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  • 251.
    Cichocka, Magdalena O.
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Ångström, Jonas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Wang, Bin
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Smeets, Stef
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    High-throughput continuous rotation electron diffraction data acquisition via software automation2018In: Journal of applied crystallography, ISSN 0021-8898, E-ISSN 1600-5767, Vol. 51, no 6, p. 1652-1661Article in journal (Refereed)
    Abstract [en]

    Single-crystal electron diffraction (SCED) is emerging as an effective technique to determine and refine the structures of unknown nano-sized crystals. In this work, the implementation of the continuous rotation electron diffraction (cRED) method for high-throughput data collection is described. This is achieved through dedicated software that controls the transmission electron microscope and the camera. Crystal tracking can be performed by defocusing every nth diffraction pattern while the crystal rotates, which addresses the problem of the crystal moving out of view of the selected area aperture during rotation. This has greatly increased the number of successful experiments with larger rotation ranges and turned cRED data collection into a high-throughput method. The experimental parameters are logged, and input files for data processing software are written automatically. This reduces the risk of human error, and makes data collection more reproducible and accessible for novice and irregular users. In addition, it is demonstrated how data from the recently developed serial electron diffraction technique can be used to supplement the cRED data collection by automatic screening for suitable crystals using a deep convolutional neural network that can identify promising crystals through the corresponding diffraction data. The screening routine and cRED data collection are demonstrated using a sample of the zeolite mordenite, and the quality of the cRED data is assessed on the basis of the refined crystal structure.

  • 252.
    Cichocka, Magdalena Ola
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Unraveling the structures of complex nanocrystalline materials by combining TEM and XRPD – development and application2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Knowledge of the three-dimensional (3D) atomic structure of materials is essential to a fundamental understanding of their properties. The key to understanding the functionality of many materials, particularly those of commercial and industrial interest, is often hidden in the details at the nanoscale. For this reason, it is very important to choose the right strategy to analyze the structure of challenging materials with complex disordered framework structures, or of the layered materials that are the subject of this thesis. Structure analysis of beam-sensitive or uniquely disordered materials can be complicated. Although there are already existing methods such as X-ray powder diffraction (XRPD), the data may exhibit reflection overlap or other problems that make structure determination difficult. To overcome these limitations for nanocrystalline materials, complementary characterization techniques can be used. Here, I will focus on 3D electron crystallography (continuous rotation electron diffraction and high-resolution electron microscopy) methods that have grown during the past years as hybrid methods for structure determination. Based on the presented materials, I will also emphasize that any kind of challenges can be a driving force for method development.  Furthermore, some of the insights gained lead to better understanding of how to collect and process 3D electron diffraction data, which could be applied to make data collection of challenging samples easier and obtain higher quality structure refinements from the data. Finally, I will try to describe the general procedures for ab initio structure elucidation of disordered nanocrystals and layered materials.

  • 253. Ciudad, Esther
    et al.
    Sanchez-Gonzalez, Estibaliz
    Borrero-Lopez, Oscar
    Guiberteau, Fernando
    Nygren, Mats
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Ortiz, Angel L.
    Sliding-wear resistance of ultrafine-grained SiC densified by spark plasma sintering with 3Y(2)O(3)+5Al(2)O(3) or Y3Al5O12 additives2013In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 69, no 8, p. 598-601Article in journal (Refereed)
    Abstract [en]

    The sliding-wear behavior of ultrafine-grained SiC densified by spark plasma sintering (SPS) with 3Y(2)O(3) + 5Al(2)O(3) or Y3Al5O12 additives was compared to elucidate the effect of the intergranular-phase source. Significantly greater sliding-wear resistance (i.e. lower mild- and severe-wear rates, and delayed mild-to-severe wear transition) is observed with the Y3Al5O12 additive, due to its carbothermal reduction during SPS resulting in a harder YAlO3 phase while reducing the intergranular phase content. Implications for the processing of superior SiC triboceramics are discussed.

  • 254. Clabbers, M. T. B.
    et al.
    van Genderen, E.
    Wan, Wei
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Wiegers, E. L.
    Gruene, T.
    Abrahams, J. P.
    Protein structure determination by electron diffraction using a single three-dimensional nanocrystal2017In: Acta Crystallographica Section D Structural Biology, ISSN 2059-7983, Vol. 73, p. 738-748Article in journal (Refereed)
    Abstract [en]

    Three-dimensional nanometre-sized crystals of macromolecules currently resist structure elucidation by single-crystal X-ray crystallography. Here, a single nanocrystal with a diffracting volume of only 0.14 mu m(3), i.e. no more than 6 x 10(5) unit cells, provided sufficient information to determine the structure of a rare dimeric polymorph of hen egg-white lysozyme by electron crystallography. This is at least an order of magnitude smaller than was previously possible. The molecular-replacement solution, based on a monomeric polyalanine model, provided sufficient phasing power to show side-chain density, and automated model building was used to reconstruct the side chains. Diffraction data were acquired using the rotation method with parallel beam diffraction on a Titan Krios transmission electron microscope equipped with a novel in-house-designed 1024 x 1024 pixel Timepix hybrid pixel detector for low-dose diffraction data collection. Favourable detector characteristics include the ability to accurately discriminate single high-energy electrons from X-rays and count them, fast readout to finely sample reciprocal space and a high dynamic range. This work, together with other recent milestones, suggests that electron crystallography can provide an attractive alternative in determining biological structures.

  • 255. Cliffe, Matthew J.
    et al.
    Wan, Wei
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Chater, Philip A.
    Kleppe, Annette K.
    Tucker, Matthew G.
    Wilhelm, Heribert
    Funnell, Nicholas P.
    Coudert, Francois-Xavier
    Goodwin, Andrew L.
    Correlated defect nanoregions in a metal-organic framework2014In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 5, p. 4176-Article in journal (Refereed)
    Abstract [en]

    Throughout much of condensed matter science, correlated disorder is a key to material function. While structural and compositional defects are known to exist within a variety of metal-organic frameworks (MOFs), the prevailing understanding is that these defects are only ever included in a random manner. Here we show-using a combination of diffuse scattering, electron microscopy, anomalous X-ray scattering and pair distribution function measurements-that correlations between defects can in fact be introduced and controlled within a hafnium terephthalate MOF. The nanoscale defect structures that emerge are an analogue of correlated Schottky vacancies in rocksalt-structured transition metal monoxides and have implications for storage, transport, optical and mechanical responses. Our results suggest how the diffraction behaviour of some MOFs might be reinterpreted, and establish a strategy of exploiting correlated nanoscale disorder as a targetable and desirable motif in MOF design.

  • 256. Cong, Rihong
    et al.
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Yang, Tao
    Li, Mingrun
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Liao, Fuhui
    Wang, Yingxia
    Lin, Jianhua
    Syntheses and Crystal Structures of Two New Bismuth Hydroxyl Borates Containing [Bi(2)O(2)](2+) Layers: Bi(2)O(2)[B(3)O(5)(OH)] and Bi(2)O(2)[BO(2)(OH)]2011In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 50, no 11, p. 5098-5104Article in journal (Refereed)
    Abstract [en]

    Two new bismuth hydroxyl borates, Bi(2)O(2)[B(3)O5-(OH)] (I) and Bi(2)O(2)[BO(2)(OH)] (II), have been synthesized under hydrothermal conditions. Their structures were determined by single-crystal and powder X-ray diffraction data, respectively. Compound I crystallizes in the orthorhombic space group Pbca with the lattice constants of a = 6.0268(3) angstrom, b = 11.3635(6) angstrom, and c = 19.348(1) angstrom. Compound II crystallizes in the monoclinic space group Cm with the lattice constants of a = 5.4676(6) angstrom, b = 14.6643(5) angstrom, c = 3.9058(1) angstrom, and beta = 135.587(6)degrees. The borate fundamental building block (FBB) in I is a three-ring unit [B(3)O(6)(OH)](4-), which connects one by one via sharing corners, forming an infinite zigzag chain along the a direction. The borate chains are further linked by hydrogen bonds, showing as a borate layer within the ab plane. The FBB in II is an isolated [BO(2)(OH)](2-) triangle, which links to two neighboring FBBs by strong hydrogen bonds, resulting in a borate chain along the a direction. Both compounds contain [Bi(2)O(2)](2+) layers, and the [Bi(2)O(2)](2+) layers combine with the corresponding borate layers alternatively, forming the whole structures. These two new bismuth borates are the first ones containing [Bi(2)O(2)](2+) layers in borates. The appearance of Bi(2)O(2)[BO(2)(OH)] (II) completes the series of compounds Bi(2)O(2)[BO(2)(OH)], Bi(2)O(2)CO(3), and Bi(2)O(2)[NO(3)(OH)] and the formation of Bi(2)O(2)[B(3)O(5)(OH)] provides another example in demonstrating the polymerization tendency of borate groups.

