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  • 1. Adrich, P.
    et al.
    Froelich, P.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum. Uppsala University, Sweden.
    Jonsell, Svante
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Yzombard, P.
    Production of antihydrogen atoms by 6 keV antiprotons through a positronium cloud2023Inngår i: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 83, nr 11, artikkel-id 1004Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report on the first production of an antihydrogen beam by charge exchange of 6.1 keV antiprotons with a cloud of positronium in the GBAR experiment at CERN. The 100 keV antiproton beam delivered by the AD/ELENA facility was further decelerated with a pulsed drift tube. A 9 MeV electron beam from a linear accelerator produced a low energy positron beam. The positrons were accumulated in a set of two Penning-Malmberg traps. The positronium target cloud resulted from the conversion of the positrons extracted from the traps. The antiproton beam was steered onto this positronium cloud to produce the antiatoms. We observe an excess over background indicating antihydrogen production with a significance of 3-4 standard deviations.

  • 2.
    Agosta, Lorenzo
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Atomistic simulations of structural and dynamical properties of liquids under geometric constraints2019Doktoravhandling, med artikler (Annet vitenskapelig)
    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.

    Fulltekst (pdf)
    Atomistic simulations of structural and dynamical properties of liquids under geometric constraints
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  • 3.
    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) (Annet vitenskapelig)
  • 4.
    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) (Annet vitenskapelig)
    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.

    Fulltekst (pdf)
    fulltext
  • 5.
    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) (Annet vitenskapelig)
    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.

    Fulltekst (pdf)
    fulltext
  • 6. 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 States2011Inngår i: ChemPhysChem, ISSN 1439-4235, E-ISSN 1439-7641, Vol. 12, nr 16, s. 2899-2902Artikkel i tidsskrift (Fagfellevurdert)
  • 7. 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 solution2013Inngår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 15, nr 5, s. 1621-1631Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 8.
    Airey, John
    et al.
    Stockholms universitet, Humanistiska fakulteten, Institutionen för ämnesdidaktik.
    Patron, Emelie
    Linnéuniversitet.
    Wikman, Susanne
    Linnéuniversitet.
    Making the Invisible Visible: The role of undergraduate textbooks in the teaching and learning of physics and chemistry2023Konferansepaper (Fagfellevurdert)
    Abstract [en]

    As disciplines, undergraduate physics and chemistry leverage a particularly wide range of semiotic systems (modes) in order to create and communicate their scientific meanings. Examples of the different semiotic systems employed are: spoken and written language, mathematics, chemical formulae, graphs, diagrams, sketches, computer simulations, hands-on work with experimental apparatus, computer simulations, etc. Individual semiotic resources within this range of semiotic systems are coordinated in specific constellations (Airey & Linder, 2009) in order to mediate scientific knowledge. In this Swedish Research Council project, we are interested in the representation of scientific phenomena that cannot be seen. The question we pose is: How is scientific knowledge mediated when we cannot directly interact with the phenomena in question through our senses?  We adopt a social semiotic approach (Airey & Linder, 2017; van Leeuwen, 2005), to investigate the ways in which two phenomena—electromagnetic fields and chemical bonds—are presented in undergraduate textbooks. To do this we carried out a semiotic audit (Airey & Erikson, 2019) of eight textbooks (four in each discipline). We note that the individual resources used have a mixture of affordances—whilst the majority retain high disciplinary affordance, others are unpacked (Patron et al. 2021) providing higher pedagogical affordance. We discuss the ways in which the resources have been combined and orchestrated (Bezemer & Jewitt, 2010) in order to attempt to make visible that which is invisible, and identify a number of potential problems. In earlier work, Volkwyn et al. (2019) demonstrated how experimental work with physics devices can make the Earth’s magnetic field accessible to students through chains of transduction. Thus, we propose that encouraging transductions across the semiotic resource systems provided in textbooks may help students to experience the invisible.

    References

    Airey, J. (2006). Physics students' experiences of the disciplinary discourse encountered in lectures in English and Swedish (Licentiate dissertation, Department of Physics, Uppsala University).

    Airey, J. (2009). Science, language, and literacy: Case studies of learning in Swedish university physics (Doctoral dissertation, Acta Universitatis Upsaliensis).

    Airey, J. (2015). Social Semiotics in Higher Education: Examples from teaching and learning in undergraduate physics. In In: SACF Singapore-Sweden Excellence Seminars, Swedish Foundation for International Cooperation in Research in   Higher Education (STINT) , 2015 (pp. 103). 

    Airey, J., & Eriksson, U. (2019). Unpacking the Hertzsprung-Russell diagram: A social semiotic analysis of the disciplinary and pedagogical affordances of a central resource in astronomy. Designs for Learning, 11(1), 99-107.

    Goodwin, C. (2015). Professional vision. In Aufmerksamkeit: Geschichte-Theorie-Empirie (pp. 387-425). Wiesbaden: Springer Fachmedien Wiesbaden.

    O’Halloran, K. (2007). Mathematical and scientific forms of knowledge: A systemic functional multimodal grammatical approach. language, Knowledge and pedagogy: functional linguistic and sociological perspective, 205-236.

    Patron, E. (2022). Exploring the role that visual representations play when teaching and learning chemical bonding: An approach built on social semiotics and phenomenography(Doctoral dissertation, Linnaeus University Press).

    Fulltekst (pdf)
    fulltext
  • 9.
    Aldener, Mattias
    Stockholms universitet.
    Pulsed laser experiments in chemical physics2001Doktoravhandling, med artikler (Annet vitenskapelig)
  • 10.
    Aleksis, Rihards
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    New solid-state NMR methods for exciting and separating anisotropic interactions of spin I=1 nuclei2022Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Solid-state NMR has become an essential tool for structural characterisation of materials, in particular systems with poor crystallinity and structural disorder. In recent years, a surge of interest has been observed for the study of paramagnetic systems, in which the interaction between nuclei and unpaired electrons allows to probe the electronic structure and properties of materials more directly. However, simultaneously this interaction leads to very broad resonances, which are difficult to acquire and interpret. While significant advancements in both NMR instrumentation and methodology have paved the way for the study of spin I=1/2 nuclei in these systems, still many issues remain to be resolved for routine investigation of quadrupolar nuclei I>1/2. In this Thesis we focus on improving both the excitation of the broad resonances and the resolution in the spectra of spin I=1 nuclei. The latter problem is addressed by developing methods for separation of the shift and the quadrupolar interactions. We introduce two new methods under static conditions, which have the advantage over previous experiments of both suppressing spectral artefacts and exhibiting a broader excitation bandwidth. Furthermore, we demonstrate for the first time an approach for separation of the anisotropic parts of the shift and quadrupolar interaction under magic-angle spinning. Secondly, to achieve broadband excitation we develop a new theoretical formalism for phase-modulated pulse sequences in rotating solids, which are applicable to nuclear spins with anisotropic interactions substantially larger than the spinning frequency, under conditions where the radio-frequency amplitude is smaller than or comparable to the spinning frequency. We apply the framework to the excitation of double-quantum spectra of 14N and design new pulse schemes with γ-encoded properties. Finally, we employ some of the new sequences together with density functional theory calculations to resolve the electronic structure of barium titanium oxhydride.

