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  • 1.
    Abou-Hamad, Edy
    et al.
    Universite Montpellier II.
    Kim, Y
    University of Pennsylvania.
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Physics.
    Goze-Bac, Christophe
    Universite Montpellier II.
    Luzzi, David
    University of Pennsylvania.
    Rubio, Angelo
    University of Basque Country.
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Physics.
    Hydrogenation of C-60 in Peapods: Physical Chemistry in Nano Vessels2009In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 113, no 20, 8583-8587 p.Article in journal (Refereed)
    Abstract [en]

    Hydrogenation of C-60 molecules inside SWNT was achieved by direct reaction with hydrogen gas at elevated pressure and temperature. Evidence for the C-60 hydrogenation in peapods is provided by isotopic engineering with specific enrichment of encapsulated species and high resolution C-13 and H-1 NMR spectroscopy with the observation of characteristic diamagnetic and paramagnetic shifts of the NMR lines and the appearance of sp(3) carbon resonances. We estimate that approximately 78% of the C-60 molecules inside SWNTs are hydrogenated to an average degree of 14 hydrogen atoms per C-60 molecule. As a consequence, the rotational dynamics of the encapsulated C60Hx molecules is clearly hindered. Our successful hydrogenation experiments open completely new roads to understand and control confined chemical reactions at the nano scale

  • 2.
    Andersson, Ove
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Filinchuk, Yaroslav
    Dmitriev, Vladimir
    Quwar, Issam
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Phase coexistence and hysteresis effects in the pressure-temperature phase diagram of NH3BH32011In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 84, no 2, 024115- p.Article in journal (Refereed)
    Abstract [en]

    The potential hydrogen storage compound NH3BH3 has three known structural phases in the temperature and pressure ranges 110–300 K and 0–1.5 GPa, respectively. We report here the boundaries between, and the ranges of stability of, these phases. The phase boundaries were located by in situ measurements of the thermal conductivity, while the actual structures in selected areas were identified by in situ Raman spectroscopy and x-ray diffraction. Below 0.6 GPa, reversible transitions involving only small hysteresis effects occur between the room-temperature tetragonal plastic crystal I4mm phase and the low-temperature orthorhombic Pmn21 phase. Transformations of the I4mm phase into the high-pressure orthorhombic Cmc21 phase, occurring above 0.8 GPa, are associated with very large hysteresis effects, such that the reverse transition may occur at up to 0.5 GPa lower pressures. Below 230 K, a fraction of the Cmc21 phase is metastable to atmospheric pressure, suggesting the possibility that dense structural phases of NH3BH3, stable at room temperature, could possibly be created and stabilized by alloying or by other methods. Mixed orthorhombic Pmn21/Cmc21 phases were observed in an intermediate pressure-temperature range, but a fourth structural phase predicted by Filinchuk et al. [ Phys. Rev. B 79 214111 (2009)] was not observed in the pressure-temperature ranges of this experiment. The thermal conductivity of the plastic crystal I4mm phase is about 0.6 W m−1 K−1 and only weakly dependent on temperature, while the ordered orthorhombic phases have higher thermal conductivities limited by phonon-phonon scattering.

  • 3. Anoshkin, Ilya
    et al.
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Nasibulin, Nasibulin
    Krasheninnikov, Arkady
    Jiang, Hua
    Nieminen, Risto
    Kauppinen, Esko
    Coronene Encapsulation in Single-Walled Carbon Nanotubes: Stacked Columns, Peapods, and Nanoribbons2014In: ChemPhysChem, ISSN 1439-4235, E-ISSN 1439-7641, Vol. 15, no 8, 1660-1665 p.Article in journal (Refereed)
    Abstract [en]

    Encapsulation of coronene inside single-walled carbon nanotubes (SWNTs) was studied under various conditions. Under high vacuum, two main types of molecular encapsulation were observed by using transmission electron microscopy: coronene dimers and molecular stacking columns perpendicular or tilted (45-608) with regard to the axis of the SWNTs. A relatively small number of short nanoribbons or polymerized coronene molecular chains were observed. However, experiments performed under an argon atmosphere (0.17 MPa) revealed reactions between the coronene molecules and the formation of hydrogen-terminated graphene nanoribbons. It was also observed that the morphology of the encapsulated products depend on the diameter of the SWNTs. The experimental results are explained by using density functional theory calculations through the energies of the coronene molecules inside the SWNTs, which depend on the orientation of the molecules and the diameter of the tubes.

  • 4. Araújo, C. Moysés
    et al.
    Ahuja, Rajeev
    Talyzin, Alexandr V
    Umeå University, Faculty of Science and Technology, Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Physics.
    Pressure-induced structural phase transition in NaBH42005In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 72, no 5, 054125- p.Article in journal (Refereed)
    Abstract [en]

    We present a combined experimental and theoretical study of the technologically important NaBH4 compound under high pressure. Using Raman spectroscopy at room temperature, we have found that NaBH4 undergoes a structural phase transformation starting at 10.0 GPa with the pure high-pressure phase being established above 15.0 GPa. In order to compare the Raman data recorded under high pressure with the low-temperature tetragonal phase of NaBH4, we have also performed a cooling experiment. The known order-disorder transition from the fcc to the tetragonal structure was then observed. However, the new high pressure phase does not correspond to this low-temperature structure. Using first-principle calculations based on the density functional theory, we show that the high-pressure phase corresponds to the alpha-LiAlH4–type structure. We have found a good agreement between the measured and calculated transition pressures. Additionally, we present the electronic structure of both the fcc and the high-pressure phases.

  • 5. Baburin, Igor A
    et al.
    Klechikov, Alexey
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Mercier, Guillaume
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Seifert, Gotthard
    Hydrogen adsorption by perforated graphene2015In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 40, no 20, 6594-6599 p.Article in journal (Refereed)
    Abstract [en]

    We performed a combined theoretical and experimental study of hydrogen adsorption in graphene systems with defect-induced additional porosity. It is demonstrated that perforation of graphene sheets results in increase of theoretically possible surface areas beyond the limits of ideal defect-free graphene (∼2700 m2/g) with the values approaching ∼5000 m2/g. This in turn implies promising hydrogen storage capacities up to 6.5 wt% at 77 K, estimated from classical Grand canonical Monte Carlo simulations. Hydrogen sorption was studied for the samples of defected graphene with surface area of ∼2900 m2/g prepared using exfoliation of graphite oxide followed by KOH activation. The BET surface area of studied samples thus exceeded the value of single-layered graphene. Hydrogen uptake measured at 77 K and 296 K amounts to 5.5 wt% (30 bar) and to 0.89 wt% (120 bar), respectively. 

