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  • 1. Amaya, Andrew J.
    et al.
    Pathak, Harshad
    Modak, Viraj P.
    Laksmono, Hartawan
    Loh, N. Duane
    Sellberg, Jonas A.
    Stockholm University, Faculty of Science, Department of Physics. SLAC National Accelerator Laboratory, United States; KTH Royal Institute of Technology, Sweden.
    Sierra, Raymond G.
    McQueen, Trevor A.
    Hayes, Matt J.
    Williams, Garth J.
    Messerschmidt, Marc
    Boutet, Sebastien
    Bogan, Michael J.
    Nilsson, Anders
    Stockholm University, Faculty of Science, Department of Physics. SLAC National Acceleratory Laboratory, United States.
    Stan, Claudiu A.
    Wyslouzil, Barbara E.
    How Cubic Can Ice Be?2017In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 8, no 14, p. 3216-3222Article in journal (Refereed)
    Abstract [en]

    Using an X-ray laser, we investigated the crystal structure of ice formed by homogeneous ice nucleation in deeply supercooled water nanodrops (r approximate to 10 nm) at similar to 225 K The nanodrops were formed by condensation of vapor in a supersonic nozzle, and the ice was probed within 100 mu s of freezing using femtosecond wide-angle X-ray scattering at the Linac Coherent Light Source free-electron X-ray laser. The X-ray diffraction spectra indicate that this ice has a metastable, predominantly cubic structure; the shape of the first ice diffraction peak suggests stacking-disordered ice with a cubicity value, chi, in the range of 0.78 +/- 0.05. The cubicity value determined here is higher than those determined in experiments with micron-sized drops but comparable to those found in molecular dynamics simulations. The high cubicity is most likely caused by the extremely low freezing temperatures and by the rapid freezing, which occurs on a similar to 1 mu s time scale in single nanodroplets.

  • 2. Battiston, S.
    et al.
    Boldrini, S.
    Saleemi, Mohsin
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). KTH Royal Institute of Technology, Sweden.
    Famengo, A.
    Fiameni, S.
    Toprak, M. S.
    Fabrizio, M.
    Influence of Al and Mg Addition on Thermoelectric Properties of Higher Manganese Silicides Obtained by Reactive Sintering2017In: Journal of Nanoscience and Nanotechnology, ISSN 1533-4880, E-ISSN 1533-4899, Vol. 17, no 3, p. 1668-1673Article in journal (Refereed)
    Abstract [en]

    Higher manganese silicides (HMS), represented by MnSix (x = 1.71-1.75), are promising p-type candidates for thermoelectric (TE) energy harvesting systems at intermediate temperature range. The materials are very attractive as they may replace lead based compounds due to their nontoxicity, low cost of starting materials, and high thermal and chemical stability. Dense pellets were obtained through fast reactive sintering by spark plasma sintering (SPS). The addition -or nanoinclusion, of Al and Mg permitted the figure of merit enhancement of the material obtained with this technique, reaching the highest value of 0.40 at 600 degrees C. Morphology, composition and crystal structure of the samples were characterized by electron microscopies, energy dispersive X-ray spectroscopy, and X-ray diffraction analyses, respectively.

  • 3.
    Bayat, Narges
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Lopes, V. R.
    Sanchez-Dominguez, M.
    Lakshmanan, R.
    Rajarao, G. K.
    Cristobal, S.
    Assessment of functionalized iron oxide nanoparticles in vitro: introduction to integrated nanoimpact index2015In: Environmental Science: Nano, ISSN 2051-8153, Vol. 2, no 4, p. 380-394Article in journal (Refereed)
    Abstract [en]

    Functionalization of super paramagnetic iron oxide NPs (SPIONs) with different coatings renders them with unique physicochemical properties that allow them to be used in a broad range of applications such as drug targeting and water purification. However, it is required to fill the gap between the promises of any new functionalized SPIONs and the effects of these coatings on the NPs safety. Nanotoxicology is offering diverse strategies to assess the effect of exposure to SPIONs in a case-by-case manner but an integrated nanoimpact scale has not been developed yet. We have implemented the classical integrated biological response (IBR) into an integrated nanoimpact index (INI) as an early warning scale of nano-impact based on a combination of toxicological end points such as cell proliferation, oxidative stress, apoptosis and genotoxicity. Here, the effect of SPIONs functionalized with tri-sodium citrate (TSC), polyethylenimine (PEI), aminopropyl-triethoxysilane (APTES) and Chitosan (chitosan) were assessed on human keratinocytes and endothelial cells. Our results show that endothelial cells were more sensitive to exposure than keratinocytes and the initial cell culture density modulated the toxicity. PEI-SPIONs had the strongest effects in both cell types while TSC-SPIONS were the most biocompatible. This study emphasizes not only the importance of surface coatings but also the cell type and the initial cell density on the selection of toxicity assays. The INI developed here could offer an initial rationale to choose either modifying SPIONs properties to reduce its nanoimpact or performing a complete risk assessment to define the risk boundaries.

  • 4. Bejhed, Rebecca S.
    et al.
    Strömme, Maria
    Svedlindh, Peter
    Ahlford, Annika
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics. Stockholm University, Science for Life Laboratory (SciLifeLab).
    Strömberg, Mattias
    Magnetic nanobeads present during enzymatic amplification and labeling for a simplified DNA detection protocol based on AC susceptometry2015In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 5, no 12, article id 127139Article in journal (Refereed)
    Abstract [en]

    Magnetic biosensors are promising candidates for low-cost point-of-care biodiagnostic devices. For optimal efficiency it is crucial to minimize the time and complexity of the assay protocol including target recognition, amplification, labeling and read-out. In this work, possibilities for protocol simplifications for a DNA biodetection principle relying on hybridization of magnetic nanobeads to rolling circle amplification (RCA) products are investigated. The target DNA is recognized through a padlock ligation assay resulting in DNA circles serving as templates for the RCA process. It is found that beads can be present during amplification without noticeably interfering with the enzyme used for RCA (phi29 polymerase). As a result, the bead-coil hybridization can be performed immediately after amplification in a one-step manner at elevated temperature within a few minutes prior to read-out in an AC susceptometer setup, i.e. a combined protocol approach. Moreover, by recording the phase angle xi = arctan(chi ''/chi'), where chi and chi '' are the in-phase and out-of-phase components of the AC susceptibility, respectively, at one single frequency the total assay time for the optimized combined protocol would be no more than 1.5 hours, often a relevant time frame for diagnosis of cancer and infectious disease. Also, applying the phase angle method normalization of AC susceptibility data is not needed. These findings are useful for the development of point-of-care biodiagnostic devices relying on bead-coil binding and magnetic AC susceptometry.

  • 5.
    Borysov, Stanislav S.
    et al.
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). KTH Royal Institute of Technology, Sweden; Los Alamos National Laboratory, USA.
    Forchheimer, Daniel
    Haviland, David B.
    Dynamic calibration of higher eigenmode parameters of a cantilever in atomic force microscopy by using tip-surface interactions2014In: Beilstein Journal of Nanotechnology, ISSN 2190-4286, Vol. 5, p. 1899-1904Article in journal (Refereed)
    Abstract [en]

    We present a theoretical framework for the dynamic calibration of the higher eigenmode parameters (stiffness and optical lever inverse responsivity) of a cantilever. The method is based on the tip-surface force reconstruction technique and does not require any prior knowledge of the eigenmode shape or the particular form of the tip-surface interaction. The calibration method proposed requires a single-point force measurement by using a multimodal drive and its accuracy is independent of the unknown physical amplitude of a higher eigenmode.

  • 6.
    Brandt, Erik G.
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Agosta, Lorenzo
    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).
    Reactive wetting properties of TiO2 nanoparticles predicted by ab initio molecular dynamics simulations2016In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 8, no 27, p. 13385-13398Article in journal (Refereed)
    Abstract [en]

    Small-sized wet TiO2 nanoparticles have been investigated by ab initio molecular dynamics simulations. Chemical and physical adsorption of water on the TiO2-water interface was studied as a function of water content, ranging from dry nanoparticles to wet nanoparticles with monolayer coverage of water. The surface reactivity was shown to be a concave function of water content and driven by surface defects. The local coordination number at the defect was identified as the key factor to decide whether water adsorption proceeds through dissociation or physisorption on the surface. A consistent picture of TiO2 nanoparticle wetting at the microscopic level emerges, which corroborates existing experimental data and gives further insight into the molecular mechanisms behind nanoparticle wetting. These calculations will facilitate the engineering of metal oxide nanoparticles with a controlled catalytic water activity.

