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  • 1.
    Adjizian, J.J.
    et al.
    Department of Chemistry, University of Sussex, Falmer, Brighton.
    Latham, Chris
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Öberg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Briddon, P.R.
    Electrical, Electronic and Computer Engineering, University of Newcastle upon Tyne.
    Heggie, M.I.
    Department of Chemistry, University of Sussex, Falmer, Brighton.
    DFT study of the chemistry of sulfur in graphite, including interactions with defects, edges and folds2013In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 62, p. 256-262Article in journal (Refereed)
    Abstract [en]

    Sulfur has several roles, desirable and undesirable, in graphitization. We perform density functional theory calculations within the local density approximation to define the structures and energetics of sulphur in graphite, including its interactions with point defects and edges, in order to understand its role in the later stages of graphitization. We find sulphur does not cross-link layers, except where there are defects. It reacts very strongly with vacancies in neighbouring layers to form a six coordinate split vacancy structure, analogous to that found in diamond. It is also highly stable at basal edge sites, where, as might be expected, the size and valency of sulfur can be easily accommodated. This suggests a role for sulphur in stabilizing graphene edges, and following from this, we show that sulfur dimers can open, i.e. unzip, folds in graphite rapidly and exothermically.

  • 2.
    Amato, Letizia
    et al.
    Technical University of Denmark.
    Heiskanen, Arto
    Technical University of Denmark.
    Hansen, Rasmus
    Technical University of Denmark.
    Gammelgaard, Lauge
    Capres A/S.
    Rindzevicius, Tomas
    Technical University of Denmark.
    Tenje, Maria
    Lunds universitet.
    Emnéus, Jenny
    Technical University of Denmark.
    Keller, Stephan
    Technical University of Denmark.
    Dense high-aspect ratio 3D carbon pillars on interdigitated microelectrode arrays2015In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 94, p. 792-803Article in journal (Refereed)
  • 3.
    Anoshkin, Ilya
    et al.
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Nefedova, Irina
    Dmitri, Lioubtchenko
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Nefedov, Igor
    Räisänen, Antti
    Single walled carbon nanotube quantification method employing the Raman signal intensity2017In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 116, p. 547-552Article in journal (Refereed)
    Abstract [en]

    A new technique for measuring the number of single walled carbon nanotubes (SWCNTs) and their concentration in a carbon nanotube layer is developed in this work. It is based on the G peak intensity of the Raman spectrum, together with precise mass and optical absorbance measurements. The dependence of the number of the carbon nanotubes on the phonon scattering intensity is observed. This method opens an opportunity for the quantitative mapping of sp2 carbon atom distribution in the SWCNT layers with a resolution limited by the focused laser spot size.

  • 4. Asanou, I. P.
    et al.
    Bulusheva, L. G.
    Dubois, M.
    Yudanov, N. F.
    Alexeev, A. V.
    Makarova, Tatiana L.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Okotrub, A. V.
    Graphene nanochains and nanoislands in the layers of room-temperature fluorinated graphite2013In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 59, p. 518-529Article in journal (Refereed)
    Abstract [en]

    Intercalated compound of graphite fluoride with n-heptane has been synthesized at room temperature using a multi-stage process including fluorination by a gaseous BrF3 and a set of intercalant exchange reactions. It was found that composition of the compound is CF0.40(C7H16)(0.04) and the guest molecules interact with the graphite fluoride layers through the van der Waals forces. Since the distance between the filled layers is 1.04 nm and the unfilled layers are separated by similar to 0.60 nm, the obtained compound can be considered as a stack of the fluorinated graphenes. These fluorinated graphenes are large in area making it possible to study local destruction of the a conjugated system on the basal plane. It was shown that fluorine atoms form short chains, while non-fluorinated sp(2) carbon atoms are organized in very narrow ribbons and aromatic areas with a size smaller than 3 nm. These pi electron nanochains and nanoislands preserved after the fluorination process are likely responsible for the value of the energy gap of the compound of similar to 2.5 eV. Variation in the size and the shape of pi electron regions within the fluorinated graphene layers could be a way for tuning the electronic and optical characteristics of the graphene-based materials.

  • 5.
    Barzegar, Hamid Reza
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Hu, Guangzhi
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Larsen, Christian
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Jia, Xueen
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Palladium nanocrystals supported on photo-transformed C-60 nanorods: effect of crystal morphology and electron mobility on the electrocatalytic activity towards ethanol oxidation2014In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 73, p. 34-40Article in journal (Refereed)
    Abstract [en]

    We report on the synthesis and decoration of high-aspect-ratio crystalline C-60 nanorods (NRs) by functionalized palladium nanoparticles with an average size of 4.78 +/- 0.66 nm. In their pristine form, C-60 NRs suffer from partial damage in the solution-based decoration process resulting in poor crystallinity. However, by modifying the NR surface via in situ photochemical transformation in the liquid state, we are able to prepare highly stable NRs that retain their crystalline structure during the decoration process. Our method thus opens up for the synthesis of highly crystalline nanocomposite hybrids comprising Pd nanoparticles and C-60 NRs. Bys measuring the electron mobility of different C-60 NRs, we relate both the effect of electron mobility and crystallinity to the final electrocatalytic performance of the synthesized hybrid structures. We show that the photo-transformed C-60 NRs exhibit highly advantageous properties for ethanol oxidation based on both a better crystallinity and a higher bulk conductivity. These findings give important information in the search for efficient catalyst support.

  • 6.
    Battie, Yann
    et al.
    LCP-A2MC, Université de Lorraine.
    Dossot, Manuel
    Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, Nancy Université, Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, UMR 7564, CNRS–University of Lorraine, LCPME UMR 7564 CNRS-Université de Lorraine.
    Allali, Naoual
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mamane, Victor
    Laboratoire de Synthèse Organométallique et Réactivité, Université Henri Poincaré - Nancy, Laboratoire de Structure et Réactivité des Systèmes Moléculaires Complexes, Nancy Université, SRSMC UMR 7565 CNRS-Université de Lorraine, Faculté des Sciences et Techniques.
    Naciri, Aotmane En
    LCP-A2MC, Université de Lorraine.
    Broch, Laurent
    LCP-A2MC, Université de Lorraine.
    Soldatov, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mild covalent functionalization of single-walled carbon nanotubes highlighted by spectroscopic ellipsometry2016In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 96, p. 557-564Article in journal (Refereed)
    Abstract [en]

    Single-walled carbon nanotubes (SWCNT) synthesized using the HiPco® process and purified thereafter were submitted to two covalent functionalization processes: i) a mild oxidation in a concentrated HNO3 solution using microwave irradiation and ii) a radical functionalization to graft methoxyphenyl groups. The samples were analyzed by Raman spectroscopy and spectroscopic ellipsometry in the energy window 0.07-4.96 eV. The complex dielectric function was analytically calculated in order to extract the real (εr) and imaginary (εi) parts of this function vs. the incident energy of the light. The ellipsometric data in the infrared part of the spectrum revealed that process i) mainly affected the amorphous carbon deposited on the surface of SWCNTs while process ii) strongly changed the electronic nature of the film due to a charge transfer between methoxyphenyl groups and SWCNTs. These results demonstrate the richness of information that spectroscopic ellipsometry is able to bring about on an entire carbon nanotube ensemble compared to Raman spectroscopy, while not suffering from limitation on their electronic structure and/or aggregate state/presence of surfactants.

  • 7. Bhattacharya, K.
    et al.
    El-Sayed, R.
    Andón, F. T.
    Mukherjee, S. P.
    Gregory, J.
    Li, H.
    Zhao, Yinchen
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Seo, W.
    Fornara, A.
    Brandner, B.
    Toprak, Muhammet Sadaka
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Leifer, K.
    Star, A.
    Fadeel, B.
    Lactoperoxidase-mediated degradation of single-walled carbon nanotubes in the presence of pulmonary surfactant2015In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 91, p. 506-517Article in journal (Refereed)
    Abstract [en]

    Carbon nanotubes (CNTs) may elicit inflammatory responses following pulmonary exposure. Conversely, enzymatic biodegradation of CNTs by inflammatory cells has also been reported. The aim of this study was to study the degradation of oxidized single-walled CNTs (ox-SWCNTs) by lactoperoxidase (LPO), a secreted peroxidase present in the airways, and whether pulmonary surfactant affects this biodegradation. To this end, ox-SWCNTs were incubated in vitro with recombinant bovine LPO + H<inf>2</inf>O<inf>2</inf> + NaSCN in the presence and absence of porcine lung surfactant (Curosurf®) and biodegradation was monitored using UV-Vis-NIR spectroscopy, Raman spectroscopy, and scanning electron microscopy. The interaction of recombinant LPO with bundles of ox-SWCNTs was confirmed by atomic force microscopy. Cell-free biodegradation of ox-SWCNTs was also observed ex vivo in murine bronchoalveolar lavage fluid in the presence of H<inf>2</inf>O<inf>2</inf> + NaSCN. Our study provides evidence for biodegradation of ox-SWCNTs with a lung surfactant 'bio-corona' and expands the repertoire of mammalian peroxidases capable of biodegradation of ox-SWCNTs. These findings are relevant to inhalation exposure to these materials, as LPO serves as an important component of the airway defense system.

