| 1. |
- Hou, Yuanyuan, et al.
(author)
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Comparative study of pressure-induced polymerization of C60 nanorods and single crystals
- 2007
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In: Journal of Physics Condensed Matter. - Bristol : Institute of Physics. - 0953-8984 .- 1361-648X. ; 19:42, s. 425207-
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Journal article (peer-reviewed)abstract
- 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.
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| 2. |
- Hou, Yuanyuan, et al.
(author)
-
Photoluminescence properties of high-pressure-polymerized C60 nanorods in the orthorhombic and tetragonal phases.
- 2006
-
In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 89:18, s. 181925-
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Journal article (peer-reviewed)abstract
- 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.
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| 3. |
- Liu, Bingbing, et al.
(author)
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Effects of silver films with different nano-particle sizes on SERS of single-walled carbon nanotubes
- 2005
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In: Chemical Journal of the Chinese Universities. - 0251-0790. ; 26:10, s. 1930-1933
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Journal article (peer-reviewed)abstract
- Surface-enhanced Raman scattering (SERS) spectra of single-walled carbon nanotubes (SWCNTs) on silver films with different nano-particle sizes from 20 to 100 nm deposited on quartz and glass substrates were studied systematically. The characteristic Raman spectral features of SWCNT G-band and D-band were analyzed. The two bands show a similar tendency with the change of nano-particle size of silver on quartz and glass substrates. The position and the intensity of the G-band are less sensitive to the films' silver particle sizes in the studied range, indicating that hexagonal carbon rings are stable and have a weak interaction with silver films. The shape of the D-band depends on the silver size. The smaller the silver particle size, the more the contribution of high frequency vibrations to the D-band, indicating that disorder carbon has a strong interaction with the active silver films.
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| 4. |
- Liu, Bingbing, et al.
(author)
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High-pressure induced polymerization of C60 nanorods
- 2005
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In: Proceedings of the Joint 20th AIRAPT and 43rd EHPRG Conf. on High Pressure Science and Technology, Karlsruhe 2005. - 3923704496 ; , s. Nanomat-O133
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Conference paper (other academic/artistic)abstract
- C60 nanorods, about 200 nm in diameter and several micrometers in length and with a rectangular cross section, have been synthesized by a simple solution-growth method. Raman spectroscopy and TEM indicate that the C60 nanorods have a fcc crystalline structure similar to that of pristine C60. Nanorods were polymerized at high temperature and high pressure below 2 GPa. Two different polymeric structures, orthorhombic and tetragonal as determined by Raman spectroscopy, have been obtained under different high temperature and high pressure conditions. The high-pressure induced polymeric samples keep the original nanometer scale rod shape.
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| 5. |
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| 6. |
- Liu, Dedi, et al.
(author)
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In situ Raman and photoluminescence study on pressure-induced phase transition in C60 nanotubes
- 2012
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In: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 43:6, s. 737-740
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Journal article (peer-reviewed)abstract
- Single crystalline C60 nanotubes having face-centered-cubic structure with diameters in the nanometer range were synthesized by a solution method. In situ Raman and photoluminescence spectroscopy under high pressure were employed to study the structural stabilities and transitions of the pristine C60 nanotubes. A phase transition, probably because of the orientational ordering of C60 molecules, from face-centered-cubic structure to simple cubic structure occurred at the pressure between 1.46 and 2.26 GPa. At above 20.41 GPa, the Raman spectrum became very diffuse and lost its fine structure in all wavenumber regions, and only two broad and asymmetry peaks initially centered at 1469 and 1570cm-1 were observed, indicating an occurrence of amorphization. This amorphous phase remained to be reversible until 31.1 GPa, and it became irreversible to the ambient pressure after the pressure cycle of 34.3 GPa was applied.
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| 7. |
- Liu, Dedi, et al.