  • 7.
    Brandt, Erik G.
    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).
    Molecular Dynamics Simulations of Adsorption of Amino Acid Side Chain Analogues and a Titanium Binding Peptide on the TiO2 (100) Surface2015In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, no 32, p. 18126-18139Article in journal (Refereed)
    Abstract [en]

    Adsorption profiles and adsorption free energies were determined for the side chain analogues of the 20 naturally occurring amino acids and a titanium binding peptide on the TiO2 (100) surface. Microsecond simulations with umbrella sampling and metadynamics were used to sample the free energy barriers associated with desolvation of strongly bound water molecules at the TiO2 surface. Polar and aromatic side chain analogues that hydrogen bond either to surface waters or directly to the metal oxide surface were found to be the strongest binders. Further, adsorption simulations of a 6 residue titanium binding peptide identified two binding modes on TiO2 (100). The peptide structure with lowest free energy was shown to be stabilized by a salt bridge between the end termini. A comparison between the free energies of the side chain analogues of the peptide sequence and the peptide itself shows that the free energy contributions are not additive. The simulations emphasize that tightly bound surface waters play a key role for peptide and protein structures when bound to inorganic surfaces in biological environments.

  • 8.
    Brandt, Erik G.
    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).
    Systematic Optimization of a Force Field for Classical Simulations of TiO2-Water Interfaces2015In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, no 32, p. 18110-18125Article in journal (Refereed)
    Abstract [en]

    Atomistic force field parameters were developed for the TiO2-water interface by systematic optimization with respect to experimentally determined crystal structures (lattice parameters) and surface thermodynamics (water adsorption enthalpy). Optimized force field parameters were determined for the two cases where TiO2 was modeled with or without covalent bonding. The nonbonded TiO2 model can be used to simulate different TiO2 phases, while the bonded TiO2 model is particularly useful for simulations of nanosized TiO2 and biomatter, including protein-surface and nanoparticle-biomembrane simulations. The procedure is easily generalized to parametrize interactions between other inorganic surfaces and biomolecules.

  • 9. Carinelli, S.
    et al.
    Kühnemund, M.
    Nilsson, Mats
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics. Stockholm University, Science for Life Laboratory (SciLifeLab).
    Pividori, M. I.
    Yoctomole electrochemical genosensing of Ebola virus cDNA by rolling circle and circle to circle amplification2017In: Biosensors & bioelectronics, ISSN 0956-5663, E-ISSN 1873-4235, Vol. 93, p. 65-71Article in journal (Refereed)
    Abstract [en]

    This work addresses the design of an Ebola diagnostic test involving a simple, rapid, specific and highly sensitive procedure based on isothermal amplification on magnetic particles with electrochemical readout. Ebola padlock probes were designed to detect a specific L-gene sequence present in the five most common Ebola species. Ebola cDNA was amplified by rolling circle amplification (RCA) on magnetic particles. Further re-amplification was performed by circle-to-circle amplification (C2CA) and the products were detected in a double-tagging approach using a biotinylated capture probe for immobilization on magnetic particles and a readout probe for electrochemical detection by square-wave voltammetry on commercial screen-printed electrodes. The electrochemical genosensor was able to detect as low as 200 ymol, corresponding to 120 cDNA molecules of L-gene Ebola virus with a limit of detection of 33 cDNA molecules. The isothermal double-amplification procedure by C2CA combined with the electrochemical readout and the magnetic actuation enables the high sensitivity, resulting in a rapid, inexpensive, robust and user-friendly sensing strategy that offers a promising approach for the primary care in low resource settings, especially in less developed countries.

  • 10.
    Cavalca, Filippo
    et al.
    Stockholm University, Faculty of Science, Department of Physics. SLAC National Accelerator Laboratory, United States.
    Ferragut, Rafael
    Aghion, Stefano
    Eilert, André
    Stockholm University, Faculty of Science, Department of Physics. SLAC National Accelerator Laboratory, United States; Stanford University, United States.
    Diaz-Morales, Oscar
    Stockholm University, Faculty of Science, Department of Physics.
    Liu, Chang
    Stockholm University, Faculty of Science, Department of Physics.
    Koh, Ai Leen
    Hansen, Thomas W.
    Pettersson, Lars G. M.
    Stockholm University, Faculty of Science, Department of Physics.
    Nilsson, Anders
    Stockholm University, Faculty of Science, Department of Physics.
    Nature and Distribution of Stable Subsurface Oxygen in Copper Electrodes During Electrochemical CO2 Reduction2017In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, no 45, p. 25003-25009Article in journal (Refereed)
    Abstract [en]

    Oxide-derived copper (OD-Cu) electrodes exhibit higher activity than pristine copper during the carbon dioxide reduction reaction (CO2RR) and higher selectivity toward ethylene. The presence of residual subsurface oxygen in OD-Cu has been proposed to be responsible for such improvements, although its stability under the reductive CO2RR conditions remains unclear. This work sheds light on the nature and stability of subsurface oxygen. Our spectroscopic results show that oxygen is primarily concentrated in an amorphous 1-2 nm thick layer within the Cu subsurface, confirming that subsurface oxygen is stable during CO2RR for up to 1 h at -1.15 V vs RHE. Besides, it is associated with a high density of defects in the OD-Cu structure. We propose that both low coordination of the amorphous OD-Cu surface and the presence of subsurface oxygen that withdraws charge from the copper sp- and d-bands might selectively enhance the binding energy of CO.

  • 11. Chen, Yanping
    et al.
    Su, Jie
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Huang, Shiliang
    Liang, Jie
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Peking University, China.
    Lin, Xiaohuan
    Liao, Fuhui
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Peking University, China.
    Wang, Yingxia
    Lin, Jianhua
    Gies, Hermann
    PKU-20: A new silicogermanate constructed from sti and asv layers2016In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 224, p. 384-391Article in journal (Refereed)
    Abstract [en]

    A new silicogermanate (PKU-20) was hydrothermally synthesized using triethylisopropylammonium cation as the structure directing agent in the presence of fluoride. Its structure was determined from a combination of synchrotron single crystal X-ray diffraction and powder X-ray diffraction data. PKU-20 crystallizes in the monoclinic space group C2/m, with the lattice parameters of a = 18.5901(6) angstrom, b = 13.9118 (4) angstrom, c = 22.2614(7) angstrom and beta = 100.1514 (12)degrees. The framework of PKU-20 is constructed from an alternate stacking of sti and asv layers. The sti layer is exactly the same as that in the STI framework, while the asv layer is a new layer sliced off from the ASV framework parallel to the (112) plane. The takeout scheme of the layer is discussed on the basis of a composite building unit D4R-/au-D4R. PKU-20 possesses a two-dimensional channel system, where the 10-ring channels parallel to the [010] direction are intercrossed by 12-ring pockets along the [101] direction.

  • 12. Cho, Hae Sung
    et al.
    Miyasaka, Keiichi
    Kim, Hyungjun
    Kubota, Yoshiki
    Takata, Masaki
    Kitagawa, Susumu
    Ryoo, Ryong
    Terasaki, Osamu
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Study of Argon Gas Adsorption in Ordered Mesoporous MFI Zeolite Framework2012In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 116, no 48, p. 25300-25308Article in journal (Refereed)
    Abstract [en]

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

  • 13. Cronholm, Pontus
    et al.
    Karlsson, Hanna L.
    Hedberg, Jonas
    Lowe, Troy A.
    Winnberg, Lina
    Elihn, Karine
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Wallinder, Inger Odnevall
    Möller, Lennart
    Intracellular Uptake and Toxicity of Ag and CuO Nanoparticles: A Comparison Between Nanoparticles and their Corresponding Metal Ions2013In: Small, ISSN 1613-6810, E-ISSN 1613-6829, Vol. 9, no 7, p. 970-982Article in journal (Refereed)
    Abstract [en]

    An increased understanding of nanoparticle toxicity and its impact on human health is essential to enable a safe use of nanoparticles in our society. The aim of this study is to investigate the role of a Trojan horse type mechanism for the toxicity of Ag-nano and CuO-nano particles and their corresponding metal ionic species (using CuCl2 and AgNO3), i.e., the importance of the solid particle to mediate cellular uptake and subsequent release of toxic species inside the cell. The human lung cell lines A549 and BEAS-2B are used and cell death/membrane integrity and DNA damage are investigated by means of trypan blue staining and the comet assay, respectively. Chemical analysis of the cellular dose of copper and silver is performed using atomic absorption spectroscopy. Furthermore, transmission electron microscopy, laser scanning confocal microscopy, and confocal Raman microscopy are employed to study cellular uptake and particle-cell interactions. The results confirm a high uptake of CuO-nano and Ag-nano compared to no, or low, uptake of the soluble salts. CuO-nano induces both cell death and DNA damage whereas CuCl2 induces no toxicity. The opposite is observed for silver, where Ag-nano does not cause any toxicity, whereas AgNO3 induces a high level of cell death. In conclusion: CuO-nano toxicity is predominantly mediated by intracellular uptake and subsequent release of copper ions, whereas no toxicity is observed for Ag-nano due to low release of silver ions within short time periods.

