Carbon Nanotubes

Vibrational characteristics of bilayer graphene sheets

by Rajib Chowdhury

Thin Solid Films
Volume 519, Issue 18, 1 July 2011, Pages 6026–6032

Bilayergraphenesheets (BLGSs) are currently receiving increasing attention. In this paper, the vibration... more Bilayergraphenesheets (BLGSs) are currently receiving increasing attention. In this paper, the vibration characteristics of BLGSs are investigated using analytical and atomistic finite element approaches. Various possible scenarios, namely different geometrical configuration (armchair and zigzag), boundary conditions, and aspect ratio are considered in the present study. The dynamic characteristics of BLGS studied have shown dependence on aspect ratio and the boundary conditions. The unique vibrational properties and large stiffness of BLGS identified in the present work make them suitable candidates for manufacturing nanosensors; electromechanical resonators also will aid the nanomaterials research community to design nanodevices.

Impaired Clearance and Enhanced Pulmonary Inflammatory/Fibrotic Response to Carbon Nanotubes in Myeloperoxidase-Deficient Mice

by Brett Allen

Advancement of biomedical applications of carbonaceous nanomaterials is hampered by their biopersistence and... more Advancement of biomedical applications of carbonaceous nanomaterials is hampered by their biopersistence and pro-inflammatory action in vivo. Here, we used myeloperoxidase knockout B6.129X1-MPO (MPO k/o) mice and showed that oxidation and clearance of single walled carbon nanotubes (SWCNT) from the lungs of these animals after pharyngeal aspiration was markedly less effective whereas the inflammatory response was more robust than in wild-type C57Bl/6 mice. Our results provide direct evidence for the participation of MPO – one of the key-orchestrators of inflammatory response – in the in vivo pulmonary oxidative biodegradation of SWCNT and suggest new ways to control the biopersistence of nanomaterials through genetic or pharmacological manipulations.

Drawing graphene nanoribbons on SiC by ion implantation

by Sefaattin Tongay

Cover Image Feb13th Applied Physics Letters

The most downloaded article in Feb 2012 and 3rd downloaded article in March 2012

We describe a straightforward technique for selective graphene growth and nanoribbon production onto 4H- and 6H-SiC.... more We describe a straightforward technique for selective graphene growth and nanoribbon production onto 4H- and 6H-SiC. The technique presented is as easy as ion implanting regions where graphene layers are desired followed by annealing to 100 degrees C below the graphitization temperature (T-G) of SiC. We find that ion implantation of SiC lowers the T-G, allowing selective graphene growth at temperatures below the T-G of pristine SiC and above T-G of implanted SiC. This results in an approach for patterning device structures ranging from a couple tens of nanometers to microns in size without using conventional lithography and chemical processing. (C) 2012 American Institute of Physics. [doi:10.1063/1.3682479]

Vibration and symmetry-breaking of boron-nitride nanotubes

by Rajib Chowdhury

Nanotechnology, 2010

The unique features of axial, torsional, transverse and radial breathing vibrations are captured for armchair and... more The unique features of axial, torsional, transverse and radial breathing vibrations are captured for armchair and zigzag singlewalled boron nitride nanotubes (BNNTs) based on molecular mechanics simulations and continuum mechanics theories. Equivalent Young's modulus 1TPa and shear modulus 0.4TPa are obtained independent of the chirality of BNNTs. In particular, a distorted optimized structure is observed for the first time for BNNTs with sufficiently large diameter and length. It is found that the deformed structures result in the behaviours of BNNTs deviating from those of classical columns/beams. Such symmetry breaking could also exert significant impacts on the structural instability (buckling) and the electronic properties of BNNTs that are sensitive to the structural symmetry.

The calibration of carbon nanotube based bio-nano sensors

by Rajib Chowdhury

Journal of Applied Physics, 107[12] (2010), pp. 124322:1-8.

We derive the calibration constants necessary for using single-walled carbon nanotubes (SWCNTs) as nano-scale mass... more We derive the calibration constants necessary for using single-walled carbon nanotubes (SWCNTs) as nano-scale mass sensors. The carbon nanotube resonators are assumed to be either in cantilevered or in bridged configurations. Two cases, namely when the added mass can be considered as a point mass and when the added mass is distributed over a larger area are considered. Closed-form transcendental equations have been derived for the frequency shift due to the added mass. Using the energy principles, generalized nondimensional calibration constants have been derived for an explicit relationship between the added mass and the frequency shift. A molecular mechanics model based on the universal force field potential is used to validate the new results presented. The results indicate that the distributed nature of the mass to be detected has considerable effect on the performance of the sensor.