    Fulltekst (pdf)
    New solid-state NMR methods for exciting and separating anisotropic interactions of spin I=1 nuclei
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  • 11.
    Aleksis, Rihards
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Nedumkandathil, Reji
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Papawassiliou, Wassilios
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Carvalho, José P.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Jaworski, Aleksander
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Häussermann, Ulrich
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Pell, Andrew J.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). Université de Lyon, France.
    Probing the electronic structure and hydride occupancy in barium titanium oxyhydride through DFT-assisted solid-state NMR2022Inngår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 24, nr 46, s. 28164-28173Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Perovskite-type oxhydrides such as BaTiO3−xHy exhibit mixed hydride ion and electron conduction and are an attractive class of materials for developing energy storage devices. However, the underlying mechanism of electric conductivity and its relation to the composition of the material remains unclear. Here we report detailed insights into the hydride local environment, the electronic structure and hydride conduction dynamics of barium titanium oxyhydride. We demonstrate that DFT-assisted solid-state NMR is an excellent tool for differentiating between the different feasible electronic structures in these solids. Our results indicate that upon reduction of BaTiO3 the introduced electrons are delocalized among all Ti atoms forming a bandstate. Furthermore, each vacated anion site is reoccupied by at most a single hydride, or else remains vacant. This single occupied bandstate structure persists at different hydrogen concentrations (y = 0.13–0.31) and a wide range of temperatures (∼100–300 K).

  • 12. Altomare, Angela
    et al.
    Eriksson, Lars
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi.
    Werner, Per-Erik
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi.
    Advances in powder pattern indexing: N-TREOR092009Inngår i: Journal of applied crystallography, ISSN 0021-8898, E-ISSN 1600-5767, Vol. 42, s. 768-775Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Powder pattern indexing can still be a challenge, despite the great recent advances in theoretical approaches, computer speed and experimental devices. More plausible unit cells, belonging to different crystal systems, are frequently found by the indexing programs, and recognition of the correct one may not be trivial. The task is, however, of extreme importance: in case of failure a lot of effort and computing time may be wasted. The classical figures of merit for estimating the unit-cell reliability {i.e.M20 [de Wolff (1968). J. Appl. Cryst.1, 108–113] and FN [Smith & Snyder (1979). J. Appl. Cryst.12, 60–65]} sometimes fail. For this reason, a new figure of merit has been introduced in N-TREOR09, the updated version of the indexing package N-TREOR [Altomare, Giacovazzo, Guagliardi, Moliterni, Rizzi & Werner (2000). J. Appl. Cryst. 33, 1180–1186], combining the information supplied by M20 with additional parameters such as the number of unindexed lines, the degree of overlap in the pattern (the so-called number of statistically independent observations), the symmetry deriving from the automatic evaluation of the extinction group, and the agreement between the calculated and observed profiles. The use of the new parameters requires a dramatic modification of the procedures used worldwide: in the approach presented here, extinction symbol and unit-cell determination are simultaneously estimated. N-TREOR09 benefits also from an improved indexing procedure in the triclinic system and has been integrated into EXPO2009, the updated version of EXPO2004 [Altomare, Caliandro, Camalli, Cuocci, Giacovazzo, Moliterni & Rizzi (2004). J. Appl. Cryst. 37, 1025–1028]. The application of the new procedure to a large set of test structures is described.

  • 13.
    Andersson, Klas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Structure, Bonding and Chemistry of Water and Hydroxyl on Transition Metal Surfaces2006Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The structure, bonding and chemistry of water and hydroxyl on metal surfaces are presented. Synchrotron based x-ray photoelectron- and x-ray absorption spectroscopy along with density functional theory calculations mainly form the basis of the results. Conditions span the temperature range 35 - 520 K and pressures from ultra-high vacuum (~10 fAtm) to near ambient pressures (~1 mAtm). The results provide, e.g, new insights on the importance of hydrogen bonding for surface chemical kinetics.

    Water adsorbs intact on the Pt(111), Ru(001) and Cu(110) surfaces at low temperatures forming 2-dimensional wetting layers where bonding to the metal (M) mainly occurs via H2O-M and M-HOH bonds. Observed isotope differences in structure and kinetics for H2O and D2O adsorption on Ru(001) are due to qualitatively different surface chemistries. D2O desorbs intact but H2O dissociates in kinetic competition with desorption similar to the D2O/Cu(110) system. The intact water layers are very sensitive to x-ray and electron induced damage.

    The mixed H2O:OH phase on Ru(001) consists of stripe-like structures 4 to 6 Ru lattice parameters wide where OH decorates the edges of the stripes. On Pt(111), two different long-range ordered mixed H2O:OH structures are found to be inter-related by geometric distortions originating from the asymmetric H-bond donor-acceptor properties of OH towards H2O.

    Water adsorption on Cu(110) was studied at near ambient conditions and compared to Cu(111). Whereas Cu(111) remains clean, Cu(110) holds significant amounts of water in a mixed H2O:OH layer. The difference is explained by the differing activation barriers for water dissociation, leading to the presence of OH groups on Cu(110) which lowers the desorption kinetics of water by orders of magnitude due to the formation of strong H2O-OH bonds. By lowering the activation barrier for water dissociation on Cu(111) by pre-adsorbing atomic O, generating adsorbed OH, similar results to those on Cu(110) are obtained.

    Fulltekst (pdf)
    FULLTEXT01
  • 14. Aristov, Maria
    et al.
    Eichhorn, Ralf
    Stockholms universitet, Nordiska institutet för teoretisk fysik (Nordita).
    Bechinger, Clemens
    Separation of chiral colloidal particles in a helical flow field2013Inngår i: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 9, nr 8, s. 2525-2530Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Stereoisomeric molecules with opposite chirality, so-called enantiomers, often vary regarding their sensory, pharmacological and toxicological properties. Such enantiomer specific effects play a central role in the development, testing and evaluation of drugs, pesticides and food related products. Accordingly, efficient techniques for separation of chiral mixtures into enantiopure compounds are of enormous practical relevance. Most current enantiomer separation methods are based on enantioselective interactions with an auxiliary substance which has to be developed and optimized for different chiral molecules in an elaborate and costly process. Here, we experimentally demonstrate the separation of micron-sized chiral particles in a helical fluid flow which is created inside a microfluidic device patterned with slanted grooves. We observe that the retention time of particles in a helical flow field strongly depends on their chirality which leads to an effective chiral separation within the channel. Our experimental results are confirmed by numerical calculations which demonstrate how the coupling of rotational and translational degrees of freedom leads to differences in the trajectories of particles with opposite chirality. Since our separation mechanism does not rely on material specific interactions, this offers considerable advantages over existing methods. We expect that our approach can be also applied at nanometre length scales by using channels with smaller diameters and with an optimized geometry.

  • 15. Ashuiev, Anton
    et al.
    Carvalho, José P.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för fysikalisk kemi.
    Andersen, Richard A.
    Geometry and electronic structure of Yb(III)[CH(SiMe3)2]3 from experimental and computational diffraction and magnetic resonance spectroscopiesManuskript (preprint) (Annet vitenskapelig)
  • 16.
    Aski, Sahar Nikkhou
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi.
    Takacs, Zoltan
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi.
    Kowalewski, Jozef
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi.
    Inclusion complexes of cryptophane–E with dichloromethane and chloroform: A thermodynamic and kinetic study using the 1D-EXSY NMR method2008Inngår i: Magnetic Resonance in Chemistry, ISSN 0749-1581, E-ISSN 1097-458X, Vol. 46, nr 12, s. 1135-1140Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Complexation equilibria and kinetics of exchange of chloroform and dichloromethane molecules between the cavity of cryptophane-E and bulk solution were investigated using NMR methods. Using one dimensional magnetization transfer (1D-EXSY type sequence), chemical exchange rates were measured in different temperature ranges, limited by the equilibrium constant values of the complexes and the boiling points of the guest substances. From the kinetic data, activation energies were calculated using the Arrhenius equation. From the temperature dependence of the association constant data, the enthalpy and entropy of complexation were estimated and compared with values for similar complexes of other cryptophanes.

