation of hydrophobically end-capped poly(ethylene oxide) in aqueous solutions. Fluorescence and light-scattering studies1996Ingår i: MACROMOLECULES, Vol. 29, nr 6, s. 2229-2243Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The association of a monodisperse model associative polymer, hydrophobically end-capped poly(ethylene oxide), denoted C(12)EO(460)C(12), in aqueous solution has been studied. The macroscopic properties have been investigated by theological methods and cor

  • 44.
    Aldehani, Mohammed
    et al.
    Univ Lancaster, Dept Engn, Lancaster LA1 4YW, England..
    Alzahrani, Faris
    Univ Lancaster, Dept Engn, Lancaster LA1 4YW, England..
    tSaoir, Meabh Nic An
    Queens Univ Belfast, Sch Chem & Chem Engn, Belfast BT7 1NN, Antrim, North Ireland..
    Fernandes, Daniel Luis Abreu
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi.
    Assabumrungrat, Suttichai
    Chulalongkorn Univ, Fac Engn, Dept Chem Engn, Ctr Excellence Catalysis & Catalyt React Engn, Bangkok, Thailand..
    Aiouache, Farid
    Univ Lancaster, Dept Engn, Lancaster LA1 4YW, England..
    Kinetics and reactive stripping modelling of hydrogen isotopic exchange of deuterated waters2016Ingår i: Chemical Engineering and Processing, ISSN 0255-2701, E-ISSN 1873-3204, Vol. 108, s. 58-73Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This work presents results of experimental kinetics and modelling of the isotopic exchange between hydrogen and water in a reactive stripping column for water dedeuteriation. The missing physical properties of deuterium and tritium isotopologues in hydrogen gas and water forms were predicted and validated using existing literature data. The kinetic model relevant to a styrene-divinyl-benzene copolymer-supported platinum catalyst was used for modelling, by Aspen plus modular package, impact of design parameters including temperature, total pressure, gas to liquid flowrate ratio, pressure drop and flow mixing, on the separation of deuterium and further the separation of tritium. The modelling by the rate-based non-equilibrium, including design correlations of model of mass and heat transfers, chemical kinetic constants, mass transfer coefficients and overall exchange rate constants, allowed access to separation trends in a good agreement with published data. The synergy between the rates of chemical isotopic exchange and gas/liquid mass transfer, and by inference the performance of reactive stripping, was particularly sensitive to high temperatures, low hydrogen flow rates, pressure drops and internals properties. Extension to tritium confirmed a slightly slower mass transport compared with deuterium leading to potentially under-estimated design features for detritiation processing when deuterium is used instead.

  • 45.
    Aldener, Mattias
    Stockholms universitet.
    Pulsed laser experiments in chemical physics2001Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
  • 46.
    Aleckovic, Ehlimana
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Andersson, Linnea
    Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Chamoun, Sherley
    Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Einarsson, Ellen
    Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Ekstedt, Ebba
    Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Eriksen, Emma
    Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Madan-Andersson, Maria
    Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Method Development for Determining the Stability of Heat Stable Proteins Combined with Biophysical Characterization of Human Calmodulin and the Disease Associated Variant D130G2016Självständigt arbete på grundnivå (kandidatexamen), 10,5 poäng / 16 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Calmodulin is a highly conserved calcium ion binding protein expressed in all eukaryotic species. The 149 amino acid residues in the primary structure are organized in seven α helices with the highly flexible central α helix connecting the two non-cooperative domains of calmodulin. Each domain contains two EF-hand motifs to which calcium ions bind in a cooperative manner, hence the binding of four calcium ions saturate one calmodulin molecule. In the cardiovascular area calmodulin is involved in the activation of cardiac muscle contraction, and mutations that arise in the genetic sequence of the protein often have severe consequences. One such consequential mutation that can arise brings about the replacement of the highly conserved aspartic acid with glycine at position 130 in the amino acid sequence. In this research, the thermal and chemical stability within the C domain of the D130G variant of human calmodulin was investigated using a new method only requiring circular dichroism spectroscopic measurements. Affinity studies within the C domain of the D130G variant of human calmodulin were performed using fluorescence spectroscopy, and the ligands chosen for this purpose were trifluoperazine and p- HTMI. All analytical experiments were performed with the C domain of wild type human calmodulin as a reference. From the new method, it was concluded that the C domain of the D130G variant of human calmodulin has a slightly decreased stability in terms of Tm and Cm values compared to the C domain of wild type human calmodulin. The affinity analyses indicated that neither trifluoperazine nor p-HTMI discriminates between the C domain of the D130G variant of human calmodulin and the C domain of wild type human calmodulin in terms of dissociation constants. The pivotal outcome from this research is that the new method is applicable for determination of the stability parameters Tm and Cm of heat stable proteins. 