  • 257. Cong, Rihong
    et al.
    Yang, Tao
    Wang, Zheming
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Liao, Fuhui
    Wang, Yingxia
    Lin, Jianhua
    Syntheses, Structure, and Luminescent Properties of Novel Hydrated Rare Earth Borates Ln(2)B(6)O(10)(OH)(4)center dot H(2)O (Ln = Pr, Nd, Sm, Eu, Gd, Dy, Ho, and Y)2011In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 50, no 5, p. 1767-1774Article in journal (Refereed)
    Abstract [en]

    Ln(2)B(6)O(10)(OH)(4)center dot H(2)O (Ln = Pr, Nd, Sm-Gd, Dy, Ho, and Y), a new series of hydrated rare earth borates, have been synthesized under hydrothermal conditions. A single crystal of Nd analogue was used for the structure determination by X-ray diffraction. It crystallizes in the monoclinic space group C2/c with lattice constants a = 21.756(4), b = 4.3671(9), c = 12.192(2) angstrom, and beta = 108.29(3)degrees. The other compounds are isostructural to Nd(2)B(6)O(10)(OH)(4)center dot H(2)O. The fundamental building block (FBB) of the polyborate anion in this structure is a three-membered ring [B(3)O(6)(OH)(2)](5-). The FBBs are connected by sharing oxygen atoms forming an infinite [B(3)O(5)(OH)(2)](3-) chain, and the chains are linked by hydrogen bonds, establishing a two-dimensional (2-D) [B(610)(OH)(4)center dot H(2)O](6-) layer. The 2-D borate layers are thus interconnected by Ln(3+) ions to form the complex three-dimensional structure. Ln(2)B(6)O(10)(OH)(4)center dot H(2)O dehydrates stepwise, giving rise to two new intermediate compounds Ln(2)B(6)O(10)(OH)(4) and Ln(2)B(6)O(11) (OH)(2). The investigation on the luminescent properties of Gd(2-2x)Eu(2x)B(6)O(10)(OH)(4)center dot H(2)O (x = 0.01-1.00) shows a high efficiency of Eu(3+) f-f transitions and the existence of the energy transfer process from Gd(3+) to Eu(3+). Eu(2)B(6)O(10)(OH)(4)center dot H(2)O and its two dehydrated products, Eu(2)B(6)O(10)(OH)(4) and Eu(2)B(6)O(11)(OH)(2), present the strongest emission peak at 620 nm ((5)D(0) -> (7)F(2) transition), which may be potential red phosphors.

  • 258. Corkett, Alex J.
    et al.
    Chen, Zheng
    Bogdanovski, Dimitri
    Slabon, Adam
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Dronskowski, Richard
    Band Gap Tuning in Bismuth Oxide Carbodiimide Bi2O2NCN2019In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 58, no 9, p. 6467-6473Article in journal (Refereed)
    Abstract [en]

    Layered bismuth oxides exhibit a broad range of tunable physical properties as a result of their excellent structural versatility which facilitates compositional substitutions at both cationic and anionic positions. Here we expand this family in a new direction through the preparation of the first example of a bismuth-containing oxide carbodiimide, Bi2O2NCN, which assumes an extended variant of the anti-ThCr2Si2 structure-type adopted by Bi(2)O(2)Ch (Ch = Se or Te) oxide chalcogenides. Electronic structure calculations reveal the title compound to be an indirect band gap semiconductor with a band gap of approximately 1.4 eV, in good agreement with the measured value of 1.8 eV, and intermediate between that of structurally related Bi2O2S (1.12 eV) and beta-Bi2O3 (2.48 eV). Mott-Schottky experiments demonstrate Bi2O2NCN to be an n-type semiconductor with a conduction band edge position of -0.37 V vs reversible hydrogen electrode. This study highlights the pseudochalcogenide nature of the N-=C=N- carbodiimide anion, which may be substituted in place of oxide or chalcogenide anions in this and potentially other structural classes as an effective means of electronic tuning.

  • 259.
    Cuadra, Steven N.
    et al.
    University of Nicaragua-Managua.
    Linderholm, Linda
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Environmental Chemistry.
    Athanasiadou, Maria
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Environmental Chemistry.
    Jakobsson, Kristina
    Lunds universitet.
    Persistent organochlorine pollutants in children working at a waste-disposal site and in young females with high fish consumption in Managua, Nicaragua2006In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 35, no 3, p. 109-116Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to assess persistent organochlorine pollutant (POP) levels in serum collected from children (11-15 years old) working and sometimes also living at the municipal waste-disposal site in Managua, located at the shore of Lake Managua, and in nonworking children living both nearby and also far away from the waste-disposal site. The influence of fish consumption was further evaluated by assessing POPS levels in serum from young women (15-24 years old) with markedly different patterns of fish consumption from Lake Managua. 2,2-bis(4-chlorophenyl)-1,1,1-trichloro-ethane (4,4’-DDT) and 2,2-bis(4-chlorophenyl)-1,1-dichloro-ethene (4,4-DDE), T-hexachlorocyclohexane (gamma-HCH), polychlorinated biphenyls, pentachlorophenol, and polychlorobiphenylols were quantified in all samples. In general, the levels observed were higher than those reported in children from developed countries, such as Germany and United States. Toxaphene, aldrin, dieldrin, and beta-HCH could not be identified in any sample. The children working at the waste-disposal site had higher levels of POPS compared with the nonworking reference groups. In children not working, there were also gradients for several POPs, according to vicinity to the waste-disposal site. Moreover, in children, as well as in young women, there were gradients according to fish consumption. The most abundant component was 4,4-DDE, but at levels still lower than those reported in children from malarious areas with a history of recent or current application of 4,4-DDT for vector control.

  • 260. Cubillas, Pablo
    et al.
    Castro, Maria
    Jelfs, Kim E.
    Lobo, Alan J. W.
    Slater, Ben
    Lewis, Dewi W.
    Wright, Paul A.
    Stevens, Sam M.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Anderson, Michael W.
    Spiral Growth on Nanoporous Silicoaluminophosphate STA-7 as Observed by Atomic Force Microscopy2009In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 9, no 9, p. 4041-4050Article in journal (Refereed)
    Abstract [en]

    Atomic force microscopy was used to study the surface of STA-7 crystals. STA-7 is a silicoaluminophosphate, nanoporous solid formed by interlinked double six ring units (D6R). Observations showed the formation of three distinct types of spirals at tow supersaturation conditions. The {001} face shows spirals with isotropic shapes and a Burgers vector of 0.9 nm, which corresponds to one D6R or one unit cell along the < 001 > direction. The {100} face contains two distinct types of spirals. The first has a Burgers vector of 0.9 rim, or half a unit cell along < 100 >. This dislocation produces a change in the ""stacking"" sequence of the D6Rs generating all overgrowth with the AEI structure. The second type is an interlaced spiral and is generated by a dislocation with a Burgers vector of 1.8 nm or one unit cell, leading to the formation of two substeps each with a different growth anisotropy. This anisotropy is directed by the shape of the substep and the energetics of template attachment. The preponderance of a surface coating of a secondary phase will have significant consequences on applications reliant on intracrystalline diffusion, such as catalysis, where, owing to diffusion limitations, the outermost structure dominates the functional properties.

  • 261. Cubillas, Pablo
    et al.
    Gebbie, James T.
    Stevens, Sam M.
    Blake, Nicola
    Umemura, Ayako
    Terasaki, Osamu
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Anderson, Michael W.
    Atomic Force Microscopy and High Resolution Scanning Electron Microscopy Investigation of Zeolite A Crystal Growth. Part 2: In Presence of Organic Additives2014In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, no 40, p. 23092-23099Article in journal (Refereed)
    Abstract [en]

    The nanoscopic details of the crystal growth of zeolite. A in the presence of the organic modifiers. diethanolmaine (DEA) and triethanolamine (TEA) has been determined using a combination of atomic force microscopy (AFM) and high-resolution scanning electron microscopy (HRSEM) coupled with Monte Carlo simulations. Crystallization of zeolite A in the presence of TEA was faster than when the growing solution contained DEA. In addition, the morphology of the final zeolite A crystals depended on the type of organic molecule, with TEA producing crystals bound only by {100} facets and DEA leading to the formation of relatively large {110} faces. These features can be explained in terms of the relative Si/Al in the growing medium and its control due to the different affinity of the organic molecules to Al. In addition, synthesis Si/Al in the growing medium and its contorl due to the different affinity of the organic molecules to Al. In additon synthesis performed at 90 degrees C showed the apperance of {211} facets Careful review of the HRSEM and AFM images, in addition to comparion with the MC simulations, reveals that these are in fact pseudofacets products of the slow dissolution of the metastable zeolite. A crsytals. This proves that the final habit of the LTA crystals can be governed by very small changes in saturation of the growing medium, and control of this parameter can prove advantageous when designing crystals for industrial applications.

  • 262. Cubillas, Pablo
    et al.
    Stevens, Sam M.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Blake, Nicola
    Umemura, Ayako
    Chong, Chin B.
    Terasaki, Osamu
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Anderson, Michael W.
    AFM and HRSEM Invesitigation of Zeolite A Crystal Growth. Part 1: In the Absence of Organic Additives2011In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 115, no 25, p. 12567-12574Article in journal (Refereed)
    Abstract [en]

    The crystallization of zeolite A by the verified synthesis method was studied by means of high-resolution scanning electron microscopy (HRSEM) and atomic force microscopy (AFM). These methods show an evolution in the growth mode of zeolite A from an adhesive type at the beginning of the synthesis (high supersaturation) to birth-and-spread growth at the end of the synthesis (low supersaturation). Additionally, HRSEM provides direct proof on the formation of zeolite A crystals at the surface of the amorphous gel and the aggregation of crystals at early stages of synthesis, which leads to intergrowth formation. For the first time, high-resolution AFM images were taken on the {110} and {111} faces of zeolite A. Growth on {110} faces takes place by a birth-and-spread mechanism, and the shape of the terraces is rectangular, with growth along the < 100 > directions being twice as fast as in the < 110 > directions. Growth on the {111} faces also takes place by a birth-and-spread mechanism via triangular-shaped terraces with edges parallel to < 110 > directions. Possible surface terminations for both faces are discussed, and crystal habit and surface topography are modeled by Monte Carlo simulations.

