Polarized Raman Study of Aligned Multiwalled Carbon Nanotubes

Rao, Apparao M.; Jório, Ado; Pimenta, M. A.; Dantas, M. S. S.; Saito, Riichiro; Dresselhaus, G.; Dresselhaus, M. S.

doi:10.1103/physrevlett.84.1820

Cited by 356 publications

(232 citation statements)

References 14 publications

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“…This characterization relies on the fact that the Raman intensity of the tangential mode of SWNTs is sensitive to the polarizer angle. The tangential mode intensity reaches a maximum when the polarized light is parallel to the nanotube axis 27 and decreases gradually as the angle of the polarizer increases from 08 (parallel to the nanotube axis) to 908 (perpendicular to the nanotube axis). The intensity begins to increase again as the angle of the polarizer increases from 908 to 1808.…”

Section: Resultsmentioning

confidence: 99%

Aligned single‐wall carbon nanotube polymer composites using an electric field

Park

Wilkinson

Banda

et al. 2006

J Polym Sci B Polym Phys

223

120

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While high shear alignment has been shown to improve the mechanical properties of single-wall carbon nanotube (SWNT)-polymer composites, this method does not allow for control over the electrical and dielectric properties of the composite and often results in degradation of these properties. Here, we report a novel method to actively align SWNTs in a polymer matrix, which permits control over the degree of alignment of the SWNTs without the side effects of shear alignment. In this process, SWNTs were aligned via AC field-induced dipolar interactions among the nanotubes in a liquid matrix followed by immobilization by photopolymerization under continued application of the electric field. Alignment of SWNTs was controlled as a function of magnitude, frequency, and application time of the applied electric field. The degree of SWNT alignment was assessed using optical microscopy and polarized Raman spectroscopy, and the morphology of the aligned nanocomposites was investigated by high-resolution scanning electron microscopy. The structure of the field induced aligned SWNTs was intrinsically different from that of shear aligned SWNTs. In the present work, SWNTs are not only aligned along the field, but also migrate laterally to form thick, aligned SWNT percolative columns between the electrodes. The actively aligned SWNTs amplify the electrical and dielectric properties of the composite. All of these properties of the aligned nanocomposites exhibited anisotropic characteristics, which were controllable by tuning the applied field parameters.

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Section: Resultsmentioning

confidence: 99%

Aligned single‐wall carbon nanotube polymer composites using an electric field

Park

Wilkinson

Banda

et al. 2006

J Polym Sci B Polym Phys

223

120

View full text Add to dashboard Cite

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“…However, some discrepancies with theoretic predictions and unusual G band intensity behaviour are found from individual SWCNT of even the simplest tube system due to depolarization effects or complex multipolar electronic resonance antenna effects [22]. Here, when compared to a SWCNT, the single TGC is a complex integrated system of co-axial tubes and the depolarization effects should be relaxed like in MWCNTs [21], leading to optical response unchanged for the polarized light. This can't be simply ascribed to the diameter variation of the onedimensional structural TGC [23].…”

Section: Methodsmentioning

confidence: 99%

“…The slight variation in the intensities may be due to the system and measurement errors, but at 20º there is a slight increase in the ω -G peak which we attribute to resonance in the innermost nanotube G mode. Obviously, these TGCs are different from SWCNTs and aligned MWCNTs [20,21], in which both show strong angular dependence of the polarized G band with the highest intensity occurring when the incident radiation is polarized parallel to the tube axis. However, some discrepancies with theoretic predictions and unusual G band intensity behaviour are found from individual SWCNT of even the simplest tube system due to depolarization effects or complex multipolar electronic resonance antenna effects [22].…”

Section: Methodsmentioning

confidence: 99%

Directly observable G band splitting in Raman spectra from individual tubular graphite cones

Shang

Silva

Jiang

et al. 2011

Carbon

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“…Besides its success in the characterization of a large range of materials, 1 Raman spectroscopy has also developed into an invaluable tool for the characterization of nanotubes. Since the first characterization of ͑disordered͒ carbon nanotube ͑CNT͒ samples, 2 the technique has been refined, including, e.g., polarized Raman studies of aligned nanotubes 3 and isolated tubes. 4 On the theoretical side, nonresonant Raman intensities of CNTs have been calculated within the bondpolarizability model.…”

mentioning

confidence: 99%

Raman spectra of BN nanotubes:Ab initioand bond-polarizability model calculations

et al. 2005

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We present ab initio calculations of the nonresonant Raman spectra of zigzag and armchair BN nanotubes. In comparison, we implement a generalized bond-polarizability model where the parameters are extracted from first-principles calculations of the polarizability tensor of a BN sheet. For light polarization along the tube axis, the agreement between model and ab initio spectra is almost perfect. For perpendicular polarization, depolarization effects have to be included in the model in order to reproduce the ab initio Raman intensities. DOI: 10.1103/PhysRevB.71.241402 PACS number͑s͒: 78.30.Ϫj, 78.20.Bh, 81.07.De, 71.15.Mb Besides its success in the characterization of a large range of materials, 1 Raman spectroscopy has also developed into an invaluable tool for the characterization of nanotubes. Since the first characterization of ͑disordered͒ carbon nanotube ͑CNT͒ samples, 2 the technique has been refined, including, e.g., polarized Raman studies of aligned nanotubes 3 and isolated tubes. 4 On the theoretical side, nonresonant Raman intensities of CNTs have been calculated within the bondpolarizability model. 5,6 The empirical parameters of this model are adapted to fit experimental Raman intensities of fullerenes and hydrocarbons. However, the transferability of the parameters and the quantitative performance in nanotubes, in particular distinguishing between metallic and semiconducting tubes, is still not clear.In this Rapid Communication, we report on the Raman spectra of boron nitride nanotubes ͑BNNTs͒. 7,8 Recently, synthesis of BNNTs in gram quantities has been reported. 9 Their characterization through Raman and infrared spectroscopy is expected to play an important role. However, due to difficulties with the sample purification no experimental data on contamination-free samples has been reported. Ab initio 10 and empirical 11,12 phonon calculations have determined the position of the peaks in the spectra. However, due to missing bond-polarizability parameters for BN, the Raman intensities have been so far addressed using the model bondpolarizability parameters of carbon. 12 Only the intensities of high-frequency modes were presented, as it was argued that the intensity of low-frequency modes are very sensitive to the bond-polarizability values. 12 Here, we derive the polarizability parameters for BN sp 2 bonds from a single hexagonal BN sheet by calculating the polarizability tensor and its variation under deformation. We compare the resulting spectra for BNNTs with full ab initio calculations. We derive conclusions about the general applicability of the bondpolarizability model for semiconducting CNTs.In nonresonant first-order Raman spectra, peaks appear at the frequencies of the optical phonons with null wave vectors. The intensities I are given in the Placzek approximation 1 as͑1͒Here e i ͑e s ͒ is the polarization of the incident ͑scattered͒ light and n = ͓exp͑ប / k B T͒ −1͔ −1 with T being the temperature. The Raman tensor A iswhere w k␥ is the kth Cartesian component of atom ␥ of the th ortho...

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Polarized Raman Study of Aligned Multiwalled Carbon Nanotubes

Cited by 356 publications

References 14 publications

Aligned single‐wall carbon nanotube polymer composites using an electric field

Aligned single‐wall carbon nanotube polymer composites using an electric field

Directly observable G band splitting in Raman spectra from individual tubular graphite cones

Raman spectra of BN nanotubes:Ab initioand bond-polarizability model calculations

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