  • 14. Dietzel, Dirk
    et al.
    de Wijn, Astrid S.
    Stockholm University, Faculty of Science, Department of Physics. Norwegian University of Science and Technology, Norway.
    Vorholzer, Matthias
    Schirmeisen, Andre
    Friction fluctuations of gold nanoparticles in the superlubric regime2018In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 29, no 15, article id 155702Article in journal (Refereed)
    Abstract [en]

    Superlubricity, or alternatively termed structural (super)lubrictiy, is a concept where ultra-low friction is expected at the interface between sliding surfaces if these surfaces are incommensurate and thus unable to interlock. In this work, we now report on sudden, reversible, friction changes that have been observed during AFM-based nanomanipulation experiments of gold nanoparticles sliding on highly oriented pyrolythic graphite. These effects can be explained by rotations of the gold nanoparticles within the concept of structural superlubricity, where the occurrence of ultra-low friction can depend extremely sensitively on the relative orientation between the slider and the substrate. From our theoretical simulations it will become apparent how even miniscule magnitudes of rotation are compatible to the observed effects and how size and shape of the particles can influence the dependence between friction and relative orientation.

  • 15. Dos Santos, Egon C.
    et al.
    Lourenco, Maicon P.
    Pettersson, Lars G. M.
    Stockholm University, Faculty of Science, Department of Physics.
    Duarte, Hélio A.
    Stability, Structure, and Electronic Properties of the Pyrite/Arsenopyrite Solid-Solid Interface-A DFT Study2017In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, no 14, p. 8042-8051Article in journal (Refereed)
    Abstract [en]

    Pyrite is the most common sulfide in the Earth. In the presence of arsenopyrite its oxidation is delayed, and instead, the arsenopyrite increases its oxidation rate, releasing As(III) and As(V) species in the medium. DFT/plane waves calculations were performed on pyrite/arsenopyrite interface models to understand the stability, structure, and electronic properties of the interface. This is the first step to understand the influence of the inlaid arsenopyrite in the pyrite oxidation mechanism. The interface is slightly stressed with minor changes in the bond lengths and lattice parameters with respect to the pure phases. The work of adhesion and the formation energy indicate that the miscibility of the two phases is not favorable, explaining the presence of large domains of either pyrite or arsenopyrite forming bulk granular regions. The valence band of the pyrite/arsenopyrite interface has large contributions from the pyrite phase, while the conduction band has large contributions from the arsenopyrite. This is consistent with the pyrite as cathode and arsenopyrite as anode in a galvanic contact. Furthermore, the interface formation shifts the valence states upward and decreases the band gap, facilitating interfacial electron transfer.

  • 16. Dumanov, E. V.
    et al.
    Podlesny, I. V.
    Moskalenko, S. A.
    Liberman, Michael A.
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Interaction of two-dimensional magnetoexcitons2017In: Physica. E, Low-Dimensional systems and nanostructures, ISSN 1386-9477, E-ISSN 1873-1759, Vol. 88, p. 77-86Article in journal (Refereed)
    Abstract [en]

    We study interaction of the two-dimensional magnetoexcitons with in-plane wave vector (k) over right arrow (parallel to) = 0, taking into account the influence of the excited Landau levels (ELLS) and of the external electric field perpendicular to the surface of the quantum well and parallel to the external magnetic field., It is shown that the account of the ELLS gives rise to the repulsion between the spinless magnetoexcitons with (k) over right arrow (parallel to) = 0 in the Fock approximation, with the interaction constant g decreasing inverse proportional to the magnetic field strength B (g(0) similar to 1/B). In the presence of the perpendicular electric field the Rashba spin-orbit coupling (RSOC), Zeeman splitting (ZS) and nonparabolicity of the heavy-hole dispersion law affect the Landau quantization of the electrons and holes. They move along the new cyclotron orbits, change their Coulomb interactions and cause the interaction between 21) magnetoexcitons with (k) over right arrow (parallel to) = 0. The changes of the Coulomb interactions caused by the electrons and by the holes moving with new cyclotron orbits are characterized by some coefficients, which in the absence of the electric field turn to be unity. The differences between these coefficients of the electron-hole pairs forming the magnetoexcitons determine their affinities to the interactions. The interactions between the homogeneous, semihomogeneous and heterogeneous magnetoexcitons forming the symmetric states with the same signs of their affinities are attractive whereas in the case of different sign affinities are repulsive. In the heterogeneous asymmetric states the interactions have opposite signs in comparison with the symmetric states. In all these cases the interaction constant g have the dependence g(0) - 1/root B.

  • 17. El-Kemary, Maged
    et al.
    Zahran, Moustafa
    Khalifa, Shaden A. M.
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute. Karolinska University Hospital, Sweden.
    El-Seedi, Hesham R.
    Spectral characterisation of the silver nanoparticles biosynthesised using Ambrosia maritima plant2016In: Micro & Nano Letters, ISSN 1750-0443, E-ISSN 1750-0443, Vol. 11, no 6, p. 311-314Article in journal (Refereed)
    Abstract [en]

    Silver nanoparticles (AgNPs) were biosynthesised by reducing silver nitrate (AgNO3) using Ambrosia maritima aqueous leaves extract. The biosynthesised AgNPs were characterised by transmission electron microscope, Fourier transform infrared spectroscopy and zeta potential analyser. The nanoparticles were generally found to be spherical in shape with average size of 30 nm and were stable at zeta potential of -26.29 mV. The data collected by cyclic voltammetry, ultraviolet-visible (UV-Vis) spectrophotometer and spectrofluorophotometer proved the characteristic electrochemical and optical properties of the biosynthesised AgNPs. The metallic nanoparticles showed an anodic peak at 0.4 mV, a surface plasmon resonance peak at 437 nm and a fluorescence emission peak at the wavelength of 467 nm. In conclusion, AgNPs biosynthesised using A. maritima proved to be compatible and feasible to be studied further in in vitro and in vivo systems. Overall, the biosynthesised AgNPs can be used as a tool applied in a broad range of industrial and medical applications.

  • 18. Engström, Anna
    et al.
    Gómez de la Torre, Teresa Zardán
    Strømme, Maria
    Nilsson, Mats E.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics. Stockholm University, Science for Life Laboratory (SciLifeLab).
    Herthnek, David
    Detection of Rifampicin Resistance in Mycobacterium tuberculosis by Padlock Probes and Magnetic Nanobead-Based Readout2013In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 8, no 4, article id e62015Article in journal (Refereed)
    Abstract [en]

    Control of the global epidemic tuberculosis is severely hampered by the emergence of drug-resistant Mycobacterium tuberculosis strains. Molecular methods offer a more rapid means of characterizing resistant strains than phenotypic drug susceptibility testing. We have developed a molecular method for detection of rifampicin-resistant M. tuberculosis based on padlock probes and magnetic nanobeads. Padlock probes were designed to target the most common mutations associated with rifampicin resistance in M. tuberculosis, i.e. at codons 516, 526 and 531 in the gene rpoB. For detection of the wild type sequence at all three codons simultaneously, a padlock probe and two gap-fill oligonucleotides were used in a novel assay configuration, requiring three ligation events for circularization. The assay also includes a probe for identification of the M. tuberculosis complex. Circularized probes were amplified by rolling circle amplification. Amplification products were coupled to oligonucleotide-conjugated magnetic nanobeads and detected by measuring the frequency-dependent magnetic response of the beads using a portable AC susceptometer.

  • 19.
    Etman, Ahmed S.
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Alexandria University, Egypt.
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Peking University, China.
    Younesi, Reza
    V2O5·nH2O nanosheets and multi-walled carbon nanotube composite as a negative electrode for sodium-ion batteries2018In: Journal of Energy Chemistry, ISSN 2095-4956Article in journal (Refereed)
    Abstract [en]

    Two dimensional (2D) transition metal oxides and chalcogenides demonstrate a promising performance in sodium-ion batteries (SIBs) application. In this study, we investigated the use of a composite of freeze dried V2O5·nH2O nanosheets and multi-walled carbon nanotube (MWCNT) as a negative electrode material for SIBs. Cyclic voltammetry (CV) results indicated that a reversible sodium-ion insertion/deinsertion into the composite electrode can be obtained in the potential window of 0.1–2.5 V vs. Na+/Na. The composite electrodes delivered sodium storage capacities of 140 and 45 mAh g−1 under applied current densities of 20 and 100 mA g−1, respectively. The pause test during constant current measurement showed a raise in the open circuit potential (OCP) of about 0.46 V, and a charge capacity loss of ∼10%. These values are comparable with those reported for hard carbon electrodes. For comparison, electrodes of freeze dried V2O5·nH2O nanosheets were prepared and tested for SIBs application. The results showed that the MWCNT plays a significant role in the electrochemical performance of the composite material.

  • 20.
    Faure, Bertrand
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Particle interactions at the nanoscale: From colloidal processing to self-assembled arrays2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Nanostructured materials are the next generation of high-performance materials, harnessing the novel properties of their nanosized constituents. The controlled assembly of nanosized particles and the design of the optimal nanostructure require a detailed understanding of particle interactions and robust methods to tune them. This thesis describes innovative approaches to these challenges, relating to the determination of Hamaker constants for iron oxide nanoparticles, the packaging of nanopowders into redispersible granules, the tuning of the wetting behavior of nanocrystals and the simulation of collective magnetic properties in arrays of superparamagnetic nanoparticles.