(author)
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Pressure-induced phase transitions of C70 nanotubes
- 2011
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In: The Journal of Physical Chemistry C. - : American Chemical Society. - 1932-7447 .- 1932-7455. ; 115:18, s. 8918-8922
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Journal article (peer-reviewed)abstract
- Single crystalline C70 nanotubes having a face-centered-cubic (fcc) structure with diameters on a nanometer scale were synthesized by a facile solution method. In situ high pressure Raman spectroscopy and X-ray diffraction have been employed to study the structural stability and phase transitions of the pristine sample. We show that the molecular orientation-related phase transition from the fcc structure to a rhombohedral structure occurs at about 1.5 GPa, which is 1 GPa higher than in bulk C70. Also, the C70 molecules themselves are more stable in the nanotubes than in bulk crystals, manifested by a partial amorphization at 20 GPa. The crystal structure of C70 nanotubes could partially return to the initial structure after a pressure cycle above 30.8 GPa, and the C70 molecules were intact up to 43 GPa. The bulk modulus of C70 nanotubes is measured to be 50 GPa, which is twice larger than that of bulk C70.
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| 8. |
- Liu, Dedi, et al.
(author)
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Synthesis and solid-state studies of self-assembled C60 microtubes
- 2011
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In: Diamond and Related Materials, vol. 20 issue 2. - : Elsevier BV. ; , s. 178-182
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Conference paper (peer-reviewed)abstract
- C60 microtubes were fabricated by a modified solution evaporation method, evaporating a solution of C60 in toluene in an atmosphere of m-xylene at room temperature. The C60 microtubes have outer diameters ranging from 2 to 8 μm. IR spectra, TG analysis and X-ray diffraction showed a solvated structure for the as-grown C60 microtubes. Through a gentle heat-treatment in vacuum, pure C60 microtubes with single crystalline fcc structure were obtained after the elimination of solvents. It is suggested that the C60 microtubes form through self-assembly from several individual C60 nanorods.
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| 9. |
- Pei, Cuiying, et al.
(author)
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Quasi 3D polymerization in C60 bilayers in a fullerene solvate
- 2017
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In: Carbon. - : Elsevier. - 0008-6223 .- 1873-3891. ; 124, s. 499-505
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Journal article (peer-reviewed)abstract
- The polymerization of fullerenes has been an interesting topic for almost three decades. A rich polymeric phase diagram of C60 has been drawn under a variety of pressure-temperature conditions. However, only linear or perpendicular linkages of C60 are found in the ordered phases. Here we used a unique bilayer structural solvate, C60∙1,1,2-trichloroethane (C60∙1TCAN), to generate a novel quasi-3D C60 polymer under high pressure and/or high temperature. Using Raman, IR spectroscopy and X-ray diffraction, we observe that the solvent molecules play a crucial role in confining the [2+2] cycloaddition bonds of C60s forming in the upper and lower layers alternately. The relatively long distance between the two bilayers restricts the covalent linkage extended in a single individual bilayer. Our studies not only enrich the phase diagram of polymeric C60, but also facilitate targeted design and synthesis of unique C60 polymers.
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| 10. |
- Shang, Yuchen, et al.
(author)
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Ultrahard bulk amorphous carbon from collapsed fullerene
- 2021
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In: Nature. - : Nature Publishing Group. - 0028-0836 .- 1476-4687. ; 599:7886, s. 599-604
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Journal article (peer-reviewed)abstract
- Amorphous materials inherit short- and medium-range order from the corresponding crystal and thus preserve some of its properties while still exhibiting novel properties1,2. Due to its important applications in technology, amorphous carbon with sp2 or mixed sp2–sp3 hybridization has been explored and prepared3,4, but synthesis of bulk amorphous carbon with sp3 concentration close to 100% remains a challenge. Such materials inherit the short-/medium-range order of diamond and should also inherit its superior properties5. Here, we successfully synthesized millimetre-sized samples—with volumes 103–104 times as large as produced in earlier studies—of transparent, nearly pure sp3 amorphous carbon by heating fullerenes at pressures close to the cage collapse boundary. The material synthesized consists of many randomly oriented clusters with diamond-like short-/medium-range order and possesses the highest hardness (101.9 ± 2.3 GPa), elastic modulus (1,182 ± 40 GPa) and thermal conductivity (26.0 ± 1.3 W m−1 K−1) observed in any known amorphous material. It also exhibits optical bandgaps tunable from 1.85 eV to 2.79 eV. These discoveries contribute to our knowledge about advanced amorphous materials and the synthesis of bulk amorphous materials by high-pressure and high-temperature techniques and may enable new applications for amorphous solids.
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