  • 17.
    Atluri, Rambabu
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi.
    Hedin, Niklas
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi.
    Garcia-Bennett, Alfonso E.
    Non-Surfactant Supramolecular Templating Synthesis of Ordered Mesoporous Silica2009Inngår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 131, nr 9, s. 3189-3191Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Hoogsteen-bonded tetrads and pentamers are formed by a large variety of organic molecules through H-donor and acceptor groups capable of inducing self-organization to form columnar and hexagonal mesophases. The biological importance of such macromolecular structures is exemplified by the assembly of guanosine-rich groups of telomere units and their implication in chromosomal replication. Folic acid is composed of a pterin group, chemically and structurally similar to guanine, conjugated to an l-glutamate moiety via a p-amino benzoic acid. Our aim has been to develop a delivery vehicle for folic acid and at the same time provide a novel synthetic route for ordered mesoporous materials without the use of amphiphilic surfactants. We present a new nonsurfactant route for the synthesis of highly ordered mesoporous materials, based on the supramolecular templating of stacked arrays of the tetramer-forming pterin groups of folic acid under a variety of synthetic conditions. This method leads to hexagonally ordered mesoporous structures with gyroid, spherical, and chiral morphologies with pores on the order of 25−30 Å in diameter and surface areas above 1000 m2/g. More importantly circular dichroism studies reveal that the folate template possesses a chiral signature within the pores in the as-synthesized solid and that chirality is transferred from the folate template to the pore surface via the aminopropyl triethoxysilane costructure directing agent used in the supramolecular assembly. This novel templating approach for ordered mesoporous materials breaks the hegemony of surfactant micellar systems for the preparation of these exciting high surface area solids and opens new opportunities for structural control, design of pore geometry, and novel applications.

  • 18.
    Baldassarre, Maurizio
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för biokemi och biofysik.
    Li, Chenge
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för biokemi och biofysik.
    Eremina, Nadejda
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för biokemi och biofysik.
    Goormaghtigh, Erik
    Barth, Andreas
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för biokemi och biofysik.
    Simultaneous Fitting of Absorption Spectra and Their Second Derivatives for an Improved Analysis of Protein Infrared Spectra2015Inngår i: Molecules, ISSN 1431-5157, E-ISSN 1420-3049, Vol. 20, nr 7, s. 12599-12622Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Infrared spectroscopy is a powerful tool in protein science due to its sensitivity to changes in secondary structure or conformation. In order to take advantage of the full power of infrared spectroscopy in structural studies of proteins, complex band contours, such as the amide I band, have to be decomposed into their main component bands, a process referred to as curve fitting. In this paper, we report on an improved curve fitting approach in which absorption spectra and second derivative spectra are fitted simultaneously. Our approach, which we name co-fitting, leads to a more reliable modelling of the experimental data because it uses more spectral information than the standard approach of fitting only the absorption spectrum. It also avoids that the fitting routine becomes trapped in local minima. We have tested the proposed approach using infrared absorption spectra of three mixed α/β proteins with different degrees of spectral overlap in the amide I region: ribonuclease A, pyruvate kinase, and aconitase.

  • 19. Barreiro-Lage, Darío
    et al.
    Chiarinelli, Jacopo
    Bolognesi, Paola
    Richter, Robert
    Zettergren, Henning
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Stockett, Mark Hugo
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Díaz-Tendero, Sergio
    Avaldi, Lorenzo
    Photofragmentation specificity of photoionized cyclic amino acids (diketopiperazines) as precursors of peptide building blocks2023Inngår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 25, nr 23, s. 15635-15646Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The photoionisation and photofragmentation of the two cyclic dipetides cyclo(alanyl-glycine) cGA and cyclo(glycyl-glycine) cGG, have been studied combining experiments and simulations. State selected fragments from the ionized molecules are detected using photo-electron photo-ion coincidence (PEPICO) measurements and specific fragmentation paths are identified and characterized via the use of ion-neutral coincidence maps. The simulations, performed using Quantum Chemistry methods, allow us to infer the fragmentation mechanisms of the ionized and excited molecules. We show that ring opening is followed by emission of the neutral fragments CO and HNCO. In the case of cGG the emission of neutral CO leads to a metastable structure that breaks producing small cationic fragments. The studied cyclic dipeptides evolve under ionizing radiation generating different small aziridin moieties and oxazolidinones. These two species are key reactants to elongate producing peptide chains. The corresponding mechanisms have been computed and show that the reaction requires very low energy and may occur in the presence of ionizing radiation.

  • 20. Battistel, Marcos D.
    et al.
    Pendrill, Robert
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Freedberg, Daron I.
    Direct Evidence for Hydrogen Bonding in Glycans: A Combined NMR and Molecular Dynamics Study2013Inngår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 117, nr 17, s. 4860-4869Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We introduce the abundant hydroxyl groups of glycans as NMR handle's and structural probes to expand the repertoire of tools for structure function studies on glycans in solution. To this end, we present the facile detection and assignment of hydroxyl groups in a Wide range of sample concentrations (0.5-1700 mM) and temperatures, ranging from -5 to 25 degrees C.,We then exploit this information to directly detect hydrogen bonds, well-known for their importance in molecular structural determination through NMR. Via HSQC-TOCSY, we were able to determine the directionality; of these hydrogen bonds in sucrose Furthermore, by means Of molecular dynamics simulations in conjunction with NMR, we establish that one Out of the three detected hydrogen bonds arises from intermolecular interactions. This finding may shed light on glycan glycan interactions and glycan recognition by proteins.

    Fulltekst (pdf)
    fulltext
  • 21. Berggren, Gustav
    et al.
    Huang, Ping
    Eriksson, Lars
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi.
    Anderlund, Magnus F.
    Synthesis, Characterization and Reactivity Study of a New Penta-Coordinated Mn(II) Complex2009Inngår i: Applied Magnetic Resonance, ISSN 0937-9347, E-ISSN 1613-7507, Vol. 36, nr 1, s. 9-24Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A penta-coordinated Mn(II) compound [dqpMnCl2] (1) (dqp = 2,6-di-(8-quinoline-yl)-pyridine) has been synthesized and its X-ray crystallographic structure is reported here. Magnetic susceptibility measurements confirmed a high-spin Mn(II) (S = 5/2) center in 1. The X-band EPR spectrum of 1 in dimethylformamide solution exhibits widely distributed transitions in the spectral range from 0 to 700 mT with particularly well-resolved hyperfine lines due to the 55Mn (I = 5/2) nucleus. The abundance of highly resolved transition lines in the spectrum facilitated the electron paramagnetic resonance spectral simulation which revealed large zero-field splitting and g-anisotropies. When dissolved, 1 exists in equilibrium with a hexa-coordinated species, the latter probably resulting from disassociation of one chlorido-ligand allowing ligation of two solvent molecules. The redox behavior of 1 was studied and was compared to that of a structural analog for which water oxidation in the presence of a chemical oxidant has been shown. The results from water oxidation trials of 1 are discussed

