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  • 1.
    Yang, Taimin
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    3D Electron Microscopy Methods and Applications: Structures from Atomic Scale to Mesoscale2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The crystal structure determines the physical properties of a material. The structure can be analysed at different levels, from atomic level, mesoscale level, all the way up to the macroscale level. Transmission Electron Microscope (TEM) is a powerful tool for studying the structure of materials at atomic scale level and mesoscale level because of the short wavelength of the electrons. At atomic scale level, structure determination using TEM can be performed in diffraction mode. The recent developments in 3D electron diffraction methods make structure determination from nano- and micron-sized crystals much easier than before. However, due to the strong interactions, electrons can be scattered multiple times through the crystal, causing the measured intensities to be less accurate than that in the X-ray case.

    In this thesis, we use the continuous rotation electron diffraction (cRED) developed in our group to investigate the structure of materials and the accuracy of this method. In the third chapter, we use cRED method to determine the structure of two aluminophosphate zeolites, PST-13 and PST-14. We presented that these structures can be built from two pairs of enantiomeric structural building units. In the fourth chapter, we show that despite the inaccuracy in measured intensities originated from dynamical effect, it is still possible to determine the structure accurately. We show that the atomic coordinates of ZSM-5 and sucrose crystal structure determined by multiple electron diffraction datasets is identical to that determined from X-ray data or neutron data. We also assessed the linearity between calculated structure factor and observed structure factor and use this as a coarse assessment indicator for diffraction data quality for protein crystals.

    Apart from atomic structure, mesoscale structures, such as mesopores, can also determine the property of materials. For the 3D structures of these nanoscale structures, we can also use TEM electron tomography techniques to investigate. In chapter five, we performed electron tomography for two different materials with mesoporous structure and illustrated the formation mechanism of mesoporous magnesium carbonate and the internal tunnel structure of hierarchical TS-1 zeolite.

  • 2.
    Sultan, Sahar
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Mathew, Aji P.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    3D PRINTED NANOCELLULOSE HYDROGEL SCAFFOLDS FOR BIOMEDICAL APPLICATIONS – POROSITY VS MECHANICAL PROPERTIES2019Conference paper (Other academic)
  • 3.
    Sultan, Sahar
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Mathew, Aji
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    3D printed nanocellulose scaffolds designed for biomedical applications2019Conference paper (Refereed)
  • 4.
    Sultan, Sahar
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Mathew, Aji P.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    3D printed porous bioscaffolds based on cellulose nanocrystals2019Conference paper (Other academic)
  • 5.
    Sultan, Sahar
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Mathew, Aji P.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    3D Printed Porous Cellulose Nanocomposite Hydrogel Scaffolds2019In: Journal of Visualized Experiments, ISSN 1940-087X, E-ISSN 1940-087X, no 146, article id e59401Article in journal (Refereed)
    Abstract [en]

    This work demonstrates the use of three-dimensional (3D) printing to produce porous cubic scaffolds using cellulose nanocomposite hydrogel ink, with controlled pore structure and mechanical properties. Cellulose nanocrystals (CNCs, 69.62 wt%) based hydrogel ink with matrix (sodium alginate and gelatin) was developed and 3D printed into scaffolds with uniform and gradient pore structure (110-1,100 µm). The scaffolds showed compression modulus in the range of 0.20-0.45 MPa when tested in simulated in vivo conditions (in distilled water at 37 °C). The pore sizes and the compression modulus of the 3D scaffolds matched with the requirements needed for cartilage regeneration applications. This work demonstrates that the consistency of the ink can be controlled by the concentration of the precursors and porosity can be controlled by the 3D printing process and both of these factors in return defines the mechanical properties of the 3D printed porous hydrogel scaffold. This process method can therefore be used to fabricate structurally and compositionally customized scaffolds according to the specific needs of patients.

  • 6. Huang, Jing
    et al.
    Xu, Bo
    Tian, Lei
    Pati, Palas Baran
    Etman, Ahmed S.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hammarstrom, Leif
    Tian, Haining
    A heavy metal-free CuInS2 quantum dot sensitized NiO photocathode with a Re molecular catalyst for photoelectrochemical CO2 reduction2019In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 55, no 55, p. 7918-7921Article in journal (Refereed)
    Abstract [en]

    Heavy metal-free CuInS2 quantum dots (QDs) were employed as a photosensitizer on a NiO photocathode to drive an immobilized molecular Re catalyst for photoelectrochemical CO2 reduction for the first time. A photocurrent of 25 mu A cm(-2) at -0.87 V vs. NHE was obtained, providing a faradaic efficiency of 32% for CO production.

  • 7. Lenzen, Dirk
    et al.
    Zhao, Jingjing
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Ernst, Sebastian-Johannes
    Wahiduzzaman, Mohammad
    Inge, A. Ken
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Fröhlich, Dominik
    Xu, Hongyi
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bart, Hans-Jörg
    Janiak, Christoph
    Henninger, Stefan
    Maurin, Guillaume
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Stock, Norbert
    A metal-organic framework for efficient water-based ultra-low-temperature-driven cooling2019In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 10, article id 3025Article in journal (Refereed)
    Abstract [en]

    Efficient use of energy for cooling applications is a very important and challenging field in science. Ultra-low temperature actuated (T-driving< 80 degrees C) adsorption-driven chillers (ADCs) with water as the cooling agent are one environmentally benign option. The nanoscale metal-organic framework [Al(OH)(C6H2O4S)] denoted CAU-23 was discovered that possess favorable properties, including water adsorption capacity of 0.37 g(H2O)/g(sorbent) around p/p(0 )= 0.3 and cycling stability of at least 5000 cycles. Most importantly the material has a driving temperature down to 60 degrees C, which allows for the exploitation of yet mostly unused temperature sources and a more efficient use of energy. These exceptional properties are due to its unique crystal structure, which was unequivocally elucidated by single crystal electron diffraction. Monte Carlo simulations were performed to reveal the water adsorption mechanism at the atomic level. With its green synthesis, CAU-23 is an ideal material to realize ultra-low temperature driven ADC devices.

  • 8. Sun, Tiedong
    et al.
    Mirzoev, Alexander
    Minhas, Vishal
    Korolev, Nikolay
    Lyubartsev, Alexander P.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Nordenskiöld, Lars
    A multiscale analysis of DNA phase separation: from atomistic to mesoscale level2019In: Nucleic Acids Research, ISSN 0305-1048, E-ISSN 1362-4962, Vol. 47, no 11, p. 5550-5562Article in journal (Refereed)
    Abstract [en]

    DNA condensation and phase separation is of utmost importance for DNA packing in vivo with important applications in medicine, biotechnology and polymer physics. The presence of hexagonally ordered DNA is observed in virus capsids, sperm heads and in dinoflagellates. Rigorous modelling of this process in all-atom MD simulations is presently difficult to achieve due to size and time scale limitations. We used a hierarchical approach for systematic multiscale coarse-grained (CG) simulations of DNA phase separation induced by the three-valent cobalt(III)-hexammine (CoHex(3+)). Solvent-mediated effective potentials for a CG model of DNA were extracted from all-atom MD simulations. Simulations of several hundred 100-bp-long CG DNA oligonucleotides in the presence of explicit CoHex(3+) ions demonstrated aggregation to a liquid crystalline hexagonally ordered phase. Following further coarse-graining and extraction of effective potentials, we conducted modelling at mesoscale level. In agreement with electron microscopy observations, simulations of an 10.2-kblong DNA molecule showed phase separation to either a toroid or a fibre with distinct hexagonal DNA packing. The mechanism of toroid formation is analysed in detail. The approach used here is based only on the underlying all-atom force field and uses no adjustable parameters and may be generalised to modelling chromatin up to chromosome size.

