SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Allotropes of carbon

138

The new three-dimensional structure that the graphene connected with SWCNTs (G-CNTs, Graphene Single-Walled Carbon Nanotubes) can solve graphene and CNTs' problems. A comprehensive study of the mechanical and electrical performance of the junctions was performed by first-principles theory. There were eight types of junctions that were constituted by armchair and zigzag graphene and (3,3), (4,0), (4,4), and (6,0) CNTs. First, the junction strength was investigated. Generally, the binding energy of armchair G-CNTs was stronger than that of zigzag G-CNTs, and it was the biggest in the armchair G-CNTs (6,0). Likewise, the electrical performance of armchair G-CNTs was better than that of zigzag G-CNTs. Charge density distribution of G-CNTs (6,0) was the most homogeneous. Next, the impact factors of the electronic properties of armchair G-CNTs were investigated. We suggest that the band gap is increased with the length of CNTs, and its value should be dependent on the combined effect of both the graphene’s width and the CNTs' length. Last, the relationship between voltage and current (U/I) were studied. The U/I curve of armchair G-CNTs (6,0) possessed a good linearity and symmetry. These discoveries will contribute to the design and production of G-CNT-based devices.

Concepts: Charge density, Allotropes of carbon, Tensile strength, Graphene, Electric charge, Graphite, Carbon, Carbon nanotube

30

Carbon nanotubes (CNTs), tubular molecular entities that consist of sp(2)-hybridized carbon atoms, are currently produced as mixtures that contain tubes of various diameters and different sidewall structures. The electronic and optical properties of CNTs are determined by their diameters and sidewall structures and so a controlled synthesis of uniform-diameter, single-chirality CNTs-a significant chemical challenge-would provide access to pure samples with predictable properties. Here we report a rational bottom-up approach to synthesize structurally uniform CNTs using carbon nanorings (cycloparaphenylenes) as templates and ethanol as the carbon source. The average diameter of the CNTs formed is close to that of the carbon nanorings used, which supports the operation of a ‘growth-from-template’ mechanism in CNT formation. This bottom-up organic chemistry approach is intrinsically different from other conventional approaches to making CNTs and, if it can be optimized sufficiently, offers a route to the programmable synthesis of structurally uniform CNTs.

Concepts: Organic compound, Chemical element, Atom, Allotropes of carbon, Graphite, Chemistry, Carbon nanotube, Carbon

30

Carbon nanotubes are used as the smallest possible scattering element for diffracting light in a highly controlled manner to produce a 2D image. An array of carbon nanotubes is elegantly patterned to produce a high resolution hologram. In response to incident light on the hologram, a high contrast and wide field of view CAMBRIDGE image is produced.

Concepts: Computer graphics, Allotropes of carbon, Diffraction, Graphite, Optics, Vision, Carbon, Carbon nanotube

28

Implantable sensors utilizing nanotechnology are at the forefront of diagnostic, medical monitoring, and biological technologies. These sensors are often equipped with nanostructured carbon allotropes, such as graphene or carbon nanotubes (CNTs), because of their unique and often enhanced properties over forms of bulk carbon, such as diamond or graphite. Because of these properties, the fundamental and applied research of these carbon nanomaterials have become some of the most cited topics in scientific literature in the past decades. The age of carbon nanomaterials is simply budding, however, and is expected to have a major impact in many areas. These areas include electronics, photonics, plasmonics, energy capture (including batteries, fuel cells, and photovoltaics), and-the emphasis of this review-biosensors and sensor technologies. The following review will discuss future prospects of the two most commonly used carbon allotropes in implantable sensors for nanomedicine and nanobiotechnology, CNTs and graphene. Sufficient further reading and resources have been provided for more in-depth and specific reading that is outside the scope of this general review. WIREs Nanomed Nanobiotechnol 2013. doi: 10.1002/wnan.1213 For further resources related to this article, please visit the WIREs website.

Concepts: Fullerene, Graphene, Nanotechnology, Allotropes of carbon, Graphite, Nanomaterials, Carbon nanotube, Carbon

28

The optical characterization of bundled and individual triple-walled carbon nanotubes was studied for the first time in detail by using resonant Raman spectroscopy. In our approach, the outer tube of a triple-walled carbon nanotube system protects the two inner tubes (or equivalently the inner double-walled carbon nanotube) from external environment interactions making them a partially isolated system. Following the spectral changes and line-widths of the radial breathing modes and G-band by performing laser energy dependent Raman spectroscopy, it is possible to extract important information as regards the electronic and vibrational properties, tube diameters, wall-to-wall distances, radial breathing mode and G-band resonance evolutions and high-curvature inter-tube interactions in isolated double- and triple-walled carbon nanotube systems.

