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  • 351. Litvinchuk, AP.
    et al.
    Lorenz, B.
    Chen, F.
    Nylen, Johanna
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Haussermann, U.
    Lidin, Sven
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Wang, LM.
    Guloy, AM.
    Optical and electronic properties of thermoelectric Zn4Sb3 across the low-temperature phase transitions2007In: Applied Physics Letters, Vol. 90, p. 181920-181920Article in journal (Refereed)
  • 352. Litvinchuk, A.P.
    et al.
    Lorenz, B.
    Chen, Feng
    Nylén, J.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Häussermann, U.
    Lidin, Sven
    Wang, Limin
    Guloy, Arnold M.
    Optical and electronic properties of thermoelectric Zn4Sb3 across the low-temperature phase transitions2007In: Applied Physical Letters, Vol. 90, p. 181920-181923Article in journal (Refereed)
  • 353.
    Liu, Jing
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Nano and Grain-Orientated Ferroelectric Ceramics Produced by SPS2007Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Nano-powders of BaTiO3, SrTiO3, Ba0.6Sr0.4TiO3, a mixture of the composition (BaTiO3)0.6(SrTiO3)0.4 with particle sizes in the range of 60 to 80 nm, and Bi4Ti3O12 with an average particle size of 100 nm were consolidated by spark plasma sintering (SPS). The kinetics of reaction, densification and grain growth were studied. An experimental procedure is outlined that allows the determination of a “kinetic window” within which dense nano-sized compacts can be prepared. It is shown that the sintering behaviour of the five powders varies somewhat, but is generally speaking fairly similar. However, the types of grain growth behaviour of these powders are quite different, exemplified by the observation that the kinetic window for the (BaTiO3)0.6(SrTiO3)0.4 mixture is 125 oC, ~75 oC for Bi4Ti3O12, ~25oC for BaTiO3 and SrTiO3, while it is hard to observe an apparent kinetic window for obtaining nano-sized compacts of Ba0.6Sr0.4TiO3. During the densification of the (BaTiO3)0.6(SrTiO3)0.4 mixture the reaction 0.6BaTiO3+0.4SrTiO3 → Ba0.6Sr0.4TiO3 takes place, and this reaction is suggested to have a self-pinning effect on the grain growth, which in turn explains why this powder has a large kinetic window. Notably, SPS offers a unique opportunity to more preciously investigate and monitor the sintering kinetics of nano-powders, and it allows preparation of ceramics with tailored microstructures.

    The dielectric properties of selected samples of (Ba, Sr)TiO3 ceramics have been studied. The results are correlated with the microstructural features of these samples, e.g. to the grain sizes present in the compacts. The ceramic with nano-sized microstructure exhibits a diffuse transition in permittivity and reduced dielectric losses in the vicinity of the Curie temperature, whereas the more coarse-grained compacts exhibit normal dielectric properties in the ferroelectric region.

    The morphology evolution, with increasing sintering temperature, of bismuth layer-structured ferroelectric ceramics such as Bi4Ti3O12 (BIT) and CaBi2Nb2O9 (CBNO) was investigated. The subsequent isothermal sintering experiments revealed that the nano-sized particles of the BIT precursor powder grew into elongated plate-like grains within a few minutes, via a dynamic ripening mechanism.

    A new processing strategy for obtaining highly textured ceramics is described. It is based on a directional dynamic ripening mechanism induced by superplastic deformation. The new strategy makes it possible to produce a textured microstructure within minutes, and it allows production of textured ferroelectric ceramics with tailored morphology and improved physical properties.

    The ferroelectric, dielectric, and piezoelectric properties of the textured bismuth layer-structured ferroelectric ceramics have been studied, and it was revealed that all textured samples exhibited anisotropic properties and improved performance. The highly textured Bi4Ti3O12 ceramic exhibited ferroelectric properties equal to or better than those of corresponding single crystals, and much better than those previously reported for grain-orientated Bi4Ti3O12 ceramics. Textured CaBi2Nb2O9 ceramics exhibited a very high Curie temperature, d33-values nearly three times larger than those of conventionally sintered materials, and a high thermal depoling temperature indicating that it is a very promising material for high-temperature piezoelectric applications.

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  • 354.
    Liu, Jing Joan
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Shen, Zhijian
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Haixue Yan, Mike Reece
    Reece, Mike
    Yanmei, Kan
    Wang, Peiling
    The Dielectric, Piezoelectric and Ferroelectric Properties of Grain-Orientated La_0.75 Bi_3.25 Ti_3 O_12 Ceramics2007In: Journal of applied physicsArticle in journal (Refereed)
  • 355.
    Liu, Jing
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Shen, Zhijian
    Nygren, Mats
    Consolidation and dielectric behaviours of Ba0.6Sr0.4TiO3 ceramics with tailored microstructures2005In: Ferroelectrics, ISSN 0015-0193, Vol. 319, p. 109-116Article in journal (Refereed)
  • 356.
    Liu, Jing
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Shen, Zhijian
    Nygren, Mats
    Kan, Yanmei
    Wang, Peiling
    SPS processing of bismuth-layer structured ferroelectric Ceramics yielding highly textured microstructures2006In: Journal of the European Ceramic Society, ISSN 0955-2219, Vol. 26, p. 3233-3239Article in journal (Refereed)
  • 357.
    Liu, Jing
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Shen, Zhijian
    Nygren, Mats
    Su, Bo
    Button, Tim W.
    Spark Plasma Sintering Behavior of nano-sized (Ba, Sr)TiO3 powders: determination of sintering parameters yielding nanostructured ceramics2006In: Journal of the American Ceramic Society, ISSN 0002-7820, Vol. 89, no 9, p. 2689-2694Article in journal (Refereed)
  • 358.
    Liu, Jing
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry, Inorganic Chemistry.
    Shen, Zhijian
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry, Inorganic Chemistry.
    Yan, Haixue
    Reece, Michael J.
    Kan, Yanmei
    Wang, Peiling
    Dielectric, piezoelectric, and ferroelectric properties of grain-orientated Bi3.25La0.75Ti3O12 ceramics2007In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 102, no 10, p. 104107-Article in journal (Refereed)
    Abstract [en]