  • 9. Zhou, Fang
    et al.
    Sultanbawa, Yasmina
    Feng, Huan
    Wang, Yong-Lei
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Meng, Qingtao
    Wang, Yue
    Zhang, Zhigiang
    Zhang, Run
    A New Red-Emitting Fluorescence Probe for Rapid and Effective Visualization of Bisulfite in Food Samples and Live Animals2019In: Journal of Agricultural and Food Chemistry, ISSN 0021-8561, E-ISSN 1520-5118, Vol. 67, no 15, p. 4375-4383Article in journal (Refereed)
    Abstract [en]

    The development of new methods for rapid and effective detection of bisulfite (HSO3-) in food samples and imaging of HSO3- intake in animals is of significant importance due to the key roles of HSO3- in food quality assurance and community health. In this work, a new responsive fluorescence probe, EQC, is reported for the quantitative detection of HSO3- in food samples and visualization of HSO3- intake in animals. Upon addition of HSO3-, the UV-vis absorption and red emission of EQC were significantly decreased within 120 s. The changes in absorption and emission spectra of EQC were rationalized by theoretical computations. The proposed reaction mechanism of EQC with HSO3- was confirmed by high-resolution mass spectrometry (HRMS) and spectroscopic titration measurements. EQC has the advantages of high sensitivity, selectivity (a detection limit of 18.1 nM), and fast response toward HSO3-, which enable rapid and effective HSO3- detection in buffer solution. The practical applications of EQC were demonstrated by the detection of HSO3- in food samples and the imaging of HSO3- intake in live animals.

  • 10. Kushwaha, Khushbu
    et al.
    Yu, Liyang
    Stranius, Kati
    Singh, Sandeep Kumar
    Hultmark, Sandra
    Iqbal, Muhammad Naeem
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Johnston, Eric
    Erhart, Paul
    Müller, Christian
    Börjesson, Karl
    A Record Chromophore Density in High-Entropy Liquids of Two Low-Melting Perylenes: A New Strategy for Liquid Chromophores2019In: Advanced Science, ISSN 2198-3844, Vol. 6, no 4, article id 1801650Article in journal (Refereed)
    Abstract [en]

    Liquid chromophores constitute a rare but intriguing class of molecules that are in high demand for the design of luminescent inks, liquid semiconductors, and solar energy storage materials. The most common way to achieve liquid chromophores involves the introduction of long alkyl chains, which, however, significantly reduces the chromophore density. Here, strategy is presented that allows for the preparation of liquid chromophores with a minimal increase in molecular weight, using the important class of perylenes as an example. Two synergistic effects are harnessed: (1) the judicious positioning of short alkyl substituents, and (2) equimolar mixing, which in unison results in a liquid material. A series of 1-alkyl perylene derivatives is synthesized and it is found that short ethyl or butyl chains reduce the melting temperature from 278 degrees C to as little as 70 degrees C. Then, two low-melting derivatives are mixed, which results in materials that do not crystallize due to the increased configurational entropy of the system. As a result, liquid chromophores with the lowest reported molecular weight increase compared to the neat chromophore are obtained. The mixing strategy is readily applicable to other pi-conjugated systems and, hence, promises to yield a wide range of low molecular weight liquid chromophores.

  • 11. 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.

  • 12. Smolders, Simon
    et al.
    Willhammar, Tom
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Krajnc, Andraž
    Sentosun, Kadir
    Wharmby, Michael T.
    Lomachenko, Kirill A.
    Bals, Sara
    Mali, Gregor
    Roeffaers, Maarten B. J.
    De Vos, Dirk E.
    Bueken, Bart
    A Titanium(IV)-Based Metal-Organic Framework Featuring Defect-Rich Ti-O Sheets as an Oxidative Desulfurization Catalyst2019In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 58, no 27, p. 9160-9165Article in journal (Refereed)
    Abstract [en]

    While titanium-based metal-organic frameworks (MOFs) have been widely studied for their (photo) catalytic potential, only a few Ti-IV MOFs have been reported owing to the high reactivity of the employed titanium precursors. The synthesis of COK-47 is now presented, the first Ti carboxylate MOF based on sheets of (TiO6)-O-IV octahedra, which can be synthesized with a range of different linkers. COK-47 can be synthesized as an inherently defective nanoparticulate material, rendering it a highly efficient catalyst for the oxidation of thiophenes. Its structure was determined by continuous rotation electron diffraction and studied in depth by X-ray total scattering, EXAFS, and solid-state NMR. Furthermore, its photoactivity was investigated by electron paramagnetic resonance and demonstrated by catalytic photodegradation of rhodamine 6G.

  • 13. Dong, Yihui
    et al.
    Laaksonen, Aatto
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Nanjing Tech University, China; Petru Poni Institute of Macromolecular Chemistry, Romania.
    Cao, Wei
    Ji, Xiaoyan
    Lu, Xiaohua
    AFM Study of pH-Dependent Adhesion of Single Protein to TiO2 Surface2019In: Advanced Materials Interfaces, ISSN 2196-7350, Vol. 6, no 14, article id 1900411Article in journal (Refereed)
    Abstract [en]

    The effect of pH-induced electrostatic conditions on the molecular interaction force of a single lysozyme molecule with TiO2 is investigated using atomic force microscopy (AFM). The force between the charged or neutral lysozyme molecule and the TiO2 surface is measured at different pH from 3.6 to 10.8. It is found to be directly proportional to the contact area, given by an effective diameter of the lysozyme molecule, and is further qualitatively verified by the AFM-measured friction coefficients. The results of the Derjaguin-Landau-Verwey-Overbeek theory show that the pH can change the surface charge densities of both lysozyme and TiO2, but the molecular interaction force at different pH is only dependent on the pH-induced effective diameter of lysozyme. The molecular interaction forces, quantified at the nanoscale, can be directly used to design high-performance liquid chromatography measurements at macroscale by tuning the retention time of a protein under varied pH conditions. They can also be applied to develop a model for predicting and controlling the chromatographic separations of proteins.