  • 8. Bhattacharya, K
    et al.
    El-Sayed, R
    Andón, FT
    Mukherjee, SP
    Gregory, J
    Li, H
    Fornara, A
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor.
    Lactoperoxidase-mediated degradation of single-walled carbon nanotubes in the presence of pulmonary surfactant2015In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 91, p. 506-517Article in journal (Refereed)
    Abstract [en]

    Carbon nanotubes (CNTs) may elicit inflammatory responses following pulmonary exposure. Conversely, enzymatic biodegradation of CNTs by inflammatory cells has also been reported. The aim of this study was to study the degradation of oxidized single-walled CNTs (ox-SWCNTs) by lactoperoxidase (LPO), a secreted peroxidase present in the airways, and whether pulmonary surfactant affects this biodegradation. To this end, ox-SWCNTs were incubated in vitro with recombinant bovine LPO + H2O2 + NaSCN in the presence and absence of porcine lung surfactant (Curosurf®) and biodegradation was monitored using UV-Vis-NIR spectroscopy, Raman spectroscopy, and scanning electron microscopy. The interaction of recombinant LPO with bundles of ox-SWCNTs was confirmed by atomic force microscopy. Cell-free biodegradation of ox-SWCNTs was also observed ex vivo in murine bronchoalveolar lavage fluid in the presence of H2O2 + NaSCN. Our study provides evidence for biodegradation of ox-SWCNTs with a lung surfactant 'bio-corona' and expands the repertoire of mammalian peroxidases capable of biodegradation of ox-SWCNTs. These findings are relevant to inhalation exposure to these materials, as LPO serves as an important component of the airway defense system.

  • 9. Bhattacharya, Kunal
    et al.
    El-Sayed, Ramy
    Andon, Fernando T.
    Mukherjee, Sourav P.
    Gregory, Joshua
    Li, Hu
    Zhao, Yichen
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Seo, Wanji
    Fornara, Andrea
    Brandner, Birgit
    Toprak, Muhammet S.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Leifer, Klaus
    Star, Alexander
    Fadeel, Bengt
    Lactoperoxidase-mediated degradation of single-walled carbon nanotubes in the presence of pulmonary surfactant (vol 91, pg 506, 2015)2015In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 95, p. 766-766Article in journal (Refereed)
  • 10.
    Bhattacharya, Kunal
    et al.
    Karolinska Inst, Inst Environm Med, Div Mol Toxicol, S-17177 Stockholm, Sweden.
    El-Sayed, Ramy
    Karolinska Inst, Inst Environm Med, Div Mol Toxicol, S-17177 Stockholm, Sweden.
    Andon, Fernando T.
    Karolinska Inst, Inst Environm Med, Div Mol Toxicol, S-17177 Stockholm, Sweden.
    Mukherjee, Sourav P.
    Karolinska Inst, Inst Environm Med, Div Mol Toxicol, S-17177 Stockholm, Sweden.
    Gregory, Joshua
    Karolinska Inst, Ctr Allergy Res, S-17177 Stockholm, Sweden;Karolinska Inst, Inst Environm Med, Div Physiol, S-17177 Stockholm, Sweden.
    Li, Hu
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Zhao, Yinchen
    Royal Inst Technol, Dept Mat & Nanophys, Funct Mat Div, S-16440 Stockholm, Sweden.
    Seo, Wanji
    Univ Pittsburgh, Dept Chem, Pittsburgh, PA 15260 USA.
    Fornara, Andrea
    SP Tech Res Inst Sweden, Unit Chem Mat & Surfaces, S-11486 Stockholm, Sweden.
    Brandner, Birgit
    SP Tech Res Inst Sweden, Unit Chem Mat & Surfaces, S-11486 Stockholm, Sweden.
    Toprak, Muhammet S.
    Royal Inst Technol, Dept Mat & Nanophys, Funct Mat Div, S-16440 Stockholm, Sweden.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Star, Alexander
    Univ Pittsburgh, Dept Chem, Pittsburgh, PA 15260 USA.
    Fadeel, Bengt
    Karolinska Inst, Inst Environm Med, Div Mol Toxicol, S-17177 Stockholm, Sweden.
    Lactoperoxidase-mediated degradation of single-walled carbon nanotubes in the presence of pulmonary surfactant2015In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 91, p. 506-517Article in journal (Refereed)
    Abstract [en]

    Carbon nanotubes (CNTs) may elicit inflammatory responses following pulmonary exposure. Conversely, enzymatic biodegradation of CNTs by inflammatory cells has also been reported. The aim of this study was to study the degradation of oxidized single-walled CNTs (ox-SWCNTs) by lactoperoxidase (LPO), a secreted peroxidase present in the airways, and whether pulmonary surfactant affects this biodegradation. To this end, ox-SWCNTs were incubated in vitro with recombinant bovine LPO + H2O2 + NaSCN in the presence and absence of porcine lung surfactant (Curosurf (R)) and biodegradation was monitored using UV-Vis-NIR spectroscopy, Raman spectroscopy, and scanning electron microscopy. The interaction of recombinant LPO with bundles of ox-SWCNTs was confirmed by atomic force microscopy. Cell-free biodegradation of ox-SWCNTs was also observed ex vivo in murine bronchoalveolar lavage fluid in the presence of H2O2 + NaSCN. Our study provides evidence for biodegradation of ox-SWCNTs with a lung surfactant 'bio-corona' and expands the repertoire of mammalian percuddases capable of biodegradation of ox-SWCNTs. These findings are relevant to inhalation exposure to these materials, as LPO serves as an important component of the airway defense system.

  • 11.
    Blank, Vladimir D.
    et al.
    Research Center for Superhard Materials, Centralnaya 7a, Troitsk, Moscow Region 142092, Russian Federation.
    Buga, Sergey G.
    Research Center for Superhard Materials, Centralnaya 7a, Troitsk, Moscow Region 142092, Russian Federation.
    Dubitsky, Gennadii A.
    Institute of Spectroscopy of the Russian Academy of Sciences, Troitsk, Moscow Region 142092, Russian Federation.
    Serebryanaya, Nadejda R.
    Research Center for Superhard Materials, Centralnaya 7a, Troitsk, Moscow Region 142092, Russian Federation.
    Popov, M. Yu.
    Research Center for Superhard Materials, Centralnaya 7a, Troitsk, Moscow Region 142092, Russian Federation.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Department of Physics.
    High-pressure polymerized phases of C601998In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 36, no 4, p. 319-343Article, review/survey (Other academic)
    Abstract [en]

    Data from recent experimental studies of C60 under high pressures are collected and analyzed, concentrating on the polymerized states where covalent intermolecular bonds have been formed through treatment of molecular C60 at high pressures and temperatures at or above room temperature. We give an overview of the observed phase transformations and the structures of metastable polymeric phases, both crystalline and disordered, as analyzed under ambient conditions, and we present and discuss a pressure-temperature diagram showing which synthesis conditions result in which final phases in the pressure range up to 20 GPa (200 kbar) and at temperatures up to 2300 K. The physical properties of the various phases are discussed whenever enough data are available. The pressure-temperature stability limits for C60 and the conditions for the transformation of C60 into graphite, diamond and chaoite-type carbon are derived.