    By dynamic forging during Spark Plasma Sintering (SPS), grain-orientated ferroelectric Bi3.25La0.75Ti3O12 (BLT) ceramics were prepared. Their ferroelectric, piezoelectric, and dielectric properties are anisotropic. The textured ceramics parallel and perpendicular to the shear flow directions have similar thermal depoling behaviors. The d(33) piezoelectric coefficient of BLT ceramics gradually reduces up to 350 degrees C; it then drops rapidly. The broadness of the dielectric constant and loss peaks and the existence of d(33) above the permittivity peak, T-m, show that the BLT ceramic has relaxor-like behavior.

  • 359.
    Ljungberg, Mathias
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Lyubartsev, Alexander
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Nilsson, Anders
    Stanford Synchrotron Radiation Lightsource.
    Pettersson, Lars
    Stockholm University, Faculty of Science, Department of Physics.
    Assessing the electric-field approximation to IR and Raman spectra of dilute HOD in D2O2009In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 131, p. 034501-Article in journal (Refereed)
    Abstract [en]

    We analyze the validity of the commonly used electric-field (E-field) approximation to vibrational OH stretch Raman spectra of dilute HOD in D2O by computing the OH stretch frequency of all molecules in several different structure models, each containing around 2000 molecules. The calculations are done at the B3LYP level using clusters containing 32 molecules centered around the molecule for which the frequencies are calculated; the large cluster size is required due to significant nonlocal contributions influencing the computed frequencies. The vibrational frequencies are determined using a six-point potential optimized discrete variable representation. Raman and infrared intensities are furthermore computed to generate the spectra. We find that a quadratic fit of E-field versus frequency gives a reasonable representation of the calculated distribution of frequencies. However, the mapping depends significantly on the structural model and is thus not universal. Anharmonic couplings are calculated for several optimized clusters showing a general trend to compress the computed frequency distributions, which is in agreement with dynamical simulations (motional narrowing).

  • 360. Lokshin, K A
    et al.
    Pavlov, Dmitriy A.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Kovba, M L
    Putilin, S N
    Antipov, E V
    Bryntse, I
    Synthesis and investigation of (Hg1-xCux)Ba2Ca2Cu3O8+δ2002In: Physica C, ISSN 0921-4534, Vol. 366, no 4, p. 263–269-Article in journal (Refereed)
  • 361. Lokshin, K A
    et al.
    Pavlov, Dmitriy A.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Putilin, S N
    Antipov, E V
    Sheptyakov, D V
    Balagurov, A M
    Enhancement of Tc in HgBa2Ca2Cu3O8+δ by fluorination2001In: Physical Review B, ISSN 1098-0121, Vol. 63, no 6, p. 064511-Article in journal (Refereed)
  • 362. Lund, K.
    et al.
    Muroyama, N.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Terasaki, O.
    Powder XRD intensity of mesoporous carbon crystal with two-dimensional symmetry: Accidental extinction in CMK-5Manuscript (Other academic)
  • 363.
    Lund, Kristina
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Structural and Morphological Studies of Mesoporous Crystals2007Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Mesoporous silica and carbon have been synthesised and characterised by X-ray diffraction (XRD), transmission and scanning electron microscopy (TEM and SEM) and nitrogen adsorption. Surface structure, size and shape (morphology) of particles have been of special interest in this work. These parameters are of importance in understanding the growth mechanism and structural characteristics of mesoporous materials overall, which has been the main aim of this thesis.

    The novel synthetic system involving preparation of AMS (anionic surfactant-templated silica) crystals, where the non-toxic N-acyl-amino acids are used as surfactant together with a co-structure directing agent, was investigated in two different surfactant systems.

    Particle size and shape of AMS solids were controlled through the addition of a polymeric dispersant, which slowed down the system dynamics. However, the response for the two synthetic systems investigated, proved to be different. Nanoparticles of cage-type cubic Fd-3m crystals were obtained in one system, whereas facetted particles formed in a near-to-equilibrium growth in the bicontinuous cubic Ia-3d case.

    The surface fine structure of mesoporous silica was observed by high resolution SEM, leading to an understanding of the pore accessibility at the particle surface of SBA-15 silica. Furthermore, discrepancies in the XRD patterns of mesoporous tube-type carbon CMK-5 with different pore diameters were observed. XRD patterns displaying accidental extinction of the 10 reflection were observed in CMK-5 samples prepared with the widest pore diameter. An analytical approach was formulated in order to simulate the variation of XRD intensity for carbon crystals with p6mm symmetry. TEM observations of inner and outer diameter of the carbon tubes were used to interpret the diminishing of certain reflections and we observed good agreement between experimental observations and our calculations.