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  • 47.
    Alexander, Shovsky
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Polyelectrolyte complexes of bottle brush copolymers: Solution and adsorption properties2011Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The aim of this thesis work was to systematically investigate the physico-chemical properties of polyelectrolyte complexes (PECs) formed by bottle brush and linear polyelectrolytes in solution and at solid / liquid interfaces. Electrostatic self-assembly of oppositely charged macromolecules in aqueous solution is a versatile strategy to construction of functional nanostructures with easily controlled properties. Bottle brush architecture, introduced into the PEC, generates a number of distinctive properties of the complexes, related to a broad range of application, such as colloidal stability and protein repellency to name a few. To utilize these materials in a wide range of applications e.g. drug delivery, the understanding of the effects of polymer architecture and solution parameters on the properties of bottle brush PECs is of paramount importance. This thesis constitutes a systematic investigation of PECs formed by a series of cationic bottle-brush polyelectrolytes and a series of anionic linear polyelectrolytes in aqueous solution. The focus of the first part of the thesis was primarily on formation and characterization of PECs in solution, whereas the adsorption properties and adsorption kinetics of bottle-brush polyelectrolytes and their complexes was investigated in the second part of the thesis work. In particular, effects of the side-chain density of the bottlebrush polyelectrolyte, concentration, mixing ratio and molecular weigh of the linearpolyelectrolyte on formation, solution properties, stability and adsorption of PECs were addressed.

    The pronounced effect of the side-chain density of the bottle-brush polyelectrolyte on the properties of stoichiometric and nonstoichiometric PECs was demonstrated. Formation of PECs by bottle-brush copolymers with high density of side-chains results in small, watersoluble, molecular complexes having nonspherical shape, independent of concentration. Whereas formation of PEC-aggregates was revealed by bottle-brush polyelectrolytes with low side chain density, the level of aggregation in these complexes is controlled by polyelectrolyte concentration. The structure of the PECs formed with low molecular weight polyanions is consistent with the picture that several small linear polyelectrolyte molecules associate with the large bottle-brush. In contrast, when complexation occurs between polyanions of high molecular weigh and the bottle-brush polymers considerably larger PECs are formed, consistent with several bottle-brush polymers associating with one high molecular weight polyanion.

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  • 48. Alison, Lauriane
    et al.
    Demirörs, Ahmet F
    Tervoort, Elena
    Teleki, Alexandra
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för farmaci. Nutritional R&D Center Formulation and Application, DSM Nutritional Products Ltd., P.O. Box 2676, 4002 Basel, Switzerland.
    Vermant, Jan
    Studart, Andre R
    Emulsions Stabilized by Chitosan-Modified Silica Nanoparticles: pH Control of Structure-Property Relations2018Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 34, nr 21, s. 6147-6160Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In food-grade emulsions, particles with an appropriate surface modification can be used to replace surfactants and potentially enhance the stability of emulsions. During the life cycle of products based on such emulsions, they can be exposed to a broad range of pH conditions and hence it is crucial to understand how pH changes affect stability of emulsions stabilized by particles. Here, we report on a comprehensive study of the stability, microstructure, and macroscopic behavior of pH-controlled oil-in-water emulsions containing silica nanoparticles modified with chitosan, a food-grade polycation. We found that the modified colloidal particles used as stabilizers behave differently depending on the pH, resulting in unique emulsion structures at multiple length scales. Our findings are rationalized in terms of the different emulsion stabilization mechanisms involved, which are determined by the pH-dependent charges and interactions between the colloidal building blocks of the system. At pH 4, the silica particles are partially hydrophobized through chitosan modification, favoring their adsorption at the oil-water interface and the formation of Pickering emulsions. At pH 5.5, the particles become attractive and the emulsion is stabilized by a network of agglomerated particles formed between the droplets. Finally, chitosan aggregates form at pH 9 and these act as the emulsion stabilizers under alkaline conditions. These insights have important implications for the processing and use of particle-stabilized emulsions. On one hand, changes in pH can lead to undesired macroscopic phase separation or coalescence of oil droplets. On the other hand, the pH effect on emulsion behavior can be harnessed in industrial processing, either to tune their flow response by altering the pH between processing stages or to produce pH-responsive emulsions that enhance the functionality of the emulsified end products.