    The non-retarded Hamaker constants for iron oxides have been calculated from their optical properties based on Lifshitz theory. The results show that the magnitude of vdW interactions in non-polar solvents has previously been overestimated up to 10 times. Our calculations support the experimental observations that oleate-capped nanoparticles smaller than 15 nm in diameter can indeed form colloidally-stable dispersions in hydrocarbons. In addition, a simple procedure has been devised to remove the oleate-capping on the iron oxide nanoparticles, enabling their use in fluorometric assays for water remediation, with a sensitivity more than 100 times below the critical micelle concentration for non-ionic surfactants.

    Nanosized particles are inherently more difficult to handle in the dry state than larger micron-sized powders, e.g. because of poor flowability, agglomeration and potential toxicity. The rheology of concentrated slurries of TiO2 powder was optimized by the addition of sodium polyacrylate, and spray-dried into fully redispersible micron-sized granules. The polymer was embedded into the granules, where it could serve as a re-dispersing aid.

    Monte Carlo (MC) simulations have been applied to the collective magnetic behavior of nanoparticle arrays of various thicknesses. The decrease in magnetic susceptibility with the thickness observed experimentally was reproduced by the simulations. Ferromagnetic couplings in the arrays are enhanced by the finite thickness, and decrease in strength with increasing thickness. The simulations indicate the formation of vortex states with increasing thickness, along with a change in their orientation, which becomes more and more isotropic as the thickness increases.

  • 21. Ferreira de Lima, Guilherme
    et al.
    Anderson Duarte, Hélio
    Pettersson, Lars G. M.
    Stockholm University, Faculty of Science, Department of Physics.
    X-ray Absorption Near-Edge Spectroscopy Calculations on Pristine and Modified Chalcopyrite Surfaces2018In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 122, no 35, p. 20200-20209Article in journal (Refereed)
    Abstract [en]

    Understanding chemical modifications on the chalcopyrite surface is an important issue to improve hydrometallurgical processes to recover copper from the mineral. X-ray absorption near-edge spectroscopy (XANES) can be used for this task, but the interpretation of the spectrum and the correlation with chemical changes in the first atomic layers are not straightforward. The present study demonstrates the potential of combining spectrum measurements with theoretical X-ray spectrum simulations to elucidate the chemistry behind weathering of important classes of minerals. We simulated the S and Fe K-edge XANES spectrum for pristine and modified chalcopyrite surfaces using periodic DFT calculations and the transition-potential model. The calculated S K-edge XANES spectra are in good agreement with experimental data and the peaks were attributed using the density of states. The simulated Fe K-edge XANES spectra do not reproduce all features observed experimentally. The effect of surface changes due to reconstruction, hydration, and oxidation on the spectrum was analyzed. Our results show that the S K-edge XANES spectrum is more sensitive to surface modifications than the Fe K-edge XANES spectrum, and this sensitivity could be used to follow the evolution of the surface.

  • 22. Gala, Fabrizio
    et al.
    Agosta, Lorenzo
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Zollo, Giuseppe
    Water Kinetics and Clustering on the (101) TiO2 Anatase Surface2016In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, no 1, p. 450-456Article in journal (Refereed)
    Abstract [en]

    (101) anatase TiO2 surface in water ambient is an important system for the interaction of biocompatible nanodevices with biological environment. Following the experimental evidence showing that water molecules are mobile at temperature as low as 190 K and tend to form clusters along the [11 (1) over bar]/[1 (11) over bar] surface directions, a complete theoretical characterization of the dynamical properties of the first water layer on the (101) anatase TiO2 surface is presented. A variety of computational techniques have been employed in the context of the transition-state theory in the harmonic regime, ranging from first-principles total energy ground-state calculations, to density functional perturbation theory, minimum energy path search, and kinetic Monte Carlo simulations, to explain the experimental results on water kinetics on the (101) anatase TiO2 surface. We have calculated the migration energy barrier of water molecules, the vibrational prefactor through the phonon density of states, and the hopping rate along two principal directions. Lastly, in a kinetic Monte Carlo context, we have simulated and clarified the dynamical processes that are on the basis of the observed experimental behavior.

  • 23.
    Garcia-Bennett, Alfonso E.
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Konig, Niclas
    Abrahamsson, Ninnie
    Kozhevnikova, Mariya
    Zhou, Chunfang
    Trolle, Carl
    Pankratova, Stanislava
    Berezin, Vladimir
    Kozlova, Elena N.
    In vitro generation of motor neuron precursors from mouse embryonic stem cells using mesoporous nanoparticles2014In: Nanomedicine, ISSN 1743-5889, E-ISSN 1748-6963, Vol. 9, no 16, p. 2457-2466Article in journal (Refereed)
    Abstract [en]

    Aim: Stem cell-derived motor neurons (MNs) are utilized to develop replacement strategies for spinal cord disorders. Differentiation of embryonic stem cells into MN precursors involves factors and their repeated administration. We investigated if delivery of factors loaded into mesoporous nanoparticles could be effective for stem cell differentiation in vitro. Materials & methods: We used a mouse embryonic stem cell line expressing green fluorescent protein under the promoter for the MN-specific gene Hb9 to visualize the level of MN differentiation. The differentiation of stem cells was evaluated by expression of MN-specific transcription factors monitored by quantitative real-time PCR reactions and immunocytochemistry. Results: Mesoporous nanoparticles have strong affiliation to the embryoid bodies, penetrate inside the embryoid bodies and come in contact with differentiating cells. Conclusion: Repeated administration of soluble factors into a culture medium can be avoided due to a sustained release effect using mesoporous silica.

  • 24.
    Gebauer, Denis
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Oliynyk, Vitaliy
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Salajkova, Michaela
    Sort, Jordi
    Zhou, Qi
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Salazar-Alvarez, German
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    A transparent hybrid of nanocrystalline cellulose and amorphous calcium carbonate nanoparticles2011In: NANOSCALE, ISSN 2040-3364, Vol. 3, no 9, p. 3563-3566Article in journal (Refereed)
    Abstract [en]

    Nanocellulose hybrids are promising candidates for biodegradable multifunctional materials. Hybrids of nanocrystalline cellulose (NCC) and amorphous calcium carbonate (ACC) nanoparticles were obtained through a facile chemical approach over a wide range of compositions. Controlling the interactions between NCC and ACC results in hard, transparent structures with tunable composition, homogeneity and anisotropy.

  • 25. Guo, Maoxiang
    et al.
    Hernández-Neuta, Iván
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics. Stockholm University, Science for Life Laboratory (SciLifeLab).
    Madaboosi, Narayanan
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics. Stockholm University, Science for Life Laboratory (SciLifeLab).
    Nilsson, Mats
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics. Stockholm University, Science for Life Laboratory (SciLifeLab).
    van der Wijngaart, Wouter
    Efficient DNA-assisted synthesis of trans-membrane gold nanowires2018In: microsystems and nanoengineering, ISSN 2055-7434, Vol. 4, article id UNSP 17084Article in journal (Refereed)
    Abstract [en]

    Whereas electric circuits and surface-based (bio) chemical sensors are mostly constructed in-plane due to ease of manufacturing, 3D microscale and nanoscale structures allow denser integration of electronic components and improved mass transport of the analyte to (bio) chemical sensor surfaces. This work reports the first out-of-plane metallic nanowire formation based on stretching of DNA through a porous membrane. We use rolling circle amplification (RCA) to generate long single-stranded DNA concatemers with one end anchored to the surface. The DNA strands are stretched through the pores in the membrane during liquid removal by forced convection. Because the liquid-air interface movement across the membrane occurs in every pore, DNA stretching across the membrane is highly efficient. The stretched DNA molecules are transformed into trans-membrane gold nanowires through gold nanoparticle hybridization and gold enhancement chemistry. A 50 fM oligonucleotide concentration, a value two orders of magnitude lower than previously reported for flat surface-based nanowire formation, was sufficient for nanowire formation. We observed nanowires in up to 2.7% of the membrane pores, leading to an across-membrane electrical conductivity reduction from open circuit to <20 Omega. The simple electrical read-out offers a high signal-to-noise ratio and can also be extended for use as a biosensor due to the high specificity and scope for multiplexing offered by RCA.

  • 26. Gómez de la Torre, Teresa Zardán
    et al.
    Herthnek, David
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics. Stockholm University, Science for Life Laboratory (SciLifeLab). Uppsala University, Sweden.
    Strømme, Maria
    A Magnetic Nanobead-Based Read-Out Procedure for Rapid Detection of DNA Molecules2017In: Journal of Nanoscience and Nanotechnology, ISSN 1533-4880, E-ISSN 1533-4899, Vol. 17, no 4, p. 2861-2864Article in journal (Refereed)
    Abstract [en]

    The presented measurement and data analysis procedure reduces the read-out time for the volumeamplified magnetic nanobead detection assay from similar to 30 min to only 2 min, providing fast, sensitive detection of DNA molecules. The molecular detection and amplification protocol was verified using samples containing rolling circle-amplified DNA products formed from synthetic Vibrio cholerae target DNA, with a limit of detection of 5 pM. The developed read-out method could be used to rapidly identify pathogens in a variety of applications including target screening in hospitals with limited resources, in out-patient settings and in the field.

