Related Experiment Video
Updated: Jul 2, 2026
09:48
Simultaneous Synthesis of Single-walled Carbon Nanotubes and Graphene in a Magnetically-enhanced Arc Plasma
Published on: February 2, 2012
Chiral-angle distribution for separated single-walled carbon nanotubes.
Yuta Sato1, Kazuhiro Yanagi, Yasumitsu Miyata
1Nanotube Research Center, National Institute of Advanced Industrial Science and Technology, and JST-CREST, Tsukuba 305-8565, Japan. yuta-sato@aist.go.jp
Nano Letters
|August 30, 2008
Summary
Chiral indices of single-walled carbon nanotubes (SWNTs) were assigned using transmission electron microscopy. Armchair and chiral SWNTs with large angles dominate metallic types, unlike semiconducting ones.
Area of Science:
- Materials Science
- Nanotechnology
- Physics
Background:
- Single-walled carbon nanotubes (SWNTs) exhibit unique electronic properties based on their chiral indices (n, m).
- Precise assignment of these indices is crucial for understanding and utilizing SWNTs.
- Density-gradient ultracentrifugation is a key method for separating SWNTs by their properties.
Purpose of the Study:
- To individually assign chiral indices of metallic and semiconducting SWNTs separated by density-gradient ultracentrifugation.
- To statistically analyze the distribution of chiral indices in separated metallic and semiconducting SWNT populations.
- To compare findings with existing spectroscopic methods.
Main Methods:
- Aberration-corrected transmission electron microscopy (TEM) operated at 80 kV for high-resolution imaging.
- Density-gradient ultracentrifugation for selective separation of SWNTs.
- Statistical analysis of assigned chiral indices (n, m) from TEM data.
Main Results:
- Metallic SWNTs predominantly showed armchair (n, n) and chiral (n, n-3) indices with large chiral angles (>20 degrees).
- No such specific index preference was observed for semiconducting SWNTs.
- Significant discrepancies were noted between TEM and spectroscopic results regarding major chiral indices and metal/semiconductor ratios.
Conclusions:
- The study identifies dominant chiral indices for metallic SWNTs, offering insights into their formation and separation.
- The findings highlight potential limitations or differences in characterization techniques for SWNTs.
- Further investigation is needed to reconcile discrepancies between TEM and spectroscopic analyses.
Related Concept Videos
02:05Prochirality
The concept of prochirality leads to the nomenclature of the individual faces of a molecule and plays a crucial role in the enantioselective reaction. It is a concept where two or more achiral molecules react to produce chiral products. A typical process is the reaction of an achiral ketone to generate a chiral alcohol. Here, the achiral reactant reacts with an achiral reducing agent, sodium borohydride, to generate an equimolar mixture of the chiral enantiomers of the product. For example, an...
02:02Chair Conformation of Cyclohexane
The chair conformation is the most stable form of cyclohexane due to the absence of angle and torsional strain. The absence of angle strain is a result of cyclohexane’s bond angle being very close to the ideal tetrahedral bond angle of 109.5° in its chair conformer. Similarly, the torsional strain is also absent owing to the perfectly staggered arrangement of bonds.
The hydrogen atoms linked to carbons are arranged in two different axial and equatorial orientations to achieve this staggered...
The hydrogen atoms linked to carbons are arranged in two different axial and equatorial orientations to achieve this staggered...
01:07Radicals: Electronic Structure and Geometry
This lesson delves into the geometry of a radical, which is influenced by the electronic structure of the molecule. The principle is similar to that of a lone pair, where the unpaired electron influences the geometry at the radical center.
Accordingly, the structure of a trivalent radical lies between the geometries of carbocations and carbanions. An sp2-hybridized carbocation is trigonal planar, while an sp3-hybridized carbanion is trigonal pyramidal. Here, the difference in geometry is...
Accordingly, the structure of a trivalent radical lies between the geometries of carbocations and carbanions. An sp2-hybridized carbocation is trigonal planar, while an sp3-hybridized carbanion is trigonal pyramidal. Here, the difference in geometry is...
04:01VSEPR Theory and the Effect of Lone Pairs
Effect of Lone Pairs of Electrons on Molecule Geometry
02:11Conformations of Cyclohexane
Cyclohexane does not exist in a planar form due to the high angle and torsional strain it would experience in the planar structure. Instead, it adopts non-planar chair and boat conformations.
The chair form is the most stable and derives its name from its resemblance to the “easy chair.” In the chair conformation, two carbon atoms are arranged out-of-plane — one above and one below, minimizing the torsional strain. In the chair form, the bond angle is very close to the ideal tetrahedral value,...
The chair form is the most stable and derives its name from its resemblance to the “easy chair.” In the chair conformation, two carbon atoms are arranged out-of-plane — one above and one below, minimizing the torsional strain. In the chair form, the bond angle is very close to the ideal tetrahedral value,...
02:30Chirality at Nitrogen, Phosphorus, and Sulfur
Chirality is most prevalent in carbon-based tetrahedral compounds, but this important facet of molecular symmetry extends to sp3-hybridized nitrogen, phosphorus and sulfur centers, including trivalent molecules with lone pairs. Here, the lone pair behaves as a functional group in addition to the other three substituents to form an analogous tetrahedral center that can be chiral.
A consequence of chirality is the need for enantiomeric resolution. While this is theoretically possible for all...
A consequence of chirality is the need for enantiomeric resolution. While this is theoretically possible for all...