  • 14. Van Rie, Jonas
    et al.
    Schütz, Christina
    Gencer, Alican
    Lombardo, Salvatore
    Gasser, Urs
    Kumar, Sugam
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Salazar-Alvarez, Germán
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Kang, Kyongok
    Thielemans, Wim
    Anisotropic Diffusion and Phase Behavior of Cellulose Nanocrystal Suspensions Jonas2019In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 35, no 6, p. 2289-2302Article in journal (Refereed)
    Abstract [en]

    In this paper, we use dynamic light scattering in polarized and depolarized modes to determine the translational and rotational diffusion coefficients of concentrated rodlike cellulose nanocrystals in aqueous suspension. Within the range of studied concentrations (1-5 wt %), the suspension starts a phase transition from an isotropic to an anisotropic state as shown by polarized light microscopy and viscosity measurements. Small-angle neutron scattering measurements also confirmed the start of cellulose nanocrystal alignment and a decreasing distance between the cellulose nanocrystals with increasing concentration. As expected, rotational and translational diffusion coefficients generally decreased with increasing concentration. However, the translational parallel diffusion coefficient was found to show a local maximum at the onset of the isotropic-to-nematic phase transition. This is attributed to the increased available space for rods to move along their longitudinal axis upon alignment. This increased parallel diffusion coefficient thus confirms the general idea that rodlike particles gain translational entropy upon alignment while paying the price for losing rotational degrees of freedom. Once the concentration increases further, diffusion becomes more hindered even in the aligned regions due to a reduction in the rod separation distance. This leads once again to a decrease in translational diffusion coefficients. Furthermore, the relaxation rate for fast mode translational diffusion (parallel to the long particle axis) exhibited two regimes of relaxation behavior at concentrations where significant alignment of the rods is measured. We attribute this unusual dispersive behavior to two length scales: one linked to the particle length (at large wavevector q) and the other to a twist fluctuation correlation length (at low wavevector q) along the cellulose nanocrystal rods that is of a larger length when compared to the actual length of rods and could be linked to the size of aligned domains.

  • 15. Liu, J.
    et al.
    Mudryk, Y.
    Smetana, Volodymyr
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Iowa State University, USA.
    Mudring, Anja-Verena
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Iowa State University, USA.
    Pecharsky, V. K.
    Anomalous effects of Sc substitution and processing on magnetism and structure of (Gd1-xScx)(5)Ge-42019In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 474, p. 482-492Article in journal (Refereed)
    Abstract [en]

    The kinetic arrest observed in the parent Gd5Ge4 gradually vanishes when a small fraction (x = 0.025, 0.05 and 0.10) of Gd is replaced by Sc in (Gd1-xScx)(5)Ge-4, and the magnetic ground state changes from antiferromagnetic (AFM) to ferromagnetic (FM). A first order phase transition coupled with the FM-AFM transition occurs at T-C = 41 K for x = 0.05 and at T-C = 53 K for x = 0.10 during heating in applied magnetic field of 1 kOe, and the thermal hysteresis is near 10 K. The first-order magnetic transition is coupled with the structural Sm5Ge4-type to Gd5Si4-type transformation. The magnetization measured as a function of applied magnetic field shows sharp metamagnetic-like behavior. At the same time, the AFM to paramagnetic transition in (Gd1-xScx)(5)Ge-4 with x = 0.10, is uncharacteristically broad indicating development of strong short-range AFM correlations above the Ned temperature. Comparison of the magnetization data of bulk, powdered, and metal-varnish composite samples of (Gd0.95Sc0.05)(5)Ge-4 shows that mechanical grinding and fabrication of a composite have little effect on the temperature of the first-order transformation, but short-range ordering and AFM/FM ratio below T-C are surprisingly strongly affected.

  • 16.
    Etman, Ahmed S.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Aqueous Exfoliation of Transition Metal Oxides for Energy Storage and Photocatalysis Applications: Vanadium Oxide and Molybdenum Oxide Nanosheets2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Two-dimensional (2D) transition metal oxides (TMOs) are a category of materials which have unique physical and chemical properties compared to their bulk counterparts. However, the synthesis of 2D TMOs commonly includes the use of environmental threats such as organic solvents. In this thesis, we developed environmentally friendly strategies to fabricate TMO nanosheets from the commercially available bulk oxides. In particular, hydrated vanadium pentoxide (V2O5∙nH2O) nanosheets and oxygen deficient molybdenum trioxide (MoO3-x) nanosheets were prepared.  The V2O5∙nH2O nanosheets were drop-cast onto multi-walled carbon nanotube (MWCNT) paper and applied as a free-standing electrode (FSE) for a lithium battery. The accessible capacity of the FSE was dependent on the electrode thickness; the thickest electrode delivered the lowest accessible capacity.  Alternatively, a composite material of V2O5∙nH2O nanosheets with 10% MWCNT (VOx-CNT composite) was prepared and two types of electrodes, FSE and conventionally cast electrode (CCE), were employed as cathode materials for lithium batteries. A detailed comparison between these electrodes was presented. In addition, the VOx-CNT composite was applied as a negative electrode for a sodium-ion battery and showed a reversible capacity of about 140 mAh g-1. On the other hand, the MoO3-x nanosheets were employed as binder-free electrodes for supercapacitor application in an acidified Na2SO4 electrolyte. Furthermore, the MoO3-x nanosheets were used as photocatalysts for organic dye degradation. The simple eco-friendly synthesis methods coupled with the potential application of the TMO nanosheets reflect the significance of this thesis in both the synthesis and the energy-related applications of 2D materials.

  • 17.
    Aleksis, Rihards
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Carvalho, José P.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Jaworski, Aleksander
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Pell, Andrew J.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Artefact-free broadband 2D NMR for separation of quadrupolar and paramagnetic shift interactions2019In: Solid State Nuclear Magnetic Resonance, ISSN 0926-2040, E-ISSN 1527-3326, Vol. 101, p. 51-62Article in journal (Refereed)
    Abstract [en]

    Two new two-dimensional, broadband, solid-state NMR experiments for separating and correlating the quadrupolar and shift interactions of spin I = 1 nuclei in paramagnetic systems are proposed. The new pulse sequences incorporate the short, high-power adiabatic pulses (SHAPs) into the shifting d-echo experiment of Walder et al. [J. Chem. Phys., 142, 014201 (2015)], in two different ways, giving double and quadruple adiabatic shifting d-echo sequences. These new experiments have the advantage over previous methods of both suppressing spectral artefacts due to pulse imperfections, and exhibiting a broader excitation bandwidth. Both experiments are analysed with theoretical calculations and simulations, and are applied experimentally to the H-2 NMR of deuterated CuCl2 center dot 2H(2)O, and two deuterated samples of the ion conductor oxyhydride BaTiO3-xHy prepared using two different methods. For the CuCl2 center dot 2H(2)O sample, both new methods obtain very high-quality spectra from which the parameters describing the shift and quadrupolar interaction tensors, and their relative orientation, were extracted. The two BaTiO3-xHy samples exhibited different local hydride environments with different tensor parameters. The H-2 spectra of these oxyhydrides exhibit inhomogeneous broadening of the H-2 shifts, and so whilst the quadrupolar interaction parameters were easily extracted, the measurement of the shift parameters was more complex. However, effective shift parameters were extracted, which combine the effects of both the paramagnetic shift tensor and the inhomogeneous broadening.

