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  • 51.
    Akhtar, Farid
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Rehman, Yaser
    Department of Metallurgical and Materials Engineering, University of Engineering and Technology Lahore, Pakistan.
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    A study of the sintering of diatomaceous earth to produce porous ceramic monolithswith bimodal porosity and high strength2010In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 201, p. 253-257Article in journal (Refereed)
    Abstract [en]

    Diatomite powder, a naturally occurring porous raw material, was used to fabricate ceramic materials withbimodal porosity and high strength. The effect of the sintering temperature on the density and porosity ofdry pressed diatomite green bodies was evaluated using mercury porosimetry and water immersionmeasurements. It was found that the intrinsic porosity of the diatomite particles with a pore size around0.2 μm was lost at sintering temperatures above 1200 °C. Maintaining the sintering temperature at around1000 °C resulted in highly porous materials that also displayed a high compressive strength. Microstructuralstudies by scanning electron microscopy and energy-dispersive X-ray analysis suggested that the porecollapse was facilitated by the presence of low melting impurities like Na2O and K2O.

  • 52.
    Akhtar, Farid
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Sjöberg, Erik
    Korelskiy, Danil
    Rayson, Mark
    Hedlund, Jonas
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Preparation of graded silicalite-1 substrates for all-zeolite membranes with excellent CO2/H-2 separation performance2015In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 493, p. 206-211Article in journal (Refereed)
    Abstract [en]

    Graded silicalite-1 substrates with a high gas permeability and low surface roughness have been produced by pulsed current processing of a thin coating of a submicron silicalite-1 powder onto a powder body of coarser silicalite-1 crystals. Thin zeolite films have been hydrothermally grown onto the graded silicalite-1 support and the all-zeolite membranes display an excellent CO2/H-2 separation factor of 12 at 0 degrees C and a CO2 permeance of 21.3 x 10(-7) mol m(-2) s(-1) Pa-1 for an equimolar CO2/H-2 feed at 505 kPa and 101 kPa helium sweep gas. Thermal cracking estimates based on calculated surface energies and measured thermal expansion coefficients suggest that all-zeolite membranes with a minimal thermal expansion mismatch between the graded substrate and the zeolite film should remain crack-free during thermal cycling and the critical calcination step.

  • 53.
    Alam, Rauful
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Das, Arindam
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Huang, Genping
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Himo, Fahmi
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Stereoselective allylboration of imines and indoles under mild conditions. An in situ E/Z isomerization of imines by allylboroxines2014In: Chemical Science, ISSN 2041-6520, E-ISSN 2041-6539, Vol. 5, no 7, p. 2732-2738Article in journal (Refereed)
    Abstract [en]

    Direct allylboration of various acyclic and cyclic aldimine, ketimine and indole substrates was performed using allylboronic acids. The reaction proceeds with very high anti-stereoselectivity for both E and Z imines. The allylboroxines formed by dehydration of allylboronic acids have a dual effect: promoting E/Z isomerization of aldimines and triggering the allylation by efficient electron withdrawal from the imine substrate.

  • 54.
    Alam, Rauful
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Diner, Colin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Jonker, Sybrand
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Catalytic Asymmetric Allylboration of Indoles and Dihydroisoquinolines with Allylboronic Acids: Stereodivergent Synthesis of up to Three Contiguous Stereocenters2016In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 55, no 46, p. 14417-14421Article in journal (Refereed)
    Abstract [en]

    The catalytic asymmetric allylboration of cyclic imines with gamma,gamma-disubstituted allylboronic acids provides products with adjacent stereocenters in high yield and stereoselectivity. Various electrophiles, including 3,4-dihydroisoquinolines and indoles, were prenylated in a fully stereodivergent fashion by switching the E/Z geometry of the allylboronate and/or the enantiomer of the BINOL catalyst. 3-Methylindole provided products with three adjacent stereocenters with high stereoselectivity in one synthetic operation.

  • 55.
    Alam, Rauful
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Mihai, Raducan
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Szabo, Kalman J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Selective Formation of Adjacent Stereocenters by Allylboration of Ketones under Mild Neutral Conditions2013In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 15, no 10, p. 2546-2549Article in journal (Refereed)
    Abstract [en]

    Allylboronic acids readily react with a broad variety of ketones, affording homoallylic alcohols with adjacent quaternary and tertiary stereocenters. The reaction proceeds with very high anti stereoselectivity even if the substituents of the keto group have a similar size. a-Keto acids react with syn stereoselectivity probably due to the formation of acyl boronate intermediates. The allylation reactions proceed without added acids/bases under mild conditions. Because of this, many functionalities are tolerated even with in situ generated allylboronic acids.

  • 56.
    Alam, Rauful
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Raducan, Mihai
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Diastereoselective allylboration of wide variety of carbonyl compounds using allylboronic acids: Construction of adjacent tertiary and quaternary centers2013In: Abstracts of papers of The American Chemical Society, American Chemical Society (ACS), 2013, Vol. 246, p. 364-ORGN-Conference paper (Refereed)
  • 57.
    Alam, Rauful
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Vollgraff, Tobias
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Synthesis of Adjacent Quaternary Stereocenters by Catalytic Asymmetric Allylboration2015In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 137, no 35, p. 11262-11265Article in journal (Refereed)
    Abstract [en]

    Allylboration of ketones with gamma-disubstituted allylboronic acids is performed in the presence of chiral BINOL derivatives. The reaction is suitable for single-step creation of adjacent quaternary stereocenters with high selectivity. We show that, with an appropriate choice of the chiral catalyst and the stereoisomeric prenyl substrate, full control of the stereo- and enantioselectivity is possible in the reaction.

  • 58. Alammar, Tarek
    et al.
    Hamm, Ines
    Grasmik, Viktoria
    Wark, Michael
    Mudring, Anja-Verena
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Iowa State University, United States; U.S. Department of Energy, United States; Ruhr-Universität Bochum, Germany.
    Microwave-Assisted Synthesis of Perovskite SrSnO3 Nanocrystals in Ionic Liquids for Photocatalytic Applications2017In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 56, no 12, p. 6920-6932Article in journal (Refereed)
    Abstract [en]

    Nanosized SrSnO3 photocatalysts have been successfully synthesized by microwave synthesis in various ionic liquids (ILs) followed by a heat treatment process to optimize the materials' crystallinity. The influence of the ILs with various cations such as 1-butyl-3-methylimidazolium ([C(4)mim](+)), 6-bis(3-methylimidazolium-1-yl)hexane ([C-6(mim)(2)](2+)), butylpyridinium ([C4Py](+)), and tetradecyltrihexylphosphonium ([P-66614](+)) and bis(trifluoromethanesulfonyl)amide ([Tf2N](-)) as the anion on the structure, crystallization, and morphology of the products was investigated. The samples were characterized by X-ray diffraction (XRD), thermogravimetry (TG), scanning electron microscopy (SEM), surface area analysis by gas adsorption, X-ray photoelectron spectroscopy (XPS), diffuse reflectance UV vis spectroscopy, and Raman and IR spectroscopy. According to structure characterization by XRD and Raman spectroscopy all samples wcrystallized phase-pure in the orthorhombic GdFeO3 perovskite structure type. SEM reveals that, on the basis of the IL, th(e) obtained SrSnO3 nanoparticles exhibit different morphologies and sizes. Rod-shaped particles are formed in [C(4)minn][Tf2N], [C-6(mim)(2)][Tf2N](2), and p [P-66614][Tf2N]. However, the particle dimensions and size distribution vary depending on the IL and range from quite thin and long needlelike partinles with a narrow size distribution obtained in [P-66614] [TfA to relatively larger particles with a broader size distribution obtained in [C-6(mim)(2)][Tf2N](2). In contrast, in [C4Py][Tf2N] nanospheres with a diameter of about 50 nm form. For these particles the highest photocatalytic activity was observed. Our investigations indicate that the improved photocatalytic activity of this material results from the synergistic effect of the relatively large surface area associated with nanosize and an appropriate energy band structure.