  • 27. Harada, Y.
    et al.
    Miyawaki, J.
    Niwa, H.
    Yamazoe, K.
    Pettersson, Lars G. M.
    Stockholm University, Faculty of Science, Department of Physics.
    Nilsson, Anders
    Stockholm University, Faculty of Science, Department of Physics.
    Probing the OH Stretch in Different Local Environments in Liquid Water2017In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 8, no 22, p. 5487-5491Article in journal (Refereed)
    Abstract [en]

    We use resonant inelastic X-ray scattering (RIXS) to resolve vibrational losses corresponding to the OH stretch where the X-ray absorption process allows us to selectively probe different structural subensembles in liquid water. The results point to a unified interpretation of X-ray and vibrational spectroscopic data in line with a picture of two classes of structural environments in the liquid at ambient conditions with predominantly close-packed high-density liquid (HDL) and occasional local fluctuations into strongly tetrahedral low-density liquid (LDL).

  • 28.
    Hernández-Neuta, Iván
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics. Stockholm University, Science for Life Laboratory (SciLifeLab).
    Pereiro, Iago
    Ahlford, Annika
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics. Stockholm University, Science for Life Laboratory (SciLifeLab).
    Ferraro, Davide
    Zhang, Qiongdi
    Viovy, Jean-Louis
    Descroix, Stéphanie
    Nilsson, Mats
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics. Stockholm University, Science for Life Laboratory (SciLifeLab).
    Microfluidic magnetic fluidized bed for DNA analysis in continuous flow mode2018In: Biosensors & bioelectronics, ISSN 0956-5663, E-ISSN 1873-4235, Vol. 102, p. 531-539Article in journal (Refereed)
    Abstract [en]

    Magnetic solid phase substrates for biomolecule manipulation have become a valuable tool for simplification and automation of molecular biology protocols. However, the handling of magnetic particles inside microfluidic chips for miniaturized assays is often challenging due to inefficient mixing, aggregation, and the advanced instrumentation required for effective actuation. Here, we describe the use of a microfluidic magnetic fluidized bed approach that enables dynamic, highly efficient and simplified magnetic bead actuation for DNA analysis in a continuous flow platform with minimal technical requirements. We evaluate the performance of this approach by testing the efficiency of individual steps of a DNA assay based on padlock probes and rolling circle amplification. This assay comprises common nucleic acid analysis principles, such as hybridization, ligation, amplification and restriction digestion. We obtained efficiencies of up to 90% for these reactions with high throughput processing up to 120 mu L of DNA dilution at flow rates ranging from 1 to 5 mu L/min without compromising performance. The fluidized bed was 20-50% more efficient than a commercially available solution for microfluidic manipulation of magnetic beads. Moreover, to demonstrate the potential of this approach for integration into micro-total analysis systems, we optimized the production of a low-cost polymer based microarray and tested its analytical performance for integrated single-molecule digital read-out. Finally, we provide the proof-of-concept for a single-chamber microfluidic chip that combines the fluidized bed with the polymer microarray for a highly simplified and integrated magnetic bead-based DNA analyzer, with potential applications in diagnostics.

  • 29.
    Hu, Jianfeng
    et al.
    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).
    Intragranular heterojunctions formed by ordered coalescence of strontium and barium titanate nanocrystals2015In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 107, p. 14-17Article in journal (Refereed)
    Abstract [en]

    Crystal growth by nanocrystal-assembly plays an important role in the synthesis and preparation of nanostructural materials. In most cases, this crystal-growth mechanism is reported to occur in unary nanocrystal systems and in solution environment. Here, we report a new observation of grain growth by ordered coalescence of nanocrystals occurring in SrTiO3-BaTiO3 binary system during solid-state sintering, which also results in unique oxide heterostructures inside coarsened grains in bulk polycrystalline materials.

  • 30.
    Hu, Jianfeng
    et al.
    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).
    Ordered coalescence of nano crystallites contributing to the rapid anisotropic grain growth in silicon nitride ceramics2013In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 69, no 3, p. 270-273Article in journal (Refereed)
    Abstract [en]

    Microstructural characterization is performed on two dense Si3N4 ceramic samples consolidated by spark plasma sintering (SPS): one fabricated using alpha-Si3N4 and the other using beta-Si3N4 as the starting powder. A novel mechanism is revealed where ordered coalescence of nano beta-crystallites accelerate the rapid beta-Si3N4 anisotropic grain growth. The rapid alpha- to beta-Si3N4 phase transformation via a high supersaturation of dissolved Si3N4 in the melt favors this mechanism. The high heating rate by SPS is essential for achieving such supersaturation.

  • 31. Huang, Jing
    et al.
    Xu, Bo
    Yuan, Chunze
    Chen, Hong
    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).
    Sun, Licheng
    Ågren, Hans
    Improved Performance of Colloidal CdSe Quantum Dot-Sensitized Solar Cells by Hybrid Passivation2014In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 6, no 21, p. 18808-18815Article in journal (Refereed)
    Abstract [en]

    A hybrid passivation strategy is employed to modify the surface of colloidal CdSe quantum dots (QDs) for quantum dot-sensitized solar cells (QDSCs), by using mercaptopropionic acid (MPA) and iodide anions through a ligand exchange reaction in solution. This is found to be an effective way to improve the performance of QDSCs based on colloidal QDs. The results show that MPA can increase the coverage of the QDs on TiO2 electrodes and facilitate the hole extraction from the photoxidized QDs, and simultaneously, that the iodide anions can remedy the surface defects of the CdSe QDs and thus reduce the recombination loss in the device. This hybrid passivation treatment leads to a significant enhancement of the power conversion efficiency of the QDSCs by 41%. Furthermore, an optimal ratio of iodide ions to MPA was determined for favorable hybrid passivation; results show that excessive iodine anions are detrimental to the loading of the QDs. This study demonstrates that the improvement in QDSC performance can be realized by using a combination of different functional ligands to passivate the QDs, and that ligand exchange in solution effective approach to introduce can be an different ligands.

  • 32. Ibrahem, Ismail
    et al.
    Iqbal, Muhammad Naeem
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Verho, Oscar
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Eivazihollagh, Alireza
    Olsén, Peter
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Edlund, Håkan
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Norgren, Magnus
    Johnston, Eric V.
    Copper Nanoparticles on Controlled Pore Glass and TEMPO for the Aerobic Oxidation of Alcohols2018In: ChemNanoMat, ISSN 2199-692X, Vol. 4, no 1, p. 71-75Article in journal (Refereed)
    Abstract [en]

    Herein, we report on the facile synthesis of a heterogeneous copper nanocatalyst and its combination with 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) for the aerobic oxidation of alcohols to their corresponding carbonyl compounds. This low cost copper nanocatalyst was found to exhibit excellent recyclability, making it a highly attractive catalytic system from an economical and environmental point of view. Extensive characterization of the catalyst by a number of techniques revealed that it was comprised of well-dispersed Cu(I/II) nanoparticles with an average size of around 6nm.

  • 33.
    Jaworski, Aleksander
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Stevensson, Baltzar
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Edén, Mattias
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    The Bearings from Rare-Earth (RE = La, Lu, Sc, Y) Cations on the Oxygen Environments in Aluminosilicate Glasses: A Study by Solid State O-17 NMR, Molecular Dynamics Simulations, and DFT Calculations2016In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, no 24, p. 13181-13198Article in journal (Refereed)
    Abstract [en]

    Aluminosilicate (AS) glasses incorporating trivalent cations of rare-earth (RE) elements exhibit a significant structural disorder and manifest building blocks incommensurate with conventional glass structure models. We present a comprehensive experimental and computational study of the O speciations in RE2O3-Al2O3-SiO2 glasses with RE = {La3+, Y3+, Lu3+, Sc3+}, where the cations are ordered according to increasing field-strength. The coexisting O-17([p])-Sip-mAlm moieties were quantified by magic-angle-spinning (MAS) O-17 nuclear magnetic resonance (NMR) experiments and atomistic molecular dynamics (MD) simulations. Experimental O-17 quadrupolar products ((C) over bar (Qn)) and isotropic chemical shifts ((delta) over bar (iso)) agreed well with predictions from density functional theory with the projector augmented wave (PAW) and gauge including PAW approaches, respectively. We highlight an observed strong influence of both {(delta) over bar (iso), (C) over bar (Qn)} NMR parameters on the average number of O-17([p])-RE3+ contacts ((q) over bar) and establish simple correlations between g and each of Sisc, and CQ, that encompass mA.1, moieties with 1 < p < 3. The quadrupolar product of each O-[p]-Sip-mAlm motif depends linearly on the all fractional ionicity of,the bonds to the 170 site, which is readily calculated from the parameter set {m, p, (q) over bar} with (q) over bar extracted from the MD-generated glass models. We rationalize and discuss the stability of each O[p]-Sip-mAlm moiety using bond valence sums evaluated on the MD-derived RE AS glass models: all comprise non-negligible populations of unconventional 0 species, such as free O2- ions (O-[0] coordinations), and oxygen triclusters (O-[3]-SiAl2 and O-[3]-Al-3). The triclusters preferentially connect high-coordination Al-[5]/Al-[6] species via edge-sharing, where the participation in corner or edge shared polyhedra is reflected in the {(delta) over bar (iso), (C) over bar (Qn)} O-17 NMR parameters.