  • 263.
    Cui, D.
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Low, J.
    Rondinella, V. V.
    Spahiu, K.
    Hydrogen catalytic effects of nanostructured alloy particles in spent fuel on radionuclide immobilization2010In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 94, no 02-jan, p. 173-178Article in journal (Refereed)
    Abstract [en]

    For the first time, hydrogen catalytic effects of fission product alloy particles nondestructively extracted from spent nuclear fuel were demonstrated. The redox sensitive radionuclides at oxidized forms Se(IV), Tc(VII), U(VI), Np(V) and Pu(VI) were found to be stable in a solution saturated with a gas mixture (Ar + 10% H-2 + 0.03% CO2) but rapidly immobilized in the same solution when contacted with the particles. In comparison, a synthetic alloy sample with similar elemental composition as the alloy particles generated in nuclear fuel displayed a smaller, but unequivocal catalytic effect. The smaller catalytic effect of synthetic alloy was apparently enhanced by a P-radiation source. The information obtained in this work contributes to improved understanding of the redox chemistry of radionuclides in nuclear waste geologic repository environments and, in particular, of the catalytic properties of these unique alloy particles.

  • 264.
    Cui, Daqing
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Environmental Chemistry.
    A Review of Beneficial Effects of Reducing Environment at the Near-Field of KBS-3 Repository2011In: Huaxue jinzhan, ISSN 1005-281X, Vol. 23, no 7, p. 1411-1428Article, review/survey (Refereed)
    Abstract [en]

    The recent research activities, i.e. relevant publications and the author's experiments on chemical behaviors of spent nuclear fuel (SNF) and canister materials at near-field of KBS-3 deep geological repository were reviewed. The advantages of reductive substances at KBS-3 repository to the spent fuel disposal safety were discussed. Using data from literatures and experiments, the author demonstrated the blocking effect of hydrogen generated for iron canister corrosion on SNF dissolution, and discussed the reaction mechanism. It is also proved that the gamma radiation expected at the early stage of disposal and micro mole level oxidative species in water solution can only slightly enhance the corrosion rate of copper canister to mu m/y level, still 10(3) times slower than that at air saturated conditions. During a long period of time after copper canister leaks, under combined effects of iron canister material, hydrogen and fission product alloy particle catalysts, SNF dissolution can be depressed or blocked, and Most radiotoxic multivalent radionuclides U, Np, Tc and Se released from SNF can be reduced and precipitated. This paper supplies scientific bases for the sitting of a SNF repository at a stable reducing area, and designing of canisters with massive iron material.

  • 265.
    Cui, Daqing
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Low, Jeanett
    Spahiu, Kastriot
    Environmental behaviors of spent nuclear fuel and canister materials2011In: Energy & Environmental Science, ISSN 1754-5692, E-ISSN 1754-5706, Vol. 4, no 7, p. 2537-2545Article in journal (Refereed)
    Abstract [en]

    The world's first spent nuclear fuel repository concept (Swedish KBS-3) is illustrated and the results of experiments on environmental behaviors of spent fuel and canister materials under a potential canister breaching at early stage of disposal are reported. In a deoxygenated synthetic groundwater (2 mM NaHCO(3)) under radiation (gamma 0.9 Gy h(-1)), inventory fraction leaching rates of fission-products ((137)Cs, (90)Sr and (99)Tc) and actinides ((238)U, (237)Np) from a spent fuel segment were found to be around 10(-6) and 10(-7) per day, respectively. A cast-iron canister surface was found to be able to immobilize (238)U, (90)Sr, (99)Tc and (237)Np dissolved from spent fuel, but a copper surface could not. In the presence of the oxidative species generated from water radiolysis, the corrosion rates of waste canister materials, copper and cast-iron were found to be 1 and 30 mm per year, respectively. The observation of insignificant dissolution of spent fuel in the leaching solution equilibrated with 0.1 atm H(2) is explained by the reducing effects of H(2) in the presence of fission-product alloy particles (Mo-Tc-Ru-Rh-Pd) as catalysts and dissolved Fe(II) in groundwater. The coating effect of ferric precipitates on spent nuclear fuel dissolution is also discussed.

  • 266.
    Cui, Daqing
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Environmental Chemistry.
    Puranen, A.
    Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi, Department of Physical, Inorganic and Structural Chemistry.
    Devoy, J.
    Scheidegger, A.
    Leupin, O. X.
    Wersin, P.
    Gens, R.
    Spahiu, K.
    Reductive immobilization of Se-79 by iron canister under simulated repository environment2009In: Journal of Radioanalytical and Nuclear Chemistry, ISSN 0236-5731, E-ISSN 1588-2780, Vol. 282, no 2, p. 349-354Article in journal (Refereed)
    Abstract [en]

    To understand the fate of Se-79 in a repository-like environment, the interactions between iron canister surface with dissolved selenite (SeO3 (2-)) and selenate (SeO4 (2-)) in anaerobic solutions have been investigated. Se(IV) immobilization on iron surface was observed to be about 100 times faster than that of Se(VI) at same conditions. An iron surface coated with a FeCO3 layer corrosion product is more reactive than a polished iron to immobilize Se(IV) and Se(VI). The reacted iron surfaces were analysed by scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS), X-ray diffraction (XRD), Raman spectrometry and micro-X-ray Absorption Spectroscopy (XAS). The result show that Se(IV) and Se(VI) were reduced and precipitated. The dominating phase was found to be FeSe2..

  • 267.
    Cui, Daqing
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Environmental Chemistry.
    Rondinella, V. V.
    Fortner, J. A.
    Kropf, A. J.
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Wronkiewicz, D. J.
    Spahiu, K.
    Characterization of alloy particles extracted from spent nuclear fuel2012In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 420, no 1-3, p. 328-333Article in journal (Refereed)
    Abstract [en]

    We characterized, for the first time, submicro- and nanosized fission product-alloy particles that were extracted nondestructively from spent nuclear fuel, in terms of noble metal (Mo-Ru-Tc-Rh-Pd-Te) composition, atomic level homogeneity and lattice parameters. The evidences obtained in this work contribute to an improved understanding of the redox chemistry of radionuclides in nuclear waste repository environments and, in particular, of the catalytic properties of these unique metal alloy particles.

  • 268. Curecheriu, Lavinia
    et al.
    Buscaglia, Maria Teresa
    Buscaglia, Vincenzo
    Zhao, Zhe
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Mitoseriu, Liliana
    Grain size effect on the nonlinear dielectric properties of barium titanate ceramics2010In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 97, no 24, p. 242909-Article in journal (Refereed)
    Abstract [en]

    The nonlinear dielectric properties of dense BaTiO(3) ceramics with grain size of 1 mu m-90 nm were investigated. In the finest ceramics, the permittivity reduces below 1000 and a remarkable nonhysteretic linear dc-tunability [epsilon(E)] is obtained at high field, above 40 kV/cm. The observed behavior was explained by considering the nanostructured ceramic as a composite formed by ferroelectric grains, whose nonlinearity is reducing, and by low-permittivity nonferroelectric grain boundaries, whose volume fraction increases when decreasing the grain size. Reducing the grain size in ferroelectric dense materials is an alternative route to accomplish the application requirements: nonhysteretic tunability and permittivity below 1000.

  • 269.
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Mid Sweden University, Sweden.
    Combined heterogeneous metal/organic catalysts for eco-friendly synthesis2015In: Pure and Applied Chemistry, ISSN 0033-4545, E-ISSN 1365-3075, Vol. 87, no 9-10, p. 1011-1019Article in journal (Refereed)
    Abstract [en]

    The interplay and synergistic cooperation between homogeneous and heterogeneous catalyst systems is of utmost importance in nature. It is also applied in chemical synthesis. Here, it can allow for new reactivity, which is not possible by the employment of a single catalyst, and promote the catalysis of multiple transformations in a one-pot sequence. This could overall lead to novel reactions and the development of sustainable chemistry. In this context, a versatile and broad synergistic strategy for the selective synthesis of valuable molecules with variable complexity and under eco-friendly conditions is disclosed. It is based on integrated heterogeneous metal/organo multiple relay catalysis, which is performed in a single reaction vessel, and allows for the assembly of complex molecules (e.g., heterocycles and carbocycles) with up to three quaternary stereocenters in a highly enantioselective fashion from simple alcohols and air/O-2.