  • 364.
    Lund, Kristina
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Garcia-Bennett, A E
    Terasaki, Osamu
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    On the use of polymeric dispersant P123 in the synthesis of bicontinuous cubic mesoporous AMS-62007In: Journal of Materials Chemistry, Vol. 17, p. 3622-2629Article in journal (Refereed)
  • 365.
    Lyubartsev, Alexander
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Interacting electrons in one dimension: A path integral Monte Carlo study2007In: Journal of Physics A, Vol. 40, p. 7151-7157Article in journal (Refereed)
  • 366.
    Lyubartsev, Alexander
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Ben-Naim, Arieh
    The Hebrew University of Jerusalem.
    One dimensional model for water and aqueous solutions. Part V. Monte Carlo simulation of dilute solutions of hard rod in waterlike particles2009In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 131, p. 204507-Article in journal (Refereed)
    Abstract [en]

    Wehave carried out Monte Carlo simulation on the primitive onedimensional model for water described earlier [A. Ben-Naim, J. Chem.Phys. 128, 024506 (2008)]. We show that by taking intoaccount second nearest neighbor interactions, one can obtain the characteristicanomalous solvation thermodynamic quantities of inert solutes in water. Thismodel clearly demonstrates the molecular origin of the large negativeentropy of solvation of an inert solute in water.

  • 367.
    Lyubartsev, Alexander
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Tu, Yaoquan
    Örebro university.
    Laaksonen, Aatto
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Hierarchical Multiscale Modelling Scheme from First Principles to Mesoscale2009In: Journal of computational and theoretical nanoscience, ISSN 1546-1963 (eISSN), Vol. 6, no 5, p. 951-959Article in journal (Refereed)
    Abstract [en]

    We present a straight-forward implementation of a practical hierarchical multiscale modelling scheme which enables us to start from first-principles atomistic computer simulation and successively coarse-grain the model by leaving out uninteresting degrees of freedom. Using the Car-Parrinello method or our recently developed highly efficient tight-binding-like approximate density-functional quantum mechanical method, we first perform ab initio simulations. From these first-principles simulations we obtain a set of atomistic pair-wise effective interaction potentials to be used as a force field with no empirical data for subsequent classical all-atom simulations while scaling up the system size 2-3 orders of magnitude. The atomistic simulations similarly provide a new set of effective potentials but at a chosen coarse-grain level suitable for large-scale mesoscopic or soft-matter simulations beyond the atomic resolution. Several examples are shown of how this scheme is done based on effective interaction potentials to tie together the various scales of modelling.

  • 368. López-Noriega, Adolfo
    et al.
    Ruiz-Hernández, Eduardo
    Terasaki, Osamu
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Stevens, Sam M.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Mesoporous Microspheres with Doubly Ordered Core-Shell Structure2009In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 21, no 1, p. 18-20Article in journal (Refereed)
  • 369.
    Ma, Guibin
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Molla-Abbassi, Alireza
    Persson, Ingmar
    Kritikos, Mikael
    Ilyukin, Andrey
    Jalilehvand, Farideh
    Kessler, Vadim
    Skripkin, Mikhail
    Sandström, Magnus
    Glaser, Julius
    Näslund, Jan
    Structure of the dimethyl sulfoxide solvated thallium(III) ion in solution and in the solid state2001In: Inorganic Chemistry, ISSN 0020-1669, Vol. 40, no 25, p. 6432-6438Article in journal (Refereed)
  • 370. Makiya, A.
    et al.
    Kunsumi, K.
    Tanaka, Satoshi
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Uematsu, K.
    Particle oriented titana ceramics prepared in a magnetic field2007In: Journal of European Ceramics Society, Vol. 27, p. 797-799Article in journal (Refereed)
  • 371. Makiya, A.
    et al.
    Tanaka, Satoshi
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Shoji, D.
    Ishikawa, T.
    Uchida, N.
    Uematsu, K.
    A quantitative evaluation method for particle orientation structure in alumina powder compacts2007In: Journal of European Ceramics Society, Vol. 27, p. 3399-3406Article in journal (Refereed)
  • 372.
    Maliniak, Arnold
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Dahlberg, Martin
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Molecular dynamics simulations of cardiolipin bilayers2008In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 112, no 37, p. 11655-11663Article in journal (Refereed)
    Abstract [en]

    Cardiolipin is a key lipid component in the inner mitochondrial membrane, where the lipid is involved in energy production, cristae structure, and mechanisms in the apoptotic pathway. In this article we used molecular dynamics computer simulations to investigate cardiolipin and its effect on the structure of lipid bilayers. Three cardiolipin/POPC bilayers with different lipid compositions were simulated: 100, 9.2, and 0% cardiolipin. We found strong association of sodium counterions to the carbonyl groups of both lipid types, leaving in the case of 9.2% cardiolipin virtually no ions in the aqueous compartment. Although binding occurred primarily at the carbonyl position, there was a preference to bind to the carbonyl groups of cardiolipin. Ion binding and the small headgroup of cardiolipin gave a strong ordering of the hydrocarbon chains. We found significant effects in the water dipole orientation and water dipole potential which can compensate for the electrostatic repulsion that otherwise should force charged lipids apart. Several parameters relevant for the molecular structure of cardiolipin were calculated and compared with results from analyses of coarse-grained simulations and available X-ray structural data.

  • 373. Manyar, Haresh G.
    et al.
    Gianotti, Enrica
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry, Structural Chemistry.
    Sakamoto, Yasuhiro
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry, Structural Chemistry.
    Terasaki, Osamu
    Coluccia, Salvatore
    Tumbiolo, Simonetta
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry, Structural Chemistry.
    Active Biocatalysts Based on Pepsin Immobilized in Mesoporous SBA-152008In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 112, no 46, p. 18110-18116Article in journal (Refereed)
    Abstract [en]

    Porcine pepsin was immobilized inside the SBA-15 mesoporous silica system through physical adsorption. A grafting step with 3-aminopropryltriethoxysilane (APTES) was performed to reduce the pore openings of the host material, in order to minimize the enzyme leaching. A detailed physical chemical characterization of hybrid materials was performed. The catalytic activity of the hybrid bioinorganic material, tested with two different substrates (hemoglobin and Z-L-glutamyl-L-tyrosine dipeptide), confirmed that pepsin was located inside the pore/channels of the silica material and that the grafting process did not affect the enzyme structure. The immobilized pepsin has maintained the necessary degree of freedom to fulfill its catalytic activity. The reusability of the so-called bioreactor was also investigated.