  • 34. Krüger, Martin
    et al.
    Reinsch, Helge
    Inge, Andrew Kentaro
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Stock, Norbert
    Effect of partial linker fluorination and linker extension on structure and properties of the Al-MOF CAU-102017In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 249, p. 128-136Article in journal (Refereed)
    Abstract [en]

    The systematic investigation of the solvothermal system Al3+/5-fluoroisophthalic acid (H(2)mBDC-5F)/isophthalic acid (H(2)mBDC)/DMF/H2O through a mixed-linker approach led to new mixed-linker CAU-10 derivatives containing 11, 28 and 44% of fluorinated linker molecules (denoted as CAU-10-H/F-11, CAU-10-H/F-28 and CAU-10-H/F-44, respectively), as determined by NMR spectroscopy. The crystal structure of CAU-10-H/F-28 was determined using the Rietveld method (space group 14(1)md, a = b = 21.3075(5), c = 10.7101(3) angstrom). The structure is built up by helical chains composed of cis corner-sharing AlO6 polyhedra. Each of these helices is interconnected to four adjacent helices with alternating rotational orientation through the carboxylate groups of mBDC(2-) linker molecules. Thus, accessible, square-shaped channels are formed. Sorption measurements revealed a high dependency of the adsorbed amount of gas on the degree of fluorination. With increasing fluorination, the total uptake decreases in N-2, H-2 and H2O sorption experiments and the hydrophobic character of the pores increases. In addition, an extended CAU-10 derivative, CAU-10-HTATB, was discovered using the tricarboxylic acid 4,4',4-s-triazine-2,4,6-triyl-tribenzoic acid (H(3)TATB) during the high-throughput investigation of the system Al3+/H(3)TATB/DMF/H2O. This new MOF, which was denoted CAU-10-HTATB, was thoroughly characterized using IR spectroscopy, thermogravimetric and elemental analysis, temperature dependent powder X-ray diffraction (PXRD) and sorption measurements. Although the compound is thermally stable up to 400 degrees C according to temperature-dependent PXRD measurements, it is not porous towards N2 molecules. The structure of CAU-10-HTATB could be also refined from PXRD data using the Rietveld method (space group l4(1)/a, a = b = 36.438 (1), c = 10.9373 (9) angstrom).

  • 35. Kupferschmidt, Natalia
    et al.
    Qazi, Khaleda Rahman
    Kemi, Cecilia
    Vallhov, Helen
    Garcia-Bennett, Alfonso E.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Gabrielsson, Susanne
    Scheynius, Annika
    Mesoporous silica particles potentiate antigen-specific T-cell responses2014In: Nanomedicine, ISSN 1743-5889, E-ISSN 1748-6963, Vol. 9, no 12, p. 1835-1846Article in journal (Refereed)
    Abstract [en]

    Aim: To study the adjuvant effect of mesoporous silica particles and their capability of modifying an already existing allergic Th2-like immune response. Materials & methods: The adjuvant effect of Santa Barbara Amorphous-15 (SBA-15) mesoporous silica particles was studied in an antigen-specific ovalbumin (OVA) system in vitro and in vivo. The capacity of the OVA-loaded SBA-15 particles (SBA-15-OVA) to modify an existing immune response was assessed in a murine allergy model. Results: SBA-15-OVA induced significantly stronger OVA-specific splenocyte proliferation compared with OVA alone. Significantly higher IFN-gamma production was observed in ex vivo OVA-stimulated splenocytes from SBA-15-OVA-immunized mice compared with mice injected with only SBA-15 or OVA. Treatment of OVA-sensitized mice with SBA-15-OVA modified the immune response with significantly lower serum levels of OVA-specific IgE and higher IgG levels compared with the alum-OVA-treated group. Conclusion: The results are promising for the continued development of mesoporous silica materials for therapeutic applications.

  • 36. Kupferschmidt, Natalia
    et al.
    Xia, Xin
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Labrador, Roberto H.
    Atluri, Rambabu
    Ballell, Lluis
    Garcia-Bennett, Alfonso E.
    In vivo oral toxicological evaluation of mesoporous silica particles2013In: Nanomedicine, ISSN 1743-5889, E-ISSN 1748-6963, Vol. 8, no 1, p. 57-64Article in journal (Refereed)
    Abstract [en]

    Background: Mesoporous silica particles are highly promising nanomaterials for biomedical applications. They can be used to improve bioavailability, solubility and drug stability and to protect drugs from the acidic conditions of the stomach, leading to increased drug effectiveness. Their biocompatibility in vivo has recieved little attention, in particular regarding oral administration. Aim: To study the oral tolerance of micron-sized nanoporous folic acid-templated material-1 (cylindrical, 2D hexagonal pore structure) and nanometer-sized anionic-surfactant-templated mesoporous silica material-6 (cylindrical, 3D cubic pore structure) mesoporous silica particles in Sprague Dawley rats. Materials & methods: A dose stepwise procedure or range finding test was followed by a consequent confirmatory test. The confirmatory test included daily administrations of 2000 and 1200 mg/kg doses for nanoporous folic acid-templated material-1 and anionic-surfactant-templated mesoporous silica material-6, respectively. Results: The maximum tolerated dose for anionic-surfactant-templated mesoporous silica material-6 was not reached. Similar results were observed for nanometer-sized anionic-surfactant-templated mesoporous silica material-1 in most of the animals, although adverse effects were observed in some animals that are most probably due to the administration by oral gavage of the formulated particles. Conclusion: The results are promising for the use of mesoporous silica materials as drug-delivery systems in oral administration.

  • 37. Kuruvilla, J.
    et al.
    Farinha, A. P.
    Bayat, Narges
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Cristobal, S.
    Surface proteomics on nanoparticles: a step to simplify the rapid prototyping of nanoparticles2017In: Nanoscale Horizons, ISSN 2055-6756, Vol. 2, no 1, p. 55-64Article in journal (Refereed)
    Abstract [en]

    Engineered nanoparticles for biomedical applications require increasing effectiveness in targeting specific cells while preserving non-target cells' safety. We developed a surface proteomics method for a rapid and systematic analysis of the interphase between the nanoparticle protein corona and the targeted cells that could implement the rapid prototyping of nanomedicines. Native nanoparticles entering in a protein-rich liquid medium quickly form a macromolecular structure called protein corona. This protein structure defines the physical interaction between nanoparticles and target cells. The surface proteins compose the first line of interaction between this macromolecular structure and the cell surface of a target cell. We demonstrated that SUSTU (SUrface proteomics, Safety, Targeting, Uptake) provides a qualitative and quantitative analysis from the protein corona surface. With SUSTU, the spatial dynamics of the protein corona surface can be studied. Data from SUSTU would ascertain the nanoparticle functionalized groups exposed at a destiny that could circumvent preliminary in vitro experiments. Therefore, this methodcould implement in the analysis of nanoparticle targeting and uptakecapability andcouldbe integrated intoa rapidprototyping strategy which is a major challenge in nanomaterials science. Data are available via ProteomeXchange with the identifier PXD004636.

  • 38. Laksmono, Hartawan
    et al.
    McQueen, Trevor A.
    Sellberg, Jonas A.
    Stockholm University, Faculty of Science, Department of Physics. SLAC National Accelerator Laboratory, USA.
    Loh, N. Duane
    Huang, Congcong
    Schlesinger, Daniel
    Stockholm University, Faculty of Science, Department of Physics.
    Sierra, Raymond G.
    Hampton, Christina Y.
    Nordlund, Dennis
    Beye, Martin
    Martin, Andrew V.
    Barty, Anton
    Seibert, M. Marvin
    Messerschmidt, Marc
    Williams, Garth J.
    Boutet, Sebastien
    Arnann-Winkel, Katrin
    Stockholm University, Faculty of Science, Department of Physics. University of Innsbruck, Austria.
    Loerting, Thomas
    Pettersson, Lars G. M.
    Stockholm University, Faculty of Science, Department of Physics.
    Bogan, Michael J.
    Nilsson, Anders
    Stockholm University, Faculty of Science, Department of Physics. SLAC National Accelerator Laboratory, USA; .
    Anomalous Behavior of the Homogeneous Ice Nucleation Rate in No-Man's Land2015In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 6, no 14, p. 2826-2832Article in journal (Refereed)
    Abstract [en]

    We present an analysis of ice nucleation kinetics from near-ambient pressure water as temperature decreases below the homogeneous limit T-H by cooling micrometer-sized droplets (microdroplets) evaporatively at 10(3)-10(4) K/s and probing the structure ultrafast using femtosecond pulses from the Linac Coherent Light Source (LCLS) free-electron X-ray laser. Below 232 K, we observed a slower nucleation rate increase with decreasing temperature than anticipated from previous measurements, which we suggest is due to the rapid decrease in water's diffusivity. This is consistent with earlier findings that microdroplets do not crystallize at <227 K, but vitrify at cooling rates of 10(6)-10(7) K/s. We also hypothesize that the slower increase in the nucleation rate is connected with the proposed fragile-to-strong transition anomaly in water.