  • 270. Córdova, Armando
    et al.
    Afewerki, Samson
    Alimohammadzadeh, Rana
    Sanhueza, Italo
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Osong, Sinke H.
    Engstrand, Per
    Ibrahem, Ismail
    A sustainable strategy for production and functionalization of nanocelluloses2019In: Pure and Applied Chemistry, ISSN 0033-4545, E-ISSN 1365-3075, Vol. 91, no 5, p. 865-874Article in journal (Refereed)
    Abstract [en]

    A sustainable strategy for the neat production and surface functionalization of nanocellulose from wood pulp is disclosed. It is based on the combination of organocatalysis and click chemistry (organoclick chemistry) and starts with nanocellulose production by organic acid catalyzed hydrolysis and esterification of the pulp under neat conditions followed by homogenization. This nanocellulose fabrication route is scalable, reduces energy consumption and the organic acid can be efficiently recycled. Next, the surface is catalytically engineered by organoclick chemistry, which allows for selective and versatile attachment of different organic molecules (e.g. fluorescent probes, catalyst and pharmaceuticals). It also enables binding of metal ions and nanoparticles. This was exemplified by the fabrication of a heterogeneous nanocellulose palladium nanoparticle catalyst, which is used for Suzuki cross-coupling transformations in water. The disclosed surface functionalization methodology is broad in scope and applicable to different nanocelluloses and cellulose based materials as well.

  • 271.
    Dahlberg, Anna-Karin
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Norrgran, Jessica
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hovander, Lotta
    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).
    Asplund, Lillemor
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Recovery discrepancies of OH-PBDEs and polybromophenols in human plasma and cat serum versus herring and long-tailed duck plasma2014In: Chemosphere, ISSN 0045-6535, E-ISSN 1879-1298, Vol. 94, p. 97-103Article in journal (Refereed)
    Abstract [en]

    Hydroxylated polybrominated diphenyl ethers (OH-PBDEs) have been identified as metabolites of polybrominated diphenyl ethers (PBDEs) and/or as natural products. The OH-PBDEs and polybromophenols have come into focus over the last decade due to their abundance in biota and their potential adverse health effects. The present recovery study aims to validate a commonly used method (published by Hovander et al. 2000) for OH-PBDE analysis in human plasma. Further, the authors intended to determine the method's applicability to serum/plasma matrices from other species than humans. The investigated matrices were human plasma, cat serum, herring- and long-tailed duck plasma. The recovery study included nine OH-PBDEs, four polybromophenols and three methoxylated PBDEs (MeO-PBDEs). Five replicates of each matrix were spiked with these compounds at two dose levels; a low dose (0.5 ng) and a high dose (5 ng) and were cleaned up according to the Hovander method. The recovery of OH-PBDEs and polybromophenols in human plasma and cat serum were high and reproducible at both dose levels whereas the recovery for herring and long-tailed duck plasma were low and insufficient with great variability amongst OH-PBDE congeners at both dose levels. Our data show that the method can be fully applied to matrices like human plasma and cat serum but not for herring and long-tailed duck plasma without further method development. Hence care needs to be taken when applying the method onto other blood matrices without validation since the present study have demonstrated that the recoveries may differ amongst OH-PBDE congeners and specie.

  • 272.
    Dahlberg, Martin
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Molecular Modeling of Cardiolipin2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Biological membranes are assembled from many different lipids. Our understanding of membrane function and morphology is dependent on linking the properties of the lipids to the properties of the membranes. In the inner mitochondrial membrane, one of the main lipids is cardiolipin, which is involved in the formation of high curvature tubular regions. In this thesis a series of molecular models of cardiolipin is presented, with the aim of providing a bottom-up understanding for its influence on model and biological membranes. The models allow detailed control over the headgroup charge and the chain volumes, which experimentally have shown to be important for the packing, mechanical, and electrostatic properties of membranes.To achieve these aims, three levels of detail were used: i) quantum chemical calculations for the cardiolipin headgroup, ii) atomistic united atom molecular dynamics simulations for cardiolipin and phosphatidylcholine lipid mixtures, and iii) coarse grained molecular dynamics simulations for larger lipid systems, including phase transitions between the micellar, lamellar, and inverse hexagonal phases, as well as mixtures of cardiolipin with zwitterionic lipids. These models are presented in the context of various experiments on cardiolipin systems done by others, and some basic theory of electrostatics and mechanics of membranes are discussed.The simple coarse grained model gave lipid phase preferences in agreement with experimental data. Relatively small amounts of partially neutralized cardiolipin molecules introduced mechanical instability in phosphatidylcholine bilayers, and showed some evidence of domain formation due to curvature frustration. The small effective headgroup volume of cardiolipin induced order in the hydrocarbon chains, partly due to strong sodium ion binding. Different types of intramolecular hydrogen bond networks in cardiolipin were described, and proton transfer between the phosphate groups within a cardiolipin molecule was estimated to have a 4-5 kcal/mol barrier. Such transfer might play a role in the surface conduction of protons at the inner mitochondrial membrane.

  • 273.
    Dahlberg, Martin
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Physical Chemistry.
    Arnold, Maliniak
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Physical Chemistry.
    Mennucci, Benedetta
    Department of Chemistry, University of Pisa.
    Marini, Alberto
    Department of Chemistry, University of Pisa.
    Quantum Chemical Modeling of the Cardiolipin Headgroup2010In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 114, no 12, p. 4375-4387Article in journal (Refereed)
    Abstract [en]

    Cardiolipin is a key lipid component in many biological membranes. Proton conduction and proton−lipid interactions on the membrane surface are thought to be central to mitochondrial energy production. However, details on the cardiolipin headgroup structure are lacking and the protonation state of this lipid at physiological pH is not fully established. Here we present ab initio DFT calculations of the cardiolipin (CL) headgroup and its 2′-deoxy derivative (dCL), with the aim of establishing a connection between structure and acid−base equilibrium in CL. Furthermore, we investigate the effects of solvation on the molecular conformations. In our model, both CL and dCL showed a significant gap between the two pKa values, with pKa2 above the physiological range, and intramolecular hydrogen bonds were found to play a central role in the conformations of both molecules. This behavior was also observed experimentally in CL. Structures derived from the DFT calculations were compared with those obtained experimentally, collected for CL in the Protein Data Bank, and conformations from previous as well as new molecular dynamics simulations of cardiolipin bilayers. Transition states for proton transfer in CL were investigated, and we estimate that protons can exchange between phosphate groups with an approximate 4−5 kcal/mol barrier. Computed NMR and IR spectral properties were found to be in reasonable agreement with experimental results available in the literature.

  • 274.
    Dahlberg, Martin
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Physical Chemistry.
    Maliniak, Arnold
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Physical Chemistry.
    Mechanical properties of coarse grained bilayers formed by cardiolipin and zwitterionic lipids2010In: Journal of Chemical Theory and Computation, ISSN 1549-9618, E-ISSN 1549-9626, Vol. 6, no 5, p. 1638-1649Article in journal (Refereed)
    Abstract [en]

    Lipid shape and charge are connected with the physical properties and biological function of membranes. Cardiolipin, a double phospholipid with four chains and the potential of changing its charge with pH, is crucially connected with mitochondrial inner membrane shape, and recent experiments suggest that local pH changes allow highly curved local geometries. Here, we use a coarse grained molecular dynamics model to investigate the mechanical properties of cardiolipin bilayers, systematically varying the headgroup charge and composition in mixtures with zwitterionic DOPC or DOPE. Low cardiolipin charge, corresponding to low pH, was found to induce bending moduli on the order of kBT, and curved microdomains. On the length scale investigated, in contrast to continuum theoretical models, we found the area modulus and bending modulus to be inversely correlated for mixtures of cardiolipin and DOPC/DOPE, explainable by changes in the effective head group volume.

  • 275. Dai, Ruihan
    et al.
    Peng, Fei
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Ji, Pengfei
    Lu, Kuangda
    Wang, Cheng
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Peking University, People’s Republic of China.
    Lin, Wenbin
    Electron crystallography reveals atomic structure of metal-organic nanoplate with Hf12(µ3-O)8(µ3-OH)8(µ2-OH)6 secondary building unit2017In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 56, no 14, p. 8128-8134Article in journal (Refereed)
    Abstract [en]

    Nanoscale metal–organic frameworks (nMOFs) have shown tremendous potential in cancer therapy and biomedical imaging. However, their small dimensions present a significant challenge in structure determination by single-crystal X-ray crystallography. We report here the structural determination of nMOFs by rotation electron diffraction (RED). Two isostructural Zr- and Hf-based nMOFs with linear biphenyldicarboxylate (BPDC) or bipyridinedicarboxylate (BPYDC) linkers are stable under intense electron beams to allow the collection of high-quality RED data, which reveal a MOF structure with M123-O)83-OH)82-OH)6 (M = Zr, Hf) secondary building units (SBUs). The nMOF structures differ significantly from their UiO bulk counterparts with M63-O)43-OH)4 SBUs and provide the foundation for clarifying the structures of a series of previously reported nMOFs with significant potential in cancer therapy and biological imaging. Our work clearly demonstrates the power of RED in determining nMOF structures and elucidating the formation mechanism of distinct nMOF morphologies.