  • 6. Chernov, Alexander I
    et al.
    Fedotov, Pavel V
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Suarez Lopez, Inma
    Anoshkin, Ilya V
    Nasibulin, Albert G
    Kauppinen, Esko I
    Obraztsova, Elena D
    Optical properties of graphene nanoribbons encapsulated in single-walled carbon nanotubes2013In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 7, no 7, 6346-6353 p.Article in journal (Refereed)
    Abstract [en]

    We report the photoluminescence (PL) from graphene nanoribbons (GNRs) encapsulated in single-walled carbon nanotubes (SWCNTs). New PL spectral features originating from GNRs have been detected in the visible spectral range. PL peaks from GNRs have resonant character, and their positions depend on the ribbon geometrical structure in accordance with the theoretical predictions. GNRs were synthesized using confined polymerization and fusion of coronene molecules. GNR@SWCNTs material demonstrates a bright photoluminescence both in infrared (IR) and visible regions. The photoluminescence excitation mapping in the near-IR spectral range has revealed the geometry-dependent shifts of the SWCNT peaks (up to 11 meV in excitation and emission) after the process of polymerization of coronene molecules inside the nanotubes. This behavior has been attributed to the strain of SWCNTs induced by insertion of the coronene molecules.

  • 7. Dmitriev, Vladimir
    et al.
    Filinchuk, Yaroslav
    Chernyshov, Dmitry
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Physics.
    Dzwilewski, Andrzej
    Umeå University, Faculty of Science and Technology, Physics.
    Andersson, Ove
    Umeå University, Faculty of Science and Technology, Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Physics.
    Kurnosov, Alexander
    Pressure-temperature phase diagram of LiBH4: Synchrotron x-ray diffraction experiments and theoretical analysis2008In: Physical Review B, ISSN 1098-0121, Vol. 77, no 17, 174112- p.Article in journal (Refereed)
    Abstract [en]

    An in situ combined high-temperature high-pressure synchrotron radiation diffraction study has been carried out on LiBH4. The phase diagram of LiBH4 is mapped to 10 GPa and 500 K, and four phases are identified. The corresponding structural distortions are analyzed in terms of symmetry-breaking atomic position shifts and anion ordering. Group-theoretical and crystal-chemical considerations reveal a nontrivial layered structure of LiBH4. The layers and their deformations define the structural stability of the observed phases.

  • 8.
    Dzwilewski, Andrzej
    et al.
    Umeå University, Faculty of Science and Technology, Physics. Umeå University, Faculty of Science and Technology, Physics.
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Physics. Umeå University, Faculty of Science and Technology, Physics. Experimental Physics.
    Bromiley, G.
    Dub, S.
    Dubrovinsky, Leonid
    Characterization of phases synthesized close to the boundary of C60 collapse at high temperature high pressure conditions2007In: Diamond and related materials, ISSN 0925-9635, E-ISSN 1879-0062, Vol. 16, no 8, 1550-1556 p.Article in journal (Other (popular science, discussion, etc.))
    Abstract [en]

    Two sets of samples were synthesized at high pressure high temperature conditions in the P-T region where C-60 molecules collapse into a nearly amorphous graphite-like hard carbon phase. For the first set, heating temperature was varied at fixed pressure and preparation time. For the second set, synthesis time was varied at fixed pressure and fixed temperature. Detailed structural characterization of samples was performed using Raman spectroscopy and powder XRD. Mechanical properties of the samples have been studied by nanoindentation method. It has been found that duration of heat treatment under high pressure is an important parameter which influences the temperature of fullerene cage collapse. Both tetragonal and rhombohedral polymeric phases transform into hard carbon phase over a rather narrow temperature interval, but the tetragonal phase shows somewhat increased stability against C-60 collapse. Viscoelastic mechanical behavior during nanoindentation was observed for fullerene polymers but not for graphite-like hard carbon phase. Possible mechanism for nucleation of the hard carbon phase in polymeric C-60 networks is discussed.

  • 9. Fedotov, Pavel V.
    et al.
    Chernov, Alexander I.
    Talyzin, Alexander V.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Anoshkin, Ilya V.
    Nasibulin, Albert G.
    Kauppinen, Esko I.
    Obraztsova, Elena D.
    Optical Study of Nanotube and Coronene Composites2013In: Journal of Nanoelectronics and Optoelectronics, ISSN 1555-130X, E-ISSN 1555-1318, Vol. 8, no 1, 16-22 p.Article, review/survey (Refereed)
    Abstract [en]

    A novel nanomaterial, graphene nanoribbons encapsulated inside single-walled carbon nanotubes (GNR@SWNT), was studied by combined optical methods. This nanomaterial was found to have a bright photoluminescence both in IR and UV-Vis spectral ranges. Its spectral features have a complicated resonant structure different from the features of initial components: coronene molecules and SWNTs. The encapsulation ability appears to correlate strongly with the geometry of SWNTs. A weak interaction between nanotube walls and encapsulated species has been discovered: no evidence of charge or energy transfer has been registered.

  • 10. Filinchuk, Yaroslav
    et al.
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Physics. Umeå University, Faculty of Science and Technology, Physics.
    Chernyshov, D.
    Dmitriev, V.
    High-pressure phase of NaBH4: Crystal structure from synchrotron powder diffraction data2007In: PHYSICAL REVIEW B, ISSN 1098-0121, Vol. 76, no 9, 092104- p.Article in journal (Refereed)
  • 11. Filinchuk, Yaroslav
    et al.
    Talyzin, Alexandr V.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Hagemann, Hans
    Dmitriev, Vladimir
    Chernyshov, Dmitry
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Cation Size and Anion Anisotropy in Structural Chemistry of Metal Borohydrides. The Peculiar Pressure Evolution of RbBH42010In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 49, no 11, 5285-5292 p.Article in journal (Refereed)
    Abstract [en]

    The pressure evolution of RbBH4 has been characterized by synchrotron powder X-ray diffraction and Raman spectroscopy up to 23 GPa. Diffraction experiments at ambient temperature reveal three phase transitions, at 3.0, 10.4, and 18 GPa (at 2.6, 7.8, and 20 GPa from Raman data), at which the space group symmetry changes in the order Fm-3m(Z=4) → P4/nmm(2) → C222(2) → I-42m(4). Crystal structures and equations of state are reported for all four phases. The three high-pressure structure types are new in the crystal chemistry of borohydrides. RbBH4 polymorphs reveal high coordination numbers (CNs) for cation and anion sites, increasing with pressure from 6 to 8, via an intermediate 4 + 4 coordination. Different arrangements of the tetrahedral BH4 group in the Rb environment define the crystal symmetries of the RbBH4 polymorphs. The structural evolution in the MBH4 series is determined by the cation’s size, as it differs drastically for M = Li (CNs = 4, 6), Na (CN = 6), and Rb. The only structure common to the whole MBH4 family is the cubic one. Its bulk modulus linearly decreases as the ionic radius of M increases, indicating that the compressibility of the material is mainly determined by the repulsive BH4···BH4 interactions.