  • 18.
    Liu, Yingxin
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Wallenberg Wood Science Center, KTH, Sweden.
    Schütz, Christina
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Wallenberg Wood Science Center, KTH, Sweden.
    Salazar-Alvarez, German
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Wallenberg Wood Science Center, KTH, Sweden.
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Assembly, Gelation, and Helicoidal Consolidation of Nanocellulose Dispersions2019In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 35, no 10, p. 3600-3606Article in journal (Refereed)
    Abstract [en]

    The ability to probe the assembly, gelation, and helicoidal consolidation of cellulose nanocrystal (CNC) dispersions at high concentrations can provide unique insight into the assembly and can assist optimized manufacturing of CNC-based photonic and structural materials. In this Feature Article, we review and discuss the concentration dependence of the structural features, characterized by the particle separation distance and the helical pitch, at CNC concentrations (c) that range from the isotropic state, over the biphasic range, to the fully liquid crystalline state. The structure evolution of CNC dispersions probed by time resolved small-angle X-ray scattering during evaporation-induced assembly highlighted the importance of gelation and consolidation at high concentrations. We briefly discuss how the homogeneity of helicoidal nanostructures in dry CNC films can be improved and present an outlook for future work.

  • 19. Wang, Tongzhou
    et al.
    Wang, Qiang
    Wang, Yucheng
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Da, Yunli
    Zhou, Wu
    Shao, Yue
    Li, Debao
    Zhan, Sihui
    Yuan, Jiayin
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Wang, Hong
    Atomically Dispersed Semi-Metallic Selenium on Porous Carbon Membrane as an Electrode for Hydrazine Fuel Cells2019In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 58, no 38, p. 13466-13471Article in journal (Refereed)
    Abstract [en]

    Electrochemically functional porous membranes of low cost are appealing in various electrochemical devices used in modern environmental and energy technologies. Herein we describe a scalable strategy to construct electrochemically active, hierarchically porous carbon membranes containing atomically dispersed semi-metallic Se, denoted SeNCM. The isolated Se atoms were stabilized by carbon atoms in the form of a hexatomic ring structure, in which the Se atoms were located at the edges of graphitic domains in SeNCM. This configuration is different from that of previously reported transition/noble metal single atom catalysts. The positively charged Se, enlarged graphitic layers, robust electrochemical nature of SeNCM endow them with excellent catalytic activity that is superior to state-of-the-art commercial Pt/C catalyst. It also has long-term operational stability for hydrazine oxidation reaction in practical hydrazine fuel cell.

  • 20.
    Agosta, Lorenzo
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Atomistic simulations of structural and dynamical properties of liquids under geometric constraints2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

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

  • 21.
    Mace, Amber
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Ecole Polytechnique Fédéralede Lausanne (EPFL), Switzerland.
    Barthel, Senja
    Smit, Berend
    Automated Multiscale Approach To Predict Self-Diffusion from a Potential Energy Field2019In: Journal of Chemical Theory and Computation, ISSN 1549-9618, E-ISSN 1549-9626, Vol. 15, no 4, p. 2127-2141Article in journal (Refereed)
    Abstract [en]

    For large-scale screening studies there is a need to estimate the diffusion of gas molecules in nanoporous materials more efficiently than (brute force) molecular dynamics. In particular for systems with low diffusion coefficients molecular dynamics can be prohibitively expensive. An alternative is to compute the hopping rates between adsorption sites using transition state theory. For large-scale screening this requires the automatic detection of the transition states between the adsorption sites along the different diffusion paths. Here an algorithm is presented that analyzes energy grids for the moving particles. It detects the energies at which diffusion paths are formed, together with their directions. This allows for easy identification of nondiffusive systems. For diffusive systems, it partitions the grid coordinates assigned to energy basins and transitions states, permitting a transition state theory based analysis of the diffusion. We test our method on CH4 diffusion in zeolites, using a standard kinetic Monte Carlo simulation based on the output of our grid analysis. We find that it is accurate, fast, and rigorous without limitations to the geometries of the diffusion tunnels or transition states.

  • 22. 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.

  • 23. Wang, Yafei
    et al.
    Xing, Leilei
    Li, Kailun
    Yu, Chenfan
    Ma, Jing
    Liu, Wei
    Shen, Zhijian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Tsinghua University, P.R. China.
    Band-Like Distribution of Grains in Selective Laser Melting Track Under Keyhole Mode2019In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 50, no 2, p. 1035-1041Article in journal (Refereed)
    Abstract [en]

    Grain structure in the melt pool under keyhole mode is complex due to complicated solidified conditions, especially in consideration of the intense fluid flow. This paper aims to clarify grain structure and grain growth mechanism in melt pool under keyhole mode in selective laser melting. The microstructure from transverse cross section and longitudinal cross section near the centerline of 316L single tracks was characterized. In the longitudinal cross section, band-like grain structure formed. It is found that fluid flow can refine the grains, and large columnar grains grow towards crystallographic < 110 > direction.

  • 24.
    Valencia, Luis
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Nomena, Emma M.
    Mathew, Aji P.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Velikov, Krassimir P.
    Biobased Cellulose Nanofibril–Oil Composite Films for Active Edible Barriers2019In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 11, no 17, p. 16040-16047Article in journal (Refereed)
    Abstract [en]

    Low-concentration oil-in-water emulsions stabilized by cellulose nanofibrils (CNFs) extracted from primary plant cell wall materials are used to prepare thin biobased CNF–oil composite films by solvent casting. Flexible, transparent, and biodegradable composite films are obtained, with increased thermal stability (up to 300 °C) as the oil concentration increases. Examination of the microstructure demonstrates a clear dependency on the oil content, as a multilayered structure where the oil phase trapped between two layers of CNFs is appreciated at high oil concentrations. The embedded oil significantly influences the mechanical and wetting properties of the films, confirming their potential for use in packaging systems. Encapsulation of curcumin in the composite films leads to an increased antioxidant (up to 30% radical scavenging activity) and antimicrobial activity, inhibiting the growth of foodborne bacteria such as Escherichia coli. The resulting composite films show promising results in the field of active packaging for applications in the food, pharmaceutical, and cosmetic industries.

  • 25.
    Dorn, Katharina V.
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). University of Stuttgart, Germany.
    Blaschkowski, Björn
    Bamberger, Heiko
    van Slageren, Joris
    Doll, Klaus
    Claus, Ralf
    Matsumoto, Yosuke
    Takagi, Hidenori
    Hartenbach, Ingo
    Black Current: Structure, Characterization, and Optoelectronic Properties of Ce3Cl3[MoO6]2019In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 25, no 33, p. 7921-7926Article in journal (Refereed)
    Abstract [en]

    The admixture of CeO2, Ce, CeCl3, and MoO3 with an excess of LiCl as flux in evacuated silica ampules leads to large black single crystals as well as a black microcrystalline powder of Ce3Cl3[MoO6] after tempering at 850 degrees C for three days. The title compound crystallizes in the hexagonal space group P6(3)/m (a=934.93(4), c=538.86(2) pm) with two formula units per unit cell. The crystal structure consists of rather unusual trigonal-prismatic [MoO6](6-) units besides Ce3+ ions in a tetra-capped trigonal-prismatic coordination, formed by four Cl- and six O2- ions. The black color is related to an optical band gap of 1.35(2) eV, which was determined by diffuse reflectance spectroscopy and confirmed by theoretical calculations. The low band gap between the 4f(1) state of cerium (HOMO) and the 5d(0) state of molybdenum (LUMO) gave rise to the idea of electronic excitation between these two states by IR irradiation, creating a drop in the resistivity of the material, which was detected by appropriate measurements.