  • 276. Dalmo, Johanna
    et al.
    Westberg, Emelie
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Environmental Chemistry.
    Barregård, Lars
    Svedbok, Lisa
    Johansson, Martin
    Törnqvist, Margareta
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Environmental Chemistry.
    Forssell-Aronsson, Eva
    Evaluation of retinol binding protein 4 and carbamoylated haemoglobin as potential renal toxicity biomarkers in adult mice treated with Lu-177-octreotate2014In: EJNMMI Research, ISSN 2191-219X, E-ISSN 2191-219X, Vol. 4, no 59Article in journal (Refereed)
    Abstract [en]

    Background: The kidneys are regarded as one of the main dose-limiting organs in the treatment of neuroendocrine tumours with Lu-177-[DOTA(0), Tyr(3)]-octreotate (Lu-177-octreotate), despite the successful use of kidney uptake blocking agents such as lysine and arginine. To avoid renal toxicity but still give each patient as high amount of Lu-177-octreotate as possible, there is a need for methods/biomarkers that indicate renal injury in an early stage of the treatment. The aim of this study was to investigate the potential of using urinary retinol binding protein 4 (RBP4) and carbamoylated haemoglobin (Hb) in blood as biomarkers of nephrotoxic effects on adult mice after Lu-177-octreotate treatment. Methods: Adult BALB/c nude mice were injected with 60 MBq or 120 MBq of Lu-177-octreotate or with saline (control). Urine was collected before injection and concentrations of urinary RBP4 and creatinine were determined 14 to 90 days after injection Blood samples were collected after 90 days, and carbamoylated N-terminal valine in Hb, formed from urea, was measured as valine hydantoin (VH) after detachment from Hb. Results: The RBP4 values increased with administered activity and time. For the 60 and 120 MBq groups, statistically significantly higher RBP4 levels (p <0.05) were found at day 60 and 90 compared to baseline, also at day 30 for 120 MBq group. For VH, the mean values were similar for the 60 MBq and control groups, while a small increase was observed for the 120 MBq group; but there were no statistically significant differences between any of the groups (p >0.05). No morphological changes in the kidney tissue were found. Conclusions: Urinary RBP4 is a promising new biomarker for radiation-induced renal toxicity. For the conditions used in this experiment, carbamoylated Hb (from urea) measured as VH may not be a sufficiently sensitive biomarker to be used for renal toxicity.

  • 277.
    Das, Arindam
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Alam, Rauful
    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.
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Stereocontrol in Synthesis of Homoallylic Amines. Syn Selective Direct Allylation of Hydrazones with Allylboronic Acids2014In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 16, no 14, p. 3808-3811Article in journal (Refereed)
    Abstract [en]

    Allylboronic acids directly react with acyl hydrazones, affording homoallylic amine derivatives. The reaction proceeds with very high syn selectivity, which is the opposite of the stereochemistry observed for allylboration of imines. The reaction can be carried out with both aromatic and aliphatic acyl hydrazones. Based on our studies the excellent syn stereochemistry can be explained by chelation control of the acyl hydrazone and the B(OH)(2) moiety.

  • 278. Datta, Shuvo Jit
    et al.
    Khumnoon, Chutharat
    Lee, Zhen Hao
    Moon, Won Kyung
    Docao, Son
    Nguyen, Thanh Huu
    Hwang, In Chul
    Moon, Dohyun
    Oleynikov, Peter
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Terasaki, Osamu
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Graduate School of EEWS, KAIST, Korea; ShanghaiTech University, China.
    Yoon, Kyung Byung
    CO2 capture from humid flue gases and humid atmosphere using a microporous coppersilicate2015In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 350, no 6258, p. 302-+Article in journal (Refereed)
    Abstract [en]

    Capturing CO2 from humid flue gases and atmosphere with porous materials remains costly because prior dehydration of the gases is required. A large number of microporous materials with physical adsorption capacity have been developed as CO2-capturing materials. However, most of them suffer from CO2 sorption capacity reduction or structure decomposition that is caused by co-adsorbed H2O when exposed to humid flue gases and atmosphere. We report a highly stable microporous coppersilicate. It has H2O-specific and CO2-specific adsorption sites but does not have H2O/CO2-sharing sites. Therefore, it readily adsorbs both H2O and CO2 from the humid flue gases and atmosphere, but the adsorbing H2O does not interfere with the adsorption of CO2. It is also highly stable after adsorption of H2O and CO2 because it was synthesized hydrothermally.

  • 279.
    Davies, Ronnie
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Rydberg, Per
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Westberg, Emelie
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Motwani, Hitesh V.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Johnstone, Erik
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Törnqvist, Margareta
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    A New General Pathway for Synthesis of Reference Compounds of N-Terminal Valine-Isocyanate Adducts2010In: Chemical Research in Toxicology, ISSN 0893-228X, E-ISSN 1520-5010, Vol. 23, no 3, p. 540-546Article in journal (Refereed)
    Abstract [en]

    Adducts to Hb could be used as biomarkers to monitor exposure to isocyanates. Particularly useful is the measurement of carbamoylation of N-terminal valines in Hb, after detachment as hydantoins. The synthesis of references from the reactive isocyanates, especially diisocyanates, has been problematic due to side reactions and polymerization of the isocyanate starting material. A simpler, safer, and more general method for the synthesis of valine adducts of isocyanates has been developed using N-[(4-nitrophenyl)-carbamate]valine methylamide (NPCVMA) as the key precursor to adducts of various mono- and diisocyanates of interest. By reacting NPCVMA with a range of isocyanate-related amines, carbamoylated valines are formed without the use of the reactive isocyanates. The carbamoylated products synthesized here were cyclized with good yields of the formed hydantoins. The carbamoylated derivative from phenyl isocyanate also showed quantitative yield in a test with cyclization tinder the conditions used in blood. This new pathway for the preparation of N-carbamoylated model compounds overcomes the above-mentioned problems in the synthesis and is a general and simplified approach, which could make such reference compounds of adducts to N-terminal valine from isocyanates accessible for biomonitoring purposes. The synthesized hydantoins corresponding to adducts from isocyanic acid, methyl isocyanate, phenyl isocyanate, and 2,6-toluene diisocyanate were characterized by LC-MS analysis. The background level of the hydantoin from isocyanic acid in human blood was analyzed with the LC-MS conditions developed.

  • 280. de Moraes, Elisangela Guzi
    et al.
    Li, Duan
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Colombo, Paolo
    Shen, Zhijian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Silicon nitride foams from emulsions sintered by rapid intense thermal radiation2015In: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 35, no 12, p. 3263-3272Article in journal (Refereed)
    Abstract [en]

    Open cell Si3N4 foams were fabricated by an emulsification process and subsequent sintering. Emulsification took place in an aqueous environment by using octane as alkane phase and a surfactant as stabilizer. Effects of different octane concentrations (50 vol% and 70 vol%) and stirring velocities (700 rpm and 1000 rpm) on porosity and pore size distribution were investigated. The shaped foams were pressureless sintered at 1600 degrees C inside a modified SPS set-up. Si3N4 foams decorated with SiC nanowires and with an average cell size of 8-41 mu m and total porosity of 80-86 vol% were obtained. The compressive strength ranged from 2.0 MPa up to 9.9 MPa. Both the foaming and sintering processes contributed to the development of different microstructures.

  • 281. Debatin, Franziska
    et al.
    Behrens, Karsten
    Weber, Jens
    Baburin, Igor A.
    Thomas, Arne
    Schmidt, Johannes
    Senkovska, Irena
    Kaskel, Stefan
    Kelling, Alexandra
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bacsik, Zoltan
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Leoni, Stefano
    Seifert, Gotthard
    Jaeger, Christian
    Guenter, Christina
    Schilde, Uwe
    Friedrich, Alwin
    Holdt, Hans-Juergen
    An Isoreticular Family of Microporous Metal-Organic Frameworks Based on Zinc and 2-Substituted Imidazolate-4-amide-5-imidate: Syntheses, Structures and Properties2012In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 18, no 37, p. 11630-11640Article in journal (Refereed)
    Abstract [en]

    We report on a new series of isoreticular frameworks based on zinc and 2-substituted imidazolate-4-amide-5-imidate (IFP-14, IFP=imidazolate framework Potsdam) that form one-dimensional, microporous hexagonal channels. Varying R in the 2-substitued linker (R=Me (IFP-1), Cl (IFP-2), Br (IFP-3), Et (IFP-4)) allowed the channel diameter (4.01.7 angstrom), the polarisability and functionality of the channel walls to be tuned. Frameworks IFP-2, IFP-3 and IFP-4 are isostructural to previously reported IFP-1. The structures of IFP-2 and IFP-3 were solved by X-ray crystallographic analyses. The structure of IFP-4 was determined by a combination of PXRD and structure modelling and was confirmed by IR spectroscopy and 1H MAS and 13C CP-MAS NMR spectroscopy. All IFPs showed high thermal stability (345400?degrees C); IFP-1 and IFP-4 were stable in boiling water for 7 d. A detailed porosity analysis was performed on the basis of adsorption measurements by using various gases. The potential of the materials to undergo specific interactions with CO2 was investigated by measuring the isosteric heats of adsorption. The capacity to adsorb CH4 (at 298 K), CO2 (at 298 K) and H2 (at 77 K) at high pressure were also investigated. In situ IR spectroscopy showed that CO2 is physisorbed on IFP-14 under dry conditions and that both CO2 and H2O are physisorbed on IFP-1 under moist conditions.

