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Studies of carbon nanomaterials based on fullerenes and carbon nanotubes
Umeå University, Faculty of Science and Technology, Department of Physics.
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Materials based on fullerenes and carbon nanotubes are very much different from most “traditional” materials, primarily because they are built from nanosized molecules with highly symmetry-dependent properties. Being the subject of a very active research field over the last twenty years, carbon nanostructures proved to be indeed extraordinary. Their splendid mechanical properties attract a great interest among material scientists. Their wide range of electrical properties, from ballistic conductors to insulators, makes them ideal candidates for future, better electronics. The possibilities seem to be nearly unlimited, with proposed applications ranging from quantum computing to medicine. However, in order to make it all happen one day, we first need to explore and understand the physics and chemistry of carbon nanomaterials. This work focuses on production and characterization of materials and structures in which fullerenes and/or carbon nanotubes are the main ingredients, and which can be produced or modified under high-pressure – high-temperature (hp-hT) conditions. Raman and photoluminescence spectroscopy, X-ray diffraction and scanning probe microscopy were employed for characterization of the samples. The research presented in this thesis is spread over a rather wide range of carbon nanomaterials. To highlight some of the main results – the first hp-hT polymerization of C60 nanorods and the C60-cubane compound is reported. The polymerization mechanism in the latter case was identified to be radically different from that in pure C60. The pressure-temperature diagram of C60-cubane is presented. A comparative study of C60 and C70 peapods under extreme p-T conditions reveals how the confinement affects the fullerenes’ ability for polymerization. Finally, in situ resistance measurements on Rb4C60 under high pressure show that the semiconducting character of this material persists at least up to 2 GPa, contradicting earlier reports on the existence of an insulator-to-metal transition and providing an insight into conduction mechanisms in this anomalous intercalated compound.

Place, publisher, year, edition, pages
Umeå: Fysik , 2007. , 115 p.
Keyword [en]
fullerenes, carbon nanotubes, fullerene polymers, intercalation compounds, high pressure, Raman spectroscopy, X-ray diffraction, atomic force microscopy, phase transitions
National Category
Other Engineering and Technologies not elsewhere specified
Identifiers
URN: urn:nbn:se:umu:diva-1312ISBN: 978-91-7264-346-8 (print)OAI: oai:DiVA.org:umu-1312DiVA: diva2:140619
Public defence
2007-09-24, KB3A9, KBC-huset, Umeå Universitet, Umeå, 10:00 (English)
Opponent
Supervisors
Available from: 2007-08-28 Created: 2007-08-28 Last updated: 2015-09-28Bibliographically approved
List of papers
1. Synthesis of thin, rectangular C60 nanorods using m-xylene as shape controller
Open this publication in new window or tab >>Synthesis of thin, rectangular C60 nanorods using m-xylene as shape controller
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2006 (English)In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 18, no 14, 1883-1888 p.Article in journal (Refereed) Published
Abstract [en]

Thin, rectangular C60 nanorods in face-centered cubic structure are synthesized by using m-xylene as a shape controller. These unusual nanorods can easily grow on various substrates. The smallest nanorods have widths smaller than 30 nm. The nanorods are highly crystalline in single phase. A significant expansion of the lattice constant is also found in the C60 nanorods when their widths decrease below about 80 nm.

 

Place, publisher, year, edition, pages
Wiley Interscience, 2006
Keyword
C60, fullerenes, nanorods, Raman spectroscopy, m-xylene, synthesis, SEM, TEM, XRD, IR, AFM, evaporation, crystallization
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:umu:diva-11952 (URN)10.1002/adma.200502738 (DOI)
Note

Agnieszka Iwasiewicz-Wabnig

Available from: 2007-11-05 Created: 2007-11-05 Last updated: 2017-12-14Bibliographically approved
2. Photoluminescence properties of high-pressure-polymerized C60 nanorods in the orthorhombic and tetragonal phases.
Open this publication in new window or tab >>Photoluminescence properties of high-pressure-polymerized C60 nanorods in the orthorhombic and tetragonal phases.
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2006 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 89, no 18, 181925- p.Article in journal (Refereed) Published
Abstract [en]

C60nanorods in two polymeric phases have been synthesized under differenthigh pressure and high temperature conditions. Orthorhombic and tetragonal phaseshave been identified from Raman spectra. The rod shape canbe kept under quasihydrostatic pressure. The photoluminescence intensity of thepolymeric C60 nanorods has been greatly enhanced compared with thatof pristine C60 nanorods. The main fluorescence band shifted from730  nm in the unpolymeric phase to 748  nm and near infrared780  nm in the orthorhombic and tetragonal phases, respectively. The enhancedphotoluminescence with tunable frequency for different polymeric C60 nanorods suggestspotential applications in luminescent nanomaterials.