  • 22. Berggren, Gustav
    et al.
    Thapper, Anders
    Anderlund, Magnus
    Eriksson, Lars
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi.
    Two tetranuclear Mn-complexes as biomimetic models of the oxygen evolving complex in Photosystem II - A synthesis, characterisation and reactivity study2009Inngår i: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 45, s. 10044-10054Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this work we report the preparation of two metallamacrocyclic tetranuclear manganese(II) complexes, [L1(4)Mn(4)](ClO4)(4) and [L2(4)Mn(4)](ClO4)(4) where L1 and L2 are the anions of the heptadentate ligands 2-((2-(bis(pyridin-2-ylmethyl) amino) ethyl)(methyl) amino) acetic acid and 2-(benzyl(2-(bis(pyridin-2-ylmethyl) amino) ethyl) amino) acetic acid), respectively. The complexes have been fully characterized by ESI-MS, elemental analysis, single-crystal X-ray diffraction, magnetic susceptibility, and EPR spectroscopy. Electrochemical reactions as well as reactions with different chemical redox reagents have been performed and a reversible two electron oxidation per manganese ion has been identified. The reaction of [L1(4)Mn(4)](ClO4)(4) with oxone or cerium(IV) results in the evolution of oxygen which makes this system interesting for future studies in the search for a functional mimic of the oxygen evolving complex in Photosystem II.

  • 23.
    Bergman, Dan
    Stockholms universitet.
    Computer simulation of topological and spatial structure in water and aqueous solutions1999Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The present thesis concerns molecular-dynamics and expanded-ensemble simulation of topological and spatial structure in water and aqueous solutions.

    First, methods for analysis of molecular pair configurations using angularly resolved density distributions were considered. It was shown that these distributions expose major features of liquid structure and that they can be used to define the hydrogen bond. Second, a method was developed for analysis of hydrogen-bond network topology. It characterizes networks in terms of the local bond patterns surrounding the water molecules and in terms of loops and chains of directed bonds.

    The methods developed have been applied to pure water, to water--acetonitrile mixtures and to charged Lennard-Jones spheres dissolved in water. Solvation structures in aqueous solutions of methylamine and tert-butyl alcohol have also been considered. The main results are: (a) In pure water, there is proton ordering around short loops, but not along chains. (b) The hydrogen-bond network in water--acetonitrile mixtures with acetonitrile mole fractions x=0.1, 0.5 and 0.9 have been characterized. As x increases from 0.1 to 0.9, the network is depleted of crosslinks, the proton ordering along chains increases and the most probable loop length decreases. For x=0.5 and 0.9 large water clusters form. (c) The hydration structures surrounding charged Lennard-Jones solutes corresponding to extrema in the solvation entropy have been characterized. Of the two solutes corresponding to the maxima, one acts as a double proton-donor and the other as a double proton-acceptor. The solute corresponding to the minimum enhances the water--water correlations. Further, the orientational and the radial parts of the two-body solute--water entropy have been calculated. The orientational part has a single maximum, whereas the radial part maintains the bimodal form of the full solvation entropy.

  • 24.
    Bergström, Lennart
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi.
    Laakssonen, Aatto
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Self-assembled Materials2009Inngår i: Encyclopedia of Complexity and Systems Science / [ed] Robert A. Meyers, Berlin: Springer , 2009, s. 7931-7953Kapittel i bok, del av antologi (Annet vitenskapelig)
  • 25.
    Berkowicz, Sharon
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    The Role of Molecular Heterogeneity in the Structural Dynamics of Aqueous Solutions2022Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Aqueous solutions constitute the basis of life, yet their complex and anomalous nature is far from well-understood. Transient molecular ordering gives rise to microscopic spatial liquid heterogeneities and fluctuations which are believed to play a key role in biochemical processes as well as in pure water, the latter of which could fundamentally alter our view on water as life's solvent. In this thesis, we experimentally investigate the structural dynamics in aqueous solutions with the aim to understand the role of molecular heterogeneity in the complex solution dynamics. To extract dynamic information, we utilize coherent light- and X-ray scattering techniques, such as dynamic light scattering (DLS) and X-ray photon correlation spectroscopy (XPCS), which can resolve structural dynamics on a broad range of length and time scales. We explore the influence of hypothesized water fluctuations in the dynamics of simple model solutes, finding that their diffusive dynamic behaviour is effectively similar and independent of solute size down to molecular scale, whilst significantly different from that of single water molecules. Secondly, in a first proof-of-concept experiment, we successfully combine the spatial resolution of nanofocused coherent X-ray beams with dynamic measurements by XPCS, the results of which indicate that `nano-XPCS' could prove a valuable tool in the quest to resolve nanoscale fluctuations. Finally, an outlook is given where the next steps in these investigations are discussed, such as the use of aqueous-organic mixtures as model systems for spatially heterogeneous dynamics in biological solutions.

  • 26.
    Berkowicz, Sharon
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    The Role of Molecular Heterogeneity in the Structural Dynamics of Aqueous Solutions2023Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The liquid-liquid critical point hypothesis suggests that liquid water exists in two liquid states with different local structures, so-called high- and low-density liquid (HDL, LDL). At ambient pressure water locally fluctuates between these two states, with the fluctuations becoming more pronounced as the liquid is supercooled. In this thesis, we explore the role of molecular heterogeneity in the structural dynamics of aqueous solutions, specifically investigating the interplay of different solutes in water with the hypothesized HDL-LDL fluctuations. In our experimental approach, we utilize coherent light and X-ray scattering techniques, including small- and wide-angle X-ray scattering (SAXS, WAXS), as well as correlation methods, such as dynamic light scattering (DLS) and X-ray photon correlation spectroscopy (XPCS), that enable us to probe structural dynamics at a broad range of length and time scales. 

    Using DLS, we measure the diffusive dynamic behaviour of differently sized nanomolecular probes in supercooled water, finding that it is effectively similar and independent of probe size down to molecular scales of ≈1 nm. In contrast to single water molecules, these probes experience a similar dynamic environment, which coincides with the bulk viscosity. These results could suggest that anomalous influence from the hypothesized water fluctuations becomes apparent first on sub-nm length scales. Furthermore, we explore how the presence of small polar-organic solutes modulates the water phase diagram, utilizing glycerol-water solutions as a model system. By outrunning freezing with the rapid evaporative cooling technique, combined with ultrafast X-ray scattering at X-ray free-electron lasers (XFELs), we are able to probe the liquid structure in deeply supercooled dilute glycerol-water solutions. Our findings indicate the existence of HDL- and LDL-like fluctuations upon supercooling, with a Widom line shifted to slightly lower temperatures compared to pure water. Further experiments on deeply supercooled glycerol-water solutions at intermediate glycerol concentrations, combining WAXS and SAXS/XPCS, provide additional insights. These results reveal a first-order-like liquid-liquid transition involving discontinuous changes in the inter-atomic liquid structure and nanoscale liquid dynamics, which precedes ice crystallization. 

    Lastly, with the aim of developing powerful tools for resolving dynamics within spatially heterogeneous systems, including aqueous solutions, we combine the spatial resolution of nanofocused coherent X-ray beams with dynamic measurements by XPCS. Here, we successfully demonstrate a first proof-of-concept experiment of so-called nanofocused XPCS at MAX IV synchrotron radiation facility. In future experiments, we plan to go beyond standard XPCS at synchrotrons, towards accessing ultrafast atomic-scale liquid dynamics by X-ray speckle visibility spectroscopy (XSVS) at XFELs.