  • 26.
    Dorn, Katharina V.
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). University of Stuttgart, Germany.
    Blaschkowski, Björn
    Netzsch, Philip
    Höppe, Henning A.
    Hartenbach, Ingo
    Blue Excitement: The Lanthanide(III) Chloride Oxidomolybdates(VI) Ln(3)Cl(3)[MoO6] (Ln = La, Pr, and Nd) and Their Spectroscopic Properties2019In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 58, no 13, p. 8308-8315Article in journal (Refereed)
    Abstract [en]

    The lanthanide(III) chloride oxidomolybdates(VI) with the empirical formula Ln(3)Cl(3)[MoO6] (Ln = La, Pr, and Nd) were synthesized by solid-state reactions utilizing the respective lanthanide trichloride, lanthanide sesquioxide (where available), and molybdenum trioxide together with lithium chloride as a fluxing agent. The title compounds crystallize in hexagonal space group P6(3)/m (a = 942-926 pm, c = 542-533 pm, Z = 2). Besides tetracapped trigonal prismatically coordinated Ln(3+) cations, noncondensed trigonal prismatic [MoO6]6(-) entities are found in the crystal structure. In addition to X-ray diffraction, the title compounds were also characterized by single-crystal Raman and infrared spectroscopy as well as measurements to determine their magnetic susceptibility and behavior at low temperatures. The most outstanding properties of the Ln(3)Cl(3)[MoO6] representatives (Ln = La, Pr, and Nd), however, are of an optical nature, because their band gaps, determined by diffuse reflectance spectroscopy, show a significant shift toward lower energies compared to those of other rare-earth metal chloride molybdates with a different polyhedral arrangement. This culminates in La3Cl3[MoO6]:Eu3+ exhibiting luminescence, which can be excited in the visible range of the electromagnetic spectrum by a blue light-emitting diode.

  • 27. Wang, Wei
    et al.
    Wang, Yahui
    Liu, Shijia
    Yahia, Mohamed
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Dong, Yinjuan
    Lei, Ziqiang
    Carbon-supported phosphatized CuNi nanoparticle catalysts for hydrazine electrooxidation2019In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 44, no 21, p. 10637-10645Article in journal (Refereed)
    Abstract [en]

    Developing non-noble metal catalysts with high performance to reduce the cost of hydrazine fuel cells is urgent. Herein, in this study, a series of carbon-supported phosphatized CuNi catalysts (P--CuxNiy/C) are designed for hydrazine oxidation reaction (HzOR) via high temperature phosphating process. Among them, the P-Cu2Ni/C is found to be a promising candidate for hydrazine electrooxidation. Electrochemical measurement results indicate that the P-Cu2Ni/C catalyst exhibits higher catalytic activity and stability for HzOR in comparison with P-CuNi/C, P-CuNi2/C, Cu2Ni/C, Cu/C and Ni/C catalysts. Additionally, HzOR kinetics are also investigated, and it proves that hydrazine electrooxidation on P-Cu2Ni/C is a diffusion controlled irreversible process. Meanwhile, physical characterization reveals that the catalysts have doped phosphorus successfully. All results demonstrate that as-prepared P-Cu2Ni/C catalyst is a promising electrocatalyst for direct hydrazine fuel cells.

  • 28. Zhang, Kaiheng
    et al.
    Deiana, Luca
    Svensson Grape, Erik
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Inge, A. Ken
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Córdova, Armando
    Catalytic Enantioselective Synthesis of Bicyclic Lactam N,S-Acetals in One Pot by Cascade Transformations2019In: European Journal of Organic Chemistry, ISSN 1434-193X, E-ISSN 1099-0690, no 29, p. 4649-4657Article in journal (Refereed)
    Abstract [en]

    A versatile strategy for the enantioselective synthesis of bicyclic lactam N,S-acetals by one-pot cascade transformations is disclosed. The transformation of readily available substrates is promoted by chiral amines and creates bicyclic or tricyclic lactam N,S-acetals with high chemo- and stereoselectivity (up to > 99.5:0.5 dr and > 99 % ee) in one-pot operations.

  • 29.
    Sultan, Sahar
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Abdelhamid, Hani Nasser
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Assuit University, Egypt.
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Mathew, Aji P.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    CelloMOF: Nanocellulose Enabled 3D Printing of Metal-Organic Frameworks2019In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 29, no 2, article id 1805372Article in journal (Refereed)
    Abstract [en]

    3D printing is recognized as a powerful tool to develop complex geometries for a variety of materials including nanocellulose. Herein, a one-pot synthesis of 3D printable hydrogel ink containing zeolitic imidazolate frameworks (ZIF-8) anchored on anionic 2,2,6,6-tetramethylpiperidine-1-oxylradical-mediated oxidized cellulose nanofibers (TOCNF) is presented. The synthesis approach of ZIF-8@TOCNF (CelloZIF8) hybrid inks is simple, fast (approximate to 30 min), environmentally friendly, takes place at room temperature, and allows easy encapsulation of guest molecules such as curcumin. Shear thinning properties of the hybrid hydrogel inks facilitate the 3D printing of porous scaffolds with excellent shape fidelity. The scaffolds show pH controlled curcumin release. The synthesis route offers a general approach for metal-organic frameworks (MOF) processing and is successfully applied to other types of MOFs such as MIL-100 (Fe) and other guest molecules as methylene blue. This study may open new venues for MOFs processing and its large-scale applications.

  • 30. Adolphsen, Jens Q.
    et al.
    Gil, Vanesa
    Sudireddy, Bhaskar R.
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Characterisation and processing of aqueous LaNi0.6Fe0.4O3 Suspensions into Porous Electrode Layers for Alkaline Water Electrolysis2019In: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 39, no 4, p. 1271-1278Article in journal (Refereed)
    Abstract [en]

    The colloidal properties and processing of aqueous LaNi0.6.Fe0.4O3 suspensions into electrode layers with hierarchical pore sizes has been investigated by light scattering, electron microscopy and rheology. We found that the colloidal stability of the oxide particles and the resulting microstructure of the electrode layers were similar when dispersing the particles at their intrinsic pH, or when adding polyvinylpyrrolidone. The addition of the ammonium salt of poly(methaacrylic acid) resulted in a poor colloidal stability and the concentrated suspensions became viscoelastic during processing. Addition of rice starch resulted in an increase of the porosity but the cast electrode layers cracked and delaminated.