  • 12. Gorkina, Alexandra L
    et al.
    Tsapenko, Alexey P
    Gilshteyn, Evgenia P
    Koltsova, Tatiana S
    Larionova, Tatiana V
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Anisimov, Anton S
    Anoshkin, Ilya V
    Kauppinen, Esko I
    Tolochko, Oleg V
    Nasibulin, Albert G
    Transparent and conductive hybrid graphene/carbon nanotube films2016In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 100, 501-507 p.Article in journal (Refereed)
    Abstract [en]

    Carbon nanomaterials (carbon nanotubes (CNTs) and graphene) are promising materials for optoelectronic applications, including flexible transparent and conductive films (TCFs) due to their extraordinary electrical, optical and mechanical properties. However, the performance of CNT- or graphene-only TCFs still needs to be improved. One way to enhance the optoelectrical properties of TCFs is to hybridize CNTs and graphene. This approach leads to creation of a novel material that exhibits better properties than its individual constituents. In this work, the novel hybrid CNT-graphene nanomaterial was fabricated by graphene oxide deposition on top of CNT films. The graphene oxide was then reduced by thermal annealing at ambient atmosphere or in H2 atmosphere. At the final step the CNT-graphene hybrids were chemically doped using gold(III) chloride. As a result, we show that the hybrids demonstrate excellent optoelectrical performance with the sheet resistance as low as 73 Ω/□ at 90% transmittance.

  • 13.
    Han, Kyoo-Hyun
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Physics.
    Dzwilewski, Andrzej
    Umeå University, Faculty of Science and Technology, Physics.
    Makarova, Tatiana
    Höhne, Roland
    Esquinazi, Pablo
    Spemann, D.
    Dubrovinsky, Leonid S.
    Magnetic properties of carbon phases synthesized using high-pressure high-temperature treatment.2005In: Physical Review B, Vol. 72, 224424- p.Article in journal (Refereed)
  • 14. Kim, Y
    et al.
    Abou-Hamad, E
    Rubio, A
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Boesch, D
    Aloni, S
    Zettl, A
    Luzi, D E
    Goze-Bac, C
    Communications: nanomagnetic shielding: high-resolution NMR in carbon allotropes2010In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 132, no 2, 021102- p.Article in journal (Refereed)
    Abstract [en]

    The understanding and control of the magnetic properties of carbon-based materials is of fundamental relevance in applications in nano- and biosciences. Ring currents do play a basic role in those systems. In particular the inner cavities of nanotubes offer an ideal environment to investigate the magnetism of synthetic materials at the nanoscale. Here, by means of 13 C high resolution NMR of encapsulated molecules in peapod hybrid materials, we report the  largest diamagnetic shifts (down to -68.3 ppm) ever observed in carbon allotropes, which is connected to the enhancement of the aromaticity of the nanotube envelope upon doping. This diamagnetic shift can be externally controlled by in situ modifications such as doping or electrostatic charging. Moreover, defects such as C-vacancies, pentagons, and chemical functionalization of the outer nanotube quench this diamagnetic effect and restore NMR signatures to slightly paramagnetic shifts compared to nonencapsulated molecules. The magnetic interactions reported here are robust phenomena independent of temperature and proportional to the applied magnetic field. The magnitude, tunability, and stability of the magnetic effects make the peapod nanomaterials potentially valuable for nanomagnetic shielding in nanoelectronics and nanobiomedical engineering.

  • 15.
    Klechikov, Alexey G.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Mercier, Guillaume
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Merino, Pilar
    Blanco, Santiago
    Merino, Cesar
    Talyzin, Alexandr V.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Hydrogen storage in bulk graphene-related materials2015In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 210, 46-51 p.Article in journal (Refereed)
    Abstract [en]

    Hydrogen sorption properties of graphene-related materials were studied by gravimetric and volumetric methods at 2931< and 77K. Rapid thermal exfoliation of different types of graphite oxide (GO) precursors yielded samples with maximal surface areas up to 850 m(2)/g, whereas surface areas up to 2300 m(2)/g were achieved by post-exfoliation activation treatments. Therefore, hydrogen storage parameters of graphene materials could be evaluated in a broad range of surface areas. The H-2 uptake vs surface area trend revealed in this study shows that hydrogen storage by graphene materials do not exceed 1 Wt% at 120 Bar H-2 at ambient temperatures. Linear increase of hydrogen adsorption vs surface area was observed at 77 K with maximal observed value of similar to 5 Wt% for 2300 m(2)/g sample. It can be concluded that bulk graphene samples obtained using graphite oxide exfoliation and activation follow standard for other nanostructured carbons hydrogen uptake trends and do not demonstrate superior hydrogen storage parameters reported in several earlier studies. Nevertheless, graphene remains to be one of the best materials for physisorption of hydrogen, especially at low temperatures.

  • 16.
    Klechikov, Alexey
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Mercier, Guillaume
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sharifi, Tiva
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Baburin, Igor A.
    Technische Universität Dresden, Theoretische Chemie, Bergstraße 66b, 01062 Dresden, Germany .
    Seifert, Gotthard
    Technische Universität Dresden, Theoretische Chemie, Bergstraße 66b, 01062 Dresden, Germany .
    Talyzin, Alexandr V.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Hydrogen storage in high surface area graphene scaffolds2015In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 51, no 83, 15280-15283 p.Article in journal (Refereed)
    Abstract [en]

    Using an optimized KOH activation procedure we prepared highly porous graphene scaffold materials with SSA values up to 3400 m2 g−1 and a pore volume up to 2.2 cm3 g−1, which are among the highest for carbon materials. Hydrogen uptake of activated graphene samples was evaluated in a broad temperature interval (77–296 K). After additional activation by hydrogen annealing the maximal excess H2 uptake of 7.5 wt% was obtained at 77 K. A hydrogen storage value as high as 4 wt% was observed already at 193 K (120 bar H2), a temperature of solid CO2, which can be easily maintained using common industrial refrigeration methods.

  • 17.
    Klechikov, Alexey
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Yu, Junchun
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Thomas, Diana
    Sharifi, Tiva
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Talyzin, Alexandr V.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Structure of graphene oxide membranes in solvents and solutions2015In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 7, no 37, 15374-15384 p.Article in journal (Refereed)
    Abstract [en]

    The change of distance between individual graphene oxide sheets due to swelling is the key parameter to explain and predict permeation of multilayered graphene oxide (GO) membranes by various solvents and solutions. In situ synchrotron X-ray diffraction study shows that swelling properties of GO membranes are distinctly different compared to precursor graphite oxide powder samples. Intercalation of liquid dioxolane, acetonitrile, acetone, and chloroform into the GO membrane structure occurs with maximum one monolayer insertion (Type I), in contrast with insertion of 2-3 layers of these solvents into the graphite oxide structure. However, the structure of GO membranes expands in liquid DMSO and DMF solvents similarly to precursor graphite oxide (Type II). It can be expected that Type II solvents will permeate GO membranes significantly faster compared to Type I solvents. The membranes are found to be stable in aqueous solutions of acidic and neutral salts, but dissolve slowly in some basic solutions of certain concentrations, e.g. in NaOH, NaHCO3 and LiF. Some larger organic molecules, alkylamines and alkylammonium cations are found to intercalate and expand the lattice of GO membranes significantly, e.g. up to similar to 35 angstrom in octadecylamine/methanol solution. Intercalation of solutes into the GO structure is one of the limiting factors for nano-filtration of certain molecules but it also allows modification of the inter-layer distance of GO membranes and tuning of their permeation properties. For example, GO membranes functionalized with alkylammonium cations are hydrophobized and they swell in non-polar solvents.