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  • 27. Berniak, Tomasz
    et al.
    Latka, Piotr
    Drozdek, Marek
    Rokicinska, Anna
    Jaworski, Aleksander
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för fysikalisk kemi.
    Leyva-Perez, Antonio
    Kustrowski, Piotr
    Covalent bonding of N-hydroxyphthalimide on mesoporous silica for catalytic aerobic oxidation of p-xylene at atmospheric pressure2024Inngår i: ChemPlusChem, E-ISSN 2192-6506Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The surface of SBA-15 mesoporous silica was modified by N-hydroxyphthalimide (NHPI) moieties acting as immobilized active species for aerobic oxidation of alkylaromatic hydrocarbons. The incorporation was carried out by four original approaches: the grafting-from and grafting-onto techniques, using the presence of surface silanols enabling the formation of particularly stable O-Si-C bonds between the silica support and the organic modifier. The strategies involving the Heck coupling led to the formation of NHPI groups separated from the SiO2 surface by a vinyl linker, while one of the developed modification paths based on the grafting of an appropriate organosilane coupling agent resulted in the active phase devoid of this structural element. The successful course of the synthesis was verified by FTIR and H-1 NMR measurements. Furthermore, the formed materials were examined in terms of their chemical composition (elemental analysis, thermal analysis), structure of surface groups (C-13 NMR, XPS), porosity (low-temperature N-2 adsorption), and tested as catalysts in the aerobic oxidation of p-xylene at atmospheric pressure. The highest conversion and selectivity to p-toluic acid were achieved using the catalyst with enhanced availability of non-hydrolyzed NHPI groups in the pore system. The catalytic stability of the material was additionally confirmed in several subsequent reaction cycles.

  • 28. Bogot, Alon
    et al.
    Poline, Mathias
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Ji, MingChao
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Dochain, Arnaud
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Simonsson, Ansgar
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Rosén, Stefan
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Zettergren, Henning
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Schmidt, Henning T.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Thomas, Richard D.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Strasser, Daniel
    The mutual neutralization of hydronium and hydroxide2024Inngår i: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 383, nr 6680, s. 285-289Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Mutual neutralization of hydronium (H3O+) and hydroxide (OH) ions is a very fundamental chemical reaction. Yet, there is only limited experimental evidence about the underlying reaction mechanisms. Here, we report three-dimensional imaging of coincident neutral products of mutual-neutralization reactions at low collision energies of cold and isolated ions in the cryogenic double electrostatic ion-beam storage ring (DESIREE). We identified predominant H2O + OH + H and 2OH + H2 product channels and attributed them to an electron-transfer mechanism, whereas a minor contribution of H2O + H2O with high internal excitation was attributed to proton transfer. The reported mechanism-resolved internal product excitation, as well as collision-energy and initial ion-temperature dependence, provide a benchmark for modeling charge-transfer mechanisms. 

  • 29. Bordoloi, Ankur
    et al.
    Sahoo, Suman
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Halligudi, S. B.
    Immobilized Molybdovanadophosphoric Acid for Selective Oxidations2013Inngår i: Catalysis surveys from Asia, ISSN 1571-1013, E-ISSN 1574-9266, Vol. 17, nr 3-4, s. 132-146Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this review, we have summarized our work on the immobilization of molybdovanadophosphoric acids onto mesoporous silica and mesoporous carbon by different approaches such as amine functionalization and ionic liquid functionalization. All catalyst materials were well characterized by various ex-situ and in situ techniques for their structural integrity and physico-chemical properties. These materials were tested in different selective oxidation processes to develop environmentally benign protocols for the synthesis of fine chemicals and tried to study their mechanisms.

  • 30.
    Borges, Lucas
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Schnappinger, Thomas
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Kowalewski, Markus
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Extending the Tavis-Cummings model for molecular ensembles: Exploring the effects of dipole self energies and static dipole momentsManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Strong coupling of organic molecules to the vacuum field of a nanoscale cavity can be used to modify their chemical and physical properties. We extend the Tavis-Cummings model for molecular ensembles and show that the often neglected interaction terms arising from the static dipole moment and the dipole self-energy are essential for a correct description of the light-matter interaction in polaritonic chemistry. On the basis of a full quantum description, we simulate the excited-state dynamics and spectroscopy of MgH+molecules resonantly coupled to an optical cavity. We show that the inclusion of static dipole moments and the dipole self-energy is necessary to obtain a consistent model. We construct an efficient two-level system approach that reproduces the main features of the real molecular system and may be used to simulate larger molecular ensembles.

  • 31. Bortolini, C.
    et al.
    Zhao, Jingjing
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Ciccone, L.
    Xu, Hongyi
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Zou, Xiaodong
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Dong, Mingdong
    Atomic Structure of Amyloid CrystalsManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

     

    A deep understanding of the self-assembly and crystallization of biomolecules as highly ordered biomaterials is crucial to enable the design and the generation of complex functional systems for cutting-edge applications in nanotechnology and biomedicine. In this work, we determined the atomic structure of Aβ16-20 crystals, a fragment of amyloid-β which aberrant folding is linked to the etiology of Alzheimer’s disease, the most common cause of dementia. We detailed the hierarchical aggregation mechanism of Aβ16-20 into highly ordered crystals and revealed that the self-assembly is reversible, leading to the formation of oligomers as an intermediate. Our structural investigation combined with molecular dynamics simulations highlights how a combination of favorable non-covalent interactions drives the efficient fast self-assembly and enhanced stability. We studied the chemical and surface properties of amyloid crystals, including their mechanical properties and their capability to transmit light; the long-rang order of Aβ16-20 crystals enables them to be used as optical waveguide materials for biologically based modulation and sensing. Our results shed new light on pathogenic amyloid assembly at the atomic level and reveal the potential of amyloid crystals for applications in nanotechnology.

  • 32.
    Boscolo Bibi, Sara
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Going for gold: A spectroelectrochemical and catalytic study of gold materials2023Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    With the increase in demand for renewable energy, understanding chemical processes is essential for improving the design of catalysts in order to achieve better performance. This thesis summarises the experimental investigation of three types of catalytic gold materials: gold oxide formed from gold films, oxide-derived gold (OD-Au) produced from gold films, and gold nanoparticles supported on metal oxides. Different spectroscopic techniques were employed, such as operando sum frequency generation (SFG) and in situ and ex situ X-ray spectroscopies. These methods allowed the probing of the electronic and chemical states of gold after oxidising electrochemical treatments. The results indicate the presence of subsurface gold oxide remnants after formation of OD-Au, which may help explain its improved catalytic properties with respect to pure gold. In addition, a mathematical model to couple the early stages of gold oxide formation with the nonlinear optical response of gold during this process is presented. This model suggests that the growth proceeds from small oxide islands to 3D oxide growth, while SFG oxidation variation is due to the suppression of the free electron density by negatively-charged adsorbing oxygen atoms. Gold oxide was also studied with both in situ and operando X-ray spectroscopies, showing the importance of a continuous electrochemical treatment during measurements to avoid beam induced effects. Furthermore, gold nanoparticles supported on metal oxides (TiO2 and γ-Fe2O3) were investigated mainly with mass spectrometry. The results indicate two different reaction pathways for oxidation of CO to CO2 depending on the type of metal oxide support. These findings could be used to help design future gold-based catalysts.