  • 12.
    Bouhafs, Chamseddine
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Zakharov, A. A.
    Lund University, Sweden.
    Ivanov, Ivan Gueorguiev
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Giannazzo, F.
    CNR IMM, Italy.
    Eriksson, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Applied Sensor Science. Linköping University, Faculty of Science & Engineering.
    Stanishev, Vallery
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Kuhne, Philipp
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Iakimov, Tihomir
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Hofmann, Tino
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. University of Nebraska Lincoln, NE 68588 USA.
    Schubert, Mathias
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. University of Nebraska Lincoln, NE 68588 USA.
    Roccaforte, F.
    CNR IMM, Italy.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Darakchieva, Vanya
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Multi-scale investigation of interface properties, stacking order and decoupling of few layer graphene on C-face 4H-SiC2017In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 116, p. 722-732Article in journal (Refereed)
    Abstract [en]

    In this work, we report a multi-scale investigation using several nano-, micro and macro-scale techniques of few layer graphene (FLG) sample consisting of large monolayer (ML) and bilayer (BL) areas grown on C-face 4H-SiC (000-1) by high-temperature sublimation. Single 1 x 1 diffraction patterns are observed by micro-low-energy electron diffraction for ML, BL and trilayer graphene with no indication of out-of-plane rotational disorder. A SiOx layer is identified between graphene and SiC by X-ray photoelectron emission spectroscopy and reflectance measurements. The chemical composition of the interface layer changes towards SiO2 and its thickness increases with aging in normal ambient conditions. The formation mechanism of the interface layer is discussed. It is shown by torsion resonance conductive atomic force microscopy that the interface layer causes the formation of non-ideal Schottky contact between ML graphene and SiC. This is attributed to the presence of a large density of interface states. Mid-infrared optical Hall effect measurements revealed Landau-level transitions in FLG that have a square-root dependence on magnetic field, which evidences a stack of decoupled graphene sheets. Contrary to previous works on decoupled C-face graphene, our BL and FLG are composed of ordered decoupled graphene layers without out-of-plane rotation. (C) 2017 Elsevier Ltd. All rights reserved.

  • 13.
    Chua, Cassandra
    et al.
    University of Cambridge, England.
    Lartsev, Arseniy
    Chalmers, Sweden.
    Sui, Jinggao
    University of Cambridge, England.
    Panchal, Vishal
    National Phys Lab, England.
    Puddy, Reuben
    University of Cambridge, England.
    Richardson, Carly
    University of Cambridge, England.
    Smith, Charles G.
    University of Cambridge, England.
    Janssen, T. J. B. M.
    National Phys Lab, England.
    Tzalenchuk, Alexander
    National Phys Lab, England; Royal Holloway University of London, England.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Kubatkin, Sergey
    Chalmers, Sweden.
    Connolly, Malcolm R.
    University of Cambridge, England.
    Observation of Coulomb blockade in nanostructured epitaxial bilayer graphene on SiC2017In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 119, p. 426-430Article in journal (Refereed)
    Abstract [en]

    We study electron transport in nanostructures patterned in bilayer graphene patches grown epitaxially on SiC as a function of doping, magnetic field, and temperature. Away from charge neutrality transport is only weakly modulated by changes in carrier concentration induced by a local side-gate. At low n-type doping close to charge neutrality, electron transport resembles that in exfoliated graphene nanoribbons and is well described by tunnelling of single electrons through a network of Coulomb-blockaded islands. Under the influence of an external magnetic field, Coulomb blockade resonances fluctuate around an average energy and the gap shrinks as a function of magnetic field. At charge neutrality, however, conduction is less insensitive to external magnetic fields. In this regime we also observe a stronger suppression of the conductance below T*, which we interpret as a sign of broken interlayer symmetry or strong fluctuations in the edge/potential disorder. (C) 2017 Elsevier Ltd. All rights reserved.

  • 14. Cui, Wen
    et al.
    Sun, Shishuai
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Department of Physics. State Key Laboratory of Superhard Materials, Jilin University, Changchun, China.
    Wang, Shuangming
    Liu, Bingbing
    Pressure induced metastable polymerization in doped C60 materials2017In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 115, p. 740-745Article in journal (Refereed)
    Abstract [en]

    High pressure Raman studies have been carried out on C60/AgNO3 and C60/Ni(OEP) up to 30 GPa. In both these doped C60 materials, pressure-induced metastable ordered polymers can be observed after pressure release. The results show that both the quenched materials contain chainlike polymers and dimers. We also find that the degree of polymerization is higher in these doped C60 materials than in bulk C60 materials after similar high pressure treatment and that C60/AgNO3 contains a higher fraction of chainlike polymers than C60/Ni(OEP) after decompression from same pressure. The results can be understood by considering the different initial lattice structures of these materials and the confinement effects of the dopants.

    The full text will be freely available from 2019-04-01 09:56
  • 15. Cui, Wen
    et al.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sun, Shishuai
    Yao, Mingguang
    Liu, Bingbing
    High pressure and high temperature induced polymerization of doped C60 materials2016In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 109, p. 269-275Article in journal (Refereed)
    Abstract [en]

    Several metastable doped C60 polymers are synthesized under high pressure and high temperature (1.5GPa, 573K and 2GPa, 700K, respectively), using C60/ferrocene (Fc, Fe(C5H5)2), C60/Ni(OEP) and C60/AgNO3 as starting materials. Raman and IR spectroscopy are used to study the polymerization of these samples after HPHT treatment. It is found that the polymerization degree is always lower than that of pure C60 treated at same conditions, which is attributed to the space limitation by the dopants. We also find that even at same conditions, the three doped materials form different polymeric phases of the doped materials. This is attributed to the unique initial lattice structures and the different degrees of spatial confinement provided by the dopants.

  • 16. Cui, Wen
    et al.
    Yao, Mingguang
    Yao, Zhen
    Ma, Fengxian
    Li, Quanjun
    Liu, Ran
    Liu, Bo
    Zou, Bo
    Cui, Tian
    Liu, Bingbing
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Reversible pressure-induced polymerization of Fe(C5H5)(2) doped C-702013In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 62, p. 447-454Article in journal (Refereed)
    Abstract [en]

    High pressure Raman, IR and X-ray diffraction (XRD) studies have been carried out on C-70(Fe(C5H5)(2))(2) (hereafter, "C-70(Fc)(2)") sheets. Theoretical calculation is further used to analyze the Electron Localization Function (ELF) and charge transfer in the crystal and thus to understand the transformation of C-70(Fc)(2) under pressure. Our results show that even at room temperature dimeric phase and one dimensional (1D) polymer phase of C-70 molecules can be formed at about 3 and 8 GPa, respectively. The polymerization is found to be reversible Upon decompression and the reversibility is related to the pressure-tuned charge transfer, as well as the overridden steric repulsion of counter ions. According to the layered structure of the intercalated ferrocene molecules formed in the crystal, we suggest that ferrocene acts as not only a spacer to restrict the polymerization of C-70 molecules within a layer, but also as charge reservoir to tune the polymerization process. This supplies a possible way for us to design the polymerization of fullerenes at suitable conditions.

  • 17. Danilchenko, Boris A.
    et al.
    Tripachko, N.A.
    Lev, S.
    Petrychuk, M.V.
    Sydoruk, V.A.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Vitusevich, S.A.
    1/f noise and mechanisms of the conductivity in carbon nanotube bundles2011In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 49, no 15, p. 5201-5206Article in journal (Refereed)
    Abstract [en]

    Experimental results are reported of the investigation of conductivity mechanisms in metallic single-wall carbon nanotube (SWCNT) bundles in a wide temperature range from 4.2 K to 300 K. The temperature dependence of the resistance and noise parameters – the logarithmic slope of the current dependence of noise as well as the normalized current noise – are compared. Remarkable changes in noise characteristics are registered at temperatures typical of the transition from hopping conductivity to Luttinger liquid conductivity and the transition from Luttinger liquid conductivity to diffusion conductivity. In the first transition region, the slope of the normalized noise level of the current changes significantly as a function of temperature. In the region of diffusion conductivity, a stronger variation of the normalized noise level is revealed. These changes in noise properties are correlated with changes in the transport characteristics of SWCNT bundles that allow us to adequately explain the mechanisms of conductivity in the system. 

  • 18.
    de Souza, Fabio A. L.
    et al.
    Fed Inst Educ Sci & Technol Espirito Santo, Ibatiba, ES, Brazil.;Univ Fed Espirito Santo, Dept Fis, Vitoria, ES, Brazil..
    Amorim, Rodrigo G.
    Univ Fed Fluminense, ICEx, Dept Fis, Volta Redonda, RJ, Brazil..
    Prasongkit, Jariyanee
    Nakhon Phanom Univ, Div Phys, Fac Sci, Nakhon Phanom 48000, Thailand.;Nanotec KKU Ctr Excellence Adv Nanomat Energy Pro, Khon Kaen 40002, Thailand..
    Scopel, Wanderlä L.
    Univ Fed Espirito Santo, Dept Fis, Vitoria, ES, Brazil..
    Scheicher, Ralph H.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Rocha, Alexandre R.
    Univ Estadual Paulista, Inst Fis Teor, Sao Paulo, Brazil.;MIT, Dept Chem Engn, Cambridge, MA 02139 USA..
    Topological line defects in graphene for applications in gas sensing2018In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 129, p. 803-808Article in journal (Refereed)
    Abstract [en]

    Topological line defects in graphene synthesized in a highly controlled manner open up new research directions for nanodevice applications. Here, we investigate two types of extended line defects in graphene, namely octagonal/pentagonal and heptagonal/pentagonal reconstructions. A combination of density functional theory and non-equilibrium Green's function methods was utilized in order to explore the application potential of this system as an electronic gas sensor. Our findings show that the electric current is confined to the line defect through gate voltage control, which combined with the enhanced chemical reactivity at the grain boundary, makes this system a highly promising candidate for gas sensor applications. As a proof of principle, we evaluated the sensitivity of a prototypical device toward NO2 molecule, demonstrating that it is indeed possible to reliably detect the target molecule.

