Double Resonant Raman Scattering in Graphite

Institut fur Festkorperphysik, Technische Universitat Berlin, Hardenbergstrasse 36, 10623 Berlin, Germany.
Physical Review Letters (Impact Factor: 7.51). 01/2001; 85(24):5214-7. DOI: 10.1103/PhysRevLett.85.5214
Source: PubMed


We find that the electronic dispersion in graphite gives rise to double resonant Raman scattering for excitation energies up to 5 eV. As we show, the curious excitation-energy dependence of the graphite $D$ mode is due to this double resonant process resolving a long-standing problem in the literature and invalidating recent attempts to explain this phenomenon. Our calculation for the $D$-mode frequency shift ( $60{\mathrm{cm}}^{\ensuremath{-}1}/\mathrm{eV}$) agrees well with the experimental value.

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    • ", two phonon double resonance Raman scattering process) as well as D band (introduction of defects) [29] [30] "
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    ABSTRACT: Two ionic liquids (ILs) gels were prepared by grinding multiwall carbon nanotubes (MWCNTs) in two kinds of ILs, and their physical and tribological properties were investigated in detail. Results demonstrate that ILs gels possess high conductivity and excellent tribological performance which mainly depends on the synergy of ILs and MWCNTs with their respective outstanding characteristics. ILs modified MWCNTs through van der Waals and π–π stacting interactions significantly improve the dispersibility and compatibility with lubricants, which greatly enhances the conductivity and tribological properties of the lubricants. The friction mechanism for the ILs gels is attributed to the synergetic lubrication of ILs and MWCNTs.
    Tribology International 08/2015; 88. DOI:10.1016/j.triboint.2015.03.026 · 1.94 Impact Factor
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    • "I D /I G ratio was used to evaluate the average size of sp 2 domain and the degree of disorder and in present case the same is 0.14 which indicates high order and low degree of structural defects as a result of efficient deoxygenation of carboxyl , epoxy and other oxygen functional groups. The position, shape and full width half maximum (FWHM) of the second-order 2D band are sensitive to the number of layers in grapheme nanoplatelets (Ni et al. 2007; Ferrari and Robertson 2000; Ni et al. 2008), which may be triggered by double-resonant effect, in other words, may be caused by changes in electronic and vibrational properties (Thomson and Reich 2000) XPS scan was adopted to confirm remnant amount of oxygen functional groups that may impair the conductive network and electrochemically active surfaces for supercapacitor applications. The survey scan plotted in Fig. 8a shows C 1 s peak at about 284.78 eV and weak O 1 s peak at about 533.3 eV, which indicates lower oxygen content and the same has been confirmed by Fig. 8b and c. "
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    ABSTRACT: Graphene Nanoplatelets were fabricated from expandable graphite by rapid microwave exfoliation. Expandable graphite was irradiated in microwave in full power for 3 min, then was soaked in mixed nitric acid and sulphuric acid at volume ratio of 1:1 for 24 h and re-irradiated, thus graphene nanoplatelets (GNPs) were obtained. Extensive characterization techniques showed that GNPs synthesized using this technique are highly pure with traces of oxide groups and without serious unrecoverable oxidation damage. GNPs synthesized by microwave technique have high crystallinity, with variable size and little layer thickness.
    02/2015; DOI:10.1007/s13204-015-0415-9
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    • "The major Raman features of graphene and graphite are G band and 2D band ($2675 cm À1 ). 2D band originates from a two phonon double resonance in Raman scattering process [25]. 2D band is also denoted as G 0 . "
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