Raman excitation profile of the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>G</mml:mi></mml:math>band in single-chirality carbon nanotubes

Moura, Luciano G.; Moutinho, Marcus V. O.; Venezuela, P.; Fantini, C.; Righi, A.; Strano, Michael S.; Pimenta, M. A.

doi:10.1103/physrevb.89.035402

Cited by 19 publications

(27 citation statements)

References 16 publications

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“…Such a picture provides a useful basis for quantifying the magnitudes of the observed REP asymmetries. Next, we apply the third-order Raman analysis of Moura et al 17 and demonstrate that it is insufficient for modeling the observed asymmetries in the armchair data. We finish with a description of how the nonCondon model may be translated to a condensed-matter formalism in which phonon-mediated mixing of excitonic states is shown to be a viable route for introducing the asymmetric behavior.…”

Section: Resultsmentioning

confidence: 99%

“…We begin here a comparison of two such potential approaches. The first is an application to our data of the third-order, non-excitonic description put forward by Moura et al 17 . The second incorporates non-Condon effects into a condensed matter formalism via the introduction of a state-mixing description.…”

Section: B Evaluation Of Third-order Non-excitonic Quantum Model Fmentioning

confidence: 99%

“…Moura et al argued that in order to reproduce the experimentally observed asymmetry in the REPs it is necessary to perform the sum in Eq. 5 for all possible values of k in the nanotube Brillouin zone, thus requiring a detailed knowledge of the matrix elements and how they vary throughout the nanotube reciprocal space 17 . This model has two important advantages: first is its capacity to reproduce qualitatively the experimental results, including the weak diameter dependence of the REP asymmetry we observe 25 .…”

Section: B Evaluation Of Third-order Non-excitonic Quantum Model Fmentioning

confidence: 99%

“…We unambiguously demonstrate that the outgoing resonance is significantly weaker than the incoming resonance for each armchair structure, indicating that the REP asymmetries are as significant for metallic structures as they are in semiconducting nanotubes. Furthermore, we apply the approach of Moura et al 17 to the armchair data and find it is unable to reproduce the observed asymmetries. We present an alternative tight-binding approach that successfully reproduces the REP asymmetries by capturing non-Condon effects as a consequence of phonon-mediated state-mixing.…”

Section: Introductionmentioning

confidence: 99%

“…Such a perspective, however, represents a challenge for modeling within an extended condensed matter framework more typically applied to carbon nanotubes. Moura et al 17 recently demonstrated that the REP asymmetry can be reproduced for some semiconducting structures within such a view, without the need to invoke non-Condon effects, by applying a third-order quantum model for Raman scattering. The model captures the nanotube band structure by summing over the full range of momentum (k ) states and includes the k-state dependence of energies and electron-phonon coupling.…”

Section: Introductionmentioning

confidence: 99%

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Asymmetric excitation profiles in the resonance Raman response of armchair carbon nanotubes

et al. 2015

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We performed tunable resonance Raman spectroscopy on samples highly enriched in the (5,5), (6,6), (7,7), and (8,8) armchair structures of metallic single-wall carbon nanotubes. We present Raman excitation profiles (REPs) for both the radial breathing mode and G-band phonons of these species. G-band excitation profiles are shown to resolve the expected incoming and outgoing resonances of the scattering process. Notably, the profiles are highly asymmetric, with the higherenergy outgoing resonance weaker than the incoming resonance. These results are comparable to the asymmetric excitation profiles observed previously in semiconducting nanotubes, introduce a new electronic type, and broaden the structural range over which the asymmetry is found to exist. Modeling of the behavior with a third-order quantum model that accounts for the k -dependence in energies and matrix elements, without including excitonic effects, is found to be insufficient for reproducing the observed asymmetry. We introduce an alternative fifth-order model in which the REP asymmetry arises from quantum interference introduced by phonon-mediated state-mixing between the E M 11 and K-momentum excitons. Such state-mixing effectively introduces a nuclear coordinate dependence in the transition dipole moment and thus may be viewed as a non-Condon effect from a molecular perspective. This result unifies a molecular-like picture of nanotube transitions (introduced by their excitonic nature) with a condensed matter approach for describing their behavior.

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Section: Resultsmentioning

confidence: 99%

Section: B Evaluation Of Third-order Non-excitonic Quantum Model Fmentioning

confidence: 99%

Section: B Evaluation Of Third-order Non-excitonic Quantum Model Fmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Asymmetric excitation profiles in the resonance Raman response of armchair carbon nanotubes

et al. 2015

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Detection of Off‐Resonance Single‐Walled Carbon Nanotubes by Enormous Surface‐Enhanced Raman Scattering

Zhang

Xia

et al. 2021

Advanced Optical Materials

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The resonant Raman spectroscopy can only detect on‐resonance single‐walled carbon nanotubes (SWNTs) within the laser resonance window. In principle, surface‐enhanced Raman scattering (SERS) spectroscopy can expand the resonance window. However, detection of off‐resonance SWNTs by SERS remains challenging due to the difficulties in locating the SWNTs exactly at the hot spots with enormous SERS enhancements. Here, polyhedral gold nanocrystals (AuNCs) are in situ prepared on SWNTs for SERS detection via a facile ultrasonic spray pyrolysis method. The fact that the edges of the AuNCs attach to the SWNTs ensures the location of SWNTs perfectly at the SERS hot spots. Consequently, the enormous SERS enhancement enables a maximum enhancement factor of (3.4 ± 0.6) × 104 for an individual SWNT, which is about two orders of magnitude higher than the maximum reported in literatures. The detection ratio of SWNTs is also dramatically increased from 33% without SERS to 76% with SERS. The existence of the polyhedral AuNCs suppresses the antenna effects of the SWNTs and allows effective enhancements of the SWNTs under various polarization conditions. The enormous enhancements also enable the detection of several new Raman bands of the SWNTs.

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Tunable filter Raman spectroscopy of purified semiconducting and metallic carbon nanotubes

Finnie

2016

Nano Res.

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KEYWORDSsingle walled carbon nanotube (SWCNT), tunable Raman spectroscopy, purity, metallicity ABSTRACT Tunable filter Raman spectroscopy is used to efficiently produce Raman excitation maps of unpurified and type-purified single walled carbon nanotubes (SWCNTs). Maps with fine excitation resolution (1 nm) are created over a wide wavelength range (727 to 980 nm), extending from metallic to semiconducting resonances. At a given wavelength, the wide bandwidth (>3,000 cm -1 ) allows the comparison of the G band with the radial breathing mode (RBM), and shows the 2D band and other less prominent bands. Materials examined included unsorted powders, aqueous sorted semiconductors, aqueous sorted metals, and polyfluorene sorted semiconductors in toluene. The Raman excitation profiles of the G band are broad, relative to the RBM bands. The maps offer evidence of minority species contamination, except in the case of the polyfluorene sorted semiconductors. Tunable Raman spectroscopy data help validate the simpler fixed wavelength Raman spectroscopy approaches to purity assessment.

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Raman excitation profile of theGband in single-chirality carbon nanotubes

Cited by 19 publications

References 16 publications

Asymmetric excitation profiles in the resonance Raman response of armchair carbon nanotubes

Asymmetric excitation profiles in the resonance Raman response of armchair carbon nanotubes

Detection of Off‐Resonance Single‐Walled Carbon Nanotubes by Enormous Surface‐Enhanced Raman Scattering

Tunable filter Raman spectroscopy of purified semiconducting and metallic carbon nanotubes

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