  • 374. Mayerhoefer, Thomas G.
    et al.
    Shen, Zhijian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    SUBLeonova, Ekaterina
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry, Physical Chemistry.
    Eden, Mattias
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry, Physical Chemistry.
    Kriltz, Antje
    Popp, Juergen
    Consolidated silica glass from nanoparticles2008In: Journal of Solid State Chemistry, ISSN 0022-4596, E-ISSN 1095-726X, Vol. 181, no 9, p. 2442-2447Article in journal (Refereed)
    Abstract [en]

    A dense silica glass was prepared by consolidating a highly dispersed silicic acid powder (particle size < 10 nm) with the Spark Plasma Sintering (SPS) technique. The glass was characterized by ellipsometry, transmission electron microscopy (TEM), infrared reflectance and transmittance spectroscopy, as well as by Raman, UV-Vis-NIR and solid-state nuclear magnetic resonance (NMR) spectroscopy. The prototypic sample showed a transmittance of about 63% compared to silica glass in the UV-Vis spectral range. Based on the results of infrared transmittance spectroscopy this lower transparency is due to the comparably high water content, which is about 40 times higher than that in silica glass. H-1 magic-angle spinning (MAS) NMR confirmed an increase in hydroxyl groups in tie sample prepared by SPS relative to that of the conventional SiO2 reference glass. Aside from the comparably high water content, we conclude from the similarity of the IR-reflectance and the Si-29 MAS NMR spectra of the SPS sample and the corresponding spectra of the conventionally prepared silica glass, that the short- and medium-range order is virtually the same in both materials. Raman spectroscopy, however, Suggests that the number of three- and four-membered rings is significantly smaller in the SPS sample compared to the conventionally prepared sample. Based on these results we conclude that it is possible to prepare glasses by compacting amorphous powders by the SPS process. The SPS process may therefore enable the preparation of glasses with compositions inaccessible by conventional methods. 

  • 375. Mayoral, Alvaro
    et al.
    Sakamoto, Yasuhiro
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry, Structural Chemistry.
    Anderson, Paul. A.
    Synthesis of copper chloride nanowires by thermal treatment in the presence of zeolite X2010In: CrystEngComm, ISSN 1466-8033, E-ISSN 1466-8033, Vol. 12, no 10, p. 3012-3018Article in journal (Refereed)
    Abstract [en]

    Copper(I) chloride nanowires have been synthesized by heating the salt in the presence of copper zeolite X (FAU structure type). Their structure and composition were studied by powder X-ray diffraction, transmission electron microscopy and energy dispersive X-ray spectroscopy. Wire growth was found to be dependent on a number of factors, the most important being the temperature of the reaction. The mechanism of wire growth, involving the occlusion of CuCl within the zeolite pores, is discussed.

  • 376. Men, Y. B.
    et al.
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Huang, Z. T.
    Zheng, Q. Y.
    Construction of 3-fold interpenetrated pcu organic frameworks from methanetetrabenzoic acid with zigzag bipyridines2009In: CrystEngComm, ISSN 1466-8033, E-ISSN 1466-8033, Vol. 11, p. 2277-2278Article in journal (Refereed)
    Abstract [en]

    Zigzag bipyridine (azpy, bipy-ete) induced crystalline assembly of the tetrahedral module methanetetrabenzoic acid to form the novel hydrogen-bonded organic framework with an unusual 3-fold interpenetrated pcu (alpha-polonium) topology.

  • 377. Men, Y. B.
    et al.
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Huang, Z. T.
    Zheng, Q. Y.
    Organic hydrogen-bonded interpenetrating diamondoid frameworks from modular self-assembly of methanetetrabenzoic acid with linkers2009In: CrystEngComm, ISSN 1466-8033, E-ISSN 1466-8033, no 11, p. 978-979Article in journal (Refereed)
    Abstract [en]

    The modular self-assembly of methanetetrabenzoic acid with similar linear linkers, phenazine and 4,4'-bipyridine, affords two different interpenetrating diamondoid frameworks which show a normal 7-fold mode of interpenetration (class Ia), and an unusual 18-fold interpenetration (class IIIb, [3 x 3 x 2]), respectively.

  • 378. Men, Yong-Biao
    et al.
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Huang, Zhi-Tang
    Zheng, Qi-Yu
    Rational Construction of 2D and 3D Borromean Arrayed Organic Crystals by Hydrogen Bonds Directed Self-Assembly2009In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 48, no 16, p. 2873-2876Article in journal (Refereed)
    Abstract [en]

    The Borromean system, which contains nontrivial three ring links (no ring is interlocked to another without the help of the third one), is a very intriguing pattern of crystal entanglements, because of the topological complexity, structural integrity, and aesthetic beauty. Herein we report the rational construction of Borromean three-fold 2D-2D entangled layers and n-Borromean 2D-3D entangled infinite layers with pure organic supramolecular synthons based on hydrogen-bond-directed self assembly.

