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Träfflista för sökning "WFRF:(Zou Bo) ;pers:(Wågberg Thomas)"

Sökning: WFRF:(Zou Bo) > Wågberg Thomas

  • Resultat 1-6 av 6
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1.
  • Zou, Yonggang, et al. (författare)
  • Raman spectroscopy study of carbon nanotube peapods excited by near-IR laser under high pressure
  • 2007
  • Ingår i: Physical Review B. - 0163-1829. ; 76:19, s. 195417-
  • 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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2.
  • Zou, Yonggang, et al. (författare)
  • Rotational dynamics of confined C60 from near-infrared Raman studies under high pressure
  • 2009
  • Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 106:52, s. 22135-22138
  • Tidskriftsartikel (refereegranskat)abstract
    • Peapods present a model system for studying the properties of dimensionally constrained crystal structures, whose dynamical properties are very important. We have recently studied the rotational dynamics of C60 molecules confined inside single walled carbon nanotube (SWNT) by analyzing the intermediate frequency mode lattice vibrations using near-infrared Raman spectroscopy. The rotation of C60 was tuned to a known state by applying high pressure, at which condition C60 first forms dimers at low pressure and then forms a single-chain, nonrotating, polymer structure at high pressure. In the latter state the molecules form chains with a 2-fold symmetry. We propose that the C60 molecules in SWNT exhibit an unusual type of ratcheted rotation due to the interaction between C60 and SWNT in the “hexagon orientation,” and the characteristic vibrations of ratcheted rotation becomes more obvious with decreasing temperature.
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3.
  • Jiang, Linhai, et al. (författare)
  • Controlled Synthesis of CeO2/Graphene Nanocomposites with Highly Enhanced Optical and Catalytic Properties
  • 2012
  • Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 116:21, s. 11741-11745
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper, CeO2 nanocubes with the (200)-terminated surface/graphene sheet composites have been prepared successfully by a simple hydrothermal method. It is found that the CeO2 nanocubes with high crystallinity and specific exposed surface are well dispersed on well-exfoliated graphene surface. The (200)-terminated surface/graphene sheet composites modified electrode showed much higher sensitivity and excellent selectivity in its catalytic performance compared to a CeO2 nanoparticle-modified electrode. The photoluminescence intensity of the CeO2 anchored on graphene is about 30 times higher than that of pristine CeO2 crystals in air. The higher oxygen vacancy concentration in CeO2 is supposed to be an important cause for the higher photoluminescence and better electrochemical catalytic performance observed in the (200)-terminated surface/graphene sheet composites. Such ingenious design of supported well-dispersed catalysts in nanostructured ceria catalysts, synthesized in one step with an exposed high-activity surface, is important for technical applications and theoretical investigations.
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4.
  • Liu, Dedi, et al. (författare)
  • Pressure-induced phase transitions of C70 nanotubes
  • 2011
  • Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society. - 1932-7447 .- 1932-7455. ; 115:18, s. 8918-8922
  • 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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5.
  • Ma, Honglei, et al. (författare)
  • Synchrotron X-ray diffraction and infrared spectroscopy studies of C60H18 under high pressure
  • 2010
  • Ingår i: Journal of Physical Chemistry Letters. - : American Chemical Society. - 1948-7185 .- 1948-7185. ; 1:4, s. 714-719
  • Tidskriftsartikel (refereegranskat)abstract
    • In situ high-pressure angle-dispersive synchrotron X-ray diffraction and high-pressure mid-infrared (IR) spectrum measurements of C60H18 were carried out up to 32 and 10.2 GPa, respectively. Our diffraction data indicated that the fcc structure of C60H18 was stable up to 32 GPa. The bulk modulus B0 was determined to be 21 ± 1.16 GPa, about 40% higher than that of C60. The C−H vibrations still existed up to 10.2 GPa, and the vibrational frequencies decreased with increasing pressure. IR-active vibrational frequencies and their corresponding eigenvectors of C60H18 were simulated by DMOL3. The effects of the hydrogen atoms attached to the fullerene molecular cage on the stability of the structure under high pressure are discussed.
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6.
  • Liu, Dedi, et al. (författare)
  • High pressure and high temperature induced polymerization of C60 nanotubes
  • 2011
  • Ingår i: CrystEngComm. - : Royal Society of Chemistry. - 1466-8033 .- 1466-8033. ; 13:10, s. 3600-3605
  • Tidskriftsartikel (refereegranskat)abstract
    • C60 nanotubes with outer diameters ranging from 400–800 nm were polymerized at 1.5 GPa, 573 K and 2.0 GPa, 700 K, respectively. Raman and photoluminescence spectroscopy were employed to characterize the polymeric phases of the treated samples. Both Raman and photoluminescence spectra showed that the C60 nanotubes transformed into the dimer and orthorhombic phases under the two different conditions, respectively. The photoluminescence peaks were tuned from visible to near infrared range. Comparative studies indicated that C60 nanotubes were more difficult to polymerize than bulk C60 material under the same conditions due to the nanoscale size effect in the C60 nanotubes.
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  • Resultat 1-6 av 6

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