| 1. |
- Cui, Wen, et al.
(författare)
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Synthesis of alkali-metal-doped C60 nanotubes
- 2011
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Ingår i: Diamond and Related Materials. - : Elsevier BV. ; , s. 93-96
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Konferensbidrag (refereegranskat)abstract
- C60 nanotubes have been synthesized by a solution–solution method. After degassing in a dynamic vacuum, the C60 nanotubes were doped with alkali metals by means of vapor evaporation method. Different temperatures have been studied to evaporate the alkali metals for the doping experiments. Raman spectrum was further employed to analyze the doping concentration of the obtained samples. It was found that all three alkali metals (Li, Na and K) used can be efficiently doped into the C60 nanotubes, forming AxC60 nanotubes. The doping concentration of Li, Na changed from low to high level, depending on the experiment temperatures, while K doping always gave saturated doping. The melt points, the ionic sizes and vapor pressures of alkali metals were thought to affect the final doping results.
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| 2. |
- Liu, Dedi, et al.
(författare)
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Pressure-induced phase transitions of C70 nanotubes
- 2011
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society. - 1932-7447 .- 1932-7455. ; 115:18, s. 8918-8922
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Tidskriftsartikel (refereegranskat)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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| 3. |
- Wang, Lin, et al.
(författare)
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Synthesis and high pressure induced amorphization of C60 nanosheets
- 2007
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 91:10, s. 103112-
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Tidskriftsartikel (refereegranskat)abstract
- C-60 nanosheets with thicknesses in the nanometer range were synthesized by a simple method. Compared to bulk C-60, the lattice of the nanosheets is expanded by about 0.4%. In situ Raman spectroscopy and energy-dispersive x-ray diffraction under high pressures have been employed to study the structure of the nanosheets. The studies indicate that the bulk modulus of the C-60 nanosheets is significantly larger than that of bulk C-60. The C-60 cages in nanosheets can persist at pressures over 30 GPa, 3 GPa higher than for bulk C-60. These results suggest that C-60 crystals in even small size will be a potential candidate of superhard materials.
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| 4. |
- Liu, Dedi, et al.
(författare)
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Effects of alcohols on shape-tuning and luminescence-enhancing of C70 nanocrystals
- 2013
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Ingår i: Optical materials (Amsterdam). - : Elsevier. - 0925-3467 .- 1873-1252. ; 36:2, s. 449-454
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Tidskriftsartikel (refereegranskat)abstract
- C70 nanotubes, nanorods and nanoparticles were produced by introducing a series of alcohols as precipitant into a C70/m-xylene solution. The effects of alcohols with different carbon chain lengths on the shape control of C70 nanocrystals were investigated. Alcohols with more than two carbon atoms in the longest chain linked to the hydroxyl groups induced the formation of C70 nanotube/rods. In contrast, alcohols containing two or fewer carbon atoms resulted in C70 nanoparticles. Structural analysis indicated that alcohol molecules exist in the C70 nanocrystals, forming solvated structures. The freshly formed C70 nanotubes and nanoparticles have orthorhombic and hexagonal solvated structures, respectively. Room temperature photoluminescence was further carried out on the solvated C70 nanocrystals to investigate their optical properties. We found that the luminescence intensities of C70 nanocrystals were significantly enhanced by the introduction of alcohols.
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| 5. |
- Liu, Dedi, et al.
(författare)
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In situ Raman and photoluminescence study on pressure-induced phase transition in C60 nanotubes
- 2012
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Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 43:6, s. 737-740
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Tidskriftsartikel (refereegranskat)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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| 6. |
- Liu, Dedi, et al.
(författare)
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Photoluminescence changes of C70 nano/submicro-crystals induced by high pressure and high temperature
- 2016
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Hollow C70 nano/submicrocrystals with a fcc lattice structure were treated under various high pressure and high temperature conditions. The energy band structure was visibly changed by the high pressure and high temperature treatment, and the luminescence of the polymerized C70 nano/submicrocrystals was tuned from the visible to the near infrared range. In-situ high pressure experiments at room temperature indicate that pressure plays a key role in the tuning of band gap and PL properties in C70 nanotubes, and temperature plays an important role in the formation of stable intermolecular bonds and thus to define the final red-shift of the PL peaks. The polymeric phases of C70 nanocrystals treated at high pressure and high temperature were identified from Raman spectra, which changed from monomers to a dimer-rich phase and finally to a phase containing larger, disordered C70 oligomers.
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| 7. |
- Wang, Lin, et al.
(författare)
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High-pressure studies of Nano/sub-micrometer C70 rods
- 2005
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Ingår i: High Energy Physics and Nuclear Physics B. - 0254-3052. ; 29:Supplement, s. 112-115
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Tidskriftsartikel (refereegranskat)abstract
- We have successfully synthesized C-70 rods in nano/sub-micrometers scale by evaporating solvent method. The diameter of the as grown C-70 rods is similar to 500 nm, and the length is similar to 10 mu m. The EDXD pattern and Raman spectroscopy for as -grown sample indicate that the as grown C-70 rod is in hcp structure. The pressure-induced structural phase transition has been studied by using DAC combined with EDXD and Raman spectroscopy methods under quasi-hydrostatic pressure up to 26.1GPa. It is found that hcp structure transforms into amorphous phase for C-70 rods in the pressure range from 23.3 to 26.1GPa, which is higher than the transformation pressure for bulk C-70 crystals. The phase transition is irreversible and it is induced by the collapse of C-70 cage.
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| 8. |
- Hou, Yuanyuan, et al.
(författare)
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Comparative study of pressure-induced polymerization of C60 nanorods and single crystals
- 2007
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Ingår i: Journal of Physics Condensed Matter. - Bristol : Institute of Physics. - 0953-8984 .- 1361-648X. ; 19:42, s. 425207-
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Tidskriftsartikel (refereegranskat)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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| 9. |
- Hou, Yuanyuan, et al.
(författare)
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Photoluminescence properties of high-pressure-polymerized C60 nanorods in the orthorhombic and tetragonal phases.
- 2006
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 89:18, s. 181925-
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Tidskriftsartikel (refereegranskat)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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| 10. |
- Liu, Bingbing, et al.
(författare)
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High pressure and high temperature induced polymeric C60 nanocrystal
- 2008
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Ingår i: Diamond and related materials, vol. 17, issue 4-5. - Amsterdam : Elsevier B.V.. ; , s. 620-623
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Konferensbidrag (refereegranskat)abstract
- In this paper, C60 nanosheets with polymeric phases have been obtained under various high pressures and high temperatures, including orthorhombic and tetragonal polymeric phases. The structures have been identified and compared with those of nanorods by photoluminescence and Raman spectroscopies. The main fluorescence band shifted from 1.70 eV in the monomeric phase to near infrared in the polymeric phase when pressure and temperature were increased. The difference of photoluminescence and Raman spectra between nanosheets and nanorods samples treated under the same conditions is probably caused by different polymerization degree in these samples because of different shapes.
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