  • 19. Delaunay, R.
    et al.
    Gatchell, Michael
    Stockholm University, Faculty of Science, Department of Physics.
    Mika, A.
    Domaracka, A.
    Adoui, L.
    Zettergren, Henning
    Stockholm University, Faculty of Science, Department of Physics.
    Cederquist, Henrik
    Stockholm University, Faculty of Science, Department of Physics.
    Rousseau, P.
    Huber, B. A.
    Shock-driven formation of covalently bound carbon nanoparticles from ion collisions with clusters of C-60 fullerenes2018In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 129, p. 766-774Article in journal (Refereed)
    Abstract [en]

    We show that the energetic processing of C-60 clusters by slow atomic projectiles leads to ultrafast (< ps) formation of large covalent carbon nanoparticles containing a few hundreds of atoms. The underlying mechanism is found to be due to impulse-driven collisions between the projectile and the nuclei of the molecules. Experimental findings are well reproduced by classical molecular dynamics simulations. The cross sections for molecular growth processes forming covalent systems which contain more than 60 carbon atoms are about 5.10(-14) cm(2) representing more than 70% of the geometrical cross sections. This demonstrates the high efficiency of the underlying processes. The formed carbon nanoparticles contain both aromatic and aliphatic structures which have also been considered as dust components in space.

  • 20.
    Ekspong, Joakim
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Boulanger, Nicolas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Gracia-Espino, Eduardo
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Surface activation of graphene nanoribbons for oxygen reduction reaction by nitrogen doping and defect engineering: An ab initio study2018In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 137, p. 349-357Article in journal (Refereed)
    Abstract [en]

    Introducing heteroatoms and creating structural defects on graphene is a common and rather successful strategy to transform its inert basal plane into an efficient metal-free electrocatalyst for oxygen reduction reaction (ORR). However, the intricate atomic configuration of defective graphenes difficult their optimization as ORR electrocatalysts, where not only a large density of active sites is desirable, but also excellent electrical conductivity is required. Therefore, we used density functional theory to investigate the current-voltage characteristics and the catalytic active sites towards ORR of nitrogen-doped and defective graphene by using 8 zig-zag graphene nanoribbons as model systems. Detailed ORR catalytic activity maps are created for ten different systems showing the distribution of catalytic hot spots generated by each defect. Subsequently, the use of both current-voltage characteristics and catalytic activity maps allow to exclude inefficient systems that exhibit either low electrical conductivity or have adsorption energies far from optimal. Our study highlights the importance of considering not only the interaction energy of reaction intermediates to design electrocatalysts, but also the electrical conductivity of such configurations. We believe that this work is important for future experimental studies by providing insights on the use of graphene as a catalyst towards the ORR reaction. 

  • 21.
    Enlund, Johannes
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electronics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Materials Science. Avdelningen för fasta tillståndets elektronik.
    Isberg, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electronics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Materials Science. elektricitetslära och åskforskning.
    Karlsson, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Materials Science. materialvetenskap.
    Nikolajeff, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Materials Science. materialvetenskap.
    Olsson, Jörgen
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electronics. fasta tillståndets elektronik.
    Twitchen, Daniel J.
    Element Six, UK.
    Anisotropic dry etching of boron doped single crystal CVD diamond2005In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 43, no 9, p. 1839-1842Article in journal (Refereed)
    Abstract [en]

    Semiconducting boron doped single-crystal CVD diamond has been patterned using aluminum masks and an inductively coupled plasma (ICP) etch system. For comparison insulating HPHT diamond samples were also patterned using the same process. Diamond etch rates above 200 nm/min were obtained with an O2/Ar discharge for a gas pressure of 2.5 mTorr using 600 W RF power. We have accomplished the fabrication of structures with a minimum feature size of 1 μm with vertical sidewalls in both CVD and HPHT diamond. The ICP etching produced smooth surfaces with a typical root-mean-square surface roughness of 3 nm. The dependence of etch rate on bias voltage was somewhat different for the two types of diamond. However, for all samples both the etch rate and anisotropy were found to improve with increasing bias voltage.

  • 22.
    Fan, Xuge
    et al.
    KTH Royal Inst Technol, Sch Elect Engn, Dept Micro & Nanosyst, SE-10044 Stockholm, Sweden..
    Elgammal, Karim
    KTH Royal Inst Technol, Sch Engn Sci, Dept Appl Phys, Elect 229, SE-16440 Kista, Sweden.;KTH Royal Inst Technol, Swedish E Sci Res Ctr SeRC, SE-10044 Stockholm, Sweden..
    Smith, Anderson D.
    KTH Royal Inst Technol, Sch Informat & Commun Technol, Dept Integrated Devices & Circuits, SE-16440 Kista, Sweden..
    Ostling, Mikael
    KTH Royal Inst Technol, Sch Informat & Commun Technol, Dept Integrated Devices & Circuits, SE-16440 Kista, Sweden..
    Delin, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. KTH Royal Inst Technol, Sch Engn Sci, Dept Appl Phys, Elect 229, SE-16440 Kista, Sweden.;KTH Royal Inst Technol, Swedish E Sci Res Ctr SeRC, SE-10044 Stockholm, Sweden..
    Lemme, Max C.
    KTH Royal Inst Technol, Sch Informat & Commun Technol, Dept Integrated Devices & Circuits, SE-16440 Kista, Sweden.;Rhein Westfal TH Aachen, Dept Elect Devices, D-52074 Aachen, Germany..
    Niklaus, Frank
    KTH Royal Inst Technol, Sch Elect Engn, Dept Micro & Nanosyst, SE-10044 Stockholm, Sweden..
    Humidity and CO2 gas sensing properties of double-layer graphene2018In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 127, p. 576-587Article in journal (Refereed)
    Abstract [en]

    Graphene has interesting gas sensing properties with strong responses of the graphene resistance when exposed to gases. However, the resistance response of double-layer graphene when exposed to humidity and gasses has not yet been characterized and understood. In this paper we study the resistance response of double-layer graphene when exposed to humidity and CO2, respectively. The measured response and recovery times of the graphene resistance to humidity are on the order of several hundred milliseconds. For relative humidity levels of less than similar to 3% RH, the resistance of double-layer graphene is not significantly influenced by the humidity variation. We use such a low humidity atmosphere to investigate the resistance response of double-layer graphene that is exposed to pure CO2 gas, showing a consistent response and recovery behaviour. The resistance of the double-layer graphene decreases linearly with increase of the concentration of pure CO2 gas. Density functional theory simulations indicate that double-layer graphene has a weaker gas response compared to single-layer graphene, which is in agreement with our experimental data. Our investigations contribute to improved understanding of the humidity and CO2 gas sensing properties of double-layer graphene which is important for realizing viable graphene-based gas sensors in the future.

  • 23.
    Fan, Xuge
    et al.
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems. KTH Royal Institute of Technology.
    Elgammal, Karim
    KTH, Centres, SeRC - Swedish e-Science Research Centre. KTH, School of Engineering Sciences (SCI), Applied Physics.
    Smith, Anderson D.
    KTH, School of Information and Communication Technology (ICT), Electronics, Integrated devices and circuits.
    Östling, Mikael
    KTH, School of Information and Communication Technology (ICT), Electronics, Integrated devices and circuits.
    Delin, Anna
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. KTH, Centres, SeRC - Swedish e-Science Research Centre. Department of Physics and Astronomy, Materials Theory Division, Uppsala University, Box 516, SE-75120 Uppsala, Sweden.
    Lemme, Max C.
    KTH, School of Information and Communication Technology (ICT), Electronics, Integrated devices and circuits. Department of Electronic Devices, RWTH Aachen University, 52074 Aachen, Germany.
    Niklaus, Frank
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems. KTH Royal Institute of Technology.
    Humidity and CO2 gas sensing properties of double-layer graphene2018In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 127, p. 576-587Article in journal (Refereed)
    Abstract [en]

    Graphene has interesting gas sensing properties with strong responses of the graphene resistance when exposed to gases. However, the resistance response of double-layer graphene when exposed to humidity and gasses has not yet been characterized and understood. In this paper we study the resistance response of double-layer graphene when exposed to humidity and CO2, respectively. The measured response and recovery times of the graphene resistance to humidity are on the order of several hundred milliseconds. For relative humidity levels of less than ~ 3% RH, the resistance of double-layer graphene is not significantly influenced by the humidity variation. We use such a low humidity atmosphere to investigate the resistance response of double-layer graphene that is exposed to pure CO2 gas, showing a consistent response and recovery behaviour. The resistance of the double-layer graphene decreases linearly with increase of the concentration of pure CO2 gas. Density functional theory simulations indicate that double-layer graphene has a weaker gas response compared to single-layer graphene, which is in agreement with our experimental data. Our investigations contribute to improved understanding of the humidity and CO2 gas sensing properties of double-layer graphene which is important for realizing viable graphene-based gas sensors in the future.

