38,652 research outputs found
Structural selective charge transfer in iodine-doped carbon nanotubes
We have investigated iodine intercalated carbon nanostructures by extended X-ray absorption fine structure (EXAFS) and Raman spectroscopies. We discuss here the charge transfer and the iodine–carbon interaction as a function of the carbon nanostructures (graphite, multi-walled, double-walled and single walled nanotubes). The results show that iodine is weakly adsorbed on the surface of all multi-walled nanotubes. By contrast, a charge transfer between iodine and single walled nanotubes is evidenced
Scanned Probe Microscopy of Electronic Transport in Carbon Nanotubes
We use electrostatic force microscopy and scanned gate microscopy to probe
the conducting properties of carbon nanotubes at room temperature. Multi-walled
carbon nanotubes are shown to be diffusive conductors, while metallic
single-walled carbon nanotubes are ballistic conductors over micron lengths.
Semiconducting single-walled carbon nanotubes are shown to have a series of
large barriers to conduction along their length. These measurements are also
used to probe the contact resistance and locate breaks in carbon nanotube
circuits.Comment: 4 page
Optimizing Growth Conditions for Coaxial Multi-Walled Carbon Nanotubes
Coaxial multi-walled carbon nanotubes have a multi-layered structure in which a core multi-walled carbon nanotube is grown inside a sheath multi-walled nanotube from a metal-catalyst nanoparticle. In this paper, we report the optimum conditions to grow coaxial multi-walled carbon nanotubes by chemical vapor deposition. The coaxial nanotubes are studied by means of transmission electron microscopy to reveal their crystallinity and morphology. Our results show that chemical vapor deposition growth at around 1000°C with a 0.04–0.07 mg/cm^3 dose of palmitic acid yields the best result
A Review of Double-Walled and Triple-Walled Carbon Nanotube Synthesis and Applications
Double- and triple-walled carbon nanotubes (DWNTs and TWNTs) consist of coaxially-nested two and three single-walled carbon nanotubes (SWNTs). They act as the geometrical bridge between SWNTs and multi-walled carbon nanotubes (MWNTs), providing an ideal model for studying the coupling interactions between different shells in MWNTs. Within this context, this article comprehensively reviews various synthetic routes of DWNTs’ and TWNTs’ production, such as arc discharge, catalytic chemical vapor deposition and thermal annealing of pea pods (i.e., SWNTs encapsulating fullerenes). Their structural features, as well as promising applications and future perspectives are also discussed. Keywords: carbon nanotubes; double-walled carbon nanotubes; triple-walled carbon nanotubes; synthesis; catalytic chemical vapor deposition; arc discharge; fullerenes; pea pod
Radial-breathing-like phonon modes of double-walled carbon nanotubes
The radial-breathing-like phonon modes (RBLMs) of the double-walled carbon
nanotubes are studied in a simple analytical model, in which the interaction
force constants (FCs) can be obtained analytically from the continuous model.
The RBLMs frequencies are obtained by solving the dynamical matrix, and their
relationship with the tube radii can be obtained analytically, offering a
powerful experimental tool for determining precisely the radii of the
multi-walled carbon nanotubes
Backscattering in carbon nanotubes : role of quantum interference effects
For similar disorder, the backscattering contribution to the conductivity,
irrelevant for metallic single-walled carbon nanotubes, is proved to become
more significant for doped semiconducting systems, as found in experiments. In
the case of multi-walled nanotubes, the intershell coupling is further shown to
enhance the contribution of backscattering for "metallic" double-walled,
whereas it remains insignificant for "metallic/semiconducting" double-walled
systems. This supports that MWNTs are long ballistic conductors close to the
charge neutrality point.Comment: 8 pages, 3 figure
Hydrogen storage in carbon nanotubes and related materials
Adsorption of hydrogen at 300 K has been investigated on well-characterized samples of carbon nanotubes, besides carbon fibres by taking care to avoid many of the pitfalls generally encountered in such measurements. The nanotube samples include single- and multi-walled nanotubes prepared by different methods, as well as aligned bundles of multi-walled nanotubes. The effect of acid treatment of the nanotubes has been examined. A maximum adsorption of ca. 3.7 wt% is found with aligned multi-walled nanotubes. Electrochemical hydrogen storage measurements have also been carried out on the nanotube samples and the results are similar to those found by gas adsorption measurements
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