Search results for "Single-Wall"
showing 10 items of 24 documents
Solid-State Synthesis of “Bamboo-Like” and Straight Carbon Nanotubes by Thermolysis of Hexa-peri-hexabenzocoronene–Cobalt Complexes
2006
Sensor Properties of Pristine and Functionalized Carbon Nanohorns
2016
Nanodispersions of pristine single-wall carbon nanohorns (i.e., p-SWCNHs) and oxidized-SWCNHs (i.e.; o-SWCNHs) were used to modify screen printed electrode (SPE). p-SWCNHs and o-SWCNHs were fully characterized by using several analytical techniques, as: HR-TEM (High Resolution-Transmission Electron Microscopy), FE-SEM/EDX (Field Emission-Scanning Electron Microscopy/Energy Dispersive X-ray Analysis), Raman spectroscopy, thermogravimetric analysis, differential thermal analysis (DTA), and the Brunauer-Emmett-Teller (BET) method. The chemically modified SPEs were also characterized with Cyclic Voltammetry (CV), using several different electro-active targets. In all cases, p-SWCNHs showed bett…
Chemical modification of carbon nanomaterials (SWCNTs, DWCNTs, MWCNTs and SWCNHs) with diphenyl dichalcogenides
2015
Control over chemical functionalization is a crucial point in the field of nanotechnology. Herein, we present the covalent functionalization of several carbon nanoforms (single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes and carbon nanohorns) by means of diphenyl dichalcogenides. These ones show different reactivity to the nanomaterials and are able to modify their electronic properties depending on the electronegativity of the functionalizing heteroatom. Theoretical calculations were also performed to support the experimental results. All the modified structured nanocarbons were thoroughly characterized by TGA Raman, XPS, UV/Vis/nIR, IR and TEM te…
Twisting graphene nanoribbons into carbon nanotubes
2011
Although carbon nanotubes consist of honeycomb carbon, they have never been fabricated from graphene directly. Here, it is shown by quantum molecular-dynamics simulations and classical continuum-elasticity modeling, that graphene nanoribbons can, indeed, be transformed into carbon nanotubes by means of twisting. The chiralities of the tubes thus fabricated can be not only predicted but also externally controlled. This twisting route is an opportunity for nanofabrication, and is easily generalizable to ribbons made of other planar nanomaterials.
Computational studies of torsional properties of single-walled carbon nanotubes
2010
Current thesis presents computational studies of the torsional twist in single walled carbon nanotubes (SWCNTs). Since SWCNTs can be viewed as rolled up graphene sheets, our aim is to explain their torsion constants via shear mod- ulus of graphene in pristine, and single- and double vacancy cases. In addition, fundamental energy gap response to torsion is investigated. Calculations of defected structures is computationally expensive as it requires larger simula- tion cell with large number of atoms. To reduce the cost of computations we take the advantage of chiral symmetry of nanotubes instead of translational one, and faster performance of density-functional tight-binding method compared …
The diffusion of carbon atoms inside carbon nanotubes
2008
We combine electron irradiation experiments in a transmission electron microscope with kinetic Monte Carlo simulations to determine the mobility of interstitial carbon atoms in single-walled carbon nanotubes. We measure the irradiation dose necessary to cut nanotubes repeatedly with a focused electron beam as a function of the separation between the cuts and at different temperatures. As the cutting speed is related to the migration of displaced carbon atoms trapped inside the tube and to their recombination with vacancies, we obtain information about the mobility of the trapped atoms and estimate their migration barrier to be about 0.25 eV. This is an experimental confirmation of the remar…
Solid-State Pyrolyses of Metal Phthalocyanines: A Simple Approach towards Nitrogen-Doped CNTs and Metal/Carbon Nanocables
2006
Solid-state pyrolysis of organometallic precursors has emerged as an alternative method for preparing carbon nanostructures such as carbon nanotubes (CNT) and carbon anions. The morphology of the tubes can be controlled by the nature of the precursors and the pyrolysis procedures, and micrometer long nanotubes, composed of metal carbide wires encased in a graphitic sheath. Cobalt phthalocyanine (CoPc) as well as iron phthalocyanine were pyrolyzed at different temperatures to obtain CNTs. HRTEM and energy-dispersion X-Ray analysis disclosed that the core consisted of long, iron-containing single crystals and that the core was fully surrounded by crystallized graphic carbon. Iron-filled carbo…
Synthetic Approaches to Functionalized Chalcogenide Nanotubes
2008
Measurements of tunneling conduction to carbon nanotubes and its sensitivity to oxygen gas
2012
We have measured the conductive properties of junctions between carbon nanotubes (CNT) and non-noble metals $M$ ($M$ = Al, Ti, Nb), which are separated by the native oxide (${M}_{\mathit{OX}}$) of the metal. Reproducible and asymmetric current-voltage characteristics were obtained from Ti/Ti${}_{\mathit{OX}}$/CNT and Nb/Nb${}_{\mathit{OX}}$/CNT junctions, while Al/Al${}_{\mathit{OX}}$/CNT exhibited no current until breakdown, which is attributed to the larger bandgap of Al${}_{\mathit{OX}}$. The conduction in the Ti- and Nb-based junctions is not due to direct tunneling since they exhibit strong temperature dependence. The presence of oxygen is shown to drastically, but reversibly, modify t…
Water-soluble carbon nanotubes through sugar azide functionalization
2011
In this work we report a covalent functionalization of pristine single-walled carbon nanotubes (SWCNTs) directly with three sugar azides, 2,3,4,6-tetra-O-acetyl-β-d-glucopyranosyl, 2,3,4,6-tetra-O-acetyl-β-d-galactopyranosyl or 2,3,4,6-tetra-O-acetyl-β-d-mannopyranosyl azide. Microwave-assisted functionalization was carried out for SWCNTs prepared with the HiPCO method. The as-prepared, new type of sugar-functionalized SWCNTs were analyzed by Raman and IR spectroscopy. Deacetylation of the functionalized tubes by sodium methoxide yielded nitrogen-linked, sugar-functionalized carbon nanotubes (CNTs) that formed stable dispersions in water. Reactivity of the sugar azides towards SWCNTs was es…