  • 18. Korobov, Mikhail V.
    et al.
    Talyzin, Aleksandr V.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Rebrikova, Anastasiya T.
    Shilayeva, Elizaveta A.
    Avramenko, Natalya V.
    Gagarin, Alexander N.
    Ferapontov, Nikolay B.
    Sorption of polar organic solvents and water by graphite oxide: thermodynamic approach2016In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 102, 297-303 p.Article in journal (Refereed)
    Abstract [en]

    Sorption of polar organic solvents CH3OH, C4H8O (THF), CH3CN, C3H7NO (DMF), C2H6OS (DMSO), C5H9NO (NMP) and water was quantitatively evaluated for Hummers (H-GO) and Brodie (B-GO) graphite oxides at T = 298K and at melting temperature (Tm) of the solvents. H-GO showed stronger sorption compared to B-GO for all studied solvents and the increase of sorption upon lowering temperature was observed for both H-GO and B-GO. Thermodynamic equations allowed to explain earlier reported "maximums" of swelling/sorption in the binary systems H-GO – solvent at Tm. The specific relation between the values of enthalpies of sorption and melting leads to the change of sign in enthalpies of sorption at Tm and causes maximal swelling/sorption. The same thermodynamic explanation was given for the "maximum" on the swelling vs. pressure dependence in B-GO and H-GO – H2O systems earlier reported at pressure of phase transition "liquid water-ice VI". Notably higher sorption of H2O was observed for H-GO compared to H-GO membrane (H-GOm) at high relative humidity (RH), RH > 0.75. Experimental sorption isotherm of H-GOm was used to simulate permeation rates of water through H-GOm and to estimate effective diffusion coefficient of water through the membrane.

  • 19. Kvashnina, K.O.
    et al.
    Guo, J.-H.
    Talyzin, Alexandr V.
    Umeå University, Faculty of Science and Technology, Physics.
    Modin, A.
    Käämbre, T.
    Butorin, S.M.
    Nordgren, Joseph
    X-ray absorption and emission study of hydrogenated fullerenes2006In: AIP Conference Proceedings vol. 837: Proceedings of ISOCHEM2005, 2006, 230-237 p.Conference paper (Refereed)
  • 20.
    Luzan, Serhiy
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Cataldo, Franco
    INAF—Osservatorio Astrofisico di Catania, Catania, Italy.
    Tsybin, Yury
    Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Thermal decomposition of C60H182009In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 113, no 30, 13133-13138 p.Article in journal (Refereed)
    Abstract [en]

    Products of thermal dehydrogenation of C 60H18(which mainly occurs at 450-600°C) were studied by XRD, Raman, IR and mass spectrometry. IR spectra indicate that dehydrogenation resulted in partial recovery of pristine C 60. XRD data indicate that the cell parameter of the face-centered cubic structure, which is higher for C 60H18(14.55 Å) than for C60(14.17 Å), remained higher following heat treatment, and heating at>500° C caused further expansion (to 14.78 Å). The increase in the cell parameter correlates with the beginning of partial fullerene cage collapse (corroborated by IR, Raman and MS data) and is suggested to result from “self-doping”.

  • 21.
    Luzan, Serhiy
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Jung, Heejin
    Department of Applied Chemistry, College of Science and Technology, Hanyang University, Republic of Korea.
    Chun, Hyungphil
    Department of Applied Chemistry, College of Science and Technology, Hanyang University, Republic of Korea.
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Hydrogen storage in Co-and Zn-based metal-organic frameworks at ambient temperature2009In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 34, no 24, 9754-9759 p.Article in journal (Refereed)
    Abstract [en]

    Hydrogen adsorption properties of some Co-and Zn-based Metal-Organic Framework (MOF) materials were studied at near ambient temperatures. Maximal hydrogen storage capacity of 0.75 wt% was found for a Zn-based material at 175 Bar hydrogen pressure and T = -4 degrees C. Hydrogen adsorption correlated linearly with BET surface area and strongly depends on temperature. Relatively low structural stability of some MOF's results in framework collapse during degassing and hydrogen adsorption measurements.

  • 22.
    Luzan, Serhiy M
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Talyzin, Alexandr V
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Effect of catalysts on the reaction of C60 with hydrogen2012In: Fullerenes, nanotubes, and carbon nanostructures (Print), ISSN 1536-383X, E-ISSN 1536-4046, Vol. 20, no 4-7, 319-323 p.Article in journal (Refereed)
    Abstract [en]

    The reaction of C-60/catalyst with hydrogen gas was studied at 400 degrees C and 50 bar of H-2 pressure. The addition of Pt- or Ni-catalysts significantly accelerated kinetics of the hydrogenation reaction and resulted in a dramatic change of the C60Hx crystal structure. Samples reacted without catalyst preserved the fcc structure typical for pristine C-60 but with expanded unit cells. Fulleranes C60Hx obtained using catalytic hydrogenation exhibited not only the fcc structure (at relatively low hydrogenation degree) but also the bcc structure of C60Hx (with x > 18). The bcc structure corresponds to highly hydrogenated material with an average volume per C-60 molecule of 817-849 angstrom(3).

  • 23.
    Luzan, Serhiy
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Comment to the “Response to “Hydrogen adsorption in Pt catalyst/MOF-5 materials”” by Li et al. [1]2011In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 139, no 1-3, 216-218 p.Article in journal (Other academic)
  • 24.
    Luzan, Serhiy
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Hydration of graphite oxide in electrolyte and non-electrolyte solutions2011In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 115, no 50, 24611-24614 p.Article in journal (Refereed)
    Abstract [en]

    Pressure induced insertion of liquid media was studied for graphite oxide (GO) immersed in excess amounts of aqueous copper acetate and sucrose solutions and compared to previous experiments with GO immersed in solute-free water media. Compression of GO in copper acetate solution resulted in significant enhancement of high pressure anomaly compared to pure water: interlayer distance reached 17.4 Å at 2.3 GPa while for pure water the maximal observed layer separation was 13.08 Å. Compression of GO in sucrose solution was found to be very similar to compression in solute-free water. These results confirm that copper ions can be pressure-inserted into GO structure while the expansion of structure is attributed to osmotic swelling. Sucrose dissolves in water in molecular form (nonelectrolyte) which results in weaker absorption into the GO structure and the absence of osmotic swelling. Pressure induced insertion of various solutions into the GO structure could possibly be promising for synthesis of new graphite intercalation materials or graphene-related composites.

  • 25.
    Luzan, Serhiy
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Hydrogen adsorption in Pt catalyst/MOF-5 materials2010In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 135, no 1-3, 201-205 p.Article in journal (Refereed)
    Abstract [en]

    Hydrogen adsorption properties of well-known MOF-5 were studied at near ambient temperature and hydrogen pressures up to 120 bar. Pristine material was doped with Pt catalysts supported on activated carbon (AC) using two previously described procedures: physical mixture of a catalyst with MOF-5 and “bridging” procedure (MOF-5 and catalyst particles connected via carbon bridges) MOF-5. The maximum hydrogen adsorption measured on doped MOF-5 was 0.43 wt.%. These values are on the same level or even less than for catalyst free MOF-5 material. Therefore, doping of MOF-5 material with Pt catalyst has not resulted in increase of hydrogen storage value. Hydrogen adsorption for the samples with added catalyst showed correlation with BET surface area, exhibited isotherms typical for physisorption and no features which could be assigned to spillover effect.

