Theory of the tangentialG-band feature in the Raman spectra of metallic carbon nanotubes

Abstract

The tangential G-band in the Raman spectra of a metallic single-wall carbon nanotube shows two peaks: a higher frequency component having the Lorentzian shape and a lower-frequency component of lower intensity with a Breit-Wigner-Fano (BWF)-type lineshape. This interesting feature has been analyzed on the basis of phonon-plasmon coupling in a nanotube. It is shown that the low-lying optical plasmon corresponding to the tangential motion of the electrons on the nanotube surface can explain the observed features. In particular, this theory can explain occurrence of both the Lorentzian and BWF lineshapes in the G-band Raman spectra of metallic single-wall carbon nanotubes. Furthermore, the theory shows that the BWF peak moves to higher frequency, has a lower intensity and a lower half width at higher diameters of the nanotube. All these features are in agreement with experimental observations. 2

Fluorescent chemosensor for pyridine based on N-doped carbon dots

“…It is common the presence of G (1600 cm À1 ) and D (1300-1350 cm À1 ) bands in carbon graphitic materials; however, here a small intensity signal ascribable to the D band is detected [53]. These spectroscopic fingerprints suggest that the hydrothermal treatment reduces an important fraction of the oxygen groups of the lactose precursor, but it does not lead to a full reduction to unsaturated sp 2 species [54]. A band at 2950 cm À1 , observed only on disordered carbons, is suggested to be a defect-induced mode [55].…”

“…Now, the contribution due to the presence of carboxylic or carboxylate groups disappears and a new contribution at 286.1 eV is more intense. This contribution is due to the presence of CAOH and CAN groups [53,54]. The N 1s core level spectrum is asymmetric due to the existence of two contributions at 399.5 eV (86%) and 401.2 eV (14%) (Fig.…”

“…The contribution at low binding energy (284.8 eV) is the most intense and is assigned to the graphitic carbon and to adventitious carbon [51,52]. The contribution at 287.5 eV is mainly derived from the presence of carbonyl groups [52,53]; and finally, the weak contribution at 289.3 eV is due to carboxylic and carboxylate groups [51,54]. The C 1s core level spectrum of N-CDs can be also decomposed in three contributions at 284.8 eV (41%), 286.1 eV (47%) and 287.8 eV (12%), but showing marked differences with respect to that of CDs (Fig.…”

Dielectric behavior of biopolymer based composites containing multi wall carbon nanotubes: Effect of filler content and aspect ratio

“…8) display three prominent features: at 1575 cm À1 we can find the G band, due to the tangential vibrations of the graphitic sp 2 carbon atoms (E 2g symmetry). At 1330 cm À1 , the so-called D (defect) band, originating from the breathing mode of the disordered graphite structure (A 1g symmetry) is observed; this peak reflects the presence of amorphous carbon mainly localized at the nanotube edges rather than defects in the tube walls [22][23][24]. A third feature is located at 2670 cm À1 , with satellite components at 2905 and 2415 cm À1 .…”

Optical phonons in carbon nanotubes: Kohn anomalies, Peierls distortions, and dynamic effects

“…97 The downshift and the broadening of the G − peak in metallic tubes is commonly attributed to the onset of a Fano resonance between plasmons and the TO phonon. [90][91][92]97,98 Such phononplasmon coupling would either need 92 Thus, all the proposed theories for phonon-plasmon coupling 90,92,98 are qualitative, require the guess of several quantities, and fail to predict in a precise, quantitative, parameter-free way the observed line shapes and their diameter dependence.…”