  • 24. Feicht, Patrick
    et al.
    Siegel, Renee
    Thurn, Herbert
    Neubauer, Jens W.
    Seuss, Maximilian
    Szabo, Tamas
    Talyzin, Alexandr V.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Halbig, Christian E.
    Eigler, Siegfried
    Kunz, Daniel A.
    Fery, Andreas
    Papastavrou, Georg
    Senker, Jurgen
    Breu, Josef
    Systematic evaluation of different types of graphene oxide in respect to variations in their in-plane modulus2017In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 114, p. 700-705Article in journal (Refereed)
    Abstract [en]

    Graphene oxide samples prepared in various laboratories following a diversity of synthesis protocols based on Brodie's (BGO) and Hummers/Offeman's (HGO) methods were compared in respect of their in plane moduli. A simple wrinkling method allowed for a spatial resolution <1.5 pm by converting the wrinkling frequency. Quite surprisingly, a drastic variation of the in-plane moduli was found spanning the range from 600 GPa for the best BGO types, which is in the region of chemically derived graphene, all the way down to less than 200 GPa for HGO types. This would suggest that there are no two equal GO samples and GO should not be regarded a compound but rather a class of materials with very variable physical properties. While large differences between Brodie's and Hummers/Offeman's types might have been expected, even within the group of Hummers/Offeman's types pronounced differences are observed that, based on C-13 solid-state NMR, were related to over-functionalization versus over-oxidation.

  • 25.
    Ferreira da Cunha, Wiliam
    et al.
    University of Brasilia, Brazil.
    Ribeiro, Luiz Antonio
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Chemistry. Linköping University, Faculty of Science & Engineering. University of Brasilia, Brazil.
    Luciano de Almeida Fonseca, Antonio
    University of Brasilia, Brazil.
    Gargano, Ricardo
    University of Brasilia, Brazil; University of Florida, FL 32611 USA; University of Florida, FL 32611 USA.
    Magela e Silva, Geraldo
    University of Brasilia, Brazil.
    Impurity effects on polaron dynamics in graphene nanoribbons2015In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 91, p. 171-177Article in journal (Refereed)
    Abstract [en]

    The impurity effects on the dynamics of polarons in armchair graphene nanoribbons are numerically investigated in the scope of a two-dimensional tight-binding approach with lattice relaxation. The results show that the presence of an impurity changes significantly the net charge distribution associated to the polaron structure. Moreover, the interplay between external electric field and the local impurities plays the role of drastically modifying the polaron dynamics. Interestingly, nanoribbons containing mobile polarons are noted to take place even when considering high impurity levels, which is associated with the highly conductive character of the graphene nanoribbons. This investigation may enlighten the understanding of the charge transport mechanism in carbon-based nanomaterials. (C) 2015 Elsevier Ltd. All rights reserved.

  • 26.
    Fu, Qilin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Machine and Process Technology. Plasmatrix Materials AB, Sweden.
    Rashid, Md Masud-Ur
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Machine and Process Technology. Plasmatrix Materials AB, Sweden.
    Nicolescu, Cornel-Mihai
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Toth, Geza
    et al.,
    High dynamic stiffness mechanical structures with nanostructured composite coatings deposited by high power impulse magnetron sputtering2016In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 98, p. 24-33Article in journal (Refereed)
    Abstract [en]

    Nanostructured Cu:CuCNx composite coatings with high static and dynamic stiffness were synthesized by means of plasma-enhanced chemical vapor deposition (PECVD) combined with high power impulse magnetron sputtering (HiPIMS). Scanning electron microscope (SEM) images and energy-dispersive X-ray spectroscopy (EDS) mapping from cross-sectioned samples reveals a multi-layered nanostructure enriched in Cu, C, N, and O in different ratios. Mechanical properties of the coatings were investigated by Vickers micro-indention and model tests. It was observed that copper inclusions as well as copper interlayers in the CNx matrix can increase mechanical damping by up to 160%. Mechanical properties such as hardness, elastic modulus and loss factor were significantly improved by increasing the discharge power of the sputtering process. Moreover the coatings loss modulus was evaluated on the basis of indentation creep measurements under room temperature. The coating with optimum properties exhibited loss modulus of 2.6 GPa. The composite with the highest damping loss modulus were applied on the clamping region of a milling machining tool to verify their effect in suppressing regenerative tool chatter. The high dynamic stiffness coatings were found to effectively improve the critical stability limit of a milling tool by at least 300%, suggesting a significant increase of the dynamic stiffness.

  • 27.
    Giusca, Cristina E.
    et al.
    National Phys Lab, England .
    Spencer, Steve J.
    National Phys Lab, England .
    Shard, Alex G.
    National Phys Lab, England .
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Kazakova, Olga
    National Phys Lab, England .
    Exploring graphene formation on the C-terminated face of SiC by structural, chemical and electrical methods2014In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 69, p. 221-229Article in journal (Refereed)
    Abstract [en]

    The properties of epitaxial graphene on the C-face of SiC are investigated using comprehensive structural, chemical and electrical analyses. By matching similar nanoscale features on the surface potential and Raman spectroscopy maps, individual domains have been assigned to graphene patches of 1-5 monolayers thick, as well as bare SiC substrate. Furthermore, these studies revealed that the growth proceeds in an island-like fashion, consistent with the Volmer-Weber growth mode, illustrating also the presence of nucleation sites for graphene domain growth. Raman spectroscopy data shows evidence of large area crystallites (up to 620 nm) and high quality graphene on the C-face of SiC. A comprehensive chemical analysis of the sample has been provided by X-ray photoelectron spectroscopy investigations, further supporting surface potential mapping observations on the thickness of graphene layers. It is shown that for the growth conditions used in this study, 5 monolayer thick graphene does not form a continuous layer, so such thickness is not sufficient to completely cover the substrate.

  • 28. 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, p. 501-507Article 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.

  • 29. Han, K-H
    et al.
    Spemann, D
    Hohne, R
    Setzer , A
    Makarova, T
    Umeå University.
    Esquinazi, P
    Butz, T
    Observation of intrinsic magnetic domains in C60 polymer - Addendum2003In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 41, no 12, p. 2425-2426Article in journal (Refereed)
  • 30. Han, K-H
    et al.
    Spemann, D
    Hohne, R
    Setzer, A
    Makarova , T
    Umeå University.
    Esquinazi, P
    Butz, T
    Observation of intrinsic magnetic domains in C-60 polymers2003In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 41, p. 785-Article in journal (Refereed)
  • 31.
    Hao, Wenming
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Keshavarzi, Neda
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Branger, Adrien
    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).
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Strong discs of activated carbons from hydrothermally carbonized beer waste2014In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 78, p. 521-531Article in journal (Refereed)
    Abstract [en]

    Strong and dense activated carbon discs (ACDs) were synthesized and studied. The discs were produced in a multistep manner from a precursor based on hydrothermally treated beer waste (HTC-BW). The precursor was processed by pulsed current processing (PCP) into ACDs. These discs were activated by physical activation in CO2 at an elevated temperature. The ACDs had surface areas of ∼500 m2/g and contained significant amounts of micro-, meso-, and macropores. The effect on the temperature during the PCP and the presence of tar in the precursor were studied with respect to the properties of the discs. The ACDs had strengths up to 7.2 MPa with densities up to 1.4 g/cm3. The density is the highest reported for discs of activated carbon.