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  • 33.
    Boscolo Bibi, Sara
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    El-Zohry, Ahmed M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Davies, Bernadette
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Grigorev, Vladimir
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Goodwin, Christopher M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Lömker, Patrick
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Holm, Alexander
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Ali-Löytty, Harri
    Garcia-Martinez, Fernando
    Schlueter, Christoph
    Soldemo, Markus
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Koroidov, Sergey
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hansson, Tony
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Multi-spectroscopy study of electrochemically-formed oxide-derived gold electrodesManuskript (preprint) (Annet vitenskapelig)
  • 34.
    Boscolo Bibi, Sara
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    El-Zohry, Ahmed M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Koroidov, Sergey
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Hansson, Tony
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Electro-oxidation and nonlinear optical response of a gold surfaceManuskript (preprint) (Annet vitenskapelig)
  • 35. Boscolo Bibi, Sara
    et al.
    Garcia-Martinez, Fernando
    Davies, Bernadette
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Grigorev, Vladimir
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Lömker, Patrick
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Kalinko, Aleksandr
    Schlueter, Christoph
    Hansson, Tony
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Soldemo, Markus
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Koroidov, Sergey
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    X-ray spectroscopy study of electrochemically oxidized goldManuskript (preprint) (Annet vitenskapelig)
  • 36.
    Brinkmann, Andreas
    Stockholms universitet.
    Dipolar recoupling in magic-angle-spinning nuclear magnetic resonance2001Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This thesis concerns the development of radio-frequency pulse sequences in magic-angle-spinning solid-state nuclear magnetic resonance.

    First, two classes of pulse sequences are presented which are synchronized with the sample rotation. Symmetry theorems are described which link the symmetry of the pulse sequences to selection rules for the recoupling and/or decoupling of certain spin interactions. Pulse sequences are demonstrated which recouple direct homonuclear dipolar interactions at high sample spinning frequencies. Several applications are shown, including the efficient excitation of double-quantum coherences, two-dimensional double-quantum spectroscopy, transfer of longitudinal magnetization and two-dimensional correlation spectroscopy. In addition, generalized Hartmann-Hahn sequences are demonstrated in which radio-frequency irradiation is applied simultaneously to two isotopic spin species. These sequences selectively recouple direct heteronuclear dipolar interactions and suppress all homonuclear interactions for both spin species. Experimental demonstrations are given of heteronuclear two-dimensional correlation spectroscopy, heteronuclear multiple-quantum spectroscopy and the estimation of heteronuclear dipolar couplings.

    Second, a magic-angle-spinning nuclear magnetic resonance method is developed which directly estimates the backbone torsional angle Psi. in peptides and proteins. The method exploits multiple-quantum 13C coherence evolving under heteronuclear 13C-15N dipolar interactions. Single torsional angles Psi are determined with an accuracy of 5-10 degrees in the tripeptides gly-gly-gly and ala-gly-gly by exploiting double-quantum and triple-quantum coherences respectively.

  • 37. Brinkmann, Andreas
    et al.
    Edén, Mattias
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för fysikalisk kemi.
    Estimating internuclear distances between half-integer quadrupolar nuclei by central-transition double-quantum sideband NMR spectroscopy2011Inngår i: Canadian journal of chemistry (Print), ISSN 0008-4042, E-ISSN 1480-3291, Vol. 89, nr 7, s. 892-899Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We demonstrate the estimation of homonuclear dipolar couplings, and thereby internuclear distances, between half-integer spin quadrupolar nuclei by central-transition (CT) double-quantum (2Q) sideband nuclear magnetic resonance (NMR) spectroscopy. It is shown that the rotor-encoded sideband amplitudes from CT 2Q coherences in the indirect dimension of the two-dimensional NMR spectrum are sensitive probes of the magnitude of the homonuclear dipolar coupling, but are significantly less affected by other NMR parameters such as the magnitudes and orientations of the electric field gradient tensors. Experimental results of employing the R2(2)(1)R2(2)(-1) recoupling sequence to the (11)B spin pair of bis(catecholato)diboron resulted in an estimation of the internuclear B-B distance as (169.6 +/- 3) pm, i.e., with a relative uncertainty of +/- 2%, and in excellent agreement with the distance of 167.8 pm determined by single-crystal X-ray diffraction.

  • 38. Bull, James N.
    et al.
    Bolognesi, Paola
    Anstöter, Cate S.
    Ashworth, Eleanor K.
    Navarro Navarrete, José E.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Zhu, Boxing
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Richter, Robert
    Pal, Nitish
    Chiarinelli, Jacopo
    Avaldi, Lorenzo
    Zettergren, Henning
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Stockett, Mark H.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Autoionization from the plasmon resonance in isolated 1-cyanonaphthalene 2023Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 158, nr 24, artikkel-id 241101Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Polycyclic aromatic hydrocarbons have widely been conjectured to be ubiquitous in space, as supported by the recent discovery of two isomers of cyanonaphthalene, indene, and 2-cyanoindene in the Taurus molecular cloud-1 using radioastronomy. Here, the photoionization dynamics of 1-cyanonaphthalene (1-CNN) are investigated using synchrotron radiation over the = 9.0–19.5 eV range, revealing that prompt autoionization from the plasmon resonance dominates the photophysics for = 11.5–16.0 eV. Minimal photo-induced dissociation, whether originating from an excited state impulsive bond rupture or through internal conversion followed by a statistical bond cleavage process, occurs over the microsecond timescale (as limited by the experimental setup). The direct photoionization cross section and photoelectron angular distributions are simulated using an ezDyson model combining Dyson orbitals with Coulomb wave photoejection. When considering these data in conjunction with recent radiative cooling measurements on 1-CNN+, which showed that cations formed with up to 5 eV of internal energy efficiently stabilize through recurrent fluorescence, we conclude that the organic backbone of 1-CNN is resilient to photodestruction by VUV and soft XUV radiation. These dynamics may prove to be a common feature for the survival of small polycyclic aromatic hydrocarbons in space, provided that the cations have a suitable electronic structure to support recurrent fluorescence.  

  • 39.
    Carravetta, Marina
    Stockholms universitet.
    Symmetry-based double quantum recoupling in solid state NMR2002Doktoravhandling, med artikler (Annet vitenskapelig)
  • 40.
    Carvalho, José P.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Probing Paramagnetic Systems by Solid-State NMR Spectroscopy2022Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Paramagnetic systems have a wide range of applications ranging from energy storage or conversion to catalytic processes, metalloproteins and light-emitting materials. Over the recent years nuclear magnetic resonance (NMR) spectroscopy has become an established tool for studying the structural and electronic properties of these systems, largely because it can provide a link between the structure and the bulk properties. This progress was only possible due to improved probe technology and better radiofrequency irradiation schemes, since the hyperfine interaction between nuclei and the unpaired electrons generally hampers both the acquisition and interpretation of the spectra and, therefore, techniques that are standard for diamagnetic systems often perform poorly when applied to paramagnetic systems.

    The aim of the present thesis is to continue the development of solid-state paramagnetic NMR and address some of the remaining limitations and bottlenecks in the acquisition and spectral interpretation. One specific area for which great improvements have been seen is the development of new broadband excitation and inversion sequences for systems under Magic-Angle Spinning (MAS) which employ adiabatic pulses. In this work, we provide a more rigorous understanding of the adiabatic pulses in solid-state MAS NMR applicable to both the design of new and improved pulse schemes, and their application in studies of an increased variety of systems, whilst avoiding potential implementation pitfalls.

    We also demonstrate how a thorough understanding of the hyperfine interaction combined with quantum chemistry calculations can link bulk magnetic properties and magnetic resonance signatures both in solid-state NMR and Electron Paramagnetic Resonance (EPR), thus providing an accurate description of the geometry and electronic configuration of an organoytterbium complex with applications in heterogeneous catalysis.

