| 1. |
- Zou, Yonggang, et al.
(författare)
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Effective polymerization of C60 in SWNTs under high pressure and simultaneous UV light irradiation
- 2007
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Ingår i: Acta Physica Sinica (Wuli Xuebao). - 1000-3290. ; 56:9, s. 5172-5175
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Tidskriftsartikel (refereegranskat)abstract
- The C-60 @ SWNT ( peapod) samples were prepared by the vapor diffusion method. Polymerization of C60 molecules in single walled carbon nanotubes (SWNTs) under high pressure and simultaneous irradiation of UV laser (325 nm) has been carried out for the first time by using diamond anvil cell. Raman spectra of the peapod samples decompressed from high pressure indicated that C60 molecules form one-dimensional orthorhombic polymer in SWNTs under UV laser irradiation at a high pressure of 21.5 GPa, which is lower than that for the polymerization of samples induced by high pressure only. The polymerization is an irreversible phase transition in the peapod.
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| 2. |
- 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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| 3. |
- Yao, Mingguang, et al.
(författare)
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Raman signature to identify the structural transition of single-wall carbon nanotubes under high pressure
- 2008
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 78:20
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Tidskriftsartikel (refereegranskat)abstract
- Raman spectra of single-walled carbon nanotubes (SWNTs) with diameters of 0.6–1.3 nm have been studied under high pressure. A “plateau” in the pressure dependence of the G-band frequencies was observed in all experiments, both with and without pressure transmission medium. Near the onset of the G-band plateau, the corresponding radial breathing mode (RBM) lines become very weak. A strong broadening of the full width at half maximum of the RBMs just before the onset of the G-band plateau suggests that a structural transition starts in the SWNTs. Raman spectra from SWNTs released from different pressures also indicate that a significant structural transition occurs during the G-band plateau process. Simulations of the structural changes and the corresponding Raman modes of a nanotube under compression show a behavior similar to the experimental observations. Based on the experimental results and the theoretical simulation, a detailed model is suggested for the structural transition of SWNTs, corresponding to the experimentally obtained Raman results in the high-pressure domain.
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| 4. |
- Zou, Yonggang, et al.
(författare)
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Raman spectroscopy study of carbon nanotube peapods excited by near-IR laser under high pressure
- 2007
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Ingår i: Physical Review B. - 0163-1829. ; 76:19, s. 195417-
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Tidskriftsartikel (refereegranskat)abstract
- A resonant Raman spectroscopy study has been carried out under high pressure, using a diamond anvil cell,on carbon nanotube peapods (C60@SWNT) synthesized in high yield in our laboratory. The Raman signal wasexcited by a near IR laser (830 nm) to avoid photopolymerization of C60 and thus obtain the intrinsic vibrationalinformation on the C60 molecules in the nanotubes. It is found that the surrounding tubes create aneffective pressure on the encapsulated C60 due to tube-fullerene interactions, resulting in a shift of the intrinsicAg(2) vibrational mode to 1474 cm−1 at ambient pressure. High pressure Raman spectroscopy indicates that(C60)2 dimers form near 1 GPa, and that a further polymerization of C60 occurs near 23 GPa, creating linearchains of covalently linked C60 molecules in the tubes.
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| 5. |
- 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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| 6. |
- 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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| 7. |
- Hou, Yuanyuan, et al.
(författare)
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Pressure-induced polymerization of nano- and submicrometer C60 rods into a rhombohedral phase
- 2006
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Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614. ; 423:1-3, s. 215-219
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Tidskriftsartikel (refereegranskat)abstract
- C-60 rods with nano- and submicrometer dimensions were polymerized at 4.5 GPa and 973 K. Raman spectroscopy showed that the material transformed into a rhombohedral polymeric structure under high pressure and high temperature (HPHT) conditions. The HPHT polymerized samples keep the original rod shape. The position dependence of photoluminescence (PL) spectra have been studied on the rhombohedral polymer C60 rods at room temperature. The intensity of the 1.74 eV peak from the rhombohedral phase varies systematically between the edge of and the middle of the rod. Our results indicate that the 1.74 eV peak originates from surface defects.
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| 8. |
- 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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| 9. |
- Liu, Bingbing, et al.
(författare)
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High pressure and high temperature induced polymeric C60 nanorods and their photoluminiscence properties.
- 2007
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Ingår i: Materials Research at High Pressure. - Warrendale : Maerials Research Society. - 9781558999442 ; , s. 99-103
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Konferensbidrag (refereegranskat)abstract
- We report that C60 nanorods of three polymeric phases have been synthesized under high pressure and high temperature and that the photoluminescence properties of these polymeric nanorods also have been studied. C60 nanorods were fabricated by a facile solution evaporation method. Raman spectra indicate that this material transformed into orthorhombic, tetragonal and rhombohedral polymeric phases under various high pressure and high temperature conditions. SEM measurements show that the shape of the nanorods can be kept under quasi-hydrostatic pressure condition. The photoluminescence intensity of the polymeric C60 nanorods has been enhanced compared with that of the pristine C60 nanorods. 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 enhanced fluorescence with adjustable frequency for different polymeric C60 nanorods makes possible potential application in luminescent nanomaterials.
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| 10. |
- Liu, Bingbing, et al.
(författare)
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High-pressure induced polymerization of C60 nanorods
- 2005
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Ingår i: 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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Konferensbidrag (övrigt vetenskapligt/konstnärligt)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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