  • 32.
    Hedman, Daniel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Larsson, Andreas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Length dependent stability of single-walled carbon nanotubes and how it affects their growth2017In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 116, p. 443-447Article in journal (Refereed)
    Abstract [en]

    Using density-functional theory the stability of armchair and zigzag single-walled carbon nanotubes and graphene nanoribbons was investigated. We found that the stability of armchair and zigzag nanotubes has different linear dependence with regard to their length, with switches in the most stable chirality occurring at specific lengths for each nanotube series. We explain these dependencies by competing edge and curvature effects. We have found that within each series armchair nanotubes are the most stable at short lengths, while zigzag nanotubes are the most stable at long lengths. These results shed new insights into why (near) armchair nanotubes are the dominant product from catalytic chemical vapor deposition growth, if templating is not used. Paradoxically, the stability of armchair nanotubes at short lengths favors their growth although zigzag nanotubes are more stable at long lengths, resulting in the production of the least stable nanotubes.

  • 33.
    Hellgren, Niklas
    et al.
    Messiah Coll, PA 17055 USA.
    Haasch, Richard T.
    University of Illinois, IL 61801 USA.
    Schmidt, Susann
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. University of Illinois, IL 61801 USA.
    Interpretation of X-ray photoelectron spectra of carbon-nitride thin films: New insights from in situ XPS2016In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 108, p. 242-252Article in journal (Refereed)
    Abstract [en]

    We report on angular-resolved x-ray photoelectron spectroscopy (XPS) studies of magnetron sputtered CNx thin films, first in situ (without air exposure), then after air exposure (for time periods ranging from minutes to several years), and finally after Ar ion etching using ion energies ranging from 500 eV to 4 keV. The as-deposited films typically exhibit two strong N1s peaks corresponding to pyridine-like, and graphite-like, at similar to 398.2 eV and similar to 400.7 eV, respectively. Comparison between in situ and air-exposed samples suggests that the peak component at similar to 402-403 eV is due only to quaternary nitrogen and not oxidized nitrogen. Furthermore, peak components in the similar to 399-400 eV range cannot only be ascribed to nitriles or pyrrolic nitrogen as is commonly done. We propose that it can also be due to a polarization shift in pyridinic N, induced by surface water or hydroxides. Argon ion etching readily removes surface oxygen, but results also in a strong preferential sputtering of nitrogen and can cause amorphization of the film surface. The best methods for evaluating and interpreting the CNx film structure and composition with ex-situ XPS are discussed. (C) 2016 Elsevier Ltd. All rights reserved.

  • 34.
    Hens, Philip
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology. University of Marburg, Germany.
    Zakharov, Alexei A.
    Lund University, Sweden.
    Iakimov, Tihomir
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Syväjärvi, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Large area buffer-free graphene on non-polar (001) cubic silicon carbide2014In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 80, p. 823-829Article in journal (Refereed)
    Abstract [en]

    Graphene is, due to its extraordinary properties, a promising material for future electronic applications. A common process for the production of large area epitaxial graphene is a high temperature annealing process of atomically flat surfaces from hexagonal silicon carbide. This procedure is very promising but has the drawback of the formation of a buffer layer consisting of a graphene-like sheet, which is covalently bound to the substrate. This buffer layer degenerates the properties of the graphene above and needs to be avoided. We are presenting the combination of a high temperature process for the graphene production with a newly developed substrate of (0 0 1)-oriented cubic silicon carbide. This combination is a promising candidate to be able to supply large area homogenous epitaxial graphene on silicon carbide without a buffer layer. We are presenting the new substrate and first samples of epitaxial graphene on them. Results are shown using low energy electron microscopy and diffraction, photoelectron angular distribution and X-ray photoemission spectroscopy. All these measurements indicate the successful growth of a buffer free few layer graphene on a cubic silicon carbide surface. On our large area samples also the epitaxial relationship between the cubic substrate and the hexagonal graphene could be clarified.

  • 35.
    Hill-Pearce, R. E.
    et al.
    National Phys Lab, England.
    Eless, V.
    National Phys Lab, England.
    Lartsev, A.
    Chalmers, Sweden.
    Martin, N. A.
    National Phys Lab, England.
    Barker Snook, I. L.
    National Phys Lab, England.
    Helmore, J. J.
    National Phys Lab, England.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Gallop, J. C.
    National Phys Lab, England.
    Hao, L.
    National Phys Lab, England.
    The effect of bilayer regions on the response of epitaxial graphene devices to environmental gating2015In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 93, p. 896-902Article in journal (Refereed)
    Abstract [en]

    The effect of a bilayer area on the electronic response to environmental gating of a monolayer graphene Hall bar device is investigated using room temperature magnetotransport and scanning Kelvin probe microscopy measurements in a controlled environment. The device is tuned through the charge neutrality point with n-p-n-junctions formed. Scanning Kelvin probe measurements show that the work function of the monolayer graphene decreases more than that of the bilayer area however magnetotransport measurements show a larger change in carrier concentration for bilayer graphene with environmental gating. Interface scattering at the boundary between the monolayer and bilayer regions also affects device response with field-dependent suppression of the conductivity observed near the charge neutrality point. Simultaneous electronic and environmental scanning Kelvin probe measurements are used to build nano-scale maps of the work function of the device surface revealing the areas of greatest work function change with environmental gating. Crown Copyright (C) 2015 Published by Elsevier Ltd. All rights reserved.

  • 36.
    Hinnemo, Malkolm
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Ahlberg, Patrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Hägglund, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Ren, Wencai
    Institute of Metal Research, Chinese Academy of Sciences.
    Cheng, Hui-Ming
    Institute of Metal Research, Chinese Academy of Sciences.
    Zhang, Shi-Li
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Zhang, Zhi-Bin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Scalable residue-free graphene for surface-enhanced Raman scattering2016In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 98, p. 567-571Article in journal (Refereed)
    Abstract [en]

    A room-temperature polymer-assisted transfer process is developed for large-area, single-layer graphene grown by means of chemical vapor deposition (CVD). This process leads to transferred graphene layers free of polymer contamination. The absence of polymer residues boosts the surface-enhanced Raman scattering (SERS) of the CVD graphene with gold nanoparticles (Au NPs) deposited atop by evaporation. The SERS enhancement of the CVD graphene reaches similar to 120 for the characteristic 2D peak of graphene, the highest enhancement factor achieved to date, when the Au NPs are at the threshold of percolation. Our simulation supported by experiment suggests that the polymer residues persistently present on the graphene transferred by the conventional polymer-assisted method are equivalent to an ultrathin film of less than 1 nm thickness. The presence of polymer residues drastically reduces SERS due to the separation of the Au NPs from the underlying graphene. The scalability of CVD graphene opens up for the possibility of graphene-based SERS sensors.

  • 37. Huber, S. E.
    et al.
    Gatchell, Michael
    Stockholm University, Faculty of Science, Department of Physics.
    Zettergren, Henning
    Stockholm University, Faculty of Science, Department of Physics.
    Mauracher, A.
    A precedent of van-der-Waals interactions outmatching Coulomb explosion2016In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 109, p. 843-850Article in journal (Refereed)
    Abstract [en]

    Fullerenes (and clusters composed of them) yield a variety of promising structural, electronic, magnetic and chemical properties, governed by their specific electronic and geometric configuration. These systems have attracted many theoretical and experimental endeavors in order to describe, explain and predict their features. The conclusive description of some specific properties has remained a challenge though, such as a sound physicochemical description of the stability of multiply charged fullerene clusters, which we explore here. We show how simple models based on classical electrostatics allow one to understand the (fragmentation) dynamics of multiply ionized fullerene aggregates without the use of elaborate and time-consuming computational quantum chemical approaches. These models successfully explain why the fullerene pentamer is the smallest dicationic cluster experimentally observed, despite its thermodynamic instability. These predictions are of importance in various fields such as cluster physics, astrochemistry, electrochemistry and solid-state chemistry.

  • 38.
    Hussami, Linda
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Inorganic Chemistry.
    Corkery, Robert W.
    Institution of Surface Chemistry.
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Inorganic Chemistry.
    Polyhedral carbon nanofoams with minimum surface area partitions produced using silica nanofoams as templates2010In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 48, no 11, p. 3121-3130Article in journal (Refereed)
    Abstract [en]

    Polyhedral silica nanofoam (PNF-SiO2) analogues of dry soap froths with minimal surface area were used as templates for making polyhedral carbon nanofoams (PNF-C). Furfuryl alcohol or triblock copolymers were used as carbon sources. The volume of carbon precursor relative to the internal pore volume of PNF-SiO2's was systematically varied between 50% and 100% in order to investigate the effect of filling fraction on internal structure of the corresponding PNF-C's. Transmission electron microscopy, small-angle X-ray scattering and nitrogen physisorption were used to characterize the samples. To aid the interpretation of the experimental data, a model for X-ray scattering from spherical shells was used to approximate scattering from the polyhedral foam cells. PNF-C's cast from the PNF-SiO2's, displayed the characteristic Plateau borders of minimal surface area foams defining interconnected, slit-like pore systems at all filling fractions. At relatively high filling fractions, inverse foam structures were obtained with the slit-like pores systems interpenetrating aggregated, close-packed, relatively low density polyhedral carbon nanoparticles co-joined by carbon struts. At relatively low filling fractions, polyhedral carbon nanofoams with relatively thin, fused double-wall structures and interconnected polyhedral pore systems were obtained.