  • 31. Heydarian, Abtin
    et al.
    Sajjadi, Seyed Abdolkarim
    Kern, Frank
    Johnsson, Mats
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Characteristics evaluation of SiC/Si nanocomposites produced by spark plasma sintering2019In: Materials Science and Technology, ISSN 0267-0836, E-ISSN 1743-2847, Vol. 35, no 10, p. 1204-1211Article in journal (Refereed)
    Abstract [en]

    SiC-Si composites are widely used either as a bulk material or as a matrix for fibre reinforced ceramics. In the current research, nanocomposites of SiC-Si with different volume fractions of Si were sintered by spark plasma sintering (SPS) for the first time. The effect of Si content and different sintering parameters on relative density, microstructure, hardness and fracture toughness of the sintered materials have been investigated. The relative density increased from about 83 to 99% by increasing the sintering temperature to 1700 degrees C, sintering time to 10 min, and pressure to 70 MPa for composites containing >20 vol.-% Si. The results revealed that the full dense SiC-20 vol.-%Si composite can be obtained by SPS at 1700 degrees C, 10 min and 70 MPa. Moreover, in this condition, the hardness and toughness of the composites reached the optimum values.

  • 32. Liang, Shuai
    et al.
    Hall, Kyle Wm.
    Laaksonen, Aatto
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Uppsala University, Sweden; Petru Poni Institute of Macromolecular Chemistry, Romania.
    Zhang, Zhengcai
    Kusalik, Peter G.
    Characterizing key features in the formation of ice and gas hydrate systems2019In: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 377, no 2146, article id 20180167Article, review/survey (Refereed)
    Abstract [en]

    Crystallization in liquids is critical to a range of important processes occurring in physics, chemistry and life sciences. In this article, we review our efforts towards understanding the crystallization mechanisms, where we focus on theoretical modelling and molecular simulations applied to ice and gas hydrate systems. We discuss the order parameters used to characterize molecular ordering processes and how different order parameters offer different perspectives of the underlying mechanisms of crystallization. With extensive simulations of water and gas hydrate systems, we have revealed unexpected defective structures and demonstrated their important roles in crystallization processes. Nucleation of gas hydrates can in most cases be characterized to take place in a two-step mechanism where the nucleation occurs via intermediate metastable precursors, which gradually reorganizes to a stable crystalline phase. We have examined the potential energy landscapes explored by systems during nucleation, and have shown that these landscapes are rugged and funnel-shaped. These insights provide a new framework for understanding nucleation phenomena that has not been addressed in classical nucleation theory. This article is part of the theme issue 'The physics and chemistry of ice: scaffolding across scales, from the viability of life to the formation of planets'.

  • 33.
    Gustafson, Karl P. J.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Görbe, Tamás
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    de Gonzalo-Calvo, Gonzalo
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Yuan, Ning
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Swedish University of Agricultural Sciences, Sweden.
    Schreiber, Cynthia L.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Shchukarev, Andrey
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Persson, Ingmar
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Chemoenzymatic Dynamic Kinetic Resolution of Primary Benzylic Amines using Pd-0-CalB CLEA as a Biohybrid Catalyst2019In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 25, no 39, p. 9174-9179Article in journal (Refereed)
    Abstract [en]

    Herein, we report on the use a biohybrid catalyst consisting of palladium nanoparticles immobilized on cross-linked enzyme aggregates of lipase B of Candida antarctica (CalB CLEA) for the dynamic kinetic resolution (DKR) of benzylic amines. A set of amines were demonstrated to undergo an efficient DKR and the recyclability of the catalysts was studied. Extensive efforts to further elucidate the structure of the catalyst are presented.

  • 34.
    Ermilova, Inna
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Lyubartsev, Alexander P.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Cholesterol in phospholipid bilayers: positions and orientations inside membranes with different unsaturation degrees2019In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 15, no 1, p. 78-93Article in journal (Refereed)
    Abstract [en]

    Cholesterol is an essential component of all animal cell membranes and plays an important role in maintaining the membrane structure and physical–chemical properties necessary for correct cell functioning. The presence of cholesterol is believed to be responsible for domain formation (lipid rafts) due to different interactions of cholesterol with saturated and unsaturated lipids. In order to get detailed atomistic insight into the behaviour of cholesterol in bilayers composed of lipids with varying degrees of unsaturation, we have carried out a series of molecular dynamics simulations of saturated and polyunsaturated lipid bilayers with different contents of cholesterol, as well as well-tempered metadynamics simulations with a single cholesterol molecule in these bilayers. From these simulations we have determined distributions of cholesterol across the bilayer, its orientational properties, free energy profiles, and specific interactions of molecular groups able to form hydrogen bonds. Both molecular dynamics and metadynamics simulations showed that the most unsaturated bilayer with 22:6 fatty acid chains shows behaviour which is most different from other lipids. In this bilayer, cholesterol is relatively often found in a “flipped” configuration with the hydroxyl group oriented towards the membrane middle plane. This bilayer has also the highest (least negative) binding free energy among liquid phase bilayers, and the lowest reorientation barrier. Furthermore, cholesterol molecules in this bilayer are often found to form head-to-tail contacts which may lead to specific clustering behaviour. Overall, our simulations support ideas that there can be a subtle interconnection between the contents of highly unsaturated fatty acids and cholesterol, deficiency or excess of each of them is related to many human afflictions and diseases.

  • 35. Liu, Xihe
    et al.
    Zhao, Congcong
    Zhou, Xin
    Eibl, Florian
    Shen, Zhijian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Tsinghua University, People’s Republic of China.
    Liu, Wei
    Meiners, Wilhelm
    CNT-reinforced AlSi10Mg composite by selective laser melting: microstructural and mechanical properties2019In: Materials Science and Technology, ISSN 0267-0836, E-ISSN 1743-2847, Vol. 35, no 9, p. 1038-1045Article in journal (Refereed)
    Abstract [en]

    Carbon nanotube (CNT)-AlSi10Mg composites were fabricated by selective laser melting (SLM). The influence of CNTs on the density, microstructure, and strength of SLM CNT-AlSi10Mg composites was investigated. The addition of CNTs over 0.1 wt-% significantly damaged the density due to the high surface energy of the CNTs. The network Si eutectic had no significant difference in either the SLM AlSi10Mg alloy or the CNT-AlSi10Mg composite. Reserved CNTs with a short scale were observed in the SLM CNT(0.5 wt-%)-AlSi10Mg composite. The ultimate tensile strength of the 0.05 wt-% CNT-AlSi10Mg composite was 441.2 +/- 0.9 MPa, which was higher than that of AlSi10Mg alloy. The grain boundary strengthening played an important role in the reinforcement of CNT-AlSi10Mg composite because of the refined grain.