  • 39.
    LaRue, Jerry
    et al.
    Stockholm University, Faculty of Science, Department of Physics. SLAC National Accelerator Laboratory, USA; Chapman University, USA; Fritz-Haber Institute of the Max-Planck-Society, Germany.
    Krejčí, O.
    Stockholm University, Faculty of Science, Department of Physics. Charles University in Prague, Czech Republic; Institute of Physics of the Czech Academy of Sciences, Czech Republic.
    Yu, L.
    Beye, M.
    Ng, M. L.
    Öberg, H.
    Stockholm University, Faculty of Science, Department of Physics.
    Xin, H.
    Mercurio, G.
    Moeller, S.
    Turner, J. J.
    Nordlund, D.
    Coffee, R.
    Minitti, M. P.
    Wurth, W.
    Pettersson, Lars G. M.
    Stockholm University, Faculty of Science, Department of Physics.
    Öström, Henrik
    Stockholm University, Faculty of Science, Department of Physics.
    Nilsson, Anders
    Stockholm University, Faculty of Science, Department of Physics.
    Abild-Pedersen, F.
    Ogasawara, H.
    Real-Time Elucidation of Catalytic Pathways in CO Hydrogenation on Ru2017In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 8, no 16, p. 3820-3825Article in journal (Refereed)
    Abstract [en]

    The direct elucidation of the reaction pathways in heterogeneous catalysis has been challenging due to the short-lived nature of reaction intermediates. Here, we directly measured on ultrafast time scales the initial hydrogenation steps of adsorbed CO on a Ru catalyst surface, which is known as the bottleneck reaction in syngas and CO2 reforming processes. We initiated the hydrogenation of CO with an ultrafast laser temperature jump and probed transient changes in the electronic structure using real-time X-ray spectroscopy. In combination with theoretical simulations, we verified the formation of CHO during CO hydrogenation.

  • 40.
    Li, Jibiao
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Yangtze Normal University, China; Uppsala University, Sweden.
    He, Xin
    Peng, Cheng
    Abuja, Rajeev
    Chemical Bonding of Unique CO on Fe(100)2018In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 122, no 16, p. 9062-9074Article in journal (Refereed)
    Abstract [en]

    At low coverage, CO molecules are known to preferentially occupy the hollow sites of Fe(100) with considerably inclined molecular orientations. This CO configuration serves as the precursor state of CO dissociation, which is particularly important in several important catalytic reactions. In this study, we present a unique bonding picture of the precursor state from the spin, charge, and orbital perspectives. From the spin and orbital views, we show the antiferromagenetic nature of the adsorbate-metal coupling, where 2 pi magnetism prevails with a dominant spin-down channel. However, contrasting tendencies are found for the two 1 pi orbitals in two orthogonal directions: the 1 pi orbital in the vertical plane loses its symmetry, whereas the other 1 pi orbital remains intact with a preserved symmetry. The 1 pi symmetry in the vertical plane favors the 1 pi -> 2 pi* excitation mechanism owing to the partial opening up of the 1 pi symmetry. In the charge perspective, we have identified a charge transfer mechanism involving the local structural Fe-I(C)-C-O motif, in which the surface slightly charges the adsorbate with additional partial electrons located at the surface Fe atoms bonded to the carbon end, whereas the charges of the metallic atoms beneath the Fe-I(C)-C-O motif are found to be depleted. In both the adsorbate and metal sides, the depletion of s electrons serves as a good measure of orbital repulsion and delocalization. Interestingly, the carbon and oxygen ends exhibit contrasting electron affinity with the metal surface: the carbon end is attractive, whereas the oxygen end is repulsive in terms of the contrasting charge rearrangement in the bonded metallic atoms.

  • 41. Li, Xin
    et al.
    Leck, Caroline
    Stockholm University, Faculty of Science, Department of Meteorology .
    Sun, Lu
    Hede, Thomas
    Stockholm University, Faculty of Science, Department of Meteorology .
    Tu, Yaoquan
    Ågren, Hans
    Cross-Linked Polysaccharide Assemblies in Marine Gels: An Atomistic Simulation2013In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 4, no 16, p. 2637-2642Article in journal (Refereed)
    Abstract [en]

    Marine polymeric gels or colloidal nano- and microgels have been shown to contribute significantly to the primary marine aerosol and cloud condensation nuclei over remote marine areas. A microscopic understanding of such biologically derived matter at the sea air interface is important for future development of global climate models, but unfortunately cannot be obtained from modern characterization techniques. In this contribution, we employ molecular dynamics simulations to reveal the atomistic details of marine polymeric gels represented by anionic polysaccharide assemblies. The ionic bonds formed between polysaccharides and metal ions in seawater as well as the hydrophobic contribution to surface area are investigated in detail, and destabilization of the assemblies upon removal of Ca2+ or acidification is explained. These results provide insight into physicochemical properties of polysaccharide-Ca2+ structures and enable future studies of their roles of in the wetting process of cloud droplet activation.

  • 42.
    Li, Yunxiang
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bernin, Diana
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Gao, Feifei
    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).
    Microporous pure-silica IZM-22017In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 237, p. 222-227Article in journal (Refereed)
    Abstract [en]

    Pure-silica IZM-2 was synthesized for the first time, and the concentration of sodium hydroxide used during synthesis affected the phase purity and size of crystals. Most of the micropores in calcined pure silica IZM-2 that was synthesized in the presence of high concentrations of sodium hydroxide were inaccessible to N-2 adsorption; however, the micropores could be rendered accessible by applying either of two different post-synthetic treatments. Pure-silica IZM-2 could also be synthesized without sodium ions using the hydroxide version of the template. In this case, the micropores were accessible to N-2 directly after calcination. The size of pure-silica IZM-2 crystals obtained increased with the concentration of sodium hydroxide, with the highest concentrations giving spherical and micrometer-sized aggregates of pure-silica IZM-2 that consisted of intergrown particles (60-500 nm). The nature of the defects in pure-silica IZM-2 was studied with a combination of H-1, and Si-29 solid-state NMR spectroscopy. As expected, direct-polarization Si-29 NMR spectroscopy showed that the number of non-condensed silica groups decreased upon calcination. Calcined samples also showed broader Si-29 NMR bands for the fully condensed silica moieties, which indicated a broader distribution of bond angles and/or bond lengths. The siloxy and silanol groups in calcined pure-silica IZM-2 were accessible to protonation as determined by H-1 NMR spectroscopy. We could not determine the structure of pure-silica IZM-2 in its aggregated form; however, further studies of the synthetic conditions could yield larger, non-aggregated crystals that would facilitate structural determination.

  • 43.
    Li, Yunxiang
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Zheng, Haoquan
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Yun, Yifeng
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bernin, Diana
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Edén, Mattias
    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).
    Gao, Feifei
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    De-agglomeration of IZM-2 zeolite crystals by post-synthetic treatment2016In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 225, p. 185-191Article in journal (Refereed)
    Abstract [en]

    Highly intergrown nanocrystals are commonly observed in zeolite samples, and the densely packed agglomerates may result in small secondary porosity, which restricts the advantage of hierarchical structures. In this work we take IZM-2 zeolite as an example to demonstrate a post-treatment method with diluted hydrofluoric acid solution, which de-agglomerates intergrown zeolite nanocrystals and improves the secondary porosity. The treated samples preserve high crystallinity, similar framework composition and distinctively higher external surface area compared to the agglomerated ones. The results show that this treatment is an effective method for de-agglomeration of intergrown nanocrystals without affecting the original framework.

  • 44. Liu, Ben
    et al.
    Yao, Huiqin
    Daniels, Robert A.
    Song, Wenqiao
    Zheng, Haoquan
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Jin, Lei
    Suib, Steven L.
    He, Jie
    A facile synthesis of Fe3C@mesoporous carbon nitride nanospheres with superior electrocatalytic activity2016In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 8, no 10, p. 5441-5445Article in journal (Refereed)
    Abstract [en]

    We report a colloidal amphiphile-templating approach to preparing nanosized Fe3C encapsulated within mesoporous nitrogen-doped carbon nanospheres (Fe3C@mCN). The obtained Fe3C@mCN hybrids having a high surface area and ultrafine Fe3C nanocrystals exhibited superior activity and durability for oxygen reduction.