  • 379. Mikhaylushkin, Arkady S.
    et al.
    Nylén, Johanna
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Häussermann, Ulrich
    Structure and Bonding of Zinc Antimonides: Complex Frameworks and Narrow Band Gaps2005In: Chemistry a european journal, Vol. 11, p. 4912-4290Article in journal (Refereed)
  • 380. Miljak, M.
    et al.
    Becker, R.
    Herak, M.
    Prester, M.
    Milat, O.
    Johnsson, Mats
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Berger, H.
    A new modification of nickel selenite NiSeO3 – crystal structure and magnetic properties2007In: Journal of Physcs: Condensed Matter, Vol. 19Article in journal (Refereed)
  • 381.
    Mink, Janos
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Skripkin, Mikhail
    Hajba, L
    Németh, C
    Abbasi, Alireza
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Sandström, Magnus
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Infrared and raman spectroscopic and theoretical studies of nonaaqua complexes of trivalent rare earth metal ions2005In: Spectrochimica Acta Part A - Molecular and Biomolecular Spectroscopy, ISSN 1386-1425, E-ISSN 1873-3557, Vol. 61, no 7, p. 1639-1645Article in journal (Refereed)
    Abstract [en]

    Infrared (IR), far-infrared (far-IR) and Raman spectra have been recorded of the hydrated lanthanide(III) trifluoromethanesulfonates, [Ln(OH2)9](CF3SO3)3, (Ln = La, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu), and also for the deuterated [La(OD2)9](CF3SO3)3 compound. This has enabled complete assignments of all seven metal–oxygen stretching modes for the first time. Force constant calculations have been performed for an LnO93+ moiety, with a tricapped trigonal prismatic oxygen atom arrangement in D3h point group symmetry.

    The lanthanide contraction in reflected in continuously increasing trends for the averaged LnO stretching frequencies and force constants with increasing inverse of ionic radii. The stretching force constants increased from 0.81 to 1.16 Ncm−1 for the LnO6 prism in the series from La to Lu, while those for the capping LnO3 bonds increased from 0.49 to 0.65 Ncm−1. The LnO stretching force constants showed a smooth correlation with the LnO bond distances to the prism oxygen atoms, while the correlation to the LnO capping oxygen atoms has a different shape, reflecting the increased ligand–ligand repulsion with decreasing lanthanide ion size.

  • 382.
    Miyasaka, Keiichi
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    A structural study into the boundary surface and associated curvature of three-dimensional mesoporous silica crystals2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Since their first discovery in the early 1990s, mesoporous crystals (MCs) have fascinated researchers in various fields because of their interesting structures and their potential uses. Electron crystallography (EC) gives the direct three-dimensional (3D) realization of a crystal as a reconstructed electrostatic potential map (EPM). Various 3D-EPMs of silica MCs with cubic symmetry have been previously obtained by EC.

    The main task in this thesis is the development of structural analyses focusing on MCs and thus to evaluate the properties of periodic mesopores within EC data. How MC structures can be described and solved by EC is discussed in terms of the interpretation of the reconstructed 3D-EPM. Assuming a regime of an equi-potential surface (EPS), a structural description for MCs is suggested as a surface that optimizes the curvature elasticity evaluated on every EPS. The geometric properties of cubic MCs so far already reconstructed by EC, are then analyzed on the basis of the optimized EPSs. The analysis provides the property of the mesopores independently from gas adsorption measurements. A large cage-like MC is further studied by in-situ synchrotron powder X-ray diffraction to help understand the nitrogen adsorption process onto the mesopore wall.

    As an additional study, a silica MC showing its crystal morphologies of icosahedron, decahedron, etc. is studied. Results by EC suggest that the spherical uni-modal cages form the cubic close packing. The morphologies observed are explained in terms of the multiple twinning, which is analogous to metal nanoparticles. The occurrence of multiple twinning in MCs is discussed in light of the synthesis condition and the shape of micelles.

  • 383.
    Miyasaka, Keiichi
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Han, Lu
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Che, Shunai
    Terasaki, Osamu
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    A lesson from the unusual morphology of silica mesoporous crystals: Growth and close packing of spherical micelles with multiple twinning2006In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 45, no 39, p. 6516-6519Article in journal (Refereed)
  • 384.
    Miyasaka, Keiichi
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Muroyama, Norihiro
    Hano, Hiroko
    Lin, Jangzheng
    Kubota, Yoshiki
    Ryoo, Ryong
    Neimark, Alexander V.
    Terasaki, Osamu
    A study of gas adsorption process of mesoporous silica SBA-16 crystal with large cage-like poresManuscript (Other academic)
  • 385.
    Miyasaka, Keiichi
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry, Structural Chemistry.
    Neimark, Alex V
    Terasaki, Osamu
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Density Functional Theory of in Situ Synchrotron Powder X-ray Diffraction on Mesoporous Crystals: Argon Adsorption on MCM-412009In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 113, no 3, p. 791-794Article in journal (Refereed)
    Abstract [en]

    Bioactive microspheres with ordered mesoporous structure have been synthesized by means of the evaporation-induced self-assembly (EISA) method and following an aerosol-assisted route. The bioactive microspheres belong to the SiO2-CaO-P2O5 systems, and the mesoporous structure closely depends on the structure-directing agent as well as its interaction with the Ca2+ cations during the mesophase formation. Among the different tested surfactants, the triblock copolymer F127 leads to hexagonal ordered structures for low CaO contents, P123 leads to wormlike mesoporous structures for any CaO content, whereas the ionic surfactant cetyltrimethyl ammonium bromide (C16TAB) does not produce accessible mesopores at the external surface, for any CaO content. All the mesoporous SiO2-CaO-P2O5 microspheres develop an apatite like layer when reacting with simulated body fluid. Preliminary tests indicate the capability to load and release triclosan with kinetic profiles that depend on the pore structure, thus showing interesting features to be used in periodontal regenerative surgery and infection profilaxis