  • 36.
    Hao, Wenming
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Taiyuan University of Technology, China.
    Liu, Yongsheng
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Neagu, Alexandra
    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).
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Shen, Zhijian
    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).
    Core-Shell and Hollow Particles of Carbon and SiC Prepared from Hydrochar2019In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, no 11, article id 1835Article in journal (Refereed)
    Abstract [en]

    The applications of silicon carbide (SiC) include lightweight materials with thermal shock resistance. In this study, core-shell C-SiC particles were synthesized by compacting and rapidly heating a hydrochar from glucose by using strong pulsed currents and infiltration of silicon vapor. Hollow particles of SiC formed on removing the carbon template. In contrast to related studies, we detected not only the pure 3C polytype (-SiC) but also significant amounts of the 2H or the 6H polytypes (-SiC) in the SiC.

  • 37. Li, Kailun
    et al.
    Wang, Dianzheng
    Xing, Leilei
    Wang, Yafei
    Yu, Chenfan
    Chen, Jinhan
    Zhang, Tao
    Ma, Jing
    Liu, Wei
    Shen, Zhijian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Tsinghua University, China.
    Crack suppression in additively manufactured tungsten by introducing secondary-phase nanoparticles into the matrix2019In: International journal of refractory metals and hard materials, ISSN 0263-4368, Vol. 79, p. 158-163Article in journal (Refereed)
    Abstract [en]

    In this study, an effective strategy was developed to suppress cracking by introducing secondary-phase ZrC nanoparticles into a tungsten (W) matrix. Pure W and W-0.5wt%ZrC bulks were additively manufactured via the laser powder bed fusion (LPBF) technique, and their cracking behaviour was compared. It was observed that the crack density of W-ZrC was reduced by 88.7% compared with that of pure W. The grains in W-ZrC were obviously refined compared with the grains in pure W, which significantly increased the cracking resistance. In addition, ZrC diminished the oxygen impurities, further increasing the cracking resistance. This study provides a promising strategy for the additive manufacturing of high-quality W by introducing secondary-phase nanoparticles into the metal matrix.

  • 38. Wang, Dian-Zheng
    et al.
    Li, Kai-Lun
    Yu, Chen-Fan
    Ma, Jing
    Liu, Wei
    Shen, Zhi-Jian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Tsinghua University, China.
    Cracking Behavior in Additively Manufactured Pure Tungsten2019In: Acta Metallurgica Sinica (English Letters), ISSN 1006-7191, E-ISSN 2194-1289, Vol. 32, no 1, p. 127-135Article in journal (Refereed)
    Abstract [en]

    In this study, near fully dense (96.5%) pure tungsten bulks were additively manufactured and the cracking behavior was investigated. A crack network with a spacing of similar to 100m was observed in the fabricated bulks. It was observed that the laser scanning strategy, which could tailor the microstructure, affected the crack distribution pattern in fabricated tungsten. The calculated surface temperature difference (7300K) was much higher than the cracking criterion (800K) of tungsten, indicating that cracking is almost inevitable in laser additive manufacturing of tungsten. It could be concluded that crack network formed because the cracks emerged in every laser molten track and then interconnected in the layer-by-layer building process.

  • 39. Wang, Dianzheng
    et al.
    Wang, Zhimin
    Li, Kailun
    Ma, Jing
    Liu, Wei
    Shen, Zhijian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Tsinghua University, China.
    Cracking in laser additively manufactured W: Initiation mechanism and a suppression approach by alloying2019In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 162, p. 384-393Article in journal (Refereed)
    Abstract [en]

    Cracking represents the main challenge for exploiting tungsten in additive manufacturing. In this study, laser powder-bed-fusion technique was applied to additively manufacture tungsten. In the built bulks, the grain boundaries were found to be rich in nanoscale gas pores. On the basis of that, a nanopore segregation induced cracking initiation mechanism was proposed. In order to control cracks, W-6wt.%Ta alloy was produced and the cracking suppression mechanism was investigated. The W-6Ta alloy is characterized by a submicron intragranular cellular structure, which composed large amount of interlocked dislocations as revealed by transmission electron microscopy. Owing to the cellular structure, the nanopores were trapped inside grains, which can reduce the cracking possibility. Moreover, the W-Ta alloy possesses higher strength (by 17%) and higher energy dissipation rate (by 52%) than pure tungsten, which both are beneficial for crack reduction.

  • 40.
    Eriksson, Lars
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Crystal structure of methyl alpha-L-rhamnopyranosyl-(1 -> 2)-alpha-L-rhamnopyranoside monohydrate2019In: Acta Crystallographica Section E: Crystallographic Communications, ISSN 2056-9890, Vol. 75, p. 854-857Article in journal (Refereed)
    Abstract [en]

    The title compound, C13H24O9 center dot H2O, a structural model for part of bacterial O-antigen polysaccharides from Shigella flexneri and Escherichia coli, crystallizes with four independent disaccharide molecules and four water molecules in the asymmetric unit. The conformation at the glycosidic linkage joining the two rhamnosyl residues is described by the torsion angles phi(H) of 39, 30, 37 and 37 degrees, and psi(H) of -32, -35, -31 and -32 degrees, which are the major conformation region known to be populated in an aqueous solution. The hexopyranose rings have the C-1(4) chair conformation. In the crystal, the disaccharide and water molecules are associated through O-H center dot center dot center dot O hydrogen bonds, forming a layer parallel to the bc plane. The layers stack along the a axis via hydrophobic interactions between the methyl groups.

  • 41.
    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.

  • 42.
    Elias-Wolff, Federico
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics. Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Lindén, Martin
    Lyubartsev, Alexander P.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Brandt, Erik G.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Curvature sensing by cardiolipin in simulated buckled membranes2019In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 15, no 4, p. 792-802Article in journal (Refereed)
    Abstract [en]

    Cardiolipin is a non-bilayer phospholipid with a unique dimeric structure. It localizes to negative curvature regions in bacteria and is believed to stabilize respiratory chain complexes in the highly curved mitochondrial membrane. Cardiolipin's localization mechanism remains unresolved, because important aspects such as the structural basis and strength for lipid curvature preferences are difficult to determine, partly due to the lack of efficient simulation methods. Here, we report a computational approach to study curvature preferences of cardiolipin by simulated membrane buckling and quantitative modeling. We combine coarse-grained molecular dynamics with simulated buckling to determine the curvature preferences in three-component bilayer membranes with varying concentrations of cardiolipin, and extract curvature-dependent concentrations and lipid acyl chain order parameter profiles. Cardiolipin shows a strong preference for negative curvatures, with a highly asymmetric chain order parameter profile. The concentration profiles are consistent with an elastic model for lipid curvature sensing that relates lipid segregation to local curvature via the material constants of the bilayers. These computations constitute new steps to unravel the molecular mechanism by which cardiolipin senses curvature in lipid membranes, and the method can be generalized to other lipids and membrane components as well.