  • 59. Alammar, Tarek
    et al.
    Hlova, Ihor Z.
    Gupta, Shalabh
    Balema, Viktor
    Pecharsky, Vitalij K.
    Mudring, Anja-Verena
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Iowa State University, USA.
    Luminescence properties of mechanochemically synthesized lanthanide containing MIL-78 MOFs2018In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 47, no 22, p. 7594-7601Article in journal (Refereed)
    Abstract [en]

    Three metal-organic framework (MOF) compounds, Ln(0.6) Gd-0.(6) {C6H (COO)(3)); Ln = Eu, Tb, and Dy with a MIL-78 structure, have been synthesized by a solvent-free mechanochemical method from stoichiometric mixtures of benzene 1,3,5-tricarboxylic acid, C6H3 (COOH)(3), also known as trimesic acid, and the respective lanthanide carbonates, Ln(2)(CO3)(3)center dot xH(2)O, Ln = Eu, Gd, Tb and Dy. MIL-78 (Ln(0.5)Gd(0.)(6)) shows the characteristic red, green, and yellow luminescence of Eu3+, Tb3+, and Dy3+, respectively. Efficient intramolecular energy transfer from the ligand triplet state to the excited states of Ln(3+) ions can be observed. The lifetimes and quantum yields of these compounds are studied and discussed in detail. Among the three compounds, the Tb3+ containing compound shows the longest lifetime and highest quantum yield due to a smaller contribution from non-radiative decay pathways and better matching of the lowest triplet energy level of the benzenetricarboxylate ligand and the resonance level of Tb3+.

  • 60. Albat, Martin
    et al.
    Inge, Andrew Kentaro
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Stock, Norbert
    Synthesis and crystal structure of three new bismuth(III) arylsulfonatocarboxylates2017In: Zeitschrift für Kristallographie - Crystalline Materials, ISSN 2194-4946, Vol. 232, no 1-3, p. 245-253Article in journal (Refereed)
    Abstract [en]

    Three new bismuth arylsulfonatocarboxylates [Bi(OH)(SB)] (1), [Bi-4(ST)(2)(HST)O-2(H2O)(2)]center dot H2O (2) and [Bi-4(ST)(2)O-3(H2O)(2)] (3) were synthesized under solvothermal reaction conditions at 180 degrees C using the potassium or sodium salt of 4-sulfobenzoic acid (H2SB) and 2-sulfoterephthalic acid (H3ST), respectively. The compounds were characterized in detail and the crystal structures were determined from single crystal X-ray diffraction data. Phase purity was confirmed by powder X-ray diffraction and elemental analysis. Structural comparisons to the only three other known bismuth sulfonatocarboxylates are presented. Due to the higher reaction temperatures employed for the synthesis of the title compounds a higher degree of condensation of the BiOx polyhedra (X = 7 or 8) to tetrameric units, 1D chains or a 2D layer is observed. Connection through the organic linker molecules leads to the formation of 3D coordination polymers in all three title compounds.

  • 61. Alexander, Jan
    et al.
    Benford, Diane
    Boobis, Alan
    Bergman, Åke
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Environmental Chemistry.
    Scientific Opinion on Hexabromocyclododecanes (HBCDDs) in Food2011In: EFSA Journal, ISSN 1831-4732, Vol. 9, no 7, p. 2296-Article in journal (Other academic)
    Abstract [en]

    EFSA was asked by the European Commission to deliver a scientific opinion on hexabromocyclododecanes (HBCDDs) in food. HBCDDs are additive flame retardants primarily used in expanded and extruded polystyrene applied as construction and packing materials, and in textiles. Technical HBCDD predominantly consists of three stereoisomers (α-, β- and γ-HBCDD). Also δ- and ε-HBCDD may be present but at very low concentrations. HBCDDs are present in the environment and likewise in biota and in food and feed. Data from the analysis of HBCDDs in 1,914 food samples were provided to EFSA by seven European countries, covering the period from 2000 to 2010. The Panel on Contaminants in the Food Chain (CONTAM Panel) selected α-, β- and γ-HBCDD to be of primary interest. Since all toxicity studies were carried out with technical HBCDD, a risk assessment of individual stereoisomers was not possible. Main targets were the liver, thyroid hormone homeostasis and the reproductive, nervous and immune systems. HBCDDs are not genotoxic. The CONTAM Panel identified neurodevelopmental effects on behaviour as the critical endpoint, and derived a benchmark dose lower confidence limit for a benchmark response of 10 % (BMDL10) of 0.79 mg/kg body weight. Due to the limitations and uncertainties in the current data base, the CONTAM Panel concluded that it was inappropriate to use this BMDL to establish a health based guidance value, and instead used a margin of exposure (MOE) approach for the health risk assessment of HBCDDs. Since elimination characteristics of HBCDDs in animals and humans differ, the Panel used the body burden as starting point for the MOE approach. The CONTAM Panel concluded that current dietary exposure to HBCDDs in the European Union does not raise a health concern. Also additional exposure, particularly of young children, to HBCDDs from house dust is unlikely to raise a health concern

  • 62. Alexander, Jan
    et al.
    Benford, Diane
    Boobis, Alan
    Bergman, Åke
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Environmental Chemistry.
    Scientific Opinion on Polybrominated Diphenyl Ethers (PBDEs) in Food2011In: EFSA Journal, ISSN 1831-4732, Vol. 9, no 5, p. 2156-Article in journal (Other academic)
  • 63. Alexander, Jan
    et al.
    Benford, Diane
    Boobis, Alan
    Bergman, Åke
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Environmental Chemistry.
    Scientific Opinion on Tetrabromobisphenol A (TBBPA) and its derivatives in food: EFSA Panel on Contaminants in the Food Chain (CONTAM)2011In: EFSA Journal, ISSN 1831-4732, Vol. 9, no 12, p. 2477-Article in journal (Refereed)
    Abstract [en]

    EFSA was asked by the European Commission to deliver a scientific opinion on tetrabromobisphenol A (TBBPA) and its derivatives in food. TBBPA and its derivatives are widely used as flame retardants. TBBPA is primarily used as reactive flame retardant covalently bound to epoxy and polycarbonate resins. TBBPA derivatives are used as either reactive or additive intermediates in polymer manufacture. Data from the analysis of TBBPA in 344 food samples were submitted to EFSA by two European countries (Norway and Spain), covering the period from 2007 to 2010. All samples were in the food group “Fish and other seafood”, and all analytical results were reported as less than the limit of quantification (LOQ) (about 1 ng/g wet weight). Toxicological studies with TBBPA have been carried out using different experimental designs with single or repeated administration during gestation, postnatally or in adulthood. The main target is thyroid hormone homeostasis. TBBPA is not genotoxic. There are no indications that TBBPA might be carcinogenic. The Panel on Contaminants in the Food Chain (CONTAM Panel) identified a lower confidence limit for a benchmark response of 10 % (BMDL10) of 16 mg/kg b.w. reported for changes in thyroid hormones as the critical reference point. Due to the limitations and uncertainties in the database, the CONTAM Panel concluded that it was inappropriate to use this BMDL to establish a health based guidance value, and therefore used a margin of exposure (MOE) approach for the health risk assessment of TBBPA. In view of the large MOEs, the CONTAM Panel concluded that current dietary exposure to TBBPA in the European Union does not raise a health concern. Also exposure of infants via human milk does not raise a health concern. Additional exposure, particularly of young children, to TBBPA from house dust is unlikely to raise a health concern.

  • 64. Alfonso E., Garcia-Bennett
    et al.
    Xiao, Changhong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Chunfang, Zhou
    Toen, Castle
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Keiichi, Miyasaka
    Osamu, Terasaki
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bicontinuous Cubic Mesoporous Materials with Biphasic Structures2011In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 17, no 48, p. 13510-13516Article in journal (Refereed)
    Abstract [en]

    The replication of amphiphilic systems within an inorganic silica matrix allows the study of the fundamental properties of mesostructural changes, that is, kinetic and structural parameters. Herein we report a detailed study of the transition between cubic bicontinuous mesostructure with space groups Ia$\bar 3$d and Pn$\bar 3$m symmetry, which are associated with the minimal G and D surfaces, respectively. The transition may be induced through micellar swelling of the anionic amphiphilic surfactant N-lauroyl alanine by trimethylbenzene. Rich kinetic behaviour is observed and has been exploited to prepare particles with biphasic structures. Transmission electron microscopy evidence indicates that there is epitaxial growth from one mesostructure to the other involving the [111] and [110] orientations of the Ia$\bar 3$d and Pn$\bar 3$m symmetry structures, respectively. From kinetic studies, we show that the formation of the Ia$\bar 3$d mesophase is preceded by a hexagonal phase (plane group p6mm) and an epitaxial relationship has been observed involving the sixfold or $\bar 3$ axis orientations of both structures. Our data suggests that the Pn$\bar 3$m mesostructure is kinetically stable at low temperatures whereas the Ia$\bar 3$d mesostructure is the more stable structure after prolonged periods of hydrothermal treatment. We present evidence from transmission electron microscopy and small-angle X-ray diffractograms and also electron crystallography modelling of the unit cells at particular points in the structural change.