Concepts: Allotropes of carbon, Graphite, Spectroscopy, Optical properties of carbon nanotubes, Carbon, Raman spectroscopy, Laser, Carbon nanotube

28

Initiated chemical vapor deposition (iCVD) has been shown to be suitable for blanketing surfaces with thin polymer coatings of ≈1-2 nm and greater. In this work, iCVD coatings of polytetrafluoroethylene (PTFE) deposited on carbon nanotube (CNT)-based surfaces show CNT-templated PTFE single crystal growth. While the coating forms disoriented agglomerates when deposited on an amorphous carbon background, “shish-kebab” structures are observed when grown on single-walled carbon nanotubes (SWCNT) as well as CNT buckypaper. It is shown that the shish-kebab structure is composed of PTFE lamellae arranged with the chain backbones running parallel to the SWCNT axis. This result allows one to control not only the surface chemistry using PTFE but also the coating surface topology.

Concepts: Potential applications of carbon nanotubes, Chemistry, Materials science, Solid, Allotropes of carbon, Chemical vapor deposition, Carbon, Carbon nanotube

27

A novel gas sensor based on hybrid platinum nanobox/single walled carbon nanotube composites shows improved gas sensing response time and sensitivity towards chlorine detection at room temperature compared to sensors fabricated from pristine carbon nanotubes. The enhanced sensor response is attributed to the improvement of the gas adsorption and charge-transfer efficiency with the incorporation of Pt nanoboxes.

Concepts: Materials science, Tensile strength, Allotropes of carbon, Graphite, Fuel cell, Carbon, Carbon nanotube

27

A scalable method to coat monochiral (7,5) semiconducting single-walled carbon nanotubes with a monolayer coating of a range of technologically useful polymers such as poly(3-hexylthiophene) (P3HT) and poly(9,9'-dioctylfluorene-co-benzothiadiazole) (F8BT) is presented. Optical spectroscopy and atomic force microscopy measurements show that the semiconducting tube purity (>99%) obtained from the selective wrapping of nanotubes by polymers such as poly(9,9-dioctylfluorenyl-2,7-diyl) (PFO) can be transferred to these other nanotube-polymer combinations by polymer exchange.

Concepts: Physical chemistry, Tensile strength, Allotropes of carbon, Polymer, Graphite, Polymers, Carbon, Carbon nanotube

27

A series of TiO2-graphene (GR), -carbon nanotube (CNT), and -fullerene (C60) nanocomposite photocatalysts with different weight addition ratios of carbon contents are synthesized via a combination of sol-gel and hydrothermal method. Their structures and properties are determined by the X-ray diffraction (XRD), UV-vis diffuse reflectance spectra (DRS), transmission electron microscopy (TEM), nitrogen adsorption-desorption and photoelectrochemical measurements. Photocatalytic selective oxidation of benzyl alcohol to benzaldehyde is employed as a model reaction to evaluate the photocatalytic activity of the TiO2-carbon (GR, CNT and C60) nanocomposites under visible light irradiation. The results reveal that incorporating TiO2 with carbon materials can extend the adsorption edge of all the TiO2-carbon nanocomposites to visible light region. For TiO2-GR, TiO2-CNT and TiO2-C60 nanocomposites, the photocatalytic activities of the composites with optimum ratios, TiO2-0.1% GR, TiO2-0.5% CNT and TiO2-1.0% C60, are very close to each other along with the irradiation time. Furthermore, the underlying reaction mechanism for the photocatalytic selective oxidation of benzyl alcohol to benzaldehyde over TiO2-carbon nanocomposites has been explored using different radicals scavengers technique, suggesting that TiO2-carbon photocatalysts follow the analogous oxidation mechanism toward selective oxidation of benzyl alcohol. The addition of different carbon materials has no significant influence on the crystal phase, particle size, and the morphology of TiO2. Therefore, it can be concluded, at least for nanocomposites of TiO2-carbon (GR, CNT and C60) obtained by the present approach, that there is no much difference in essence on affecting the photocatalytic performance of semiconductor TiO2 among these three different carbon allotropes, GR, CNT and C60. Our findings point to the importance of a comparative study of semiconductor-carbon photocatalysts on drawing a relatively objective conclusion rather than separately emphasizing the unique role of GR and joining the graphene gold rush.

Concepts: Fullerene, Electron, Nanomaterials, Allotropes of carbon, Photocatalysis, Graphite, Carbon nanotube, Carbon

27

Fine count two-ply yarn supercapacitors are constructed from carbon nanotube yarns and polyaniline nanowires. The thread-like supercapacitors possess excellent electrochemical capacity and are very strong and flexible. When being woven or knitted into wearable electronic devices, alone or in combination with conventional textile yarns, the two-ply yarn supercapacitors can be flexed and stretched repeatedly without significant loss of capacitance.

Concepts: Allotropes of carbon, Yarn, Textile, Graphite, Nanoflower, Weaving, Carbon, Carbon nanotube