Enhanced Photocurrent Efficiency of a Carbon Nanotube p-n Junction Electromagnetically Coupled to a Photonic Structure

by Bryan Wong

Journal of Physics D: Applied Physics, 42, 055111 (2009)

Color Detection Using Chromophore-Nanotube Hybrid Devices

by Bryan Wong

Nano Letters, 9, 1028 (2009)

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- Featured as "Issues and Events" in "Physics Today"
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Spectroscopic Properties of Nanotube-Chromophore Hybrids

by Bryan Wong

ACS Nano, 5, 7767 (2011)

Ab initio calculations of electron affinity and ionization potential of carbon nanotubes

by Fabio Trani

Francesco Buonocore, Fabio Trani, Domenico Ninno, Andrea Di Matteo, Giovanni Cantele, and Giuseppe Iadonisi
Nanotechnology 19, 025711 (2008)
http://dx.doi.org/10.1088/0957-4484/19/02/025711

Effects of mechanical alloying on an Al6061–CNT composite fabricated by semi-solid powder processing

by Yufeng Wu

Paper published in:

Materials Science and Engineering: A

Volume 538, 15 March 2012, Pages 164–172

For powder-based metal composite manufacturing, mechanical alloying has been widely used to disperse the clustered... more For powder-based metal composite manufacturing, mechanical alloying has been widely used to disperse the clustered carbon nanotubes (CNTs) in the metal matrix. However, the effects of mechanical alloying time and CNT dispersion on the microstructure and mechanical properties of the metal–CNT composite have not been fully investigated. In this study, aluminum alloy 6061 (Al6061)–CNT composites were synthesized by semi-solid powder processing from powders that had been mechanically alloyed for different durations. The powder morphology, microstructure, hardness, flexural strength, fracture surface, and composition of the Al6061–CNT composites were analyzed. The results showed that the multi-walled CNT agglomerates were first crushed into thin layers and then dispersed during the mechanical alloying procedure. The CNTs on the surfaces of Al6061 particles at various mechanical alloying times showed that the CNT length decreased quickly to about 1.2 m after 1 h of mechanical alloying and below 1 m after 3 h from the original length of over 5 m. The grains of the Al6061–CNT composites deformed severely during the mechanical alloying process. The hardness improved as the mechanical alloying time
increased. However, the bend test and fracture surface indicated reduction of the composite ductility with increasing mechanical alloying time. Compositional analysis also showed formation of aluminum carbide (Al4C3) due to the CNT addition. In addition, a modified shear lag model was used to predict the strength of Al6061–CNT at different mechanical alloying times.

Large scale 3D vertical assembly of single-wall carbon nanotubes at ambient temperatures

by Evin Gultepe

We demonstrate three-dimensional directed assembly of single-wall carbon nanotubes (SWNT) into porous alumina... more We demonstrate three-dimensional directed assembly of single-wall carbon nanotubes (SWNT) into porous alumina nanotemplates on silicon substrates by means of electrophoresis and dielectrophoresis at ambient temperatures. Assembled SWNT provided an interconnection between the surface and base of the nanotemplate. I–V measurements clearly show that the connection between silicon and SWNT is established inside the templates. This technique is particularly useful for large scale, rapid, 3D assembly of SWNT over centimeter square areas under mild conditions for nanoscale electronics applications.

http://www.iop.org/EJ/abstract/0957-4484/19/45/455309/

Analytical model for nanowire and nanotube transistors covering both dissipative and ballistic transport

by Giuseppe Iannaccone

Synthesis of Carbon Nanomaterials through Up-Cycling Agricultural and Municipal Solid Wastes

by Chuanwei Zhuo

Microstructural analysis of carbon nanomaterials produced from pyrolysis/combustion of Styrene-Butadiene-Rubber (SBR)

by Chuanwei Zhuo

Synthesis of bamboo-like carbon nanotubes on a copper foil by catalytic chemical vapor deposition from ethanol

by Jiangtao Zhu

Bamboo-like carbon nanotubes (CNTs) were synthesized on a copper foil by catalytic chemical vapor deposition (CVD)... more Bamboo-like carbon nanotubes (CNTs) were synthesized on a copper foil by catalytic chemical vapor deposition (CVD) from ethanol. The effects of temperature (700-1000 °C) and duration (5-60 min) on the growth of CNTs were investigated. Morphology and structure of the CNTs were characterized by scanning and transmission electron microscopy and Raman spectroscopy. The yield and size of the CNTs increased with temperature. Those prepared at 700 °C had a copper droplet tip and those at 800-900 °C had a copper nanoparticle inside. An amorphous carbon film consisted of a porous and non-porous layer was observed on the surface of the copper substrate, and the CNTs were really grown from this carbon film. The thickness of the carbon film increased from 187 to 900 nm when the duration increased from 5 to 60 min. It was also found that the copper foil became porous after ethanol CVD treatment. The growth mechanism of the CNTs, carbon film and motion of copper catalyst were discussed. It is proposed that a carbon film first deposited on the top surface of the copper foil while the top surface of the copper foil partially melted and migrated across the carbon film, where CNTs formed.