  • 65.
    Ali, S. K. Imran
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Kremer, Reinhard K.
    Johnsson, Mats
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hydrothermal Synthesis of the Oxofluoride FeSbO2F2-An Anti-ferromagnetic Spin S=5/2 Compound2017In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 56, no 8, p. 4662-4667Article in journal (Refereed)
    Abstract [en]

    The new oxofluoride compound FeSbO2F2 was synthesized by hydro thermal techniques at 230 degrees C. Its crystal structure was determined from single-crystal Xray diffraction data. The compound crystallizes in the monoclinic space group C2/c with one crystallographic site for Fe3+ and SP3+, respectively. The crystal structure is made of [FeO2F4] octahedra and seesaw [SbO4] building blocks. These are connected to form [FeO2F2] layers and [SbO2] chains that bond together via the oxygen atoms to form the three-dimensional framework structure. Magnetic susceptibility and heat capacity measurements indicate long-range anti-ferromagnetic ordering below a Neel temperature of similar to 175 K Two-dimensional anti-ferromagnetic short-range order in the square planar net of the Fe3+ cations extends to temperatures far above the Neel temperature.

  • 66.
    Ali, Sk Imran
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Johnsson, Mats
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Antimony oxofluorides - a synthesis concept that yields phase pure samples and single crystals2016In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 45, no 30, p. 12167-12173Article in journal (Refereed)
    Abstract [en]

    The single crystals of the new isostructural compounds Sb3O4F and Y0.5Sb2.5O4F and the two previously known compounds M-SbOF and alpha-Sb3O2F5 were successfully grown by a hydrothermal technique at 230 degrees C. The new compound Sb3O4F crystallizes in the monoclinic space group P2(1)/c: a = 5.6107(5) angstrom, b = 4.6847(5) angstrom, c = 20.2256(18) angstrom, p = 94.145(8)degrees, z = 4. The replacing part of Sb with Y means a slight increase in the unit cell dimensions. The compounds M-SbOF and alpha-Sb3O2F5 have not been grown as single crystals before and it can be concluded that hydrothermal synthesis has proved to be a suitable technique for growing single crystals of antimony oxofluorides because of the relatively low solubility of such compounds compared to other antimony oxohalides that most often have been synthesised at high temperatures by solid state reactions or gas-solid reactions.

  • 67.
    Ali, Sk Imran
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Kremer, Reinhard K.
    Johnsson, Mats
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hydrothermal Synthesis and Magnetic Characterization of the Quaternary Oxide CoMo2Sb2O102016In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 55, no 21, p. 11490-11496Article in journal (Refereed)
    Abstract [en]

    The new quaternary layered oxide CoMo2Sb2O10 was synthesized by hydrothermal synthesis techniques, and its structure was determined from single-crystal X-ray diffraction data. CoMo2Sb2O10 crystallizes in the monoclinic space group C2/c with one Sb3+, Mo6+, and Co2+ atom site per unit cell, respectively. The crystal structure contains building units consisting of [Co2O8](n), [Mo2O8](n), and [SbO2](n) chains. These are connected through corner sharing to form charge neutral [CoMo2Sb2O10](n) layers. Thermal decomposition of CoMo2Sb2O10 starts at 550 degrees C. The magnetic susceptibility follows a Curie Weiss law above 50 K with a Curie constant of C = 3.46 emu K mol(-1) corresponding to an effective moment of mu(eff) = 5.26 mu(B) per cobalt atom and a Curie-Weiss temperature theta = -13.2 K. Short-range anti-ferromagnetic ordering dominates below 5 K. Magnetic susceptibility and heat capacity data can be successfully modeled by the predictions from an Ising linear chain with an intrachain spin exchange of ca. -7.8 K.

  • 68.
    Ali, Sk Imran
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). University of Kalyani, India.
    Lidin, Sven
    Johnsson, Mats
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Crystal Structure of the Disordered Non-Centrosymmetric Compound Fe0.43Mo2.56SbO9.52019In: Crystals, ISSN 2073-4352, Vol. 9, no 1, article id 40Article in journal (Refereed)
    Abstract [en]

    Single crystals of Fe0.43Mo2.56SbO9.5 were obtained by hydrothermal techniques at 230 degrees C. The crystal structure was determined from single crystal X-ray diffraction data. The compound crystallizes in the non-centrosymmetric space group Pc with unit cell parameters a = 4.0003(2) angstrom, b = 7.3355(3) angstrom, c = 12.6985(6) angstrom, = 90 degrees. The crystal structure comprises five crystallographically independent M atoms and one Sb3+ atom, M atoms are of two kinds of partially occupied sites Mo6+ and Fe3+. The building blocks consist of [SbO3O0.5O0.5E] octahedra (E = lone electron pair) and [(Mo/Fe)O-6] octahedra. The M = (Mo, Fe) and O atoms are arranged in a distorted hexagonal 2D-net, not the Sb atoms. The distortion of the net and consequently the symmetry reduction results mainly from the location of the Sb atoms. Disorder manifests itself as a splitting of the metal sites and as a consequent shortening of the Mo-Fe distances. Six (Mo/Fe)O-6 octahedra are connected to form a pseudohexagonal channel. The Sb3+ atom is displaced from the pseudo-six-fold axis.

  • 69. Ali, Sk Imran
    et al.
    Zhang, Weiguo
    Halasyamani, P. Shiv
    Johnsson, Mats
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Zn3Sb4O6F6: Hydrothermal synthesis, crystal structure and nonlinear optical properties2017In: Journal of Solid State Chemistry, ISSN 0022-4596, E-ISSN 1095-726X, Vol. 256, p. 158-161Article in journal (Refereed)
    Abstract [en]

    Zn3Sb4O6F6 has been synthesized hydrothermally at 230 degrees C. The crystal structure was determined from single crystal X-ray diffraction data. It crystallizes in the cubic non-centrosymmetric space group I-43m with the unit cell parameter a = 8.1291(4) angstrom and is isostructural with M3Sb4O6F6 (M = Co, Ni). The new compound is the first oxofluoride containing Zn2+ and a p-element cation with a stereochemically active lone pair. The crystal structure is made up by [ZnO2F4] octahedra forming a network via corner sharing at F-atoms and [SbO3] trigonal pyramids that form [Sb4O6] cages that connect via the O-atoms to the Zn-atoms. Powder second harmonic generation (SHG) measurements using 1064 nm radiation on Zn3Sb4O6F6 indicate an SHG intensity of approximately 40 x alpha-SiO2.

  • 70. Alkarmo, Walid
    et al.
    Ouhib, Farid
    Aqil, Abdelhafid
    Thomassin, Jean-Michel
    Yuan, Jiayin
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Gong, Jiang
    Vertruyen, Bénédicte
    Detrembleur, Christophe
    Jérôme, Christine
    Poly(ionic liquid)-Derived N-Doped Carbons with Hierarchical Porosity for Lithium- and Sodium-Ion Batteries2019In: Macromolecular rapid communications, ISSN 1022-1336, E-ISSN 1521-3927, Vol. 40, no 1, article id 1800545Article in journal (Refereed)
    Abstract [en]

    The performance of lithium- and sodium-ion batteries relies notably on the accessibility to carbon electrodes of controllable porous structure and chemical composition. This work reports a facile synthesis of well-defined N-doped porous carbons (NPCs) using a poly(ionic liquid) (PIL) as precursor, and graphene oxide (GO)-stabilized poly(methyl methacrylate) (PMMA) nanoparticles as sacrificial template. The GO-stabilized PMMA nanoparticles are first prepared and then decorated by a thin PIL coating before carbonization. The resulting NPCs reach a satisfactory specific surface area of up to 561 m(2) g(-1) and a hierarchically meso- and macroporous structure while keeping a nitrogen content of 2.6wt%. Such NPCs deliver a high reversible charge/discharge capacity of 1013 mA h g(-1) over 200 cycles at 0.4A g(-1) for lithium-ion batteries, and show a good capacity of 204 mAh g(-1) over 100 cycles at 0.1A g(-1) for sodium-ion batteries.