  • 26.
    Luzan, Serhiy
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Tsybin, Yury O.
    Biomolecular Mass Spectrometry Laboratory, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Reaction of C60 with Hydrogen gas: In Situ monitoring and pathways2011In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 115, no 23, 11484-11492 p.Article in journal (Refereed)
    Abstract [en]

    Kinetics and pathways of C60 reaction with hydrogen gas were studied in a broad temperature interval and over extended periods of time. Specifically, hydrogenation was monitored in situ at high temperature and high hydrogen pressure conditions using the gravimetric method. The shape of gravimetric curve was found to depend on hydrogenation temperature: at 350–400 °C saturation of the sample weight was achieved, whereas at 420–440 °C the sample weight reached the maximum and decreased upon prolonged hydrogenation. The weight decrease is due to fullerene cage fragmentation with formation of light hydrocarbons evaporating from the sample. Hydrogenation products were studied by X-ray diffraction, MALDI TOF and APPI FT-ICR mass spectrometry, liquid chromatography, and elemental analysis. Hydrogenation pathways (from C60H18 up to C60H56) and possible mechanisms of hydrogenation-induced fragmentation of fulleranes are discussed.

  • 27.
    Martin, Natalia M.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Luzan, Serhiy
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Department of Physics.
    High-temperature reactions of C60 with polycyclic aromatic hydrocarbons2010In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 368, no 1-2, 49-57 p.Article in journal (Refereed)
    Abstract [en]

    Fullerenes are proposed as a precursor for preparation of nanocarbon materials using controlled collapse of cage structure by high temperature reaction with polycyclic aromatic hydrocarbons. The chemical modification of C60 by reaction with anthracene and coronene was studied over a broad temperature interval. The products of the reaction were characterized by X-ray diffraction, and Raman and IR spectroscopy. Mono- and multi-adducts of C60 with anthracene were obtained in the temperature interval 290–400 °C. Above 400 °C the C60 adducts are not stable and decompose back to C60 and anthracene. No chemical adducts of C60 with coronene were found below 500 °C. Above this temperature fullerite structure was found to expand reflecting interaction with coronene melt and vapor. The reactions of C60 with anthracene and C60 with coronene at temperatures above 650 °C resulted in fullerene cage collapse and formation of nanocarbons. These nanocarbons were found to store up to 0.45 wt% of hydrogen at ambient temperatures despite negligible surface area. 

  • 28.
    Mercier, Guillaume
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Klechikov, Alexey
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Hedenstrom, Mattias
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Johnels, Dan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Baburin, Igor A.
    Seifert, Gotthard
    Mysyk, Roman
    Talyzin, Alexandr V.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Porous Graphene Oxide/Diboronic Acid Materials: Structure and Hydrogen Sorption2015In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, no 49, 27179-27191 p.Article in journal (Refereed)
    Abstract [en]

    Solvothermal reaction of graphite oxide (GO) with benzene-1,4-diboronic acid (DBA) was reported previously to result in formation of graphene oxide framework (GOP) materials. The theoretical structure of GOFs consists of graphene layers separated by benzene-diboronic "pillars" with similar to 1 nm slit pores thus providing the opportunity to use it as a model material to verify the effect of a small pore size on hydrogen adsorption. A set of samples with specific surface area (SSA) in the range of similar to 50-1000 m(2)/g were prepared using variations of synthesis conditions and GO/DBA proportions. Hydrogen storage properties of GOF samples evaluated at 293 and 77 K were found to be similar to other nanocarbon trends in relation to SSA values. Structural characterization of GO/DBA samples showed all typical features reported as evidence for formation of a framework structure such as expanded interlayer distance, increased temperature of thermal exfoliation, typical features in FTIR spectra, etc. However, the samples also exhibited reversible swelling in polar solvents which is not compatible with the idealized GOF structure linked by benzenediboronic molecular pillars. Therefore, possible alternative nonframework models of structures with pillars parallel and perpendicular to GO planes are considered.

  • 29. Quesnel, Etienne
    et al.
    Roux, Frédéric
    Emieux, Fabrice
    Faucherand, Pascal
    Kymakis, Emmanuel
    Volonakis, George
    Giustino, Feliciano
    Martín-García, Beatriz
    Moreels, Iwan
    Alkan Gürsel, Selmiye
    Bayrakçeken Yurtcan, Ayşe
    Di Noto, Vito
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Baburin, Igor
    Tranca, Diana
    Seifert, Gotthard
    Crema, Luigi
    Speranza, Giorgio
    Tozzini, Valentina
    Bondavalli, Paolo
    Pognon, Grégory
    Botas, Cristina
    Carriazo, Daniel
    Singh, Gurpreet
    Rojo, Teófilo
    Kim, Gunwoo
    Yu, Wanjing
    Grey, Clare
    Pellegrini, Vittorio
    Graphene-based technologies for energy applications, challenges and perspectives2015In: 2D Materials, ISSN 2053-1583, Vol. 2, no 3, 1-16 p.Article in journal (Refereed)
    Abstract [en]

    Here we report on technology developments implemented into the Graphene Flagship European project for the integration of graphene and graphene-related materials (GRMs) into energy application devices. Many of the technologies investigated so far aim at producing composite materials associating graphene or GRMs with either metal or semiconducting nanocrystals or other carbon nanostructures (e.g., CNT, graphite). These composites can be used favourably as hydrogen storage materials or solar cell absorbers. They can also provide better performing electrodes for fuel cells, batteries, or supercapacitors. For photovoltaic (PV) electrodes, where thin layers and interface engineering are required, surface technologies are preferred. We are using conventional vacuum processes to integrate graphene as well as radically new approaches based on laser irradiation strategies. For each application, the potential of implemented technologies is then presented on the basis of selected experimental and modelling results. It is shown in particular how some of these technologies can maximize the benefit taken from GRM integration. The technical challenges still to be addressed are highlighted and perspectives derived from the running works emphasized.

  • 30. Rezania, B.
    et al.
    Severin, Nikolai
    Talyzin, Alexandr V.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Rabe, Juergen P.
    Hydration of bilayered graphene oxide2014In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 14, no 7, 3993-3998 p.Article in journal (Refereed)
    Abstract [en]

    The hydration of graphene oxide (GO) membranes is the key to understand their remarkable selectivity in permeation of water molecules and humidity-dependent gas separation. We investigated the hydration of single GO layers as a function of humidity using scanning force microscopy, and we determined the single interlayer distance from the step height of a single GO layer on top of one or two GO layers. This interlayer distance grows gradually by approximately 1 A upon a relative humidity (RH) increase in the range of 2 to similar to 80% and the immersion into liquid water increases the interlayer distance further by another 3 A. The gradual expansion of the single interlayer distance is in good agreement with the averaged distance measured by X-ray diffraction on multilayered graphite oxides, which is commonly explained with an interstratification model. However, our experimental design excludes effects connected to interstratification. Instead we determine directly if insertion of water into GO occurs strictly by monolayers or the thickness of GO layers changes gradually. We find that hydration with up to 80% RH is a continuous process of incorporation of water molecules into single GO layers, while liquid water inserts as monolayers. The similarity of hydration for our bilayer and previously reported multilayered materials implies GO few and even bilayers to be suitable for selective water transport.