  • 282.
    Debatin, Franziska
    et al.
    Universität Potsdam.
    Thomas, Arne
    Technische Universität Berlin.
    Kelling, Alexandra
    Universität Potsdam.
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bacsik, Zoltan
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Senkovska, Irena
    Technische Universität Dresden.
    Kaskel, Stefan
    Technische Universität Dresden.
    Junginger, Matthias
    Universität Potsdam.
    Mueller, Holger
    Universität Potsdam.
    Schilde, Uwe
    Universität Potsdam.
    Jaeger, Christian
    Federal Institute for Materials Research and Testing, Berlin.
    Friedrich, Alwin
    Universität Potsdam.
    Holdt, Hans-Juergen
    Universität Potsdam.
    In Situ Synthesis of an Imidazolate-4-amide-5-imidate Ligand and Formation of a Microporous Zinc-Organic Framework with H-2-and CO2-Storage Ability2010In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 49, no 7, p. 1258-1262Article in journal (Refereed)
  • 283.
    Deiana, Luca
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Dziedzic, Pawel
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zhao, Gui-Ling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ullah, Farman
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lin, Shuangzheng
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Dynamic kinetic asymmetric transformation (DYKAT) by combination of amine and transition metal cascade catalysis2010In: Abstracts of Papers, 239th ACS National Meeting, San Francisco, CA, United States, March 21-25, 2010, Washington, D C: American Chemical Society , 2010Conference paper (Other academic)
  • 284.
    Deiana, Luca
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ghisu, Lorenza
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Afewerki, Samson
    Verho, Oscar
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Johnston, Eric V.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bacsik, Zoltan
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Mid-Sweden University, Sweden.
    Enantioselective Heterogeneous Synergistic Catalysis for Asymmetric Cascade Transformations2014In: Advanced Synthesis and Catalysis, ISSN 1615-4150, E-ISSN 1615-4169, Vol. 356, no 11-12, p. 2485-2492Article in journal (Refereed)
    Abstract [en]

    A modular design for a novel heterogeneous synergistic catalytic system, which simultaneously activates the electrophile and nucleophile by the combined activation modes of a separate metal and non-metal catalyst, for asymmetric cascade transformations on a solid surface is disclosed. This modular catalysis strategy generates carbocycles (up to 97.5: 2.5 er) as well as spirocyclic oxindoles (97.5: 2.5 to > 99: 0.5 er), containing all-carbon quaternary centers, in a highly enantioselective fashion via a one-pot dynamic relay process.

  • 285.
    Deiana, Luca
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Jiang, Yan
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Palo-Nieto, Carlos
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Afewerki, Samson
    Incerti-Pradillos, Celia A.
    Verho, Oscar
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Johnston, Eric V.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Mid Sweden University, Sweden.
    Combined Heterogeneous Metal/Chiral Amine: Multiple Relay Catalysis for Versatile Eco-Friendly Synthesis2014In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 53, no 13, p. 3447-3451Article in journal (Refereed)
    Abstract [en]

    Herein is described a versatile and broad synergistic strategy for expansion of chemical space and the synthesis of valuable molecules (e.g. carbocycles and heterocycles), with up to three quaternary stereocenters, in a highly enantioselective fashion from simple alcohols (31examples, 95:5 to >99.5:0.5 e.r.) using integrated heterogeneous metal/chiral amine multiple relay catalysis and air/O-2 as the terminal oxidant. A novel highly 1,4-selective heterogeneous metal/amine co-catalyzed hydrogenation of enals was also added to the relay catalysis sequences.

  • 286. Deng, Hexiang
    et al.
    Grunder, Sergio
    Cordova, Kyle E.
    Valente, Cory
    Furukawa, Hiroyasu
    Hmadeh, Mohamad
    Gandara, Felipe
    Whalley, Adam C.
    Liu, Zheng
    Asahina, Shunsuke
    Kazumori, Hiroyoshi
    O'Keeffe, Michael
    Terasaki, Osamu
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Stoddart, J. Fraser
    Yaghi, Omar M.
    Large pore apertures in a series of metal organic frameworks2012In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 336, no 6084, p. 1018-1023Article in journal (Refereed)
    Abstract [en]

    We report a strategy to expand the pore aperture of metal-organic frameworks (MOFs) into a previously unattained size regime (>32 angstroms). Specifically, the systematic expansion of a well-known MOF structure, MOF-74, from its original link of one phenylene ring (I) to two, three, four, five, six, seven, nine, and eleven (II to XI, respectively), afforded an isoreticular series of MOF-74 structures (termed IRMOF-74-I to XI) with pore apertures ranging from 14 to 98 angstroms. All members of this series have non-interpenetrating structures and exhibit robust architectures, as evidenced by their permanent porosity and high thermal stability (up to 300 degrees C). The pore apertures of an oligoethylene glycol-functionalized IRMOF-74-VII and IRMOF-74-IX are large enough for natural proteins to enter the pores.

  • 287.
    Deng, Hong-Ping
    et al.
    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.
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Allylic sp (3) C-H borylation of alkenes via allyl-Pd intermediates: an efficient route to allylboronates2014In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 50, no 65, p. 9207-9210Article in journal (Refereed)
    Abstract [en]

    Palladium catalyzed allylic C-H functionalization was performed using exocyclic alkene substrates. Multi-component synthesis of stereodefined homoallylic alcohols could be performed using a reaction sequence involving allylic C-H borylation and allylation of aldehydes.

  • 288.
    Dey, Kalpana R.
    et al.
    Leibniz Univ Hannover, Inst Mineral, Hannover, Germany .
    Debnath, Tapas
    Leibniz Univ Hannover, Inst Mineral, Hannover, Germany .
    Ruescher, Claus H.
    Leibniz Univ Hannover, Inst Mineral, Hannover, Germany .
    Sundberg, Margareta
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Hussain, Altaf
    Univ Dhaka, Dept Chem, Dhaka 1000, Bangladesh .
    Synthesis and characterization of niobium doped hexagonal tungsten bronze in the systems, Cs(x)Nb(y)W(1-y)O(3)2011In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 46, no 5, p. 1388-1395Article in journal (Refereed)
    Abstract [en]

    Samples of nominal compositions, Cs(0.25)Nb (y) W(1-y) O(3) and Cs(0.3)Nb (y) W(1-y) O(3) with 0.0 a parts per thousand currency sign y a parts per thousand currency sign 0.25 and 0.0 a parts per thousand currency sign y a parts per thousand currency sign 0.3 were synthesized using appropriate amounts of Cs(2)WO(4), WO(3) and WO(2) in evacuated and closed silica glass tubes at 800 A degrees C. The polycrystalline products contain hexagonal shaped crystals of up to 15 mu m diameter as long as y a parts per thousand currency sign 0.15. X-ray powder patterns of the samples reveal the formation of hexagonal tungsten bronze (HTB-I) type phase with y < 0.1. A mixture of HTB-I and an analogous less reduced hexagonal tungsten bronze (HTB-II) type phase is seen when y a parts per thousand yen 0.1. HTB-II content increases with increasing y, revealing close similarity to bronzoid type phases when y = x. Results of SEM/EDX analysis also support a partial substitution of tungsten by niobium in the HTB-I type phase. Infrared absorption and optical reflectivity data shows the effect of increasing amount of non-metallic phase for y > 0.1 and the effect of counterdoping by Nb(5+)/W(5+) substitution in the metallic HTB-I type phase for y a parts per thousand currency sign 0.1, respectively. Reinvestigations in the system Rb(0.3)Nb (y) W(1-y) O(3) (0.0 a parts per thousand currency sign y a parts per thousand currency sign 0.175) show similar results with increasing content of HTB-II type phase related with y.

  • 289. Di Marcantonio, M.
    et al.
    Namanga, J. E.
    Smetana, Volodymyr
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Gerlitzki, N.
    Vollkommer, F.
    Mudring, Anja-Verena
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bacher, G.
    Nannen, E.
    Green-yellow emitting hybrid light emitting electrochemical cell2017In: Journal of Materials Chemistry C, ISSN 2050-7526, E-ISSN 2050-7534, Vol. 5, no 46, p. 12062-12068Article in journal (Refereed)
    Abstract [en]

    Light-emitting electrochemical cells (LECs) are attractive candidates for future low-cost lighting applications such as light-emitting smart tags, thanks to their simplicity, fully solution-based fabrication and flexibility. However, high brightness and efficiency in combination with satisfactory operation lifetimes need to be achieved for different emission colours bearing future device commercialization in mind. LECs emitting in the yellow-green spectral range, where the human eye is most sensitive are thereby particularly attractive. Here we present an improved hybrid LEC based on an Ir-iTMC, [Ir(4-Fppy)(2)(pbpy)][PF6] (4-Fppy = 2-(4-fluorophenyl) pyridinato, pbpy = 6-phenyl-2,2'-bipyridine) emitting at 557 nm. It features a luminance of 2400 cd m(-2) when driven at a constant voltage of 4 V, and a lifetime of 271 h at a luminance of 1500 cd m(-2) under pulsed current operation. The hybrid LEC shows an enhanced performance compared to a LEC solely based on the Ir-ITMC where operation lifetimes of 165 h at a luminance above 1200 cd m(-2) under pulsed current operation conditions were observed. The performance improvement was achieved by addition of a solution-processed ZnO nanoparticle film on top.