  • 71. Alm, Henrik
    et al.
    Scholz, Birger
    Kultima, Kim
    Nilsson, Anna
    Andren, Per E.
    Savitski, Mikhail M.
    Bergman, Åke
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Stigson, Michael
    Fex-Svenningsen, Asa
    Dencker, Lennart
    In Vitro Neurotoxicity of PBDE-99: Immediate and Concentration-Dependent Effects on Protein Expression in Cerebral Cortex Cells2010In: Journal of Proteome Research, ISSN 1535-3893, E-ISSN 1535-3907, Vol. 9, no 3, p. 1226-1235Article in journal (Refereed)
    Abstract [en]

    Polybrominated diphenyl ethers (PBDEs) are commonly used flame retardants in various consumer products. Pre- and postnatal exposure to congeners of PBDEs disrupts normal brain development in rodents. Two-dimensional difference gel electrophoresis (2D-DIGE) was used to analyze concentration-dependent differences in protein expression in cultured cortical cells isolated from rat fetuses (GD 21) after 24 h exposure to PBDE-99 (3, 10, or 30 mu M). Changes on a post-translational level were studied using a 1 h exposure to 30 mu M PBDE-99. The effects of 24 h exposure to 3 and 30 mu M PBDE-99 on mRNA levels were measured using oligonucleotide microarrays. A total of 62, 46, and 443 proteins were differentially expressed compared to controls after 24 h of exposure to 3, 10, and 30 mu M PDBE-99, respectively. Of these, 48, 43, and 238 proteins were successfully identified, respectively. We propose that the biological effects of low-concentration PBDE-99 exposure are fundamentally different than effects of high-concentration exposure. Low-dose PBDE-99 exposure induced marked effects on cytoskeletal proteins, which was not correlated to cytotoxicity or major morphological effects, suggesting that other more regulatory aspects of cytoskeletal functions may be affected. Interestingly, 0.3 and 3 mu M, but not 10 or 30 mu M increased the expression of phosphorylated (active) Gap43, perhaps reflecting effects on neurite extension processes.

  • 72. Amiri, Omid
    et al.
    Salavati-Niasari, Masoud
    Farangi, Mostafa
    Mazaheri, Mehdi
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bagheri, Samira
    Stable Plasmonic-Improved dye Sensitized Solar Cells by Silver Nanoparticles Between Titanium Dioxide Layers2015In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 152, p. 101-107Article in journal (Refereed)
    Abstract [en]

    Novel metal nanoparticles (NPs) are introduced as light-harvesting antennae to enhance photocurrent of photovoltaic cells. In this work, we examined the plasmonic enhancement of photocurrent in dye-sensitized solar cells with deposition of Ag NPs between different TiO2 layers. The I-V measurement showed clearly that the open-circuit voltage (V-OC) of cells doesn't depend on Ag existence in our cells configuration extremely, however the short-circuit photocurrent density (JSC) strongly depends on it. Deposition of Ag NPs on packing TiO2 layer (T1) and transparent layer of TiO2 (T-2) both had acceptable results. The solar cells performance by treatment of Ag was studied and the results indicated that time treatment of AgNO3 and KBH4 is a key parameter which has effect on the PCE of the device. Low time (1 min), hardly shows any effect while medium time (2 min) shows significant effect on device performance. Meanwhile to improve the stability of these cells, we have proposed a new sealing method to fabricate promising stabile dye synthesized solar cells.

  • 73. An, Di
    et al.
    Li, Hezhen
    Xie, Zhipeng
    Zhu, Tianbin
    Luo, Xudong
    Shen, Zhijian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Tsinghua University, China.
    Ma, Jing
    Additive manufacturing and characterization of complex Al2O3 parts based on a novel stereolithography method2017In: International Journal of Applied Ceramic Technology, ISSN 1546-542X, E-ISSN 1744-7402, Vol. 14, no 5, p. 836-844Article in journal (Refereed)
    Abstract [en]

    In this work, we prepared Al2O3 ceramic green parts with complex geometry and architecture using an additive manufacturing process based on stereolithography. The rheological and thermal behavior of Al2O3 slurry was firstly examined and used to establish the conditions for molding and debinding. As opposed to previous researches that only focused on manufacture techniques, the sintering behavior and densification process were systematically investigated. In addition, special attentions were paid to the evolution of microstructure between green bodies and sintered parts. The results showed that debound parts were equipped with uniform particle packing and narrow pore size distribution. The dimensions of the Al2O3 parts changed anisotropically with the different processing steps. The densification process was greatly accelerated by the decrease in pore size and annihilating of interconnected pores in which significant grain growth was observed above 1450 degrees C. The sintered part also had a homogeneous microstructure and no interface between adjacent layers. High densification (relative density of 99.1%) and much desirable Vickers hardness (17.9 GPa) of Al2O3 parts were achieved at the sintering temperature of 1650 degrees C.

  • 74.
    Anderlund, Magnus F.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zheng, J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ghiladi, M.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kritikos, Mikael
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Rivière, Erik
    Sun, Licheng
    Girerd, Jean-Jaques
    Åkermark, Björn
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    A New, Dinuclear High Spin Manganese(III) Complex with Bridging Phenoxy and Methoxy Groups. Structure and Magnetic Properties2006In: Inorganic Chemistry Communications, ISSN 1387-7003, E-ISSN 1879-0259, Vol. 9, no 12, p. 1195-1198Article in journal (Refereed)
    Abstract [en]

    A new μ-phenoxy-μ-metoxy di-manganese(III) complex with the trisphenolic ligand, 2,6-bis[((2-hydroxybenzyl)(2-pyridylmethyl)amino)methyl]-4-methylphenol, was isolated as a perchlorate salt. The X-ray structure shows that the two manganese(III) ions are in a distorted octrahedral enviroment with approximately perpendicular Jahn–Teller axes. Investigation of the molar magnetic susceptibility reveals a ferromagnetic coupling between the two high-spin manganese(III) ions. Fitting of the data led to g = 2 and J = 12.5 cm−1

  • 75.
    Andersson, Linnéa
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Shaping Macroporous Ceramics: templated synthesis, X-ray tomography and permeability2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Macroporous ceramic materials have found widespread technological application ranging from particulate filters in diesel engines, tissue engineering scaffolds, and as support materials in carbon capture processes. This thesis demonstrates how the pore space of macroporous alumina can be manipulated, analysed in three-dimensions (3D) using visualisation techniques, and functionalised with a CO2-adsorbing material.

    A novel method was developed to produce macroporous alumina materials: by combining sacrificial templating with thermally expandable polymeric microspheres and gel-casting of an alumina suspension. This method offers a versatile production of macroporous ceramics in which the level of porosity and the pore size distribution can easily be altered by varying the amount and type of spheres. The permeability to fluid flow could be regulated by controlling the connectivity of the pore space and the size of the smallest constrictions between the pores. Sacrificial templating with particle-coated expandable spheres significantly increased the fraction of isolated pore clusters and reduced both the sizes and the numbers of connections between neighbouring pores, compared to templating with un-coated spheres.

    The macroporous alumina materials were characterised with X-ray micro-computed tomography (μ-CT). The 3D data-sets obtained by X-ray μ-CT were used to calculate the spatial variation in porosity, the throat and pore size distributions and to calculate the permeability to fluid flow. The throat and pore size distributions were also able to be accurately quantified in only one extrusion and intrusion cycle with water-based porosimetry; a relatively novel and simple characterisation technique. The pore walls of the macroporous alumina materials were also coated with zeolite films by a colloidal processing technique. The CO2-uptake of the coated alumina materials and of hierarchically porous monoliths of zeolites was evaluated and compared.

  • 76.
    Andersson, Linnéa
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Akhtar, Farid
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Ojuva, Arto
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Colloidal processing and CO2-capture performance of hierarchically porous Al2O3-zeolite 13X composites2012In: Journal of Ceramic Science and Technology, ISSN 2190-9385, Vol. 3, no 1, p. 9-16Article in journal (Refereed)
    Abstract [en]

    Hierarchically porous composites for CO2-capture have been produced by coating the inner walls of foam-like macroporous alumina monoliths, produced by templated synthesis, with microporous zeolite 13X particles. Homogeneous and dense coatings of the particulate adsorbent were obtained when the impregnation process was performed at a pH above 9. At this pH-level the colloidally stable suspensions of the negatively charged zeolite 13X particles could fill all the voids of the highly connected pore space of the alumina supports and attach to the monolith walls, which had been pre-coated with poly(ethylene imine). A CO2-uptake as high as 5 mmol CO2/g zeolite 13X was achieved for alumina-zeolite 13X composites through minimisation of the added inorganic binder, kaolin, to only 3.0 wt% with respect to zeolite content, and through optimisation of the thermal treatment.