Keyword
C60, fullerenes, high pressure, polymers, nanorods, photoluminiscence, Raman spectroscopy, orthorhombic, tetragonal
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:umu:diva-11949 (URN)10.1063/1.2378396 (DOI)
Note

Agnieszka Iwasiewicz-Wabnig

Available from: 2007-11-05 Created: 2007-11-05 Last updated: 2017-12-14Bibliographically approved
3. Polymerization of the rotor-stator compound C60-cubane under pressure.
Open this publication in new window or tab >>Polymerization of the rotor-stator compound C60-cubane under pressure.
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2007 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 75, no 2, 024114- p.Article in journal (Refereed) Published
Abstract [en]

Cubane, C8H8, can be inserted into the octahedral voids of fullerene lattices to create a family of rotor-stator compounds. We have investigated the structural phase behavior of C60 center dot C8H8 by annealing a number of samples for up to 3 h at selected temperatures in the range 380-870 K under pressures up to 2 GPa. The high-pressure treated materials were then investigated under ambient conditions using Raman spectroscopy and x-ray diffraction. C60 center dot C8H8 is found to have at least five different structural phases depending on treatment conditions. In addition to the known cubic and orthorhombic structures observed at atmospheric pressure, we find two polymeric states with pseudocubic and pseudoorthorhombic structures, respectively, based on the two original lattices and created by heating in different pressure ranges. These materials are believed to be copolymers of C60 and decomposition products of cubane. In contrast to the polymeric states of C60 the present polymer structures are determined by the topology of the original lattices rather than by the molecular structure. Above 700 K we find a carbon-rich amorphous state created when the cubane finally decomposes, releasing its hydrogen content in the form of hydrocarbons.

Keyword
polymerisation, fullerenes, C60, cubane, annealing, high pressure, Raman spectroscopy, X-ray diffraction, co-polymer, voids (solid)
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:umu:diva-11956 (URN)10.1103/PhysRevB.75.024114 (DOI)
Note

Selected for Virtual J. Nanoscale Sci. & Technol. vol. 15, issue 5 (Febr. 2007). Selected for Virtual J. Biol. Phys. Res. vol. 13, issue 3 (Febr. 2007)

Available from: 2007-10-19 Created: 2007-10-19 Last updated: 2017-12-14Bibliographically approved
4. Pressure-temperature phase diagram of the rotor-stator compound C60-cubane
Open this publication in new window or tab >>Pressure-temperature phase diagram of the rotor-stator compound C60-cubane
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2007 (English)In: Solid State Communications, ISSN 0038-1098, E-ISSN 1879-2766, Vol. 143, no 4-5, 208-212 p.Article in journal (Refereed) Published
Abstract [en]

When the rotor–stator compound C60·C8H8 is treated at temperatures above about 450 K under high-pressure conditions, fullerene-based copolymers are formed. Earlier results have shown the existence of two types of polymers, a “low-pressure” pseudo-cubic copolymer similar to that formed at atmospheric pressure, and a “high-pressure” phase tentatively identified as a pseudo-orthorhombic copolymer structurally based on the known low-temperature phase. In this communication we show that the reaction boundary between the polymers occurs at pressures near 1 GPa. From this result it follows that the slope of the cubic–orthorhombic phase line in the pristine material is 305 K GPa−1, significantly larger than the slope observed for the corresponding rotational transition in pure C60.

Keyword
Fullerenes, Raman spectroscopy, X-ray diffraction, high pressure, cubane, rotor-stator compound, fullerene co-polymer
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:umu:diva-16867 (URN)10.1016/j.ssc.2007.05.029 (DOI)
Available from: 2007-10-18 Created: 2007-10-18 Last updated: 2017-12-14Bibliographically approved
5. Discriminated structural behaviour of C60 and C70 peapods under extreme conditions
Open this publication in new window or tab >>Discriminated structural behaviour of C60 and C70 peapods under extreme conditions
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2007 (English)In: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 79, no 5, 56003- p.Article in journal (Refereed) Published
Abstract [en]

We studied structural changes in C60 and C70 peapods—i.e. C60 and C70 chains inserted inside single-walled carbon nanotubes—when submitted to high pressure and temperature conditions. X-ray diffraction experiments showed that while C60 molecules polymerize inside nanotubes at pressures and temperatures consistent with polymerization in bulk C60 phases, no polymerization is observed in C70 peapods, even at pressures and temperatures above the threshold for polymerization in bulk C70. Tubular confinement in the nanotube container prevents the monomers to rearrange in the way needed for polymerization. This result testifies for the strong influence of confinement on the behaviour of C70.