  • 43.
    Li, Duan
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). National University of Defense Technology, People’s Republic of China.
    Liu, Yongsheng
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Northwestern Polytechnical University, People’s Republic of China.
    Zhong, Yuan
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Liu, Leifeng
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Adolfsson, Erik
    Shen, Zhijian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Dense and strong ZrO2 ceramics fully densified in <15 min2019In: Advances in Applied Ceramics: Structural, Functional and Bioceramics, ISSN 1743-6753, E-ISSN 1743-6761, Vol. 118, no 1-2, p. 23-29Article in journal (Refereed)
    Abstract [en]

    Crack-free zirconia ceramics were consolidated via sintering by intense thermal radiation (SITR) approach at 1600-1700 degrees C for 3-5 min. The resulted ceramic bulks can achieve a relative density up to 99.6% with a grain size of 300-1200 nm. Their bending strength, Vickers hardness and indentation toughness values are up to 1244 +/- 139 MPa, 13.3 +/- 0.3 GPa and 5.5 +/- 0.1 MPa m(1/2), respectively. Quantitative Raman and XRD analysis show the presence of minor m phase on the natural surface (<7%), fracture surface (<10%) and indentation areas (<15%). It reveals that the SITR method is efficient for rapidly manufacturing zirconia ceramics with desired density, fine grained microstructure and good mechanical properties that are strongly demanded in dental applications.

  • 44. Li, Hezhen
    et al.
    Song, Lu
    Sun, Jialin
    Ma, Jing
    Shen, Zhijian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Tsinghua University, People’s Republic of China.
    Dental ceramic prostheses by stereolithography-based additive manufacturing: potentials and challenges2019In: Advances in Applied Ceramics: Structural, Functional and Bioceramics, ISSN 1743-6753, E-ISSN 1743-6761, Vol. 118, no 1-2, p. 30-36Article in journal (Refereed)
    Abstract [en]

    The current method for making dental ceramic prostheses in a subtractive manner causes a severe waste of materials while requires excessive manual works that bring in the uncertainty for control of quality. The rapid development and commercialisation of additive manufacturing (AM) has aroused interest and wonders both in material and dental communities about their potentials and challenges in fabricating of ceramic prostheses in a materials-saving manner. In this work, AM approach was applied to fabricate the dental bridges and implants made of zirconia. The achieved geometries and dimensional accuracy are used to demonstrate the potential of this technique in fabricating of dental ceramic prostheses, whereas the observed macro and micro defects formed during the treatment process is used to reveal the challenges facing in order to adapt this technology into real dental practice. Suggestions are provided for future development of the technology, particularly on minimising the processing defects.

  • 45.
    Liu, Peng
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Milletto, Charles
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Monti, Susanna
    Zhu, Chuantao
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Mathew, Aji P.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Design of ultrathin hybrid membranes with improved retention efficiency of molecular dyes2019In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 9, no 49, p. 28657-28669Article in journal (Refereed)
    Abstract [en]

    Ultrathin layers of 2,2,6,6-Tetramethyl-1-piperidinyloxy (TEMPO) Oxidized Cellulose Nanofibers (TOCNF) embedded with Graphene Oxide nanosheets (GOs) in different ratios were built, via the blade coating technique, on a polyvinylidene difluoride (PVDF) substrate to obtain superior membranes for separating water pollutants from aqueous media. Cellulose nanofiber-graphene oxide hybrid materials have shown a great potential for water purification due to their active microporous structure with extended areas rich in negatively charged carboxyl functional groups capable of adsorbing positively charged contaminants efficiently. In contrast to the pristine free-standing TOCNF films, which are completely impermeable, the ultrathin (68 nm thick) hybrid coating with a 100 : 1 TOCNF : GO ratio showed a stable water permeability (816 +/- 3.4 L m(-2) h(-1) bar(-1)) higher than that of common polymeric membranes, and a very efficient size selectivity during filtration of water contaminated by various types of dyes. The membranes had high retention efficiency (82-99%) for dyes with hydrated radii greater than approximate to 0.5 nm due to the favorable combination of electrostatic/hydrophobic interactions with the hybrid matrices and steric entrapment controlled by the pore size. This was confirmed by theoretical calculations that revealed both the structure and dynamic behavior of the dyes in the complex environment of the membranes.

  • 46. Dong, Yihui
    et al.
    Ji, Xiaoyan
    Laaksonen, Aatto
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Nanjing Tech University, China; Uppsala University, Sweden; Petru Poni Institute of Macromolecular Chemistry, Romania.
    Cao, Wei
    An, Rong
    Lu, Linghong
    Lu, Xiaohua
    Determination of the small amount of proteins interacting with TiO2 nanotubes by AFM-measurement2019In: Biomaterials, ISSN 0142-9612, E-ISSN 1878-5905, Vol. 192, p. 368-376Article in journal (Refereed)
    Abstract [en]

    Detecting the small amounts of proteins interacting effectively with the solid film electrodes surface still remains a challenge. To address this, in this work, a new approach was proposed by the combination of the adhesion forces and the molecular interaction measured with AFM. Cytochrome c (Cyt C) interacting effectively with TiO2 nanotube arrays (TNAs) was chosen as a probe. The amounts of Cyt C molecules interacting effectively on TNAs surface (C-TNA) range from 5.5x10(-12) to 7.0x10(-12) mol/cm(2) (68.2-86.8 ng/cm(2)) and they are comparable with the values obtained by the electrochemistry method in the literature, in evidence of the accuracy of this AFM-based approach. The reliability of the proposed approach was further verified by conducting Surface Enhanced Raman Scattering (SERS) measurements and estimating the enhancement factor (EF). This interaction-based AFM approach can be used to accurately obtain the small amounts of adsorbed substances on the solid film electrodes surface in the applications such as biosensors, biocatalysis, and drug delivery, etc.

  • 47.
    Wang, Bin
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Development of rotation electron diffraction as a fully automated and accurate method for structure determination2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Over the past decade, electron diffraction methods have aroused more and more interest for micro-crystal structure determination. Compared to traditional X-ray diffraction, electron diffraction breaks the size limitation of the crystals studied, but at the same time it also suffers from much stronger dynamical effects. While X-ray crystallography has been almost thoroughly developed, electron crystallography is still under active development. To be able to perform electron diffraction experiments, adequate skills for using a TEM are usually required, which makes ED experiments less accessible to average users than X-ray diffraction. Moreover, the relatively poor data statistics from ED data prevented electron crystallography from being widely accepted in the crystallography community.

    The thesis focused on both application and method development of continuous rotation electron diffraction (cRED) technique. The cRED method was first applied to a beam sensitive metal-organic framework sample, Co-CAU-36, and the structure was determined and refined within one working day. More importantly, the guest molecules in the pores were also located using only electron diffraction data. To facilitate general users to perform cRED data collection for useful data, software was developed to automate the overall data collection procedure. Through combination of hierarchical cluster analysis tools, the automatically collected data showed comparable quality to those from recent publications, and thus were useful for structure determination and even phase identification. To deal with dynamical refinement for ED data, a frame orientation refinement algorithm was designed to calculate accurate frame orientations for rotation data. Accuracy for the method was validated and compared to an existing software, and the behavior of TEM goniometer was studied by applying the method to an experimental data set.

  • 48.
    Kerdphon, Sutthichat
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.