  • 45.
    Liu, Chang
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Lourenco, Maicon P.
    Hedström, Svante
    Stockholm University, Faculty of Science, Department of Physics.
    Cavalca, Filippo
    Stockholm University, Faculty of Science, Department of Physics. SLAC National Accelerator Laboratory, United States.
    Diaz-Morales, Oscar
    Stockholm University, Faculty of Science, Department of Physics.
    Duarte, Hélio A.
    Nilsson, Anders
    Stockholm University, Faculty of Science, Department of Physics.
    Pettersson, Lars G. M.
    Stockholm University, Faculty of Science, Department of Physics.
    Stability and Effects of Subsurface Oxygen in Oxide-Derived Cu Catalyst for CO2 Reduction2017In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, no 45, p. 25010-25017Article in journal (Refereed)
    Abstract [en]

    Oxide-derived copper (OD-Cu) catalysts are promising candidates for the electrochemical CO2 reduction reaction (CO2RR) due to the enhanced selectivity toward ethylene over methane evolution, which has been linked to the presence of subsurface oxygen (O-sb). In this work, O-sb is investigated with theoretical methods. Although O-sb is unstable in slab models, it becomes stabilized within a manually reduced OD-Cu nanocube model which was calculated by self-consistent charge density functional tight binding (SCC-DFTB). The results obtained with SCC-DFTB for the full nanocube were confirmed with subcluster models extracted from the nanocube, calculated with both density functional theory (DFT) and SCC-DFTB. The. higher stability of O-sb in the nanocube is attributed to the disordered structure and greater flexibility. The adsorption strength of CO on Cu(100) is enhanced by O-sb withdrawing electron density from the Cu atom, resulting in reduction of the sigma-repulsion. Hence, the coverage of CO may be increased, facilitating its dimerization.

  • 46. Lopes, Viviana R.
    et al.
    Loitto, Vesa
    Audinot, Jean-Nicolas
    Bayat, Narges
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Gutleb, Arno C.
    Cristobal, Susana
    Dose-dependent autophagic effect of titanium dioxide nanoparticles in human HaCaT cells at non-cytotoxic levels2016In: Journal of Nanobiotechnology, ISSN 1477-3155, E-ISSN 1477-3155, Vol. 14, article id 22Article in journal (Refereed)
    Abstract [en]

    Background: Interactions between nanoparticles and cells are now the focus of a fast-growing area of research. Though many nanoparticles interact with cells without any acute toxic responses, metal oxide nanoparticles including those composed of titanium dioxide (TiO2-NPs) may disrupt the intracellular process of macroautophagy. Autophagy plays a key role in human health and disease, particularly in cancer and neurodegenerative diseases. We herein investigated the in vitro biological effects of TiO2-NPs (18 nm) on autophagy in human keratinocytes (HaCaT) cells at non-cytotoxic levels. Results: TiO2-NPs were characterized by transmission electron microscopy (TEM) and dynamic light scattering techniques. Cellular uptake, as evaluated by TEM and NanoSIMS revealed that NPs internalization led to the formation of autophagosomes. TiO2-NPs treatment did not reduce cell viability of HaCaT cells nor increased oxidative stress. Cellular autophagy was additionally evaluated by confocal microscopy using eGFP-LC3 keratinocytes, western blotting of autophagy marker LC3I/II, immunodetection of p62 and NBR1 proteins, and gene expression of LC3II, p62, NBR1, beclin1 and ATG5 by RT-qPCR. We also confirmed the formation and accumulation of autophagosomes in NPs treated cells with LC3-II upregulation. Based on the lack of degradation of p62 and NBR1 proteins, autophagosomes accumulation at a high dose (25.0 mu g/ml) is due to blockage while a low dose (0.16 mu g/ml) promoted autophagy. Cellular viability was not affected in either case. Conclusions: The uptake of TiO2-NPs led to a dose-dependent increase in autophagic effect under non-cytotoxic conditions. Our results suggest dose-dependent autophagic effect over time as a cellular response to TiO2-NPs. Most importantly, these findings suggest that simple toxicity data are not enough to understand the full impact of TiO2-NPs and their effects on cellular pathways or function.

  • 47. Maldonado, P.
    et al.
    Godinho, José
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Evins, L. Z.
    Oppeneeer, P. M.
    Ab Initio Prediction of Surface Stability of Fluorite Materials and Experimental Verification2013In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, no 13, p. 6639-6650Article in journal (Refereed)
    Abstract [en]

    Utilizing first-principle simulations [based on density functional theory (DFT) corrected for on-site Coulomb interactions (DFT+U)], we develop a model to explain the experimental stability in solution of materials having the fluorite structure, such as CaF2 and CeO2. It is shown that the stability of a surface is mainly dependent on its atomic structure and the presence of sites where atoms are deficiently bonded. Using as reference planes the surfaces with low surface formation energies, viz., (111), (100), and (110), our results reveal the relation between the surface energy of any Miller-indexed plane and the surface energy of those reference planes, being dependent on the fluorite surface structure only. Therefore, they follow the same trend for CaF2 and CeO2. Comparison with experimental results shows a correlation between the trends of dry surface energies and surface stabilities during dissolution of both CaF2 and CeO2, even though the chemical processes of dissolution of CeO2 and CaF2 are different. A deviation between ab initio predictions and experiments for some surfaces highlights the sensitivity of the developed model to the treatment of surface dipolar moments.

  • 48.
    Mayence, Arnaud
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Wery, Madeleine
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Wetterskog, Erik
    Svedlindh, Peter
    Tai, Cheuk-Wai
    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).
    Interfacial strain and defects in asymmetric Fe-Mn oxide hybrid nanoparticles2016In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 8, no 29, p. 14171-14177Article in journal (Refereed)
    Abstract [en]

    Asymmetric Fe-Mn oxide hybrid nanoparticles have been obtained by a seed-mediated thermal decomposition-based synthesis route. The use of benzyl ether as the solvent was found to promote the orientational growth of Mn1-xO onto the iron oxide nanocube seeds yielding mainly dimers and trimers whereas 1-octadecene yields large nanoparticles. HRTEM imaging and HAADF-STEM tomography performed on dimers show that the growth of Mn1-xO occurs preferentially along the edges of iron oxide nanocubes where both oxides share a common crystallographic orientation. Fourier filtering and geometric phase analysis of dimers reveal a lattice mismatch of 5% and a large interfacial strain together with a significant concentration of defects. The saturation magnetization is lower and the coercivity is higher for the Fe-Mn oxide hybrid nanoparticles compared to the iron oxide nanocube seeds.

  • 49. McFarland, Hannah L.
    et al.
    Ahmed, Towfiq
    Zhu, Jian-Xin
    Balatsky, Alexander V.
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Los Alamos National Laboratory, New Mexico.
    Haradsen, Jason T.
    First-Principles Investigation of Nanopore Sequencing Using Variable Voltage Bias on Graphene-Based Nanoribbons2015In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 6, no 13, p. 2616-2621Article in journal (Refereed)
    Abstract [en]

    In this study, we examine the mechanism of nanopore-based DNA sequencing using a voltage bias across a graphene nanoribbon. Using density function theory and a nonequilibrium Green's function approach, we determine the transmission spectra and current profile for adenine, guanine, cytosine, thymine, and uracil as a function of bias voltage in an energy minimized configuration. Utilizing the transmission current, we provide a general methodology for the development of a three nanopore graphene-based device that can be used to distinguish between the various nucleobases for DNA/RNA sequencing. From our analysis, we deduce that it is possible to use different transverse currents across a multinanopore device to differentiate between nucleobases using various voltages of 0.5, 1.3, and 1.6 V. Overall, our goal is to improve nanopore design to further DNA/RNA nucleobase sequencing and biomolecule identification techniques.

  • 50. Moskalenko, Sveatoslav A.
    et al.
    Podlesny, Igor V.
    Dumanov, Evgheni V.
    Liberman, Michael A.
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Novikov, Boris V.
    Dispersion laws of the two-dimensional cavity magnetoexciton-polaritons2016In: Journal of Nanophotonics, ISSN 1934-2608, Vol. 10, no 3, article id 036006Article in journal (Refereed)
    Abstract [en]

    The energy spectrum of the two-dimensional cavity magnetoexciton-polaritons has been investigated previously, using exact solutions for the Landau quantization (LQ) of conduction electrons and heavy holes (hhs) provided by the Rashba method. Two lowest LQ levels for electrons and three lowest Landau levels for hhs lead to the construction of the six lowest magnetoexciton sates. They consist of two dipole-active, two quadrupole-active, and the two forbidden quantum transitions from the ground state of the crystal to the magnetoexciton states. The interaction of the four optical-active magnetoexciton states with the cavity-mode photons with a given circular polarization and with well-defined incidence direction leads to the creation of five magnetoexciton-polariton branches. The fifth-order dispersion equation is examined by using numerical calculations and the second-order dispersion equation is solved analytically, taking into account only one dipole-active magnetoexciton state in the point of the in-plane wave vector (k) over right arrow || = 0. The effective polariton mass on the lower polariton branch, the Rabi frequency, and the corresponding Hopfield coefficients are determined in dependence on the magnetic-field strength, the Rashba spin-orbit coupling parameters, and the electron and hole g-factors. (C) 2016 Society of Photo-Optical Instrumentation Engineers (SPIE).

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