Keyword
Peapods, C60@SWNT, C70@SWNT, high pressure, fullerene polymer, X-ray diffraction, topochemical reaction
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:umu:diva-16872 (URN)10.1209/0295-5075/79/56003 (DOI)
Available from: 2007-10-18 Created: 2007-10-18 Last updated: 2017-12-14Bibliographically approved
6. Comparative study of pressure-induced polymerization of C60 nanorods and single crystals
Open this publication in new window or tab >>Comparative study of pressure-induced polymerization of C60 nanorods and single crystals
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2007 (English)In: Journal of Physics Condensed Matter, ISSN 0953-8984, Vol. 19, no 42, 425207- p.Article in journal (Refereed) Published
Abstract [en]

In this paper, we report a comparative study of pressure-induced polymerization in C60 nanorods and bulk single crystals, treated simultaneously under various pressures and temperatures in the same experiment. For both materials, orthorhombic, tetragonal and rhombohedral phases have been produced under high pressure and high temperature. The structures have been identified and compared between the two sample types by Raman and photoluminescence spectroscopy. There are differences between the Raman and photoluminescence spectra from the two types of materials for all polymeric phases, but especially for the tetragonal phase. From the comparison between nanorods and bulk samples, we tentatively assign photoluminescence peaks for various polymeric phases.

Place, publisher, year, edition, pages
Bristol: Institute of Physics, 2007
Keyword
C60, polymer, nanorod, Raman scattering, Photoluminescence, orthorhombic, tetragonal, rhombohedral, high pressure
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:umu:diva-16952 (URN)10.1088/0953-8984/19/42/425207 (DOI)
Available from: 2007-10-23 Created: 2007-10-23 Last updated: 2015-09-28Bibliographically approved
7. Low-temperature optical studies of C60-cubane rotor-stator compound
Open this publication in new window or tab >>Low-temperature optical studies of C60-cubane rotor-stator compound
2008 (English)In: Journal of Physics: Conference Series, vol. 100, part 5: Proceedings of the joint 17th International Vacuum Congress (IVC-17), 13th International Conference on Surface Science (ICSS-13), and the 2007 International Conference on Nanoscience and Technology (ICN+T 2007), 2–6 July 2007, Stockholm, Sweden, Institute of Physics (IOP), 2008, 052091- p.Conference paper, Published paper (Refereed)
Abstract [en]

We present here low-temperature Raman and photoluminescence spectra of the C60-cubane rotor-stator compound. We show the continuous evolution of Raman spectra between 77 K and room temperature, with no sharp transition visible at 140 K, the orientational ordering temperature. Low-temperature luminescence spectra of C60 in C60-cubane compound are found to be shifted and better resolved then spectra for pristine C60 at the corresponding temperatures, showing relatively weaker intermolecular interactions. In fact, the solid-state luminescence of C60-cubane is similar to free-molecule C60 luminescence spectra.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2008
Series
Journal of Physics Conference Series, ISSN 1742-6596 ; 100
Keyword
Fullerenes, photoluminescence, Raman spectroscopy, high pressure, cubane, rotor-stator compound, fullerene co-polymer
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:umu:diva-9420 (URN)10.1088/1742-6596/100/5/052091 (DOI)
Conference
Joint 17th International Vacuum Congress (IVC-17), 13th International Conference on Surface Science (ICSS-13), and the 2007 International Conference on Nanoscience and Technology (ICN+T 2007), 2–6 July 2007, Stockholm, Sweden
Note

Open access

Available from: 2008-04-01 Created: 2008-04-01 Last updated: 2015-09-28Bibliographically approved
8. No insulator-metal transition in Rb4C60 under pressure below 2 GPa
Open this publication in new window or tab >>No insulator-metal transition in Rb4C60 under pressure below 2 GPa
(English)In: Physical Review BArticle in journal (Refereed) Submitted
Identifiers
urn:nbn:se:umu:diva-2475 (URN)
Available from: 2007-08-28 Created: 2007-08-28 Last updated: 2015-09-28Bibliographically approved
9. Strain effects on Raman spectra of tetragonally polymerized C60 single crystals
Open this publication in new window or tab >>Strain effects on Raman spectra of tetragonally polymerized C60 single crystals
(English)Manuscript (Other academic)
Identifiers
urn:nbn:se:umu:diva-2476 (URN)
Available from: 2007-08-28 Created: 2007-08-28 Last updated: 2015-09-28Bibliographically approved

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