  • 77.
    Andersson, Linnéa
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Jones, Anthony C.
    Knackstedt, Mark A.
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Permeability, pore connectivity and critical pore throat control of expandable polymeric sphere templated macroporous alumina2011In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 59, no 3, p. 1239-1248Article in journal (Refereed)
    Abstract [en]

    We have regulated the permeability in macroporous alumina materials by manipulating the connectivity of the pore phase and the sizes of the smallest constrictions between connected pores. Templating with particle-coated expandable polymeric spheres (EPS) significantly increased the fraction of isolated pore clusters, and reduced both the sizes and the number of connections with neighboring pores, as determined by three-dimensional evaluation with X-ray micro-computed tomography. The stable particle coating, applied onto the EPS surfaces using polyelectrolyte multilayers, reduced the volume expansion and the coalescence of the EPS at elevated temperatures, which reduced the simulated permeability by as much as two orders of magnitude compared to templating with uncoated EPS in materials of similar porosities. We show that the Katz-Thompson model accurately predicts the permeability for the macroporous alumina materials with porosities of 46-76%. This suggests that the permeability to fluid flow in these materials is governed by the smallest constrictions between connected pores: the critical pore throat diameter.

  • 78.
    Andersson, Linnéa
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Jones, Anthony C.
    Department of Applied Mathematics, Research School of Physical Sciences and Engineering, Australian National University, Canberra, ACT 0200, Australia.
    Knackstedt, Mark A.
    Department of Applied Mathematics, Research School of Physical Sciences and Engineering, Australian National University, Canberra, ACT 0200, Australia.
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Three-dimensional structure analysis by X-ray micro-computed tomography of macroporous alumina templated with expandable microspheres2010In: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 30, no 12, p. 2547-2554Article in journal (Refereed)
    Abstract [en]

    The three-dimensional (3D) structures of macroporous alumina, produced by a novel method that combines gel casting with expandable polymericmicrospheres as a sacrificial templating material, have been characterised by X-ray micro-computed tomography (µ-CT). The grey-scale intensitytomogram data produced by the X-ray µ-CT was segmented into porous and solid phases and the individual pores were identified. We comparedtwo-dimensional slices of the analysed data with the corresponding scanning electron microscopy images and showed that the structural featuresof the pores were well reproduced in the X-ray µ-CT images. 3D visualisations of the pore structure and the pore network were also shown. Theopen porosity obtained from X-ray µ-CT corresponded well with the porosity derived from mercury porosimetry for pores larger than the voxeldimension (3 µm). The quantitative analysis also yielded information on the spatial variations in porosity and the number of connected neighboursof pores. The 3D data was used to relate the calculated permeability to the open porosity.

  • 79.
    Andersson, Linnéa
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Larsson, Per Tomas
    Department of Fibre and Polymer Technology, School of Chemical Science and Engineering, Royal Institute of Technology.
    Wågberg, Lars
    Department of Fibre and Polymer Technology, School of Chemical Science and Engineering, Royal Institute of Technology.
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Wallenberg Wood Science Center, Stockholm.
    Evaluating pore space in macroporous ceramics with water-based porosimetry2013In: Journal of The American Ceramic Society, ISSN 0002-7820, E-ISSN 1551-2916, Vol. 96, no 6, p. 1916-1922Article in journal (Refereed)
    Abstract [en]

    We show that water-based porosimetry (WBP), a facile, simple, and nondestructive porosimetry technique, accurately evaluates both the pore size distribution and throat size distribution of sacrificially templated macroporous alumina. The pore size distribution and throat size distribution derived from the WBP evaluation in uptake (imbibition) and release (drainage) mode, respectively, were corroborated by mercury porosimetry and X-ray micro-computed tomography (μ-CT). In contrast with mercury porosimetry, the WBP also provided information on the presence of “dead-end pores” in the macroporous alumina.

  • 80. Andersson, Ove
    et al.
    Häussermann, Ulrich
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    A Second Glass Transition in Pressure Collapsed Type II Clathrate Hydrates2018In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 122, no 15, p. 4376-4384Article in journal (Refereed)
    Abstract [en]

    Type II clathrate hydrates (CHs) M-17 H2O, with M = tetrahydrofuran (THF) or 1,3-dioxolane, are known to collapse, or amorphize, on pressurization to similar to 1.3 GPa in the temperature range 77-140 K. On heating at 1 GPa, these pressure-amorphized CH states show a weak, stretched sigmoid-shaped, heat-capacity increase because of a glass transition. Here we use thermal conductivity and heat capacity measurements to show that also type II CH with M = cyclobutanone (CB) collapses on isothermal pressurization and undergoes a similar, weak, glass transition upon heating at 1 GPa. Furthermore, we reveal for both THF CH and CB CH a second, much more pronounced, glass transition at temperatures above the thermally weak glass transition on heating in the 0.2-0.7 GPa range. This result suggests the general occurrence of two glass transitions in water-rich (94 mol %) pressure-collapsed CHs. Because of a large increase in dielectric permittivity concurrently as the weak heat capacity increase, the first glass transition must be due to kinetic unfreezing of water molecules. The thermal features of the second glass transition, measured on isobaric temperature cycling, are typical of a glass liquid glass transition, which suggests that pressure-amorphized CHs transform reversibly to liquids.

  • 81.
    Apostolopoulou-Kalkavoura, Varvara
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Gordeyeva, Korneliya
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Lavoine, Nathalie
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Thermal conductivity of hygroscopic foams based on cellulose nanofibrils and a nonionic polyoxamer2018In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 25, no 2, p. 1117-1126Article in journal (Refereed)
    Abstract [en]

    Nanocellulose-based lightweight foams are promising alternatives to fossil-based insulation materials for energy-efficient buildings. The properties of cellulose-based materials are strongly influenced by moisture and there is a need to assess and better understand how the thermal conductivity of nanocellulose-based foams depends on the relative humidity and temperature. Here, we report a customized setup for measuring the thermal conductivity of hydrophilic materials under controlled temperature and relative humidity conditions. The thermal conductivity of isotropic foams based on cellulose nanofibrils and a nonionic polyoxamer, and an expanded polystyrene foam was measured over a wide range of temperatures and relative humidity. We show that a previously developed model is unable to capture the strong relative humidity dependence of the thermal conductivity of the hygroscopic, low-density nanocellulose- and nonionic polyoxamer-based foam. Analysis of the moisture uptake and moisture transport was used to develop an empirical model that takes into consideration the moisture content and the wet density of the investigated foam. The new empirical model could predict the thermal conductivity of a foam with a similar composition but almost 3 times higher density. Accurate measurements of the thermal conductivity at controlled temperature and relative humidity and availability of simple models to better predict the thermal conductivity of hygroscopic, low-density foams are necessary for the development of nanocellulose-based insulation materials.

  • 82. Aramburo, Luis R.
    et al.
    Karwacki, Lukasz
    Cubillas, Pablo
    Asahina, Shunsuke
    de Winter, D. A. Matthijs
    Drury, Martyn R.
    Buurmans, Inge L. C.
    Stavitski, Eli
    Mores, Davide
    Daturi, Marco
    Bazin, Philippe
    Dumas, Paul
    Thibault-Starzyk, Frederic
    Post, Jan A.
    Anderson, Michael W.
    Terasaki, Osamu
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Weckhuysen, Bert M.
    The Porosity, Acidity, and Reactivity of Dealuminated Zeolite ZSM-5 at the Single Particle Level: The Influence of the Zeolite Architecture2011In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 17, no 49, p. 13773-13781Article in journal (Refereed)
    Abstract [en]

    A combination of atomic force microscopy (AFM), high-resolution scanning electron microscopy (HR-SEM), focused-ion-beam scanning electron microscopy (FIB-SEM), X-ray photoelectron spectroscopy (XPS), confocal fluorescence microscopy (CFM), and UV/Vis and synchrotron-based IR microspectroscopy was used to investigate the dealumination processes of zeolite ZSM-5 at the individual crystal level. It was shown that steaming has a significant impact on the porosity, acidity, and reactivity of the zeolite materials. The catalytic performance, tested by the styrene oligomerization and methanol-to-olefin reactions, led to the conclusion that mild steaming conditions resulted in greatly enhanced acidity and reactivity of dealuminated zeolite ZSM-5. Interestingly, only residual surface mesoporosity was generated in the mildly steamed ZSM-5 zeolite, leading to rapid crystal coloration and coking upon catalytic testing and indicating an enhanced deactivation of the zeolites. In contrast, harsh steaming conditions generated 550 nm mesopores, extensively improving the accessibility of the zeolites. However, severe dealumination decreased the strength of the Bronsted acid sites, causing a depletion of the overall acidity, which resulted in a major drop in catalytic activity.