  • 386.
    Molla-Abbassi, Alireza
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Eriksson, Lars
    Mink, Janos
    Persson, Ingmar
    Sandström, Magnus
    Skripkin, Mkhail
    Ullström, Ann-Sofi
    Lindqvist-Reis, Patric
    Stucture and bonding of bisaquamercury(II) and trisaquathallium(III) trifluoromethanesulfonate2002In: Journal of the Chemical Society. Dalton transactions, ISSN 1364-5447, no 23, p. 4357-4364Article in journal (Refereed)
  • 387.
    Molla-Abbassi, Alireza
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Skripkin, Mikhail
    Kritikos, Mikael
    Persson, Ingmar
    Mink, Janos
    Sandström, Magnus
    Dimethyl sulfoxide solvates of the aluminium(III), gallium(III) and indium(III) ions: A crystallographic, EXAFS and vibrational spectroscopic study2003In: Journal of the Chemical Society. Dalton transactions, ISSN 1364-5447, no 9, p. 1746-1753Article in journal (Refereed)
  • 388. Monteverde, M
    et al.
    Núñez-Regueiro, M
    Acha, C
    Lokshin, K A
    Pavlov, Dmitriy A.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Putilin, S N
    Antipov, E V
    Fluorinated Hg-1223 under pressure: the ultimate Tc of the cuprates?2004In: Physica. C, Superconductivity, ISSN 0921-4534, E-ISSN 1873-2143, Vol. 408-410, p. 23-24Article in journal (Refereed)
    Abstract [en]

    High pressure experiments have revealed that Tc is affected by two main pressure-dependent parameters: the doping level of the CuO2 planes and by an intrinsic factor. The origin of the intrinsic factor is still unclear as, depending on the experiment, it is associated with the reduction of the c or the a lattice parameters. F incorporation into the Hg-1223 structure yields an enhancement of Tc up to a susceptibility onset of 138 K, mainly related to a compression of the a crystallographic axis. We have obtained a new high Tc record (166 K ± 1.5 K) by applying pressure (23 GPa) in the fluorinated Hg-1223 superconductor optimally doped. Tc increases with increasing pressure, reaching different maximum values, depending on the F doping level, and decreases for a further increase of pressure. This saturation of Tc may be the highest Tc that can be obtained for the cuprates, considering the particular structural characteristics of this system.

  • 389. Moser, D
    et al.
    Bull, DJ
    Sato, T
    Noreus, D
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Kyoi, D
    Sakai, T
    Kitamura, N
    Yusa, H
    Taniguchi, T
    Kalisvaart, WP
    Notten, P
    Structure and stability of high pressure synthesized Mg-TM hydrides (TM = Ti, Zr, Hf, V, Nb and Ta) as possible new hydrogen rich hydrides for hydrogen storage.2009In: Journal of Materials Chemistry, Vol. 19, no 43, p. 8150-Article in journal (Refereed)
    Abstract [en]

    A series of hydrogen rich Mg6–7TMH14–16 (TM = Ti, Zr, Hf, V, Nb and Ta) hydrides have been synthesized at 600 °C in a high pressure anvil cell above 4 GPa. All have structures based on a fluorite type metal atom subcell lattice with a ≈ 4.8 Å. The TM atom arrangements are, however, more ordered and can best be described by a superstructure where the 4.8 Å FCC unit cell axis is doubled. The full metal atom structure corresponds to the Ca7Ge type structure. This superstructure was also observed from electron diffraction patterns. The hydrogen atoms were found from powder X-ray diffraction using synchrotron radiation to be located in the two possible tetrahedral sites. One coordinates three Mg atoms and one TM atom and another coordinates four Mg atoms. These types of new hydrogen rich hydrides based on immiscible metals were initially considered as metastable but have been observed to be reversible if not fully dehydrogenated. In this work, DFT calculations suggest a mechanism whereby this can be explained: with H more strongly bonded to the TM, it is in principle possible to stepwise dehydrogenate the hydride. The remaining hydrogen in the tetrahedral site coordinating the TM would then act to prevent the metals from separating, thus making the system partially reversible

  • 390.
    Moustiakimov, Marat
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    X-ray structural studies of lanthanide alkoxides2003Doctoral thesis, comprehensive summary (Other academic)
    Abstract [sv]

    A number of homo- and hetero-metallic lanthanide (oxo-)isopropoxides with the general composition LnxMyO(OiPr)p(HOiPr)q has been structurally characterized by means of single crystal X-ray diffraction. The studied compounds may be divided into five groups by the geometry of their metal-oxygen core.

    1) M5O(OiPr)13 (M = Er, Eu, Gd) and [(Eu2+)(Eu3+)4O(OiPr)12(HOiPr)]*(HOiPr). In this system the flexibility of the close-packed molecular framework with respect to orientation of the molecules and the possibility to incorporate solvent molecules has been shown.

    2) (Tb0.9Er0.1)4TiO(OiPr)14, Er4SbO(OiPr)13 and Er2M2TiO(OiPr)14 (M = La, Sc). Three geometrically distinct metal positions may be identified in the common M4TiO(OiPr)14 system, so that metal composition may be stated as M2M’2Ti. The successful substitution in the Er4TiO(OR)14 molecule of Ti for Sb and of two Er atoms for La has been performed.

    3) M[Al(OiPr)4]3 (M = Nd, Eu). The phase transition from orthorhombic modification at room temperature to monoclinic at 110 K has been observed when M = Nd. Both compounds form pseudo-merohedrally twinned crystals at low temperature.