  • 290. DiGangi, Joseph
    et al.
    Blum, Arlene
    Bergman, Åke
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    de Wit, Cynthia A.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Lucas, Donald
    Mortimer, David
    Schecter, Arnold
    Scheringer, Martin
    Shaw, Susan
    Webster, Tomas F.
    San Antonio Statement on brominated and chlorinated flame retardants2010In: Environmental Health Perspectives, ISSN 0091-6765, Vol. 118, no 12, p. A516-A518Article in journal (Refereed)
  • 291. Ding, Huimin
    et al.
    Li, Jian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Peking University, China.
    Xie, Guohua
    Lin, Guiqing
    Chen, Rufan
    Peng, Zhengkang
    Yang, Chuluo
    Wang, Baoshan
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Peking University, China.
    Wang, Cheng
    An AIEgen-based 3D covalent organic framework for white light-emitting diodes2018In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 9, article id 5234Article in journal (Refereed)
    Abstract [en]

    The design and synthesis of three-dimensional covalent organic frameworks (3D COFs) have still been considered as a big challenge. Here we report the design and synthesis of an AIEgen-based 3D COF (3D-TPE-COF), with a high surface area (1084 m(2)g(-1)). According to powder X-ray diffraction and continuous rotation electron diffraction analyses, 3D-TPE-COF is identified to adopt a seven-fold interpenetrated pts topology. Interestingly, 3D-TPE-COF emits yellow fluorescence upon excitation, with a photoluminescence quantum yield of 20%. Moreover, by simply coating 3D-TPE-COF onto a commercial blue light-emitting diode (LED), a prototype white LED (WLED) under continuously driving without degradation for 1200 h was demonstrated. The present work suggests the possibility of using COF materials for stable WLEDs, which will greatly inspire us to design and synthesize fluorescent 3D COFs and facilitate the development of COF-based WLEDs in future.

  • 292. Dingemans, Milou M L
    et al.
    de Groot, Aart
    van Kleef, Regina G D M
    Bergman, Åke
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Environmental Chemistry.
    van den Berg, Martin
    Vijverberg, Henk P M
    Westerink, Remco H S
    Hydroxylation increases the neurotoxic potential of BDE-47 to affect exocytosis and calcium homeostasis in PC12 cells.2008In: Journal of Environmental Health Perspectives, ISSN 0091-6765, E-ISSN 1552-9924, Vol. 116, no 5, p. 637-43Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: Oxidative metabolism, resulting in the formation of hydroxylated polybrominated diphenyl ether (PBDE) metabolites, may enhance the neurotoxic potential of brominated flame retardants. OBJECTIVE: Our objective was to investigate the effects of a hydroxylated metabolite of 2,2',4,4'-tetra-bromodiphenyl ether (BDE-47; 6-OH-BDE-47) on changes in the intracellular Ca2+ concentration ([Ca2+]i) and vesicular catecholamine release in PC12 cells. METHODS: We measured vesicular catecholamine release and [Ca2+]i using amperometry and imaging of the fluorescent Ca2+-sensitive dye Fura-2, respectively. RESULTS: Acute exposure of PC12 cells to 6-OH-BDE-47 (5 microM) induced vesicular catecholamine release. Catecholamine release coincided with a transient increase in [Ca2+]i, which was observed shortly after the onset of exposure to 6-OH-BDE-47 (120 microM). An additional late increase in [Ca2+]i was often observed at &gt; or =1 microM 6-OH-BDE-47. The initial transient increase was absent in cells exposed to the parent compound BDE-47, whereas the late increase was observed only at 20 microM. Using the mitochondrial uncoupler carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone (FCCP) and thapsigargin to empty intracellular Ca2+ stores, we found that the initial increase originates from emptying of the endoplasmic reticulum and consequent influx of extracellular Ca2+, whereas the late increase originates primarily from mitochondria. CONCLUSION: The hydroxylated metabolite 6-OH-BDE-47 is more potent in disturbing Ca2+ homeostasis and neurotransmitter release than the parent compound BDE-47. The present findings indicate that bioactivation by oxidative metabolism adds considerably to the neurotoxic potential of PBDEs. Additionally, based on the observed mechanism of action, a cumulative neurotoxic effect of PBDEs and ortho-substituted polychlorinated biphenyls on [Ca2+]i cannot be ruled out.

  • 293. Dingemans, Milou M. L.
    et al.
    Heusinkveld, Harm J.
    Bergman, Åke
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    van den Berg, Martin
    Westerink, Remco H. S.
    Bromination Pattern of Hydroxylated Metabolites of BDE-47 Affects Their Potency to Release Calcium from Intracellular Stores in PC12 Cells2010In: Journal of Environmental Health Perspectives, ISSN 0091-6765, E-ISSN 1552-9924, Vol. 118, no 4, p. 519-525Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: Brominated flame retardants, including the widely used polybrominated diphenyl ethers (PBDEs), have been detected in humans, raising concern about possible neurotoxicity. Recent research demonstrated that the hydroxylated metabolite 6-OH-BDE-47 increases neurotransmitter release by releasing calcium ions (Ca2+) from intracellular stores at much lower concentrations than its environmentally relevant parent congener BDE-47. Recently, several other hydroxylated BDE-47 metabolites, besides 6-OH-BDE-47, have been detected in human serum and cord blood. OBJECTIVE AND METHODS: To investigate the neurotoxic potential of other environmentally relevant PBDEs and their metabolites, we examined and compared the acute effects of BDE-47, BDE-49, BDE-99, BDE-100, BDE-153, and several metabolites of BDE-47-6-OH-BDE-47 (and its methoxylated analog 6-MeO-BDE-47), 6'-OH-BDE-49, 5-OH-BDE-47, 3-OH-BDE-47, and 4'-OH-BDE-49 on intracellular Ca2+ concentration ([Ca2+](i)), measured using the Ca2+-responsive dye Fura-2 in neuroendocrine pheochromocytoma (PC12) cells. RESULTS: In contrast to the parent PBDEs and 6-MeO-BDE-47, all hydroxylated metabolites induced Ca2+ release from intracellular stores, although with different lowest observed effect concentrations (LOECs). The major intracellular Ca2+ sources were either endoplasmic reticulum (ER; 5-OH-BDE-47 and 6'-OH-BDE-49) or both ER and mitochondria (6-OH-BDE-47, 3-OH-BDE-47, and 4'-OH-BDE-49). When investigating fluctuations in [Ca2+](i), which is a more subtle end point, we observed lower LOECs for 6-OH-BDE-47 and 4'-OH-BDE-49, as well as for BDE-47. CONCLUSIONS: The present findings demonstrate that hydroxylated metabolites of BDE-47 cause disturbance of the [Ca2+](i). Importantly, shielding of the OH group on both sides with bromine atoms and/or the ether bond to the other phenyl ring lowers the potency of hydroxylated PBDE metabolites.

  • 294. Dingemans, Milou M L
    et al.
    Heusinkveld, Harm J
    de Groot, Aart
    Bergman, Åke
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Environmental Chemistry.
    van den Berg, Martin
    Westerink, Remco H S
    Hexabromocyclododecane (HBCD) inhibits depolarization-induced increase in intracellular calcium levels and neurotransmitter release in PC12 cells.2009In: Toxicol Sci, ISSN 1096-0929, Vol. 107, no 2, p. 490-498Article in journal (Other academic)
    Abstract [en]

    Environmental levels of the brominated flame retardant (BFR) hexabromocyclododecane (HBCD) have been increasing. HBCD has been shown to cause adverse effects on learning and behavior in mice, as well as on dopamine uptake in rat synaptosomes and synaptic vesicles. For other BFRs, alterations in the intracellular Ca(2+) homeostasis have been observed. Therefore, the aim of this study was to investigate whether the technical HBCD mixture and individual stereoisomers affect the intracellular Ca(2+) concentration ([Ca(2+)](i)) in a neuroendocrine in vitro model (PC12 cells). [Ca(2+)](i) and vesicular catecholamine release were measured using respectively single-cell Fura-2 imaging and amperometry. Exposure of PC12 cells to the technical HBCD mixture or individual stereoisomers did neither affect basal [Ca(2+)](i), nor the frequency of basal neurotransmitter release. However, exposure to HBCD (0 - 20 muM) did cause a dose-dependent reduction of a subsequent depolarization-evoked increase in [Ca(2+)](i). This effect was apparent only when HBCD was applied at least 5 min before depolarization (maximum effect after 20 min exposure). The effects of alpha- and beta-HBCD were comparable to that of the technical mixture, whereas the inhibitory effect of gamma-HBCD was larger. Using specific blockers of L-, N- or P/Q-type voltage-gated Ca(2+) channels (VGCCs) it was shown that the inhibitory effect of HBCD is not VGCC-specific. Additionally, the number of cells showing depolarization-evoked neurotransmitter release was markedly reduced following HBCD exposure. Summarizing, HBCD inhibits depolarization-evoked [Ca(2+)](i) and neurotransmitter release. As increasing HBCD levels should be anticipated, these findings justify additional efforts to establish an adequate exposure, hazard and risk assessment.