  • 83. Asahina, Shunsuke
    et al.
    Suga, Mitsuo
    Takahashi, Hideyuki
    Jeong, Hu Young
    Galeano, Carolina
    Schueth, Ferdi
    Terasaki, Osamu
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Korea Advanced Institute of Science & Technology (KAIST), South Korea.
    Direct observation and analysis of york-shell materials using low-voltage high-resolution scanning electron microscopy: Nanometal-particles encapsulated in metal-oxide, carbon, and polymer2014In: APL materials, ISSN 2166-532X, Vol. 2, no 11, p. 113317-Article in journal (Refereed)
    Abstract [en]

    Nanometal particles show characteristic features in chemical and physical properties depending on their sizes and shapes. For keeping and further enhancing their features, the particles should be protected from coalescence or degradation. One approach is to encapsulate the nanometal particles inside pores with chemically inert or functional materials, such as carbon, polymer, and metal oxides, which contain mesopores to allow permeation of only chemicals not the nanometal particles. Recently developed low-voltage high-resolution scanning electron microscopy was applied to the study of structural, chemical, and electron state of both nanometal particles and encapsulating materials in york-shell materials of Au@C, Ru/Pt@C, Au@TiO2, and Pt@Polymer. Progresses in the following categories were shown for the york-shell materials: (i) resolution of topographic image contrast by secondary electrons, of atomic-number contrast by back-scattered electrons, and of elemental mapping by X-ray energy dispersive spectroscopy; (ii) sample preparation for observing internal structures; and (iii) X-ray spectroscopy such as soft X-ray emission spectroscopy. Transmission electron microscopy was also used for characterization of Au@C. (C) 2014 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.

  • 84. Asahina, Shunsuke
    et al.
    Takami, Seiichi
    Otsuka, Takeshi
    Adschiri, Tadafumi
    Terasaki, Osamu
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Exploitation of Surface-Sensitive Electrons in Scanning Electron Microscopy Reveals the Formation Mechanism of New Cubic and Truncated Octahedral CeO(2) Nanoparticles2011In: ChemCatChem, ISSN 1867-3880, E-ISSN 1867-3899, Vol. 3, no 6, p. 1038-1044Article in journal (Refereed)
    Abstract [en]

    Development of new analytical tools for nanostructures directly contributes to the study of catalysts. By using scanning electron microscopy (SEM) with a newly designed signal enhancer, we study cubic and truncated octahedral cerium oxide (CeO(2)) nanoparticles, which are composed of smaller primary octahedral CeO(2) and are formed through bond formation with hexanedioic acid. The signal enhancer is designed to efficiently collect secondary electrons of kinetic energy less than 10 eV; thus, it greatly improves the S/N ratio. On the basis of the observed SEM images and electron backscattered diffraction patterns of the cross section of the nanoparticles, we discuss the formation mechanism of the nanoparticles and speculate that the primary CeO(2) nanocrystals share their edges in the cubic nanoparticles and truncated octahedral nanoparticles. These results will contribute to the preparation of nanostructured metal oxide surfaces with controlled morphologies that could enhance catalytic activity.

  • 85. Asahina, Shunsuke
    et al.
    Uno, Shinobu
    Suga, Mitsuo
    Stevens, Sam
    Klingstedt, Miia
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Okano, Yasuyuki
    Kudo, Masato
    Schuth, Ferdi
    Anderson, Michael
    Adschiri, Tadafumi
    Terasaki, Osamu
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    A new HRSEM approach to observe fine structures of novel nanostructured materials2011In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 146, no 1-3, p. 11-17Article in journal (Refereed)
    Abstract [en]

    A new approach for observing fine structures of novel thin, nanostructured materials called through the employed to observe interesting features on a variety of new, catalyticallyimportant hierarchically porous rattlespheres.

  • 86. Asfaw, Habtom D.
    et al.
    Roberts, Matthew R.
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Younesi, Reza
    Valvo, Mario
    Nyholm, Leif
    Edstrom, Kristina
    Nanosized LiFePO4-decorated emulsion-templated carbon foam for 3D micro batteries: a study of structure and electrochemical performance2014In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 6, no 15, p. 8804-8813Article in journal (Refereed)
    Abstract [en]

    In this article, we report a novel 3D composite cathode fabricated from LiFePO4 nanoparticles deposited conformally on emulsion-templated carbon foam by a sot-gel method. The carbon foam is synthesized via a facile and scalable method which involves the carbonization of a high internal phase emulsion (polyHIPE) polymer template. Various techniques (XRD, SEM, TEM and electrochemical methods) are used to fully characterize the porous electrode and confirm the distribution and morphology of the cathode active material. The major benefits of the carbon foam used in our work are closely connected with its high surface area and the plenty of space suitable for sequential coating with battery components. After coating with a cathode material (LiFePO4 nanoparticles), the 3D electrode presents a hierarchically structured electrode in which a porous layer of the cathode material is deposited on the rigid and bicontinuous carbon foam. The composite electrodes exhibit impressive cyclability and rate performance at different current densities affirming their importance as viable power sources in miniature devices. Footprint area capacities of 1.72 mA h cm(-2) at 0.1 mA cm(-2) (lowest rate) and 1.1 mA h cm(-2) at 6 mA cm(-2) (highest rate) are obtained when the cells are cycled in the range 2.8 to 4.0 V vs. lithium.

  • 87. Asfaw, Habtom D.
    et al.
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Nyholm, Leif
    Edström, Kristina
    Over-Stoichiometric NbO2 Nanoparticles for a High Energy and Power Density Lithium Microbattery2017In: chemnanomat, ISSN 2199-692X, Vol. 3, no 9, p. 646-655Article in journal (Refereed)
    Abstract [en]

    Effective utilization of active materials in microbatteries can be enhanced by rational design of the electrodes. There is an increasing trend of using 3D electrodes that are coated in nanosized active materials to boost both energy and power densities. This article focuses on the fabrication of 3D electrodes based on monolithic carbon foams coated in over-stoichiometric NbO2 nanoparticles. The electrodes exhibit remarkable energy and power densities at various current densities when tested in lithium microbatteries. An areal capacity of around 0.7mAhcm(-2) and energy density up to 45mWhcm(-3) have been achieved. More than half of the areal capacity can be accessed at a current density of about 11mAcm(-2), with the corresponding energy and power densities being 21mWhcm(-3) and 1349mWcm(-3). These values are comparable to those of microsupercapacitors containing carbon and MnO2 nanomaterials. Furthermore, the electrochemical reversibility improves progressively upon cycling along with substantial increase in the charge transfer kinetics of the electrode. Based on impedance analyses almost a fourfold decrease in the charge transfer resistance has been observed over 25 cycles. Such enhancement of the electronic properties of NbO2 can account for the high electrochemical rate performance of the 3D electrodes.

  • 88. Ashour, Radwa M.
    et al.
    Abdelhamid, Hani Nasser
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Abdel-Magied, Ahmed F.
    Abdel-Khalek, Ahmed A.
    Ali, M. M.
    Uheida, A.
    Muhammed, Mamoun
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Dutta, Joydeep
    Rare Earth Ions Adsorption onto Graphene Oxide Nanosheets2017In: Solvent extraction and ion exchange, ISSN 0736-6299, E-ISSN 1532-2262, Vol. 35, no 2, p. 91-103Article in journal (Refereed)
    Abstract [en]

    Graphene oxide (GO) was synthesized and used as a coagulant of rare earth elements (REEs) from aqueous solution. Stability and adsorption capacities were exhibited for target REEs such as La(III), Nd(III), Gd(III), and Y(III). The parameters influencing the adsorption capacity of the target species including contact time, pH, initial concentration, and temperature were optimized. The adsorption kinetics and thermodynamics were studied. The method showed quantitative recovery (99%) upon desorption using HNO3 acid (0.1 M) after a short contact time (15 min).