  • 39. Hussami, Linda L
    et al.
    Corkery, Robert W
    YKI – Ytkemiska institutet.
    Kloo, Lars
    Polyhedral carbon nanofoams with minimum surface area partitions produced using silica nanofoams as templates2010In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 48, no 11, p. 3121-3130Article in journal (Refereed)
    Abstract [en]

    Polyhedral silica nanofoam (PNF-SiO2) analogues of dry soap froths with minimal surface area were used as templates for making polyhedral carbon nanofoams (PNF-C). Furfuryl alcohol or triblock copolymers were used as carbon sources. The volume of carbon precursor relative to the internal pore volume of PNF-SiO2's was systematically varied between 50% and 100% in order to investigate the effect of filling fraction on internal structure of the corresponding PNF-C's. Transmission electron microscopy, small-angle X-ray scattering and nitrogen physisorption were used to characterize the samples. To aid the interpretation of the experimental data, a model for X-ray scattering from spherical shells was used to approximate scattering from the polyhedral foam cells. PNF-C's cast from the PNF-SiO2's, displayed the characteristic Plateau borders of minimal surface area foams defining interconnected, slit-like pore systems at all filling fractions. At relatively high filling fractions, inverse foam structures were obtained with the slit-like pores systems interpenetrating aggregated, close-packed, relatively low density polyhedral carbon nanoparticles co-joined by carbon struts. At relatively low filling fractions, polyhedral carbon nanofoams with relatively thin, fused double-wall structures and interconnected polyhedral pore systems were obtained.

  • 40.
    Ivanov, Ivan Gueorguiev
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Ul Hassan, Jawad
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Iakimov, Tihomir
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Zakharov, Alexei A.
    Lund University, Sweden .
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Layer-number determination in graphene on SiC by reflectance mapping2014In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 77, p. 492-500Article in journal (Refereed)
    Abstract [en]

    We report a simple, handy and affordable optical approach for precise number-of-layers determination of graphene on SiC based on monitoring the power of the laser beam reflected from the sample (reflectance mapping) in a slightly modified micro-Raman setup. Reflectance mapping is compatible with simultaneous Raman mapping. We find experimentally that the reflectance of graphene on SiC normalized to the reflectivity of bare substrate (the contrast) increases linearly with similar to 1.7% per layer for up to 12 layers, in agreement with theory The wavelength dependence of the contrast in the visible is investigated using the concept of ideal fermions and compared with existing experimental data for the optical constants of graphene. We argue also that the observed contrast is insensitive to the doping condition of the sample, as well as to the type of sample (graphene on C- or Si-face of 4H or 6H SiC, hydrogen-intercalated graphene). The possibility to extend the precise layer counting to similar to 50 layers makes reflectivity mapping superior to low-energy electron microscopy (limited to similar to 10 layers) in quantitative evaluation of graphene on the C-face of SiC. The method is applicable for graphene on other insulating or semiconducting substrates.

  • 41.
    Jacques, Eric
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Hellqvist Kjell, Maria
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Zenkert, Dan
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    The effect of lithium-intercalation on the mechanical properties of carbon fibres2014In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 68, p. 725-733Article in journal (Refereed)
    Abstract [en]

    Carbon fibres (CFs) can be used as lightweight structural electrodes since they have high specific tensile stiffness and ultimate tensile strength (UTS), and high lithium (Li)-intercalation capability. This paper investigates the relationship between the amount of intercalated Li and the changes induced in the tensile stiffness and UTS of polyacrylonitrile-based CF tows. After a few electrochemical cycles the stiffness was not degraded and independent of the measured capacity. A drop in the UTS of lithiated CFs was only partly recovered during delithiation and clearly larger at the highest measured capacities, but remained less than 40% at full charge. The reversibility of this drop with the C-rate and measured capacity supports that the fibres are not damaged, that some Li is irreversibly trapped in the delithiated CFs and that reversible strains develop in the fibre. However, the drop in the strength does not vary linearly with the measured capacity and the drop in the ultimate tensile strain remains lower than the CF longitudinal expansion at full charge. These results suggest that the loss of strength might relate to the degree of lithiation of defectives areas which govern the tensile failure mode of the CFs.

  • 42.
    Jacques, Eric
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Kjell, Maria
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Zenkert, Dan
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Behm, Mårten
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Expansion of carbon fibres induced by lithium intercalation for structural electrode applications2013In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 59, p. 246-254Article in journal (Refereed)
    Abstract [en]

    Carbon fibres (CFs) can work as lightweight structural electrodes in CF-reinforced composites able to store energy as lithium (Li)-ion batteries. The CF has high stiffness and strength-to-weight ratios and a carbonaceous microstructure which enables Li intercalation. An innovative in situ technique for studying the longitudinal expansion of the CF and the relationship with the amount of intercalated Li is described in the present paper. The polyacrylonitrile-based CFs, T800H and unsized IMS65, were chosen for their electrochemical storage capacities. It was found that the CF expands during lithiation and contracts during delithiation. At the first electrochemical cycle, the expansion is partly irreversible which supports that the first-cycle capacity loss partly relates to Li trapped in the CF structure. For the following cycles, the capacity and the expansion are reversible. The expansion, which might relate to tensile stress, increases up to 1% as the measured capacity approaches the theoretical limit of 372 mAh/g for Li storage in graphite. Minor additional expansions due to the uneven distribution of intercalated Li in the CF structure were measured before and after lithiations. Using scanning electron microscope images the transverse expansion of fully lithiated CFs was estimated to about 10% of the cross-section area.

  • 43. Jehova Gonzalez, Viviana
    et al.
    Gracia-Espino, Eduardo
    Umeå University, Faculty of Science and Technology, Department of Physics. Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Morelos-Gomez, Aaron
    Lopez-Urias, Florentino
    Terrones, Humberto
    Terrones, Mauricio
    Biotin molecules on nitrogen-doped carbon nanotubes enhance the uniform anchoring and formation of Ag nanoparticles2015In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 88, p. 51-59Article in journal (Refereed)
    Abstract [en]

    An efficient method for anchoring silver nanoparticles (Ag-NPs) on the surface of nitrogendoped multi-walled carbon nanotubes (CNx-MWCNTs) is reported. The process involves the attachment of biotin molecules on the surface of CNx-MWCNTs (both, pristine and acid treated) that act as a reducing agent for AgNO3, thus generating an efficient and homogeneous coating of Ag-NPs (similar to 3 nm in diameter). The reduction of AgNO3 on either pristine CNx-MWCNTs or acid treated CNx-MWCNTs (without biotin) results in Ag-NPs of large diameters and size distribution, in addition to a low anchoring efficiency. We confirmed that the use of biotin substantially improves the Ag-NPs anchoring efficiency, especially on acid treated CNx-MWCNTs. In order to elucidate the mechanism whereby Ag-NPs strongly bind to the surface of CNx-MWCNTs, density functional theory (DFT) calculations were carried out. These revealed the existence of covalent bonds established between one side of the biotin molecule and the CNx-MWCNT surface through oxygen atoms, leaving accessible the exposed sulfur atoms at the other end, which further provided an excellent interaction with the Ag-NPs via S Ag bonds. Finally, we demonstrate that these Ag-NPs coated CNx-MWCNTs could be used as efficient sensors of CS2. (c) 2015 Elsevier Ltd. All rights reserved.

  • 44.
    Karlsson, Linda
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Mockuté, Aurelija
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Sigurdur Ingason, Arni
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Ta, Huy Q.
    Polish Academic Science, Poland; Sungkyunkwan University, South Korea; Soochow University, Peoples R China; Soochow University, Peoples R China.
    Rummeli, Mark H.
    Polish Academic Science, Poland; Soochow University, Peoples R China; Soochow University, Peoples R China; IFW Dresden, Germany.
    Rosén, Johanna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Persson, Per O. Å.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Residue reduction and intersurface interaction on single graphene sheets2016In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 100, p. 345-350Article in journal (Refereed)
    Abstract [en]

    Large regions of pristine graphene are essential to applications which rely on the ideal graphene properties. Common methods for transferring chemical vapour deposition grown graphene to suitable substrates leaves metal oxide particles and poly(methyl methacrylate) (PMMA) residues on opposing surfaces, which degrade the properties. A common method to reduce the residues include annealing in vacuum or in argon, however, residues remain on the graphene sheet. The present investigation reports on the metal oxide particle ripening and PMMA decomposition on a single graphene sheet during in-situ annealing up to 1300 degrees C in a transmission electron microscope. It is shown that the PMMA residues are increasingly reduced at elevated temperatures although the reduction is strongly correlated to the metal oxide particle coverage on the opposing graphene surface. This is shown to occur as a consequence of an electrostatic interaction between the residues and that this prevents the establishment of large clean areas. (C) 2016 Elsevier Ltd. All rights reserved.