  • 295. Dingemans, Milou M. L.
    et al.
    Heusinkveld, Harm J.
    de Groot, Aart
    Bergman, Åke
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Environmental Chemistry.
    van den Berg, Martin
    Westerink, Remco H. S.
    Hexabromocyclododecane Inhibits Depolarization-Induced Increase in Intracellular Calcium Levels and Neurotransmitter Release in PC12 Cells2009In: Toxicological Sciences, ISSN 1096-6080, E-ISSN 1096-0929, Vol. 107, no 2, p. 490-497Article in journal (Refereed)
    Abstract [en]

    Environmental levels of the brominated flame retardant (BFR) hexabromocyclododecane (HBCD) have been increasing. HBCD has been shown to cause adverse effects on learning and behavior in mice, as well as on dopamine uptake in rat synaptosomes and synaptic vesicles. For other BFRs, alterations in the intracellular Ca2+ homeostasis have been observed. Therefore, the aim of this study was to investigate whether the technical HBCD mixture and individual stereoisomers affect the intracellular Ca2+ concentration ([Ca2+](i)) in a neuroendocrine in vitro model (PC12 cells). [Ca2+](i) and vesicular catecholamine release were measured using respectively single-cell Fura-2 imaging and amperometry. Exposure of PC12 cells to the technical HBCD mixture or individual stereoisomers did neither affect basal [Ca2+](i), nor the frequency of basal neurotransmitter release. However, exposure to HBCD (0-20 mu M) did cause a dose-dependent reduction of a subsequent depolarization-evoked increase in [Ca2+](i). This effect was apparent only when HBCD was applied at least 5 min before depolarization (maximum effect after 20 min exposure). The effects of alpha- and beta-HBCD were comparable to that of the technical mixture, whereas the inhibitory effect of gamma-HBCD was larger. Using specific blockers of L-, N- or P/Q-type voltage-gated Ca2+ channels (VGCCs) it was shown that the inhibitory effect of HBCD is not VGCC-specific. Additionally, the number of cells showing depolarization-evoked neurotransmitter release was markedly reduced following HBCD exposure. Summarizing, HBCD inhibits depolarization-evoked [Ca2+](i) and neurotransmitter release. As increasing HBCD levels should be anticipated, these findings justify additional efforts to establish an adequate exposure, hazard and risk assessment.

  • 296. Dingemans, Milou M. L.
    et al.
    van den Berg, Martin
    Bergman, Åke
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Westerink, Remco H. S.
    Calcium-Related Processes Involved in the Inhibition of Depolarization-Evoked Calcium Increase by Hydroxylated PBDEs in PC12 Cells2010In: Toxicological Sciences, ISSN 1096-6080, E-ISSN 1096-0929, Vol. 114, no 2, p. 302-309Article in journal (Refereed)
    Abstract [en]

    In vitro studies indicated that hydroxylated polybrominated diphenyl ethers (OH-PBDEs) have an increased toxic potential compared to their parent congeners. An example is the OH-PBDE–induced increase of basal intracellular Ca2+ concentration ([Ca2+]i) by release of Ca2+ from endoplasmic reticulum (ER) and mitochondria and/or influx of extracellular Ca2+. ER and mitochondria regulate Ca2+ homeostasis in close association with voltage-gated Ca2+ channels (VGCCs). Therefore, effects of (OH-)PBDEs on the depolarization-evoked (100mM K+) net increase in [Ca2+]i (depolarization-evoked [Ca2+]i) were measured in neuroendocrine pheochromocytoma cells using the Ca2+-responsive dye Fura-2. OH-PBDEs dose dependently inhibited depolarization-evoked [Ca2+]i. This inhibition was potentiated by a preceding increase in basal [Ca2+]i. Especially at higher concentrations of OH-PBDEs (5–20μM), large increases in basal [Ca2+]i strongly inhibited depolarization-evoked [Ca2+]i. The inhibition appeared more sensitive to increases in basal [Ca2+]i by Ca2+ release from intracellular stores (by 3-OH-BDE-47 or 6′-OH-BDE-49) compared to those by influx of extracellular Ca2+ (by 6-OH-BDE-47 or 5-OH-BDE-47). The expected [Ca2+]i difference close to the membrane suggests involvement of Ca2+-dependent regulatory processes close to VGCCs. When coapplied with depolarization, some OH-PBDEs induced also moderate direct inhibition of depolarization-evoked [Ca2+]i. Polybrominated diphenyl ethers and methoxylated BDE-47 affected neither basal nor depolarization-evoked [Ca2+]i, except for BDE-47, which moderately increased fluctuations in basal [Ca2+]i and depolarization-evoked [Ca2+]i. These findings demonstrate that OH-PBDEs inhibit depolarization-evoked [Ca2+]i depending on preceding basal [Ca2+]i. Related environmental pollutants that affect Ca2+ homeostasis (e.g., polychlorinated biphenyls) may thus also inhibit depolarization-evoked [Ca2+]i, justifying further investigation of possible mixture effects of environmental pollutants on Ca2+ homeostasis.

  • 297. Disch, S.
    et al.
    Hermann, R. P.
    Wetterskog, Erik
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Podlesnyak, A. A.
    An, K.
    Hyeon, T.
    Salazar-Alvarez, German
    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).
    Brueckel, Th.
    Spin excitations in cubic maghemite nanoparticles studied by time-of-flight neutron spectroscopy2014In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 89, no 6, p. 064402-Article in journal (Refereed)
    Abstract [en]

    We have determined the field dependence of collective magnetic excitations in iron oxide nanoparticles of cubic shape with 8.42(2) nm edge length and a narrow log normal size distribution of 8.2(2)% using time-of-flight neutron spectroscopy. The energy dependence of the uniform precession modes was investigated up to 5 T applied field and yields a Lande factor g = 2.05(2) as expected for maghemite (gamma-Fe2O3) nanoparticles. A large effective anisotropy field of B-A,B-eff = 0.45(16) T was determined, in excellent agreement with macroscopic measurements. This anisotropy is attributed to enhanced shape anisotropy in these monodisperse cubic nanoparticles. The combination of our results with macroscopic magnetization information provides a consistent view of the energy scales of superparamagnetic relaxation and collective magnetic excitations in magnetic nanoparticles.

  • 298. Disch, Sabrina
    et al.
    Wetterskog, Erik
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hermann, Raphael P.
    Korolkov, Denis
    Busch, Peter
    Boesecke, Peter
    Lyon, Olivier
    Vainio, Ulla
    Salazar-Alvarez, German
    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).
    Brueckel, Thomas
    Structural diversity in iron oxide nanoparticle assemblies as directed by particle morphology and orientation2013In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 5, no 9, p. 3969-3975Article in journal (Refereed)
    Abstract [en]

    The mesostructure of ordered arrays of anisotropic nanoparticles is controlled by a combination of packing constraints and interparticle interactions, two factors that are strongly dependent on the particle morphology. We have investigated how the degree of truncation of iron oxide nanocubes controls the mesostructure and particle orientation in drop cast mesocrystal arrays. The combination of grazing incidence small-angle X-ray scattering and scanning electron microscopy shows that mesocrystals of highly truncated cubic nanoparticles assemble in an fcc-type mesostructure, similar to arrays formed by iron oxide nanospheres, but with a significantly reduced packing density and displaying two different growth orientations. Strong satellite reflections in the GISAXS pattern indicate a commensurate mesoscopic superstructure that is related to stacking faults in mesocrystals of the anisotropic nanocubes. Our results show how subtle variation in shape anisotropy can induce oriented arrangements of nanoparticles of different structures and also create mesoscopic superstructures of larger periodicity.

  • 299. Disch, Sabrina
    et al.
    Wetterskog, Erik
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hermann, Raphaël
    Salazar-Alvarez, German
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Busch, Peter
    Brückel, Thomas
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Kamali, Saeed
    Shape Induced Symmetry in Self-Assembled Mesocrystals of Iron Oxide Nanocubes2011In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 11, no 4, p. 1651-1656Article in journal (Refereed)
    Abstract [en]

    Grazing incidence small-angle scattering and electron microscopy have been used to show for the first time that nonspherical nanoparticles can assemble into highly ordered body-centered tetragonal mesocrystals. Energy models accounting for the directionality and magnitude of the van der Waals and dipolar interactions as a function of the degree of truncation of the nanocubes illustrated the importance of the directional dipolar forces for the formation of the initial nanocube clusters and the dominance of the van der Waals multibody interactions in the dense packed arrays.

  • 300. Dish, Sabina
    et al.
    Wetterskog, Erik
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hermann, Raphäel P.
    Wiedenmann, A.
    Vainio, U.
    Salazar-Alvarez, German
    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).
    Brückel, Thomas
    Quantitative spatial magnetization distribution in iron oxide nanocubes and nanospheres by polarized small-angle neutron scattering2012In: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 14, p. 013025-Article in journal (Refereed)
    Abstract [en]

    By means of polarized small-angle neutron scattering, we have resolved the long-standing challenge of determining the magnetization distribution in magnetic nanoparticles in absolute units. The reduced magnetization, localized in non-interacting nanoparticles, indicates strongly particle shape-dependent surface spin canting with a 0.3(1) and 0.5(1) nm thick surface shell of reduced magnetization found for similar to 9 nm nanospheres and similar to 8.5 nm nanocubes, respectively. Further, the reduced macroscopic magnetization in nanoparticles results not only from surface spin canting, but also from drastically reduced magnetization inside the uniformly magnetized core as compared to the bulk material. Our microscopic results explain the low macroscopic magnetization commonly found in nanoparticles.

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