  • 89.
    Asp, V
    et al.
    Department of Environmental Toxicology, Uppsala University.
    Cantillana, T
    Stockholm University, Faculty of Science, Department of Environmental Chemistry.
    Bergman, Åke
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Brandt, I
    Department of Environmental Toxicology, Uppsala University.
    Chiral effects in adrenocorticolytic action of o,p'-DDD (mitotane) in human adrenal cells2010In: Xenobiotica, ISSN 0049-8254, E-ISSN 1366-5928, Vol. 40, no 3, p. 177-183Article in journal (Refereed)
    Abstract [en]

    1. Adrenocortical carcinoma (ACC) is a rare malignant disease with poor prognosis. The main pharmacological choice, o,p'-DDD (mitotane), produces severe adverse effects. 2. Since o,p'-DDD is a chiral molecule and stereoisomers frequently possess different pharmacokinetic and/or pharmacodynamic properties, we isolated the two o,p'-DDD enantiomers, (R)-(+)-o,p'-DDD and (S)-(-)-o,p'-DDD, and determined their absolute structures. 3. The effects of each enantiomer on cell viability and on cortisol and dehydroepiandrosterone (DHEA) secretion in the human adrenocortical cell line H295R were assessed. We also assayed the o, p'-DDD racemate and the m,p'- and p,p'-isomers. 4. The results show small but statistically significant differences in activity of the o, p'-DDD enantiomers for all parameters tested. The three DDD isomers were equally potent in decreasing cell viability, but p, p'- DDD affected hormone secretion slightly less than the o,p'- and m,p'-isomers. 5. The small chiral differences in direct effects on target cells alone do not warrant single enantiomer administration, but might reach importance in conjunction with possible stereochemical effects on pharmacokinetic processes in vivo.

  • 90.
    Asplund, L
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Environmental Chemistry.
    Löfstrand, K
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Environmental Chemistry.
    Malmvärn, A
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Environmental Chemistry.
    Nylund, K
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Eriksson, U
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bergman, Åke
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Environmental Chemistry.
    OH-PBDEs and MeO-PBDEs in swedish marine and fresh water environment- an overview2010In: Organohalogen Compounds, 2010Conference paper (Other academic)
  • 91.
    Atluri, Rambabu
    et al.
    Uppsala universitet.
    Bacsik, Zoltan
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Garcia-Bennett, Alfonso E.
    Uppsala universitet.
    Structural variations in mesoporous materials with cubic Pm(3)over-barn symmetry2010In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 133, no 1-3, p. 27-35Article in journal (Refereed)
    Abstract [en]

    The fine structural details of mesoporous materials possessing Pmn symmetry prepared with varying amphiphilic surfactants under acid and alkaline conditions are investigated using electron crystallography and sorption studies. The structural data derived is used to understand the parameters that govern the formation of cavity–windows and to propose synthetic strategies in order to control independently the size of the cavities and cavity–windows. Results support that whilst attainment of Pmn cubic packing is due to the overall surfactant geometry, the formation of cavity–windows is associated with the hydration layer formed at the interphase between the surfactant and the silica wall. The charge density at the micelle surface may be tailored using two strategies: (i) using dicationic gemini surfactants at low pHs resulting in an increase in the hydration layer; or (ii) by using co-structure directing agents such as organoalkoxysilanes which reduce the hydration layer surrounding the micelles. The latter leads to the formation of higher cavity sizes and may be useful for tuning fine structural details of mesoporous materials when considering their use in important applications such as gas separation.

  • 92. Atluri, Rambabu
    et al.
    Iqbal, Muhammad Naeem
    Bacsik, Zoltan
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Villaescusa, Luis Angel
    Garcia-Bennett, Alfonso E.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry. alfonso@mmk.su.se.
    Self-Assembly Mechanism of Folate-Templated Mesoporous Silica2013In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 29, no 38, p. 12003-12012Article in journal (Refereed)
    Abstract [en]

    A method to form ordered mesoporous silica based on the use of folate supramolecular templates has been developed. Evidence based on in situ small-angle X-ray scattering (SAXS), electron microscopy, infrared spectroscopy, and in situ conductivity measurements are used to investigate the organic inorganic interactions and synthesis mechanism. The behavior of folate molecules in solution differs distinctively from that of surfactants commonly used for the preparation of ordered mesoporous silica phases, notably with the absence of a critical micellar concentration. In situ SAXS studies reveal fluctuations in X-ray scattering intensities consistent with the condensation of the silica precursor surrounding the folate template and the growth of the silica mesostructure in the initial stages. High-angle X-ray diffraction shows that the folate template is well-ordered within the pores even after a few minutes of synthesis. Direct structural data for the self-assembly of folates into chiral tetramers within the pores of mesoporous silica provide evidence for the in register stacking of folate tetramers, resulting in a chiral surface of rotated tetramers, with a rotation angle of 30 degrees. Additionally, the self-assembled folates within pores were capable of adsorbing a considerable amount of CO2 gas through the cavity space of the tetramers. The study demonstrates the validity of using a naturally occurring template to produce relevant and functional mesoporous materials.

  • 93. Atzori, Alessio
    et al.
    Liggi, Sonia
    Laaksonen, Aatto
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Stockholm University, Science for Life Laboratory (SciLifeLab). University of Cagliari, Italy.
    Porcu, Massimiliano
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Università di Cagliari, Italy.
    Lyubartsev, Alexander P.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Saba, Giuseppe
    Mocci, Francesca
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Stockholm University, Science for Life Laboratory (SciLifeLab). Università di Cagliari, Italy.
    Base sequence specificity of counterion binding to DNA: what can MD simulations tell us?2016In: Canadian journal of chemistry (Print), ISSN 0008-4042, E-ISSN 1480-3291, Vol. 94, no 12, p. 1181-1188Article in journal (Refereed)
    Abstract [en]

    Nucleic acids are highly charged biopolymers whose secondary structure is strongly dependent on electrostatic interactions. Solvent molecules and ions are also believed to play an important role in mediating and directing both sequence recognition and interactions with other molecules, such as proteins and a variety of ligands. Therefore, to fully understand the biological functions of DNA, it is necessary to understand the interactions with the surrounding counterions. It is well known that monovalent counterions can bind to the minor groove of DNA with consecutive sequences of four, or more, adenine and thymine (A-tracts) with relatively long residence times. However, much less is known about their binding to the backbone and to the major groove. In this work, we used molecular dynamics simulations to both investigate the interactions between the backbone and major groove of DNA and one of its physiological counterions (Na+) and evaluate the relationship between these interactions and the nucleotide sequence. Three dodecamers, namely CGAAAATTTTCG, CGCTCTAGAGCG, and CGCGAATTCGCG, were simulated using the Toukan-Rahman flexible SPC water model and Smith and Dang parameters for Na+, revealing a significant sequence dependence on the ion binding to both backbone and major groove. In the absence of experimental data on the atomistic details of the studied interactions, the reliability of the results was evaluated performing the simulations with additional sets of potential parameters for ions and solvent, namely the A. qvist or the Joung and Cheatham ion parameters and the TIP3P water model. This allowed us to evaluate the results by verifying which features are preserved independently from the parameters adopted.

  • 94. Auer, Henry
    et al.
    Nedumkandathil, Reji
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Häussermann, Ulrich
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Kohlmann, Holger
    The Hydrogenation of the Zintl Phase NdGa Studied by in situ Neutron Diffraction2019In: Zeitschrift für Anorganische und Allgemeines Chemie, ISSN 0044-2313, E-ISSN 1521-3749, Vol. 645, no 3, p. 175-181Article in journal (Refereed)
    Abstract [en]

    The hydrogenation of the Zintl phase NdGa was studied by in situ neutron powder diffraction. We find a compositional range of 0.1 < x < 0.8 in NdGaH1+x. Hydrogen atoms are located in two different positions, in HNd4 tetrahedra, and close to the polyanionic chains. For the latter, the Ga-H distance in NdGaH1.66 is quite long (ca. 200 pm) with a trigonal bipyramidal Nd3Ga2 surrounding of hydrogen atoms. Hydrogen poor NdGaH<1 phases as known for similar systems were not observed. The changing hydrogen content shows no measureable effect on the unit cell volume, but on lattice parameter ratios. Superstructures occur for 0.53 < x < 0.66 and 0.73 < x < 0.8, leading to a doubling or tripling of the lattice parameter a. They are probably caused by partial hydrogen ordering. The threefold superstructure contains a (1)[(Ga-H-Ga-H-Ga)(6-)] moiety with hydrogen bridging two gallium chains.