    4) [(Eu3+)2(Eu2+)2(OiPr)10(HOiPr)3]*2(HOiPr) is probably the first mixed valence Eucontaining alkoxide structurally characterized. It also exhibits rare four-dentate [OiPr]1- ligand.

    5) Er4Cs2O(OiPr)12 and Er4(Na0.75Er0.25)2O(OiPr)13(HOiPr). The two chemically related phases display similar molecular geometry with distorted octahedral configuration of metal atoms. Yet the relative arrangement of two alkali elements within the octahedron is different: trans for Na and cis for Cs.

  • 391.
    Muroyama, N.
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Ohsuna, T.
    Ryoo, R.
    Kubota, Y.
    Terasaki, O.
    An Analytical Approach to Determine the Pore Shape and Size of MCM-41 Materials from X-ray Diffraction Data2006In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 110, no 22, p. 10630-10635Article in journal (Refereed)
  • 392.
    Muroyama, N.
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Yoshimura, A.
    Kubota, Y.
    Ryoo, R.
    Takata, M.
    Terasaki, O.
    Argon adsorption on MCM-48 mesoporous crystal studied by in situ synchrotron powder X-ray diffractionManuscript (Other academic)
  • 393.
    Muroyama, Norihiro
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Studies of inorganic crystal structures and gas adsorption process in mesoporous crystals: New approach through analysis of electron charge distribution by synchrotron powder X-ray diffraction2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Using synchrotron powder XRD experiments, I studied (i) structures of silica mesoporous MCM-41 and MCM-48 crystals, (ii) gas adsorption processes of Ar and N2 in the mesopores of the mesoporous crystals, and (iii) bonding features of CaAl2-xZnx crystals through the analysis of electron charge density distributions.

    In the case of mesoporous crystals, the following two different approaches were taken depending on the number of observed X-ray reflections

    1. The analytical expression was chosen and further developed to study the size and shape of the mesopores with the plane group of p6mm by powder XRD experiments. For MCM-41, following the determination of the mesopores’ size and shape, and the thickness of the adsorbed gas layer as a function of the gas pressure were successfully observed. In addition, for carbon pipe mesoporous crystals CMK-5, the carbon pipe thickness was determined and the diffraction pattern was discussed quantitatively focusing on the “accidental extinction.”

    2. Maximum entropy method (MEM) was used for the structural study of MCM-48 (3D bicontinuous Ia-3d ) and for the gas adsorption process within the mesopores.

    By adopting the MEM approach, the study of “bonding electrons” and associated atomic displacements from the ideal Kagome net in the Laves phase CaAl2-xZnx were observed. In particular, the two Kagome nets in the C36 structure showed different feature in the electron density distributions between each other.

  • 394.
    Muroyama, Norihiro
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Yoshimura, Arisa
    Kubota, Yoshiki
    Miyasaka, Keiichi
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Ohsuna, Tetsu
    Ryoo, Ryong
    Ravikovitch, Peter.I.
    Neimark, Alexander.V.
    Takata, Masaki
    Terasaki, Osamu
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Argon adsorption on MCM-41 mesoporous crystal studied by in situ synchrotron powder X-ray diffraction2008In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 112, no 29, p. 10803-10813Article in journal (Refereed)
    Abstract [en]

    Equilibrium argon adsorption from the gas phase on mesoporous MCM-41 silica of hexagonal structure is directly studied by in situ synchrotron powder X-ray diffraction (XRD) measurements at SPring-8. The diffraction intensity data is analyzed by extending the previously developed analytical formula for the crystal structure factors of MCM-41 to account for argon adsorbed in the pores. It is clearly observed that argon adsorbs in layers on the pore walls at low gas pressures and exhibits sudden capillary condensation as the gas pressure increased. The proposed method of interpretation of XRD data allows one to calculate the density ratio between the silica wall and condensed argon, the pore size, and the pore wall fluctuation/roughness, together with the thickness of the adsorbed layer as a function of the gas pressure. The results of in situ XRD experiments are compared with the results of argon adsorption volumetric experiments. The adsorption data are interpreted with the quench solid density functional theory (QSDFT), which takes into account the pore wall roughness. The perfect agreement of the QSDFT isotherm predicted from the adsorption data and the XRD recalculated isotherm suggests that the adsorption porosimetry and XRD measurements can be reconciled provided a proper interpretation of the experimental data.

  • 395. Nakata, Yoshiki
    et al.
    Tsuchida, Kunio
    Miyanaga, Noriaki
    Furusho, Hirotoshi
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Liquidly process in femtosecond laser processing2009In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 255, no 24, p. 9761-9763Article in journal (Refereed)
    Abstract [en]

    Nano-sized water-crown like structure in array was firstly generated onmetallic thin film by interfering femtosecond laser processing. We named the structure as ‘‘nanocrown’’. Ridges are standing on the edge of each ablated hole. The shapes of ridges are spike, nano-waterdrop and bead on column. The radius of the top of a spike was just 7 nm, which is far smaller than that of nanobump generated in the previous work. The self-rising in liquidly process result in the generation of mesoscopic nanostructure with the size between nanohorn or nanotube and micron structures processed by machining or lithography. This is a new surface modification technique in top-down technology.