  • 45.
    Khranovskyy, Volodymyr
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Shtepliuk, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Ivanov, Ivan Gueorguiev
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Tsiaoussis, I.
    Aristotle University of Thessaloniki, Thessaloniki, Greece.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Light emission enhancement from ZnO nanostructured films grown on Gr/SiC substrates2016In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 99, p. 295-301Article in journal (Refereed)
    Abstract [en]

    We report on the application of a single layer graphene substrates for the growth of polycrystalline ZnO films with advanced light emission properties. Unusually high ultraviolet (UV) and visible (VIS) photoluminesce was observed from the ZnO/Gr/SiC structures in comparison to identical samples without graphene. The photoluminescence intensity depends non-monotonically on the films thickness, reaching its maximum for 150 nm thick films. The phenomena observed is explained as due to the dual graphene role: i) the dangling bond free substrate, providing growth of relaxed thin ZnO layers ii) a back reflector active mirror of the Fabry-Perot cavity that is formed. The reported results demonstrate the potential of two-dimensional carbon materials integration with light emitting wide band gap semiconductors and can be of practical importance for the design of future optoelectronic devices.

  • 46. Kim, Jong Min
    et al.
    Guccini, Valentina
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Seong, Kwang-dong
    Oh, Jiseop
    Salazar-Alvarez, Germán
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Piao, Yuanzhe
    Extensively interconnected silicon nanoparticles via carbon network derived from ultrathin cellulose nanofibers as high performance lithium ion battery anodes2017In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 118, p. 8-17Article in journal (Refereed)
    Abstract [en]

    Silicon is a good alternative to conventional graphite anode but it has bad cycling and rate performance. To overcome these severe problems, extensively interconnected silicon nanoparticles using carbon network derived from ultrathin cellulose nanofibers were synthesized. Ultrathin cellulose nanofibers, an abundant and sustainable material, entangle each silicon nanoparticle and become extensively interconnected carbon network after pyrolysis. This wide range interconnection provides an efficient electron path by decreasing the likelihood that electrons experience contact resistivity and also suppresses the volume expansion of silicon during lithiation. In addition, Ultrathin cellulose nanofibers are carboxylated and therefore adhesive to silicon nanoparticles through hydrogen bonding. This property makes ultrathin cellulose the perfect carbon source when making silicon composites. As a consequence, it exhibits 808 mAh g(-1) of the reversible capacity after 500 cycles at high current density of 2 A g(-1) with a coulombic efficiency of 99.8%. Even at high current density of 8 A g(-1), it shows a high reversible discharge capacity of 464 mAh g(-1). Moreover, extensively interconnected carbon network prevents the formation of a brittle electrode with a water-based binder. Therefore, this remarkable material has a huge potential for LIBs applications.

  • 47.
    Klechikov, Alexey
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    You, Shujie
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Lackner, Lukas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sun, Jinhua
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Iakunkov, Artem
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Rebrikova, Anastasia
    Umeå University, Faculty of Science and Technology, Department of Physics. Department of Chemistry, Moscow State University, Moscow, Russia.
    Korobov, Mikhail
    Baburin, Igor
    Seifert, Gotthard
    Talyzin, Aleksandr V.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Graphite oxide swelling in molten sugar alcohols and their aqueous solutions2018In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 140, p. 157-163Article in journal (Refereed)
    Abstract [en]

    Graphite oxides (GO) are intercalated rapidly by one to several layers of solvent when immersed in liquid but the GO solvates are typically unstable on air due to solvent evaporation. Here we study swelling of GO in solvents (sugar alcohols) with melting temperature point above ambient. Using in situ synchrotron radiation XRD experiments we demonstrated GO swelling in molten xylitol and sorbitol. The expanded GO structure intercalated with one layer of xylitol or sorbitol is preserved upon solidification of melt and cooling back to ambient conditions. The structure of solid solvates of GO with xylitol and sorbitol is based on non-covalent interaction and pristine GO can be recovered by washing in water. Intercalation of xylitol and sorbitol into GO structure in aqueous solutions yields similar but less ordered structure of GO/sugar alcohol solid solvates. Very similar inter-layer distance was observed for GO intercalated by sugar alcohols in melt and for GO immersed in sugar solutions. This result shows that sugar alcohols penetrate into GO inter-layer space without hydration shell forming 2D layers with orientation parallel to graphene oxide sheets. Therefore, hydration diameter of molecules should not be considered as decisive factor for permeation through graphene oxide inter-layers in multilayered membranes.

  • 48. 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, p. 297-303Article 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.

  • 49.
    Kumar, Vijay
    et al.
    University of Borås, Faculty of Textiles, Engineering and Business.
    Haspel, Henrik
    MTA-SZTE “Lendület” Porous Nanocomposites Research Group, Rerrich Bela ter 1., Szeged, Hungary; Department of Applied and Environmental Chemistry, University of Szeged, Rerrich Bela ter 1., Szeged, Hungary.
    Nagy, Krisztina
    MTA-SZTE “Lendület” Porous Nanocomposites Research Group, Rerrich Bela ter 1., Szeged, Hungary; Department of Applied and Environmental Chemistry, University of Szeged, Rerrich Bela ter 1., Szeged, Hungary.
    Rawal, Amit
    Department of Textile Technology, Indian Institute of Technology Delhi, Hauz Khas, New Delhi, India.
    Kukovecz, Akos
    MTA-SZTE “Lendület” Porous Nanocomposites Research Group, Rerrich Bela ter 1., Szeged, Hungary; Department of Applied and Environmental Chemistry, University of Szeged, Rerrich Bela ter 1., Szeged, Hungary.
    Leveraging compressive stresses to attenuate the electrical resistivity of buckypaper2016In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 110, p. 62-68Article in journal (Refereed)
    Abstract [en]

    Buckypaper (BP) is a planar film that consists of random network of multiwall carbon nanotubes (MWCNTs) held together by weak van der Waals interactions at tube-tube junctions. Although individual carbon nanotubes (CNTs) possess remarkable electrical properties, the electrical resistance of pristine BP is usually too high for practical applications. However, the electrical resistivity of BP can be attenuated by applying modest compressive stresses. Herein, we report an analytical model for predicting the electrical resistivity of BP under defined level of compressive strain. The predictive piezoresistive model of BP was developed by formulating a direct relationship with the structural parameters, physical and electrical properties of CNTs. The basis of the piezoresistive model relied upon the geometrical probability approach in combination with classical Hertzian contact mechanics and constriction resistance techniques. A comparison has been made between the theoretical and experimental results of electrical resistivity of BPs with varying densities. A reasonably good quantitative agreement was obtained between the theory and experiments. The main source of error was caused by the uncertainty in the measurement of the initial BP thickness. Through theoretical modeling, the initial volume fraction of CNTs was found to be one of the key parameters that modulated the piezoresistive behavior of BP.

  • 50.
    Larsson, Karin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Tian, Yuan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Effect of surface termination on the reactivity of nano-sized diamond particle surfaces for bio applications2018In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 134, p. 244-254Article in journal (Other academic)
    Abstract [en]

    Nanodiamond has displayed some unique physical and chemical properties compared to bulk diamond, which broadens its applications invarious areas. The here presented investigations have focused on the combined effect of diamond surface planes and termination on surface reactivity. Then especially towards adhered important biomolecules for bone regeneration and vascularization. Moreover, a more detailed picture of nanodiamond quantum confinements is still missing from a theoretical point of view. An evaluation of realistic models for nano-diamond (ND) particles of various sizes will here be presented. In addition, the adhesions of various biomolecules, both in vacuum and in a liquid environment, as a function of surface plane and termination, will also be presented. It was shown possible to model nanodiamond particles of size larger than 2 nm with (100) and (111) surface planes. For the situation with biomolecule adhesion to the nanodiamond surfaces, there is a large similarity between the results for the diamond (111) and (100)-2x1surfaces. For both of these surfaces, even though the water solvation will create much stronger biomolecular adhesion energies, there is a resemblance in order of adhesion energy for the various systems (i.e., solvated vs. non-solvated).

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