  • 31.
    Sundqvist, Bertil
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Andersson, Ove
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Quwar, Issam
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Talyzin, Alexandr V.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Low temperature phase diagram of NH3BH32011In: Materials Research Society Symposium Proceedings: Proceedings of Symposium EE: Solid-State Chemistry of Inorganic Materials VIII / [ed] P.S. Halasyamani, D.G. Mandrus, K.-S. Choi and S.J. Clarke, Cambridge: Cambridge University Press , 2011, mrsf10-1309-ee06-25- p.Conference paper (Refereed)
    Abstract [en]

    The pressure-temperature (p-T) phase diagram of NH3BH3 has been investigated by thermal conductivity measurements up to 1.5 GPa at temperatures between 100 and 300 K, and the phase boundaries between the three known structural phases have been identified. The transformation between the room temperature tetragonal I4mm phase and the low temperature orthorhombic Pmn21 phase (Tc = 218 K at p = 0) shows only a small hysteresis. The transformation into the high pressure orthorhombic Cmc21 phase (at 1.0 GPa near 292 K) has a very strong hysteresis, up to Δp = 0.5 GPa, and below 230 K a fraction of this phase is metastable even at atmospheric pressure.

  • 32.
    Sundqvist, Bertil
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Andersson, Ove
    Umeå University, Faculty of Science and Technology, Physics.
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Physics.
    Phase transitions in hydrogen storage compounds under pressure2007In: Journal of Physics Condensed Matter, vol. 19, issue 42: Proceedings of the 3rd Asian Conference on High Pressure, Lijiang City 2006, Bristol: Intitute of Physics , 2007, 425201- p.Conference paper (Refereed)
    Abstract [en]

    Solid, hydrogen-rich compounds, such as alkali metal hydrides, MAH4, where

    M is an alkali metal and A is boron or aluminium, may be used for hydrogen

    storage. We briefly review recent high-pressure work in this field aimed at

    exploring the phase behaviour, and especially the possibility to find highly

    dense new structures. In particular we present experimental data on the

    structure, lattice dynamics, phase diagrams, and thermal properties obtained by

    us and others by Raman scattering, x-ray diffraction, and thermal conductivity

    measurements under pressure between 100 and 400 K. From these data and the

    results of theoretical calculations we map observed structural phases and phase

    transitions in the pressure–temperature plane for the materials that have so far

    been investigated under pressure.

  • 33.
    Sundqvist, Bertil
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Physics.
    Andersson, Ove
    Umeå University, Faculty of Science and Technology, Physics.
    Complex hydrides studied by Raman spectroscopy and thermal conductivity measurements under high pressure2006In: Hydrogen Storage Technologies: Proceedings of Symposium Z at the 2006 MRS Fall Meeting, Boston, MA, USA; Materials Research Society Symposium Proceedings vol. 971E, Warrendale: Materials Research Society , 2006, 7-12 p.Conference paper (Refereed)
    Abstract [en]

    The pressure-temperature phase diagrams of alkali metal alanates and borohydrides are of large current interest, and we have recently studied phase transformations under pressure in several of these materials. We here report Raman studies of KBH4 under pressure at room temperature, showing a phase transition near 6 GPa. Although no structural information is yet available, the similarity between KBH4 and NaBH4 suggests the new structure is orthorhombic. We also report studies on LiBH4 showing that the high pressure phase of this material is metastable to zero pressure below 200 K.

  • 34.
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Comment on "Laser controlled magnetism in hydrogenated fullerene films": [J. Appl. Phys. 109, 083941 (2011)]2013In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 113, no 3, 036101- p.Article in journal (Other academic)
    Abstract [en]

    Hydrogenation of C-60 films with formation of single hydrogen adduct reported by Makarova et al. [J. Appl. Phys. 109, 083941 (2011); Phys. Status Solidi B 246, 2778 (2009)] was supported only by several features found in Raman spectra of treated samples. However, no spectra were shown for untreated samples. Data shown in this comment prove that all Raman peaks assigned by Makarova et al. [J. Appl. Phys. 109, 083941 (2011); Phys. Status Solidi B 246, 2778 (2009)] to effects of hydrogenation can be found in spectra of pristine untreated commercial C-60 powder. These peaks represent some second order vibrations of C-60 as well as some possible solvent impurities. Therefore, all magnetic effects reported in this study should be assigned to unknown effects but not necessarily to hydrogenation. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4775821]

  • 35.
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Feasibility of H2–THF–H2O clathrate hydrates for hydrogen storage applications2008In: International Journal of Hydrogen Energy, Vol. 33, no 1, 111-115 p.Article in journal (Refereed)
    Abstract [sv]

    Hydrogen storage capacity of hydrogen clathrate hydrates H2–THF–H2O was directly measured using gravimetric method. The amount of hydrogen stored in a bulk piece of ice was below even after prolonged exposure to hydrogen at . It is confirmed that fine dispersion of material is required to improve kinetics of hydrogen uptake. To achieve a fine dispersion of ice grains, it is proposed to use rather common light framework materials with size of pore sizes of about as a support media. The samples dispersed in foamed polyurethane showed measurable hydrogen uptake at pressure and release. However, the amount of stored hydrogen was found maximum on the level of .

  • 36.
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Fulleranes by direct reaction with hydrogen gas at elevated conditions2010In: Fulleranes: the hydrogenated fullerenes / [ed] Franco Cataldo, Susana Iglesias-Groth, Dordrecht: Springer Netherlands, 2010, 85-103 p.Chapter in book (Other academic)
    Abstract [en]

    Reaction of solid fullerenes with hydrogen gas occurs with or without catalysts at elevated conditions. Composition of hydrofullerene mixture obtained in this reaction depends strongly on temperature (350–450°C), hydrogen pressure (typically 10–120 bar) and duration of treatment. Saturation of hydrogenation occurs after tens of hours, depending on temperature of reaction. In case of extra strong hydrogenation prolonged reaction leads to formation of fulleranes with composition C60Hx approaching number of hydrogen atoms X = 60. These fulleranes are highly unstable and decompose first with formation of fragmented hydrofullerenes with progressively smaller number of carbon atoms C59, C58, C57 etc., followed by collapse of cage structure. Since the collapse occurs at the conditions of high temperature and high hydrogen pressure, all breaking C–C bonds are saturated immediately with hydrogen and new C–H bonds are formed. Therefore, large fragments of fullerane molecules are able to survive and large polycyclic aromatic hydrocarbons (PAH’s) formed as a result of cage structure collapse.

