Isolation of single-walled carbon nanotube enantiomers by density differentiation

Green, Alexander A.; Duch, Matthew C.; Hersam, Mark C.

doi:10.1007/s12274-009-9006-y

Cited by 159 publications

(230 citation statements)

References 35 publications

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“…A closer examination of the species remaining in the "armchair-enriched" sample indicates that any metallic species with a chiral angle smaller than ≈23-24 • is significantly suppressed by the DGU process, indicating that the three-surfactant DGU method has a critical chiral angle below which enrichment does not occur and suggesting the possible role of chiral-angle-specific steric interactions between chiral surfactants, such as DOC and SC, and a particular (n, m) nanotube geometry. 112,119 Further evidence for this effect is suggested by the relative abundances of species within the unsorted sample which is in aqueous suspension by DOC. Raman measurements by Fantini et al 96 and Maultzsch et al 97 on aqueous dispersions of HiPco material suspended by the achiral surfactant SDS indicate that all members of a particular metallic 2n+m family, including zigzag species, are present.…”

Section: Resonant Raman Scattering Spectroscopy Of Armchair-enricmentioning

confidence: 99%

Fundamental optical processes in armchair carbon nanotubes

Hároz

Duque

et al. 2013

Nanoscale

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Single-wall carbon nanotubes provide ideal model 1-D condensed matter systems in which to address fundamental questions in many-body physics, while, at the same time, they are leading candidates for building blocks in nanoscale optoelectronic circuits. Much attention has been recently paid to their optical properties, arising from 1-D excitons and phonons, which have been revealed via photoluminescence, Raman scattering, and ultrafast optical spectroscopy of semiconducting carbon nanotubes. On the contrary, dynamical properties of metallic nanotubes have been poorly explored, although they are expected to provide a novel setting for the study of electron-hole pairs in the presence of degenerate 1-D electrons. In particular, (n,n)-chirality, or armchair, metallic nanotubes are truly gapless with massless carriers, ideally suited for dynamical studies of Tomonaga-Luttinger liquids. Unfortunately, progress towards such studies has been slowed by the inherent problem of nanotube synthesis whereby both semiconducting and metallic nanotubes are produced. Here, we use post-synthesis separation methods based on density gradient ultracentrifugation and DNAbased ion-exchange chromatography to produce aqueous suspensions strongly enriched in armchair nanotubes. Through resonant Raman spectroscopy of the radial breathing mode phonons, we provide macroscopic and unambiguous evidence that density gradient ultracentrifugation can enrich armchair nanotubes. Furthermore, using conventional, optical absorption spectroscopy in the nearinfrared and visible range, we show that interband absorption in armchair nanotubes is strongly excitonic. Lastly, by examining the G-band mode in Raman spectra, we determine that observation of the broad, lower frequency (G − ) feature is a result of resonance with non-armchair "metallic" nanotubes. These findings regarding the fundamental optical absorption and scattering processes in metallic carbon nanotubes lay the foundation for further spectroscopic studies to probe many-body physical phenomena in one dimension.

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Section: Resonant Raman Scattering Spectroscopy Of Armchair-enricmentioning

confidence: 99%

Fundamental optical processes in armchair carbon nanotubes

Hároz

Duque

et al. 2013

Nanoscale

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“…8 For the expression of the stereoisomers of chiral SWNTs, a variety of terms have been used so far; LH and RH, 4 r and l, 39 L and R, 40 (n 1 ,n 2 ) and (n 2 ,n 1 ), 41 ZL and ZR, 1 and AL and AR. 1 Since stereochemistry of SWNTs have been discussed experimentally in several articles, 4,18,3335,42 definite nomenclature is required for the stereochemistry of SWNTs. 38 In this paper, M and P terminology 4,8,3335 is proposed to define left-and right-handed helical structures of SWNTs on the basis of the definition of ZL and ZR (Figure 2).…”

Section: ç Structures Of Swntsmentioning

confidence: 99%

Optical Resolution of Single-Walled Carbon Nanotubes through Molecular Recognition with Chiral Diporphyrin Nanotweezers

Peng¹,

Wang²,

Bauri³

et al. 2010

Chemistry Letters

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Single-walled carbon nanotubes (SWNTs) have either chiral or achiral form, and synthesized chiral SWNTs include both leftand right-handed structures in equal amounts. Recently, a racemic mixture was found to be resolved through molecular recognition with gable-type chiral diporphyrins, namely, nanotweezers. This novel separation method for SWNTs allowed optical resolution of SWNTs for the first time. The chiral nanotweezers consist of two chiral porphyrins and rigid spacer in between. Therefore, they have potential to discriminate not only the handedness but also the diameters or alignments of the hexagons of SWNTs. We have prepared the following three types of chiral nanotweezers; m-phenylene-, 2,6-pyridylene-, and 3,6-carbazolylene-bridged diporphyrins. In the extraction of SWNTs, different selectivities have been observed among the nanotweezers. This can be attributed to the differences in their structures; namely, the dihedral angles and the distance of the two porphyrins. In this review, we would like to discuss the relationship between the structures of the nanotweezers and the results of the optical and (n,m) enrichments of the extracted SWNTs.

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“…Arnold et al firstly described the sorting of DNAwrapped SWCNTs by DGU, 34 this technique has been well developed for SWCNT sorting with multiple purposes, such as separation by m/s, diameter and chirality, even the separation of the mirror-image isomers of seven (n,m) species. [35][36][37][38][39][40][41] In this process, SWCNT suspension is added to centrifuge tubes containing liquid mixtures arranged to form a spatially varying density profile. Under strong centrifugation, SWCNT species are separated by migrating to regions matching their individual densities.…”

Section: Density Gradient Ultracentrifugationmentioning

confidence: 99%

“…Green et al reported that by using chiral surfactant, such as sodium cholate, leftand right-handed SWCNTs can be discriminated. 38 This sorting strategy can be employed for simultaneous enrichment of SWCNTs by handedness and roll-up vector having diameters ranging from 0.7 to 1.5 nm. However, simultaneously sorting many SWCNTs species in a single step still is a bottleneck.…”

Section: Density Gradient Ultracentrifugationmentioning

confidence: 99%