  • 95. Aulin, Christian
    et al.
    Salazar-Alvarez, German
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Lindström, Tom
    High strength, flexible and transparent nanofibrillated cellulose-nanoclay biohybrid films with tunable oxygen and water vapor permeability2012In: NANOSCALE, ISSN 2040-3364, Vol. 4, no 20, p. 6622-6628Article in journal (Refereed)
    Abstract [en]

    A novel, technically and economically benign procedure to combine vermiculite nanoplatelets with nanocellulose fibre dispersions into functional biohybrid films is presented. Nanocellulose fibres of 20 nm diameters and several micrometers in length are mixed with high aspect ratio exfoliated vermiculite nanoplatelets through high-pressure homogenization. The resulting hybrid films obtained after solvent evaporation are stiff (tensile modulus of 17.3 GPa), strong (strength up to 257 MPa), and transparent. Scanning electron microscopy (SEM) shows that the hybrid films consist of stratified nacre-like layers with a homogenous distribution of nanoplatelets within the nanocellulose matrix. The oxygen barrier properties of the biohybrid films outperform commercial packaging materials and pure nanocellulose films showing an oxygen permeability of 0.07 cm(3) mu m m(-2) d(-1) kPa(-1) at 50% relative humidity. The oxygen permeability of the hybrid films can be tuned by adjusting the composition of the films. Furthermore, the water vapor barrier properties of the biohybrid films were also significantly improved by the addition of nanoclay. The unique combination of excellent oxygen barrier behavior and optical transparency suggests the potential of these biohybrid materials as an alternative in flexible packaging of oxygen sensitive devices such as thin-film transistors or organic light-emitting diode displays, gas storage applications and as barrier coatings/laminations in large volume packaging applications.

  • 96. Avila, M.
    et al.
    Burks, T.
    Akhtar, Farid
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Gothelid, M.
    Lansaker, P. C.
    Toprak, M. S.
    Muhammed, M.
    Uheida, A.
    Surface functionalized nanofibers for the removal of chromium(VI) from aqueous solutions2014In: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 245, p. 201-209Article in journal (Refereed)
    Abstract [en]

    Polyacrylonitrile (PAN) nanofibers functionalized with amine groups (PAN-NH2) were prepared using a simple one-step reaction route. The PAN-NH2 nanofibers were investigated for the removal of chromium(VI) from aqueous solutions. The adsorption and the kinetic characteristics were evaluated in batch process. The adsorption process showed pH dependence and the maximum Cr(VI) adsorption occurred at pH = 2. The Langmuir adsorption model described well the experimental adsorption data and estimated a maximum loading capacity of 156 mg/g, which is a markedly high value compared to other adsorbents reported. The kinetics studies indicated that the equilibrium was attained after 90 min and the experimental data followed a pseudo-second order model suggesting a chemisorption process as the rate limiting step. X-ray Photoelectron Spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR) revealed that the adsorption of Cr(VI) species on PAN-NH2 was facilitated through both electrostatic attraction and surface complexation. High desorption efficiency (> 90%) of Cr(VI) was achieved using diluted base solutions that may allow the reuse of PAN-NH2 nanofibers.

  • 97.
    Aziz, Baroz
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Synthesis and modification of potential CO2 adsorbents: Amine modified silica and calcium carbonates2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The prospect of rapid changes to the climate due to global warming is subject of public concern. The need to reduce the emissions of atmospheric green house gases and in particular carbon dioxide is greater than ever. Extensive research is performed to find new solutions and new materials, which tackles this problem in economically benign way. This thesis dealt with two potential adsorbents for post combustion  carbon capture, namely, amine modified silica and calcium carbonates. We modified porous silica with large surface area by propyl-amine groups to enhance the carbon dioxide adsorption capacity and selectivity. Experimental parameters, such as reaction time, temperature, water content, acid and heat treatment of silica substrate were optimized using a fractional factorial design. Adsorption properties and the nature of formed species upon reaction of CO2 and amine-modified silica were studied by sorption and infrared spectroscopy. Physisorbed and chemisorbed amount of adsorbed CO2 were, for the first time, estimated directly in an accurate way. The effects of temperature and moisture on the CO2 adsorption properties were also studied.

    Crystallization of calcium carbonate as a precursor to calcium oxide, which can be used as carbon dioxide absorbent, was studied in the second part of this thesis. Structure of different amorphous phases of calcium carbonate was studied in detail. Crystallization of calcium carbonate with and without additives was studied. Parameters like stirring rate, temperature, pH and polymer concentration showed to be important in selection of phase and morphology. An aggregation mediated crystallization was postulated to explain the observed morphologies. 

  • 98.
    Aziz, Baroz
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Gebauer, Denis
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Kinetic control of particle-mediated calcium carbonate crystallization2011In: CrystEngComm, ISSN 1466-8033, E-ISSN 1466-8033, Vol. 13, no 14, p. 4641-4645Article in journal (Refereed)
    Abstract [en]

    By changing the temperature, pH, stirring rate, or time for calcium carbonate crystallization, complex shapes of aggregated calcium carbonates formed. Such shapes have earlier been ascribed to specific interactions with specialized additives. Without polymeric additives, aggregates of vaterite transformed more rapidly into calcite aggregates under slow than under fast stirring. With an anionic polyelectrolyte added, vaterite was stabilized. Larger polycrystalline aggregates of vaterite formed under rapid than under slow stirring, indicative of a particle mediated growth of aggregates controlled by convective currents. The size of the underlying nanoparticles was temperature dependent, with grain sizes of similar to 20 to 50 nm at 20 degrees C and similar to 350 nm at 90 degrees C. The small differences in free energy between the anhydrous polymorphs of calcium carbonate made both kinetic and equilibrium dependencies important.

  • 99.
    Aziz, Baroz
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Bacsik, Zoltán
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Quantification of chemisorption and physisorption of carbon dioxide on porous silica modified by propylamines: Effect of amine density2012In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 159, p. 42-49Article in journal (Refereed)
    Abstract [en]

    Detailed molecular aspects of carbon dioxide sorption on porous silica with different amounts of tethered and cross-linked n-propylamine groups were investigated. Infrared spectroscopy was applied to directly quantify physisorbed and chemisorbed CO2 on the amine modified silicas. The fractions of physisorbed CO2 and various chemisorbed species were determined as functions of CO2 pressure and the amine density on the modified silica. Physisorbed CO2 was a minor portion of the total CO2 uptake at low pressures, but it’s contribution increased to ∼35% at 1 bar of CO2 when the propylamine surface density was low or medium (0.87-1.67 NH2/nm2). Chemisorption of CO2 dominated when the propylamine content was high (2.74 NH2/nm2). The quantities of propylammonium propylcarbamate ion pairs increased with increasing propylamine content. At low or medium amine surface densities (0.87-1.67 NH2/nm2) this increase was approximately proportional to the amine density, but the quantity of ion pairs increased very significantly when the propylamine content was high (2.74 NH2/nm2). This dependency on amine density is consistent with the idea that a sufficiently close proximity of propylamine groups allows a formation of ion pairs. The relative fractions of carbamic acid and silylpropylcarbamate were significant for materials on which ion pairs could not form. Furthermore, the quantities of carbamic acid increased with increasing amine densities suggesting that the ion pairs have a role to stabilize the labile carbamic acid through hydrogen bonds.

  • 100.
    Aziz, Baroz
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Zhao, Guoying
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Carbon Dioxide Sorbents with Propylamine Groups-Silica Functionalized with a Fractional Factorial Design Approach2011In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 27, no 7, p. 3822-3834Article in journal (Refereed)
    Abstract [en]

    Mesoporous silica particles (Davisil) were functionalized with aminopropyltriethoxysilane (APTES) in a fractional factorial design with 19 different synthesis and uptake experiments. The number of amino groups and the uptake of CO(2) were optimized in a 2(V)(5-1) design. Most important to functionalizationwas the amount of water present during synthesis, the reaction time, and pretreating the silica with a mineral acid; certain two-way interactions were shown to be statistically significant as well. Modifications performed at 110 or 80 degrees C showed no significant differences concerning amine content or uptake of CO(2). Properly choosing center points for the discrete variables is problematic and is somewhat related to the lack of fit with respect to CO(2) uptake; the regression was good. Solid-state (29)Si NMR showed that the APTES was mainly fully condensed. Specific surface areas did not correlate with the number of n-propylamine groups on the silica, which is indicative of differential levels of heterogeneity in the coverage of propylamines. The uptake of CO(2) and N(2) was measured from -20 to 70 degrees C and from 0 to 1 bar and parametrized by the Freundlich isotherm. Amine-modified silica adsorbed significant amounts of CO(2), especially at the low partial pressure, which is important for CO(2) capture from flue gas. At such pressures, samples with a high density of amine (4 amines/nm(2)) showed a much higher uptake of CO(2) than did those with densities of similar to 2-3 amines/nm(2), reflecting differential tendencies to form propylammonium-propylcarbamate ion pairs; these require close proximity among amine groups to form. Water affected the uptake of carbon dioxide in different ways. Certain samples took up more moist CO(2) gas than dry CO(2), and others took up less moist CO(2) than dry CO(2), which is indicative of differential tendencies toward water adsorption. We conclude that experimental design is a time-efficient approach to the functionalization of silica with propylamine groups.

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