  • 37.
    Talyzin, Alexandr
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Andersson, Ove
    Umeå University, Faculty of Science and Technology, Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Physics.
    Kurnosov, Alexander
    Dubrovinsky, Leonid
    High pressure phase transition in LiBH42007In: Journal of Solid State Chemistry, ISSN 0022-4596, Vol. 180, no 2, 510-7 p.Article in journal (Refereed)
    Abstract [en]

    The high-pressure phase transition from ambient pressure alpha-LiBH4 to high-pressure beta-LiBH4 was observed by Raman spectroscopy and X-ray diffraction between 0.8 and 1.1 GPa. The phase boundary between these two phases was mapped over a large range of temperatures using thermal conductivity studies and differential thermal analysis. The structure of the high-pressure phase could not be identified due to small number of experimentally observed reflections, but it was shown that it is different from previously reported theoretical predictions.

  • 38.
    Talyzin, Alexandr
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Anoshkin, Ilya
    Aalto University.
    Krasheninnikov, Arkady
    Aalto University.
    Nieminen, Risto
    Nasibulin, Albert
    Aalto University.
    Jiang, Hua
    Aalto University.
    Kauppinen, Esko
    Aalto University.
    Synthesis of Graphene Nanoribbons Encapsulated in Single-Walled Carbon Nanotubes2011In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 11, no 10, 4352-4356 p.Article in journal (Refereed)
    Abstract [en]

    A novel material, graphene nanoribbons encapsulated in single-walled carbon nanotubes (GNR@SWNT), was synthesized using confined polymerization and fusion of polycyclic aromatic hydrocarbon (PAH) molecules. Formation of the GNR is possible due to confinement effects provided by the one-dimensional space inside nanotubes, which helps to align coronene or perylene molecules edge to edge to achieve dimerization and oligomerization of the molecules into long nanoribbons. Almost 100% filling of SWNT with GNR is achieved while nanoribbon length is limited only by the length of the encapsulating nanotube. The PAH fusion reaction provides a very simple and easily scalable method to synthesize GNR@SWNT in macroscopic amounts. First-principle simulations indicate that encapsulation of the GNRs is energetically favorable and that the electronic structure of the encapsulated GNRs is the same as for the free-standing ones, pointing to possible applications of the GNR@SWNT structures in photonics and nanoelectronics.

  • 39.
    Talyzin, Alexandr
    et al.
    Umeå University, Faculty of Science and Technology, Physics. Umeå University, Faculty of Science and Technology, Physics.
    Dzwilewski, Andrzej
    Umeå University, Faculty of Science and Technology, Physics. Umeå University, Faculty of Science and Technology, Physics.
    Dubrovinsky, Leonid
    Setzer, A.
    Esquinazi, Pablo
    Structural and magnetic properties of polymerized C60 with Fe2007In: European Physical Journal B: Condensed Matter Physics, ISSN 1434-6028, E-ISSN 1434-6036, Vol. 55, no 1, 57-62 p.Article in journal (Refereed)
    Abstract [en]

    We provide evidence that high-pressure high-temperature (2.5 GPa and 1040 K) treatment of mixtures of iron with fullerene powders leads to the complete transformation of iron into iron carbide Fe3C. The comparison of the magnetic properties (Curie temperature and magnetic moment) of the here studied samples and those for the ferromagnetic polymer Rh-C-60 indicates that the main ferromagnetic signal reported in those samples is due to Fe3C and not related to the ferromagnetism of carbon as originally interpreted. Taking into account the results obtained in this study the original paper on "Magnetic carbon" [Nature 413, 716 (2001)] was recently retracted.

  • 40.
    Talyzin, Alexandr
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Dzwilewski, Andrzej
    Umeå University, Faculty of Science and Technology, Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Physics.
    Tsybin, Y.
    Purcell, J.M.
    Marshall, A.G.
    Shulga, Y.
    McCammon, C.
    Dubrovinsky, Leonid
    Hydrogenation of C60 at 2 GPa Pressure and High Temperature.2006In: Chemical Physics, ISSN 0301-0104, Vol. 325, no 2-3, 445-451 p.Article in journal (Refereed)
    Abstract [en]

    Hydrogenation of C60 at 2 GPa and 723–823 K was performed with thermal decomposition of LiAlH4 as a hydrogen source. Analysis

    of hydrogenation products showed that the method can produce not only C60H36, but also hydrofullerides C60Hx with 44 < x < 52.

    Unlike other hydrogenation methods in which pristine C60 reacts with hydrogen, the high pressure/high temperature conditions result

    first in C60 polymerization into a tetragonal phase which later reacts with hydrogen. It is suggested that hydrogen first attacks intermolecular

    carbon–carbon bonds, resulting in complete depolymerization of C60 at a later stage of the hydrogenation process. This model

    suggests the possibility to select starting points for hydrogenation by choosing specific polymeric structures of C60. Hydrogenated polymeric

    C60 was identified as an intermediate reaction product. Characterization of highly reduced material was performed by Raman and

    IR spectroscopy, X-ray diffraction, and atmospheric pressure photoionization Fourier transform ion cyclotron resonance mass

    spectrometry.

  • 41.
    Talyzin, Alexandr
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Dzwilewski, Andrzej
    Umeå University, Faculty of Science and Technology, Physics.
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Physics.
    Temperature dependence of C60 Raman spectra up to 840 K.2006In: Solid State Communications, Vol. 140, 178-181 p.Article in journal (Refereed)
  • 42.
    Talyzin, Alexandr
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Hausmaninger, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    You, Shujie
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Szabo, Tamas
    Department of Physical Chemistry and Materials Science, University of Szeged, Szeged, Hungary.
    The structure of graphene oxide membranes in liquid water, ethanol and water – ethanol mixtures2014In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 6, 272-281 p.Article in journal (Refereed)
    Abstract [en]

    The structure of graphene oxide (GO) membranes was studied in situ in liquid solvents using synchrotron radiation X-ray diffraction in a broad temperature interval. GO membranes are hydrated by water similarly to precursor graphite oxide powders but intercalation of alcohols is strongly hindered, which explains why the GO membranes are permeated by water and not by ethanol. Insertion of ethanol into the membrane structure is limited to only one monolayer in the whole studied temperature range, in contrast to precursor graphite oxide powders, which are intercalated with up to two ethanol monolayers (Brodie) and four ethanol monolayers (Hummers). As a result, GO membranes demonstrate the absence of “negative thermal expansion” and phase transitions connected to insertion/de-insertion of alcohols upon temperature variations reported earlier for graphite oxide powders. Therefore, GO membranes are a distinct type of material with unique solvation properties compared to parent graphite oxides even if they are composed of the same graphene oxide flakes.