Metal-Free Synthesis of Carbon Nanotubes Filled with Calcium Silicate

by Jiangtao Zhu

A new metal-free catalyst CaSiO3 was developed to grow carbon nanotubes (CNTs) on a pyrolytic graphite paper tape by... more A new metal-free catalyst CaSiO3 was developed to grow carbon nanotubes (CNTs) on a pyrolytic graphite paper tape by an ethanol catalytic chemical vapor deposition method at 1200-1400 oC. The prepared CNTs with a droplet tip had a multi-walled structure and were filled with amorphous CaSiO3. Temperature, determining the melting of CaSiO3, was critical for the growth of the CNTs. This new catalyst is suggested to follow the similar roles of transition metals in the growth of CNTs by a molten state to absorb carbon and form CNTs after reaching saturation.

Label-free detection of Staphylococcus aureus in skin using real-time potentiometric biosensors based on carbon nanotubes and aptamers

by Gustavo Zelada-Guillen

Published in 'Biosensors & Bioelectronics', 2011

In this paper we report the first biosensor that is able to detect Staphylococcus aureus in real-time. A network of... more In this paper we report the first biosensor that is able to detect Staphylococcus aureus in real-time. A network of single-walled carbon nanotubes (SWCNTs) acts as an ion-to-electron potentiometric transducer and anti-S. aureus aptamers are the recognition element. Carbon nanotubes were functionalized with aptamers using two different approaches: (1) non-covalent adsorption of drop-casted pyrenil-modified aptamers onto the external walls of the SWCNTs; and (2) covalent bond formation between amine-modified aptamers and carboxylic groups previously introduced by oxidation at the ends of the SWCNTs. Both of these approaches yielded functional biosensors but there were large differences in the minimum detectable bacteria concentration and sensitivity values. With covalent functionalization, the minimum concentration detected was 8 × 102 colony-forming units (CFU)/mL and the sensitivity was 0.36 mV/Decade. With the non-covalent approach, the sensitivity was higher (1.52 mV/Decade) but the minimum concentration detected was greatly affected (107 CFU/mL). In both cases, potential as a function of Decade of bacteria concentration was linear. Functional biosensors were used to test real samples from freshly excised pig skin, contaminated with the target microorganism, as a surrogate for human skin.

Rectification at Graphene-Semiconductor Interfaces: Zero-Gap Semiconductor-Based Diodes

by Sefaattin Tongay

Electrical Characteristics of Carbon Nanotube Devices Prepared with Single Oxidative Point Defects

by Landon Prisbrey

J. Phys. Chem. C, 116 1961-1965 (2012)
http://dx.doi.org/10.1021/jp208870c

A thorough understanding of how electrons pass through point defects in carbon nanotubes is crucial for building... more A thorough understanding of how electrons pass through point defects in carbon nanotubes is crucial for building carbon nanotube devices. We have generated point defects in the sidewalls of pristine carbon nanotubes via voltage pulses from a conducting atomic force microscope probe and studied the resulting changes in electron transport properties. We find that the incorporation of an oxidative defect leads to a variety of possible electrical signatures including sudden switching events, resonant scattering, and breaking of the symmetry between electron and hole transport. We discuss the relationship between these different electronic signatures and the chemical structure/charge state of the defect. Tunneling through a defect-induced Coulomb barrier is modeled with numerical Verlet integration of Schrodinger’s equation and compared with experimental results.

Cientistas medem a liberação de gases do efeito estufa e destruição de ecossistemas causada pelo mega-incêndio de Roraima em 1997/98.

by Philip Fearnside

Barbosa, R.I. & P.M. Fearnside. 2003. Cientistas medem a liberação de gases do efeito estufa e destruição de ecossistemas causada pelo mega-incêndio de Roraima em 1997/98. Hipertexto. Brasília: Canal Ciência / IBICT,  http://www.canalciencia.ibict.br/pesquisa/0115-Gases-do-efeito-estufa-e-destruicao-de-ecossistemas-em-roraima.html