  • 49.
    Allardice, Jesse R.
    et al.
    Univ Cambridge, Cavendish Lab, JJ Thomson Ave, Cambridge CB3 OHE, England.
    Thampi, Arya
    Univ Cambridge, Cavendish Lab, JJ Thomson Ave, Cambridge CB3 OHE, England.
    Dowland, Simon
    Univ Cambridge, Cavendish Lab, JJ Thomson Ave, Cambridge CB3 OHE, England.
    Xiao, James
    Univ Cambridge, Cavendish Lab, JJ Thomson Ave, Cambridge CB3 OHE, England.
    Gray, Victor
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Fysikalisk kemi. Univ Cambridge, Cavendish Lab, JJ Thomson Ave, Cambridge CB3 OHE, England.
    Zhang, Zhilong
    Univ Cambridge, Cavendish Lab, JJ Thomson Ave, Cambridge CB3 OHE, England.
    Budden, Peter
    Univ Cambridge, Cavendish Lab, JJ Thomson Ave, Cambridge CB3 OHE, England.
    Petty, Anthony J., II
    Univ Kentucky, Ctr Appl Energy Res, Res Pk Dr, Lexington, KY 40511 USA.
    Davis, Nathaniel J. L. K.
    Univ Cambridge, Cavendish Lab, JJ Thomson Ave, Cambridge CB3 OHE, England;Victoria Univ Wellington, MacDiarmid Inst Adv Mat & Nanotechnol, Dodd Walls Ctr Photon & Quantum Technol, Sch Chem & Phys Sci, Wellington 6140, New Zealand.
    Greenham, Neil C.
    Univ Cambridge, Cavendish Lab, JJ Thomson Ave, Cambridge CB3 OHE, England.
    Anthony, John E.
    Univ Kentucky, Ctr Appl Energy Res, Res Pk Dr, Lexington, KY 40511 USA.
    Rao, Akshay
    Univ Cambridge, Cavendish Lab, JJ Thomson Ave, Cambridge CB3 OHE, England.
    Engineering Molecular Ligand Shells on Quantum Dots for Quantitative Harvesting of Triplet Excitons Generated by Singlet Fission2019Ingår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 141, nr 32, s. 12907-12915Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Singlet fission is an exciton multiplication process in organic molecules in which a photogenerated spin-singlet exciton is rapidly and efficiently converted to two spin-triplet excitons. This process offers a mechanism to break the Shockley-Queisser limit by overcoming the thermalization losses inherent to all single-junction photovoltaics. One of the most promising methods to harness the singlet fission process is via the efficient extraction of the dark triplet excitons into quantum dots (QDs) where they can recombine radiatively, thereby converting high-energy photons to pairs of low-energy photons, which can then be captured in traditional inorganic PVs such as Si. Such a singlet fission photon multiplication (SF-PM) process could increase the efficiency of the best Si cells from 26.7% to 32.5%, breaking the Shockley-Queisser limit. However, there has been no demonstration of such a singlet fission photon multiplication (SF-PM) process in a bulk system to date. Here, we demonstrate a solution-based bulk SF-PM system based on the singlet fission material TIPS-Tc combined with PbS QDs. Using a range of steady-state and time-resolved measurements combined with analytical modeling we study the dynamics and mechanism of the triplet harvesting process. We show that the system absorbs >95% of incident photons within the singlet fission material to form singlet excitons, which then undergo efficient singlet fission in the solution phase (135 +/- 5%) before quantitative harvesting of the triplet excitons (95 +/- 5%) via a low concentration of QD acceptors, followed by the emission of IR photons. We find that in order to achieve efficient triplet harvesting it is critical to engineer the surface of the QD with a triplet transfer ligand and that bimolecular decay of triplets is potentially a major loss pathway which can be controlled via tuning the concentration of QD acceptors. We demonstrate that the photon multiplication efficiency is maintained up to solar fluence. Our results establish the solution-based SF-PM system as a simple and highly tunable platform to understand the dynamics of a triplet energy transfer process between organic semiconductors and QDs, one that can provide clear design rules for new materials.

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  • 50. Allouche, Joachim
    et al.
    Tyrode, Eric
    Laboratorio FIRP, Ingeniería Química, Universidad de Los Andes, Avenida Don Tulio Febres, Mérida .
    Sadtler, Veronique
    Choplin, Lionel
    Salager, Jean-Louis
    Simultaneous Conductivity and Viscosity Measurements as a Technique To Track Emulsion Inversion by the Phase-Inversion-Temperature Method2004Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 20, nr 6, s. 2134-2140Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Two kinds of transitions can occur when an emulsified water-oil-ethoxylated nonionic surfactant system is cooled under const. stirring. At a water-oil ratio close to unity, a transitional inversion takes place from a water-in-oil (W/O) to an oil-in-water (O/W) morphol. according to the so-called phase-inversion-temp. method. At a high water content, a multiple W/O/W emulsion changes to a simple O/W emulsion. The continuous monitoring of both the emulsion cond. and viscosity allows the identification of several phenomena that take place during the temp. decrease. In all cases, a viscosity max. is found on each side of the three-phase behavior temp. interval and correlates with the attainment of extremely fine emulsions, where the best compromise between a low-tension and a not-too-unstable emulsion is reached. The studied system contains Polysorbate 85, a light alkane cut oil, and a sodium chloride brine. All transitions are interpreted in the framework of the formulation-compn. bidimensional map.

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