    Lastly, we explore the development of methods suitable for quadrupolar nuclei (spin I>1/2) in paramagnetic systems which have, so far, lagged behind their spin 1/2 counterparts. We focus more specifically on half-integer quadrupoles for which we propose a new method of processing Multiple-Quantum and Satellite-Transition MAS spectra which permits the separation of shift and quadrupolar interactions into orthogonal dimensions and evaluate the performance and limitations of the state-of-the-art methods for extraction of both quadrupolar and shift anisotropy tensor parameters on structurally complex systems.

    We anticipate that the work developed throughout this thesis can help extend the fields of application of solid-state paramagnetic NMR.

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    Probing Paramagnetic Systems by Solid-State NMR Spectroscopy
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  • 41.
    Carvalho, José P.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för fysikalisk kemi.
    Papawassiliou, Wassilios
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Pell, Andrew J.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). Université de Lyon, France.
    Half-integer-spin quadrupolar nuclei in magic-angle spinning paramagnetic NMR: The case of NaMnO2Manuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    A combination of solid-state NMR methods for the extraction of shift and quadrupolar parameters for half-integer nuclei in the structurally complex NaMnO2 Na-ion cathode material, under magic-angle spinning (MAS) is presented. We show that the integration of the Magic-Angle Turning experiment with Rotor-Assisted Population transfer can be used both to identify shifts and to extract a range of magnitudes for their quadrupolar coupling. We also demonstrate the applicability of the the two-dimensional one pulse (TOP) based double-sheared Satellite Transition Magic-Angle Spinning (TOP-STMAS) showing how it can yield a spectrum with separated shift and second-order quadrupolar anisotropies, which in turn can be used to analyse a quadrupolar lineshape free of bulk magnetic susceptibility induced shift dispersion and determine both isotropic shift and quadrupolar products. Combining all these experiments, the shift and quadrupolar parameters for all observed Na environments were extracted and yielded excellent agreement with the density functional theory (DFT) based models that were reported in previous literature. We expect these methods to open the door for new possibilities for solid-state NMR to probe half-integer quadrupolar nuclei in paramagnetic materials and other systems exhibiting large shift dispersion. 

  • 42.
    Castro, Vasco
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi.
    Solid-State NMR Characterization of Lipid Membranes2008Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This thesis deals with the study of lipid bilayer systems by solid-state nuclear magnetic resonance. Two-dimensional 1H-13C separated local field experiments under magic-angle spinning were employed to investigate structural and dynamical modifications of cell membranes, resulting from the addition of compounds with some biological relevance. For further interpretation of the segmental order obtained from the 2D experiments other methods, such as 31P-NMR, 2H-NMR and molecular dynamics simulations, were also employed.

    The work presented in this thesis can be divided into two parts. The first part refers to the setup of experimental conditions. Heating and hydration effects were addressed in order to define both the temperature of the system as well as the number of water molecules per lipid necessary to fully hydrate the bilayer. Application of this experimental setup to lipid membrane systems with biological relevance constitutes the second part. The interaction of monogalactosyl- diacylglycerol, the most abundant lipid on earth, with dimyristoylphosphatidylcholine, was studied, which resulted in a frustrated bilayer. Furthermore, small molecules of local anesthetics, with focus on lidocaine, were inserted in the model membrane with the purpose of understanding the influence of local anesthetics on lipid bilayers.

  • 43.
    Castro, Vasco
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi.
    Stevensson, Baltzar
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi.
    Dvinskikh, Sergey V.
    Division of Physical Chemistry, Royal Institute of Technology, SE-10044 Stockholm, Sweden.
    Högberg, Carl-Johan
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi.
    Lyubartsev, Alexander P.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi.
    Zimmermann, Herbert
    Department of Biophysics, Max-Planck-Institut für Medizinische Forschung, Jahnstrasse 29, D-69120 Heidelberg, Germany.
    Sandström, Dick
    Bruker BioSpin Scandinavia AB, Sweden.
    Maliniak, Arnold
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi.
    NMR investigations of interactions between anesthetics and lipid bilayers2008Inngår i: Biochimica et Biophysica Acta - Biomembranes, ISSN 0005-2736, E-ISSN 1879-2642, Vol. 1178, nr 11, s. 2604-2611Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

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

  • 44.
    Cavalleri, Matteo
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Local Structure of Hydrogen-Bonded Liquids2004Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Ordinary yet unique, water is the substance on which life is based. Water seems, at first sight, to be a very simple molecule, consisting of two hydrogen atoms attached to one oxygen. Its small size belies the complexity of its action and its numerous anomalies, central to a broad class of important phenomena, ranging from global current circulation, terrestrial water and CO2 cycles to corrosion and wetting. The explanation of this complex behavior comes from water's unique ability to form extensive three-dimensional networks of hydrogen-bonds, whose nature and structures, in spite of a great deal of efforts involving a plethora of experimental and theoretical techniques, still lacks a complete scientific understanding.

    This thesis is devoted to the study of the local structure of hydrogen-bonded liquids, with a particular emphasis on water, taking advantage of a combination of core-level spectroscopies and density functional theory spectra calculations. X-ray absorption, in particular, is found to be sensitive to the local hydrogen-bond environment, thus offering a very promising tool for spectroscopic identification of specific structural configurations in water, alcohols and aqueous solutions. More specifically, the characteristic spectroscopic signature of the broken hydrogen-bond at the hydrogen side is used to analyze the structure of bulk water, leading to the finding that most molecules are arranged in two hydrogen-bond configurations, in contrast to the picture provided by molecular dynamics simulations. At the liquid-vapor interface, an interplay of surface sensitive measurements and theoretical calculations enables us to distinguish a new interfacial species in equilibrium with the gas. In a similar approach the cluster form of the excess proton in highly concentrated acid solutions and the different coordination of methanol at the vacuum interface and in the bulk can also be clearly identified.

    Finally the ability of core-level spectroscopies, aided by sophisticated density functional theory calculations, to directly probe the valence electronic structure of a system is used to observe the nature of the interaction between water molecules and solvated ions in solution. Water around transition metal ions is found to interact with the solute via orbital mixing with the metal d-orbitals. The hydrogen-bond between water molecules is explained in terms of electrostatic interactions enhanced by charge rehybridization in which charge transfer between connecting molecules is shown to be fundamental.

    Fulltekst (pdf)
    FULLTEXT01
  • 45. Chen, Chen
    et al.
    Huang, Congcong
    Waluyo, Iradwikanari
    Nordlund, Dennis
    Weng, Tsu-Chien
    Sokaras, Dimosthenis
    Weiss, Thomas
    Bergmann, Uwe
    Pettersson, Lars G.M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Nilsson, Anders
    Solvation structures of protons and hydroxide ions in water2013Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 138, nr 15, s. 154506-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    X-ray Raman spectroscopy (XRS) combined with small-angle x-ray scattering (SAXS) were used to study aqueous solutions of HCl and NaOH. Hydrated structures of H+ and OH- are not simple mirror images of each other. While both ions have been shown to strengthen local hydrogen bonds in the hydration shell as indicated by XRS, SAXS suggests that H+ and OH- have qualitatively different long-range effects. The SAXS structure factor of HCl (aq) closely resembles that of pure water, while NaOH (aq) behaves similar to NaF (aq). We propose that protons only locally enhance hydrogen bonds while hydroxide ions induce tetrahedrality in the overall hydrogen bond network of water.

