13C NMR study of 13C-enriched single-wall carbon nanotubes synthesized by catalytic decomposition of methane

Hayashi, Shigenobu; Hoshi, Fumiyuki; Ishikura, Takefumi; Yumura, Motoo; Ohshima, Satoshi

doi:10.1016/s0008-6223(03)00428-7

Cited by 46 publications

(63 citation statements)

References 15 publications

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“…This value compares reasonably well with the estimate of 128 ppm for δ TMS graphene of a perfect graphene layer (with zero density of states at the Fermi level) 8,25 . For a nanotube with a diameter of 1.2 nm, like the ones common in experimental samples, we obtain a δ iso ≈ 125 ppm, in excellent agreement with experiment 7,8,9,22 . Note that, as already indicated in Refs.…”

Section: Tms Isosupporting

confidence: 86%

“…in the samples. These impurities, which are added as a catalyst during the production of the nanotubes, lead to very broad magicspinning angle (MAS) spectra, with widths of about 30-50 ppm 7,8,9 . However, we expect this situation to change soon, due to new production techniques that use water 10 or alcohol 11 to enhance the activity and the lifetime of the catalysts.…”

Section: Introductionmentioning

confidence: 99%

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Magnetic response and NMR spectra of carbon nanotubes fromab initiocalculations

2006

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We present ab initio calculations of the magnetic susceptibility and of the 13 C chemical shift for carbon nanotubes, both isolated and in bundles. These calculations are performed using the recently proposed gauge-including projector augmented-wave approach for the calculation of magnetic response in periodic insulating systems. We have focused on the semiconducting zigzag nanotubes with diameters ranging from 0.6 to 1.6 nm. Both the susceptibility and the isotropic shift exhibit a dependence with the diameter (D) and the chirality of the tube (although this dependence is stronger for the susceptibility). The isotropic shift behaves asymptotically as α/D + 116.0, where α is a different constant for each family of nanotubes. For a tube diameter of around 1.2 nm, a value normally found in experimental samples, our results are in excellent agreement with experiments. Moreover, we calculated the chemical shift of a double-wall tube. We found a diamagnetic shift of the isotropic lines corresponding to the atoms of the inner tube due to the effect of the outer tube. This shift is in good agreement with recent experiments, and can be easily explained by demagnetizing currents circulating the outer tube.

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Section: Tms Isosupporting

confidence: 86%

Section: Introductionmentioning

confidence: 99%

Magnetic response and NMR spectra of carbon nanotubes fromab initiocalculations

2006

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“…5) The 13 C-NMR technique has also been applied to reveal the unusual electronic properties of SWCNTs. [6][7][8][9][10][11] However, to our knowledge, NMR observations have been limited to the SWCNT samples mixed with both metallic and semiconducting SWCNTs. This substantially hampered the study of the individual properties of SWCNTs, which sensitively depend on the detailed electronic structure.…”

mentioning

confidence: 99%

“…This observation is consistent with those in earlier experiments using solid-state high resolution NMR, in which two NMR peaks with different isotropic shifts were observed. 7,9,10) iso can be due to the magnetic interaction between the conduction-electron spin and the 13 C-nuclear spin (called isotropic Knight shift) through direct and indirect (core polarization) interactions. A suitable theoretical calculation 21) indicated iso $ À1:5 ppm for a metallic SWCNT with a diameter 1.45 nm.…”

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confidence: 99%

¹³C-NMR Shift of Highly Concentrated Metallic and Semiconducting Single-Walled Carbon Nanotubes

et al. 2013

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Single-walled carbon nanotubes (SWCNTs) have novel electronic properties originating from their unique onedimensional (1D) structures. 1) Their electronic properties are well correlated with the geometrical structure represented by the chiral index ðn; mÞ. Such global features were confirmed using several experimental techniques, such as scanning tunneling microscopy, 2,3) optical absorption, 4) and photoemission spectroscopy. 5) The 13 C-NMR technique has also been applied to reveal the unusual electronic properties of SWCNTs. 6-11) However, to our knowledge, NMR observations have been limited to the SWCNT samples mixed with both metallic and semiconducting SWCNTs. This substantially hampered the study of the individual properties of SWCNTs, which sensitively depend on the detailed electronic structure. One such interesting property is the magnetic response or orbital susceptibility as in other carbon network systems. 12,13) In this connection, we report here the first determination of a 13 C-NMR shift tensor, which is closely related to the orbital susceptibility in metallic and semiconducting SWCNTs.The highly concentrated metallic and semiconducting SWCNTs (more than $95%) with a mean diameter of 1.45 nm were prepared by the method described in Ref. 14; the extractions of metallic and semiconducting SWCNTs from pristine SWCNTs, the Arc-SO SWCNT soot (Meijo Nano-Carbon), were accomplished by the density gradient ultracentrifugation (DGU) technique. Each sample was characterized on the basis of photoabsorption (Shimadzu UV-3600), electrical resistance, 15) and powder X-ray diffraction (XRD) at the BL8B station in the Photon Factory facility, KEK, Japan (see Fig. 1). Note that there is no trace of graphitized carbon and ferromagnetic impurity particles in the XRD profiles. This is consistent with the previous magnetization measurement (see Fig. S.3. in Ref. 15).We observed the 13 C isotope of natural abundance (1.1%). Each sample ($18 mg) was sealed in a quartz tube with helium of $1 atm after sufficient evacuation at 800 K. For semiconducting SWCNTs, two samples of different batches, #1 and #2, were examined. The NMR spectra were obtained by Fourier transformation of the latter half of the spin-echo signal that appeared after the =2-pulse sequence, using a phase-coherent pulsed spectrometer. The =2 pulse width was 6.0 s. The radiated rf field frequency was varied over a range of the NMR spectral width of about 20 kHz to examine spectral distortion effects due to the finite pulse widths. The 13 C-NMR shift was determined with respect to the 13 C resonance in tetramethylsilane (TMS).Figure 2 presents 13 C-NMR spectra of the metallic and semiconducting SWCNTs, along with that of solid C 60 obtained at 4.2 K, where the rotational motion of C 60 completely freezes. Note that the spectrum of solid C 60 is reproduced by a reported shift tensor. 16) Then, we find that the spectra of the SWCNTs have the same characteristic features as those for aromatic carbons having sp 2 hybridization. 7,[17][18][19] The 33 axis sho...

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“…There have been several reports on NMR in nonaligned nanotubes, both experimental [39][40][41][42][43][44][45][46][47] and theoretical. 16,[48][49][50] First, we should note that the field varies discontinuously on the cylinder surface due to the induced surface current.…”

Section: Magnetic-field Distributionmentioning

confidence: 99%