  • 396. Napat, C.
    et al.
    Tanaka, Satoshi
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Uematsu, K.
    Development of packing structure of tape casting2007In: Journal of Ceramics Society of Japan, Vol. 115, p. 136-140Article in journal (Refereed)
  • 397.
    Ng, Jovice Boon Sing
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Harnessing Mesoporous Spheres - transport studies and biotechnological applications2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Applications in controlled release and delivery calls for a good understanding of molecular transport within the carrier material and the dominating release mechanisms. It is clear that a better understanding of hindered transport and diffusion of guest molecules is important when developing new porous materials, e.g., surfactant templated silica spheres, for biotechnological applications. Confocal laser scanning microscopy was used to quantify the bulk release and intraparticle transport of small charged fluorescent dyes, and fluorescently-tagged neutral dextran, from mesoporous silica spheres. The time dependent release and the concentration profiles within the spheres have been used to analyze the release mechanisms using appropriate models. While the small, non-adsorbing anionic dye is released following a simple diffusion driven process, the concentration of the cationic dye varies radially within the spheres after loading. The release of the cationic dye is controlled by diffusion after an initial period of rapid release, which could be due to a significant fraction of the cationic dye that remains permanently attached to the negatively charged walls of the mesoporous silica spheres. The diffusion of dextran and the resulting flat concentration profiles could be related to the complex structural feature of the cylindrical pores close to the surface, and a possible conformational change of the dextran with the concentration. The stability and leaching of a catalytic enzyme, lipase, immobilized in hydrophobilized mesoporous support has also been quantified. Colloidal monodisperse mesoporous silica spheres were synthesized and transmission electron microscopy showed that the inner pore structure display a radially extending pores. The mesoporous spheres were used as solid supports for a lipid membrane incorporated with a multi-subunit redox-driven proton pump, which was shown to remain functional.

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  • 398.
    Ng, Jovice Boon Sing
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Brismar, Hjalmar
    Kamali-Zare, Padideh
    Release and molecular transport of cationic and anionic fluorescent molecules in mesoporous silica spheres2008In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, no 19, p. 11096-11102Article in journal (Refereed)
    Abstract [en]

    We describe here a method for study of bulk release and local molecular transport within mesoporous silica spheres. We have analyzed the loading and release of charged fluorescent dyes from monodisperse mesoporous silica (MMS) spheres with an average pore size of 2.7 nm. Two different fluorescent dyes, one cationic and one anionic, have been loaded into the negatively charged porous material and both the bulk release and the local molecular transport within the MMS spheres have been quantified by confocal laser scanning microscopy. Analysis of the time-dependent release and the concentration profiles of the anionic dye within the spheres show that the spheres are homogeneous and that the release of this nonadsorbing dye follows a simple diffusion-driven process. The concentration of the cationic dye varies radially within the MMS spheres after loading; there is a significantly higher concentration of the dye close to the surface of the spheres (forming a “skin”) compared to that at the core. The release of the cationic dye is controlled by diffusion after an initial period of rapid release. The transport of the cationic dye within the MMS spheres of the dye from the core to near the surface is significantly faster compared to the transport within the surface “skin”. A significant fraction of the cationic dye remains permanently attached to the negatively charged walls of the MMS spheres, preferentially near the surface of the spheres. Relating bulk release to the local molecular transport within the porous materials provides an important step toward the design of new concepts in controlled drug delivery and chromatography.

  • 399.
    Ng, Jovice Boon Sing
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry, Inorganic Chemistry.
    Kamali-Zare, Padideh
    Division of Cell Physics, Department of Applied Physics, AlbaNova, KTH.
    Sörensen, Malin
    YKI, Institute of Surface Chemistry.
    Alberius, Peter
    YKI, Institute of Surface Chemistry.
    Brismar, Hjalmar
    Division of Cell Physics, Department of Applied Physics, AlbaNova, KTH.
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry, Inorganic Chemistry.
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry, Inorganic Chemistry.
    Intraparticle Transport and Release of Dextran in Silica Spheres with Cylindrical Mesopores2010In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 6, no 1, p. 466-470Article in journal (Refereed)
    Abstract [en]

    The transport of oligomeric molecules in silica spheres with cylindrical mesopores has been quantified and related to the features of the internal structures in the spherical particles and the interactions at the polymer-pore interface. An emulsion-solvent-evaporation method was used to produce silica spheres having cylindrical mesopores with an average pore diameter of 6.5 nm. The transport of dextran molecules (fluorescently tagged) with molecular weights of 3000 and 10000 g/mol were quantified using confocal laser scanning microscopy (CLSM). The intraparticle concentrations profiles in the dextran-containing spheres were flat at all times, suggesting that the underpinning diffusion is not fully isotropic and the release is controlled by the pores close to the external surface of the spheres. The release of dextran into the solution is characterized by an initial burst, followed by a long-term sustained release. This behaviour cannot be described by a spherical model with a single diffusion constant (or a surface-induced mass transfer resistance). The release follows a logarithmic time-dependency that can be described by a Temkin model.

  • 400.
    Ng, Jovice Boon Sing
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Vasiliev, Petr
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    The radial dependence of the spatial mesostructure of monodisperse mesoporous silica spheres2008In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 112, p. 589-596Article in journal (Refereed)
    Abstract [en]

    The pore structure of monodisperse mesostructured silica spheres has been investigated by a combination of X-ray diffraction, nitrogen sorption isotherms and transmission electron microscopy (TEM). The radial dependence of the mesostructure has been obtained by TEM analysis of thin microtomed slices taken at different distance from the particle core. A structural model is proposed based on the TEM observations where bundles of the hexagonally ordered cylindrical channels bend and twist, without any preferred direction, close to the particle core and attain a radially extended structure closer to the particle surface. Thermal calcination results in a pore shrinkage of about 16% and some loss of the long-range mesostructure while radiative disintegration and partial removal of the organic template by an UV/Ozone treatment had a negligible effect on the inorganic framework in terms of pore size or spatial pore arrangement.

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