  • 46. Chen, Chun Lin
    et al.
    Furusho, Hirotoshi
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi.
    Mori, Hirotaro
    In situ TEM observation of decomposition of high-purity sapphire2009Inngår i: Philosophical Magazine Letters, ISSN 0950-0839, E-ISSN 1362-3036, Vol. 89, nr 2, s. 113-119Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The decomposition of agr-Al2O3 under 200 keV electron irradiation has been investigated by in situ high-resolution electron microscopy (HREM). It was confirmed that aluminium precipitated from agr-Al2O3 under 200 keV electron irradiation for less than 1 min over the temperature range from 700 to 1273 K. The electron dose rate was of the order of 1023 e m-2 s-1 and the vacuum level of the microscope was better than 10-6 Pa. The mechanisms of agr-Al2O3 decomposition were discussed based on two possible decomposition models: the thermally activated atom movement and the forced atom displacement

  • 47.
    Chen, Hong
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för oorganisk kemi och strukturkemi.
    Deng, Youqian
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Yu, Zhengbao
    Zhao, Huishuang
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Yao, Qingxia
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för oorganisk kemi och strukturkemi.
    Zou, Xiaodong
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för oorganisk kemi och strukturkemi.
    Bäckvall, Jan-E.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Sun, Junliang
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    3D Open-Framework Vanadoborate as a Highly Effective Heterogeneous Pre-catalyst for the Oxidation of Alkylbenzenes2013Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 25, nr 24, s. 5031-5036Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Three three-dimensional (3D) open-framework vanadoborates, denoted as SUT-6-Zn, SUT-6-Mn, and SUT-6-Ni, were synthesized using diethylenetriamine as a template. SUT-6-Zn, SUT-6-Mn, and SUT-6-Ni are isostructural and built from (VO)(12)O-6 B18O36(OH)(6) clusters bridged by ZnO5, MnO6, and NiO6 polyhedra, respectively, to form the 3D frameworks. SUT-6 is the first vanadoborate with a 3D framework. The framework follows a semiregular hxg net topology with a 2-fold interpenetrated diamond-like channel system. The amount of template used in the synthesis played an important role in the dimensionality of the resulting vanadoborate structures. A small amount of diethylenetriamine led to the formation of this first 3D vanadoborate framework, while an increased amount of diethylenetriamine resulted in vanadoborates with zero-dimensional (0D) and one-dimensional (1D) structures. SUT-6-Zn was proved to be an efficient heterogeneous precatalyst for the oxidation of alkylbenzenes.

  • 48. Cho, Hae Sung
    et al.
    Deng, Hexiang
    Miyasaka, Keiichi
    Dong, Zhiyue
    Cho, Minhyung
    Neimark, Alexander V.
    Kang, Jeung Ku
    Yaghi, Omar M.
    Terasaki, Osamu
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK). Graduate School of Energy, Environment, Water and Sustainability, South Korea.
    Extra adsorption and adsorbate superlattice formation in metal-organic frameworks2015Inngår i: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 527, nr 7579, s. 503-U193Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Metal-organic frameworks (MOFs) have a high internal surface area and widely tunable composition(1,2), which make them useful for applications involving adsorption, such as hydrogen, methane or carbon dioxide storage(3-9). The selectivity and uptake capacity of the adsorption process are determined by interactions involving the adsorbates and their porous host materials. But, although the interactions of adsorbate molecules with the internal MOF surface(10-17) and also amongst themselves within individual pores(18-22) have been extensively studied, adsorbate-adsorbate interactions across pore walls have not been explored. Here we show that local strain in the MOF, induced by pore filling, can give rise to collective and long-range adsorbate-adsorbate interactions and the formation of adsorbate superlattices that extend beyond an original MOF unit cell. Specifically, we use in situ small-angle X-ray scattering to track and map the distribution and ordering of adsorbate molecules in five members of the mesoporous MOF-74 series along entire adsorption-desorption isotherms. We find in all cases that the capillary condensation that fills the pores gives rise to the formation of 'extra adsorption domains'-that is, domains spanning several neighbouring pores, which have a higher adsorbate density than non-domain pores. In the case of one MOF, IRMOF-74-V-hex, these domains form a superlattice structure that is difficult to reconcile with the prevailing view of pore-filling as a stochastic process. The visualization of the adsorption process provided by our data, with clear evidence for initial adsorbate aggregation in distinct domains and ordering before an even distribution is finally reached, should help to improve our understanding of this process and may thereby improve our ability to exploit it practically.

  • 49. Cho, Hae Sung
    et al.
    Miyasaka, Keiichi
    Kim, Hyungjun
    Kubota, Yoshiki
    Takata, Masaki
    Kitagawa, Susumu
    Ryoo, Ryong
    Terasaki, Osamu
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för oorganisk kemi och strukturkemi.
    Study of Argon Gas Adsorption in Ordered Mesoporous MFI Zeolite Framework2012Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 116, nr 48, s. 25300-25308Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An ordered mesoporous MFI zeolite material (Meso-MFI) was prepared by using CMK-type mesoporous carbons as a hard template. The Meso-MFI exhibits both structural and adsorption differences compared to the conventional bulk MFI zeolite. To study the argon (Ar) adsorption process in Meso-MFI, an in situ gas adsorption powder X-ray diffraction (XRD) analysis was performed using synchrotron X-ray source. Structural rearrangement of the mesoporous MFI zeolite upon Ar adsorption at low temperature (83 K) was intensively studied together with Ar adsorption process in Meso-MFI. We observed that a structural transition of the Meso-MFI zeolite framework from monoclinic (P2(1)/n) to orthorhombic (Pnma) occurred at around 126 Pa at 83 K. Positions of Ar atoms are determined as a function of the Ar gas pressure through Rietveld refinement of powder XRD data. Ar atoms are observed at straight channels, sinusoidal channels, and the intersection of these channels at low pressure. As gas pressure increases, Ar atoms in the pore intersection are pulled off from the intersection toward the straight and sinusoidal channels. The pore shape of the straight channel is changed accordingly with the amount of adsorbed Ar atoms within the pores from circular to oval. These results indicate that Ar adsorption induces not only continuous rearrangement of framework atoms but also symmetry change in the Meso-MFI. A molecular simulation study combined with Rietveld refinement of in situ XRD data provided a full understanding of the adsorption process of Ar in Meso-MFI.

  • 50.
    Coates, Michael R.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Banerjee, Ambar
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Jay, Raphael M.
    Uppsala Universitet.
    Wernet, Philippe
    Uppsala Universitet.
    Odelius, Michael
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Theoretical Investigation of Transient Speciesfollowing Photodissociation of Ironpentacarbonylin Ethanol SolutionManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Photodissociation of ironpentacarbonyl in solution generates transient species indifferent electronic states, which we have studied theoretically. From ab initio moleculardynamics simulations in ethanol solutions, the close-shell parent compound 1Fe(CO)5 is found to interact weakly with the solvent, whereas the irontetracarbonyl species,formed after photodissociation, has a strongly spin-dependent behavior. It coordinatesa solvent molecule tightly in the singlet state (1Fe(CO)4) and weakly in the tripletstate (3Fe(CO)4). Alternative forms of coordination between 1Fe(CO)4 and functionalgroups of the ethanol molecule are simulated, and quantum chemical calculations ofthe energy landscape for the coordinated irontetracarbonyl give information aboutthe inter-conversion of different transient species in solution. Furthermore, insights1from the simulations challenge the previously proposed mechanism of chain walkingfor undercoordinate metal carbonyls in solution. Thereby, we gain insight into bothintersystem crossing in solvated irontetracarbonyl and its exchange in coordinationbetween Fe−OH and Fe−HC.

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