  • 43.
    Talyzin, Alexandr
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Jacob, A.
    Hydrogen adsorption by ball milled C602005In: Journal of Alloys and Compounds, Vol. 395, 154-8 p.Article in journal (Refereed)
  • 44.
    Talyzin, Alexandr
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Klechikov, Alexey
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Korobov, Mikhail
    Rebrikova, Anastasiya T
    Avramenko, Nataliya V
    Gholami, M Fardin
    Severin, Nikolai
    Rabe, Jürgen P
    Delamination of graphite oxide in a liquid upon cooling.2015In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 7, no 29, 12625-30 p.Article in journal (Refereed)
    Abstract [en]

    Graphite oxide (GO) in liquid acetonitrile undergoes a transition from an ordered phase around ambient temperature to a gel-like disordered phase at temperatures below 260 K, as demonstrated by in situ X-ray diffraction. The stacking order of GO layers is restored below the freezing point of acetonitrile (199 K). The reversible swelling transition between a stacked crystalline phase and an amorphous delaminated state observed upon cooling provides an unusual example of increased structural disorder at lower temperatures. The formation of the gel-like phase is attributed to the thermo-responsive conformational change of individual GO flakes induced by stronger solvation. Scanning force microscopy demonstrates that GO flakes deposited onto a solid substrate from acetonitrile dispersions at a temperature below 260 K exhibit corrugations and wrinkling which are not observed for the flakes deposited at ambient temperature. The thermo-responsive transition between the delaminated and stacked phases reported here can be used for sonication-free dispersion of graphene oxide, micro-container applications, or the preparation of new composite materials.

  • 45.
    Talyzin, Alexandr
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Langenhorst, F.
    Dubrovinskaya, Natalia
    Dub, S.
    Dubrovinsky, Leonid S.
    Structural characterization of the hard fullerite phase obtained at 13 GPa and 830 K2005In: Physical Review B, Vol. 71, no 11, 115424- p.Article in journal (Refereed)
  • 46.
    Talyzin, Alexandr
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Luzan, Serhiy
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Pressure-induced insertion of liquid acetone into the graphite oxide structure2010In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 114, no 11, 7004-7006 p.Article in journal (Refereed)
    Abstract [en]

    An expansion of the graphite oxide structure due to pressure-induced insertion of acetone solvent was observed upon compression at 0.9 GPa. However, conversion into the expanded high-pressure phase is not complete, with the high-pressure and the ambient-pressure phases coexisting even at pressures up to 4.5 GPa. The phase transformation is not correlated with the solidification point of acetone, a behavior similar to that of the graphite oxide/alcohol systems and unlike that of the previously studied graphite oxide/water system. It can be concluded that pressure-induced insertion of solvent into the graphite oxide structure occurs not only for protic solvents (water, methanol, ethanol) but also for aprotic polar solvents (acetone).

  • 47.
    Talyzin, Alexandr
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Luzan, Serhiy
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Temperature dependent structural breathing of hydrated graphite oxide in H2O  2011In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 49, no 6, 1894-1899 p.Article in journal (Refereed)
    Abstract [en]

    Hydration of graphite oxide by excess of water was studied in the temperature interval 295–230 K. A structural breathing effect is found for fully hydrated graphite oxide near the water solidification/melting point. Expansion of hydrated graphite oxide structure due to insertion of additional water occurs upon cooling down from ambient temperature to the point of water media freezing. Cooling down below the point of water medium solidification results in stepwise contraction of graphite oxide interlayer distance by 25% due to partial withdrawal of water from the hydrated structure. Heating back from 230 K to ambient temperature results in graphite oxide structure expansion due absorption of water from medium, thus making a reversible cycle. The effect of structure breathing is important for any chemical treatments performed with graphite oxide in solution, e.g. graphite oxide functionalization and conversion into graphene-related materials.

  • 48.
    Talyzin, Alexandr
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Luzan, Serhiy
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Anoshkin, Ilya
    NanoMaterials Group, Department of Applied Physics and Center for New Materials Aalto University, Aalto, Espoo, Finland.
    Nasibulin, Albert
    NanoMaterials Group, Department of Applied Physics and Center for New Materials Aalto University, Aalto, Espoo, Finland.
    Jiang, Hua
    NanoMaterials Group, Department of Applied Physics and Center for New Materials Aalto University, Aalto, Espoo, Finland.
    Kauppinen, Esko
    NanoMaterials Group, Department of Applied Physics and Center for New Materials Aalto University, Aalto, Espoo, Finland.
    Mikoushkin, Valery
    Ioffe Physical-Technical Institute of the Russian Academy of Sciences, St. Petersburg, Russia.
    Shnitov, Vladimir
    Ioffe Physical-Technical Institute of the Russian Academy of Sciences, Petersburg, Russia.
    Marchenko, Dmitry
    Institute of Physics, St. Petersburg State University, St. Petersburg, Russia.
    Noréus, Dag
    Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, Stockholm, Sweden.
    Hydrogenation, purification, and unzipping of carbon nanotubes by reaction with molecular hydrogen: road to graphane nanoribbons2011In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 5, no 6, 5132-5140 p.Article in journal (Refereed)
    Abstract [en]

    Reaction of single-walled carbon nanotubes (SWNTs) with hydrogen gas was studied in a temperature interval of 400-550 C and at hydrogen pressure of 50 bar. Hydrogenation of nanotubes was observed for samples treated at 400-450 C with about 1/3 of carbon atoms forming covalent C-H bonds, whereas hydrogen treatment at higher temperatures (550 C) occurs as an etching. Unzipping of some SWNTs into graphene nanoribbons is observed as a result of hydrogenation at 400-550 C. Annealing in hydrogen gas at elevated conditions for prolonged periods of time (72 h) is demonstrated to result also in nanotube opening, purification of nanotubes from amorphous carbon, and removal of carbon coatings from Fe catalyst particles, which allows their complete elimination by acid treatment.

  • 49.
    Talyzin, Alexandr
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Luzan, Serhiy
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Leifer, Klaus
    Akhtar, S.
    Fetzer, John
    Cataldo, Franco
    Tsybin, Yury
    Coronene fusion by heat treatment: road to nanographenes2011In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 115, no 27, 13207-13214 p.Article in journal (Refereed)
    Abstract [en]

    The reactions of coronene dehydrogenation and fusion upon heat treatment in the temperature range of 500–700 °C were studied using XRD, TEM, Raman, IR, and NEXAFS spectroscopy. The formation of a coronene dimer (dicoronylene) was observed at temperatures 530–550 °C; dicoronylene can easily be separated using sublimation with a temperature gradient. An insoluble and not sublimable black precipitate was found to form at higher temperatures. Analysis of the data shows that dimerization of coronene is followed at 550–600 °C by oligomerization into larger molecules. Above 600 °C amorphization of the material and formation of graphitic nanoparticles was observed. Coronene fusion by annealing is proposed as a road to synthesis of larger polycyclic aromatic hydrocarbons and nanographenes.

  • 50.
    Talyzin, Alexandr
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Solozhenko, Vladimir L.
    Kurakevych, Oleksandr O.
    Szabó, Tamás
    Dékány, Imre
    Kurnosov, Alexandr
    Dmitriev, Vladimir
    Colossal Pressure-Induced Lattice Expansion of Graphite Oxide in the Presence of Water2008In: Angewandte Chemie International Edition, Vol. 47, no 43, 8268-8271 p.Article in journal (Refereed)
12 1 - 50 of 73
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