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Related Concept Videos

¹H NMR: Long-Range Coupling01:27

¹H NMR: Long-Range Coupling

2.8K
The coupling interactions of nuclei across four or more bonds are usually weak, with J values less than 1 Hz. While these are usually not observed in spectra, the presence of multiple bonds along the coupling pathway can result in observable long-range coupling.
In alkenes, spin information is communicated via σ–π overlap, as seen in allylic (four-bond) and homoallylic (five-bond) couplings. These coupling interactions are stronger when the σ bond is parallel to the alkene...
2.8K
Spin–Spin Coupling: One-Bond Coupling01:17

Spin–Spin Coupling: One-Bond Coupling

1.5K
Coupling interactions are strongest between NMR-active nuclei bonded to each other, where spin information can be transmitted directly through the pair of bonding electrons. While nuclei polarize their electrons to the opposite spins, the bonding electron pair has opposite spins. Configurations with antiparallel nuclear spins are expected to be lower in energy. When coupling makes antiparallel states more favorable, J is considered to have a positive value. The one-bond coupling constant, 1J,...
1.5K
Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)01:22

Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)

1.6K
Vicinal or three-bond coupling is commonly observed between protons attached to adjacent carbons. Here, nuclear spin information is primarily transferred via electron spin interactions between adjacent C‑H bond orbitals. This generally favors the antiparallel arrangement of spins, so 3J values are usually positive.
The extent of coupling depends on the C‑C bond length, the two H‑C‑C angles, any electron-withdrawing substituents, and the dihedral angle between the involved orbitals. The...
1.6K
Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)01:20

Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)

1.9K
Two NMR-active nuclei bonded to a central atom can be involved in geminal or two-bond coupling. Geminal coupling is commonly seen between diastereotopic protons in chiral molecules and unsymmetrical alkenes, among others.
The central atom need not be NMR-active because its electrons are affected by the electron polarization of the spin-active atoms. However, spin information is transmitted less effectively than in one-bond coupling, and 2J values are usually weaker than 1J values. The energy of...
1.9K
Network Covalent Solids02:18

Network Covalent Solids

16.4K
Network covalent solids contain a three-dimensional network of covalently bonded atoms as found in the crystal structures of nonmetals like diamond, graphite, silicon, and some covalent compounds, such as silicon dioxide (sand) and silicon carbide (carborundum, the abrasive on sandpaper). Many minerals have networks of covalent bonds.
To break or to melt a covalent network solid, covalent bonds must be broken. Because covalent bonds are relatively strong, covalent network solids are typically...
16.4K

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Related Experiment Video

Updated: Mar 3, 2026

Fabrication of Low Temperature Carbon Nanotube Vertical Interconnects Compatible with Semiconductor Technology
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Structural Properties of Double-Walled Carbon Nanotubes Driven by Mechanical Interlayer Coupling.

Ahmed Ghedjatti1, Yann Magnin2, Frédéric Fossard1

  • 1Laboratoire d'Etude des Microstructures, ONERA-CNRS , BP 72, 92322 Châtillon Cedex, France.

ACS Nano
|April 28, 2017
PubMed
Summary

Researchers analyzed double-walled carbon nanotubes (DWNTs) using advanced electron microscopy. They discovered a non-random orientation between the inner and outer tubes, indicating a mechanical coupling influenced by tube dimensions and stacking domains.

Keywords:
DWNTHRTEMatomic-scale modelingmechanical couplingstatistical analysis

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Area of Science:

  • Materials Science
  • Nanotechnology
  • Condensed Matter Physics

Background:

  • Double-walled carbon nanotubes (DWNTs) are crucial nanomaterials with unique properties.
  • Understanding the structural relationship between concentric walls is key to controlling DWNT behavior.
  • Previous studies often lacked detailed statistical analysis of DWNT structures.

Purpose of the Study:

  • To structurally identify double-walled carbon nanotubes (DWNTs) using advanced microscopy.
  • To investigate the orientational relationship between the inner and outer tubes of DWNTs.
  • To elucidate the underlying mechanisms responsible for the observed structural coupling.

Main Methods:

  • Utilized a latest-generation transmission electron microscope for high-resolution imaging.
  • Performed statistical analysis on a large dataset of identified nano-objects (DWNTs).
  • Employed atomic-scale modeling to simulate and interpret structural interactions.

Main Results:

  • Demonstrated a non-random orientation between the inner and outer walls of DWNTs.
  • Identified evidence of mechanical coupling between the concentric tubes.
  • Atomic-scale modeling attributed coupling to incommensurate domains influenced by tube diameters and helicities.

Conclusions:

  • The structural coupling in DWNTs is significant and not coincidental.
  • Incommensurate domains play a critical role in the strain reduction and stacking orientation of inner tubes.
  • Findings provide insights into controlling DWNT structure and properties for advanced applications.