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Vibrational cluster calculations of zig-zag carbon single-wall nanotubes
2000-07-01
The results of theoretical cluster calculations of positions of the vibrational IR and Raman active modes of zig-zag carbon single-wall nanotubes of small diameter are presented. These results might be significant for fast diagnostics of the structure of synthesized carbon single-wall nanotubes. (orig.)
2009-01-01
Under hydrostatic pressure, the equivalent elastic moduli of a zigzag single-walled carbon nanotube (SWNT) are analytically determined by energy conservation, with the consideration of the covalent bond deformation. The theoretical predictions on the transverse mechanical properties of a zigzag SWNT agree reasonably well with those given by the molecular structures mechanics simulations and also the ab initio calculations. From the simple geometry calculation, the circumferential strain is about 2-3 times of the axial strain of a zigzag SWNT under hydrostatic pressure. The bulk modulus of a zigzag SWNT is found to be 3/7 times of its radial Young's modulus
Useful vacancies in Single Wall Carbon Nanotubes
2008-07-15
The electronic and structural properties of zigzag and armchair single-wall carbon nanotubes (SWCNT) with a single vacancy or two vacancies located at various distances have been obtained within the frame of the Density Function Theory (DFT) and a Molecular Dynamics method. It is found that the vacancy defects interact at long ranges in armchair SWCNTs unlike the short-range interaction in zigzag SWCNTs. The density of states for different vacancy densities shows that the local energy gap shrinks with the vacancy density increase. This and other results of the investigation provide insight into understanding the relation between the local deformation of a defective nanotube and its measurable electronic properties.
Parameterization of Theoretical Methods in the Calculation of Nano-expulsion Energies
2008-05-30
The present work encompasses an investigation of the adsorption properties of small dimer species onto a zigzag single walled carbon nanotube (ZNT for short). To perform this analysis we have considered the zigzag (8, 0) system with a length of 13.5 angstroms that has a diameter of 6.3 angstroms. Various theoretical DFT and ab initio approaches were used to attempt to parameterize an ideal method for the calculation of expulsion energies for nanotube species.
Effective masses for zigzag nanotubes in magnetic fields
2007-03-05
We consider the Schr\\"odinger operator with a periodic potential on quasi-1D models of zigzag single-wall carbon nanotubes in magnetic field. The spectrum of this operator consists of an absolutely continuous part (intervals separated by gaps) plus an infinite number of eigenvalues with infinite multiplicity. We obtain identities and a priori estimates in terms of effective masses and gap lengths.
2006-06-02
Using Coulomb correlation parameters appropriate for $\\pi$-conjugated polymers (PCPs), and a nearest neighbor hopping integral that is arrived at by fitting the energy spectra of three zigzag semiconducting single-walled carbon nanotubes (S-SWCNTs), we are able to determine quantitatively the exciton energies and exciton binding energies of 29 S-SWCNTs within a semiempirical $\\pi$-electron Hamiltonian that has been widely used for PCPs. Our work establishes the existence of a deep and fundamental relationship between PCPs and S-SWCNTs.
Stability of sp carbon (carbyne) chains
2009-01-01
An sp carbon chain, which contains only one carbon atom in its cross section, is generally considered unstable. In this Letter, however, the DFT calculations showed that an isolated sp carbon chain is more stable than the smallest armchair (3,0) and zigzag (2,2) single-walled carbon nanotubes (SWCNT). This is consistent with the fact that an isolated sp carbon chain was observed by high-resolution transmission electron microscopy, but isolated (3,0) and (2,2) SWCNTs were never produced. Nevertheless, the sp chain is less stable than lager SWCNTs
Electronic structure and optical properties of single walled ZnSe nanotubes
2010-01-01
Based on the first principle calculations with the generalized gradient approximation we investigate the structure, electronic and optical properties of ZnSe single-walled nanotubes (ZnSe-SWNTs). It is found that contrary to the carbon and BN single-walled nanotubes the band gaps of all the ZnSe-SWNTs are independent of the diameters and chirality. Moreover, the optical properties calculations of the dielectric function ε(ω) with different light polarization direction exhibit moderate optical anisotropy. When the light polarization is perpendicular to the zigzag axis, ZnSe-SWNTs seem to exhibit red-shift effect with the increase in diameters. For the light polarization is parallel to the axis, the main peaks of the dielectric spectrum remain unchanged in position and shape ...
The adsorption of methanol at the defective site of single-walled carbon nanotube
2010-01-01
The adsorption of methanol on the perfect and defective single-walled carbon nanotubes (SWCNTs) has been investigated using effective cluster models in conjunction with density functional theory. It has been found that methanol is adsorbed very weakly on the sidewall of perfect SWCNT, which is in agreement with experiment observation. In contrast, it is quite interesting to find that methanol is not only strongly chemisorbed at the zigzag edge site of defective SWCNT, but also the O-H bond of methanol is completely dissociated. This suggests that the zigzag edge of SWCNT can be the active site for adsorption and activation of methanol. However, the adsorption of methanol at the armchair edge of SWCNT is rather weak, hence suggesting the crucial effect of local edge carbon atoms arrangement on the adsorption behavior of methanol on carbon nanotubes
2010-01-01
Using molecular dynamic simulation (MDS), effects of chirality and Van der Waals interaction on Youngs modulus, elastic compressive modulus, bending, tensile, and compressive stiffness, and critical axial force of double-walled carbon nanotube (DWCNT) and its inner and outer tubes are considered. Achieving the highest safety factor, mechanical properties have been investigated under applied load on both inner and outer tubes simultaneously and on each one of them separately. Results indicate that as a compressive element, DWCNT is more beneficial than single-walled carbon nanotube (SWCNT) since it carries two times higher compression before buckling. Except critical axial pressure and tensile stiffness, in other parameters zigzag DWCNT shows higher amounts than armchair type. Outer tube ha...
Exciton effect in deformed carbon nanotubes
2007-07-04
The exciton states in deformed single-walled carbon nanotubes (SWNTs), under two kinds of strain, i.e., uniaxial and torsional, are theoretically studied in the Su-Schrieffer-Heeger (SSH) model, supplemented by long-range Coulomb interactions. It is found that for semiconducting zigzag tubes, the exciton binding energy E{sub b} and the (quasi-)continuum edge E{sub c} are very sensitive to the uniaxial strain, but not to the torsional one, showing two different kinds of variation behaviour of E{sub b} with increasing uniaxial strain, of which one decreases monotonically, and the other first increases and then decreases. Additionally, the excitons in torsionally distorted armchair tubes and uniaxially strained metallic zigzag tubes have also been studied, showing increased E{sub b} and E{sub c} with increasing strain.
Nerve agents interacting with single wall carbon nanotubes: Density functional calculations
2010-01-01
First-principles calculations based on density functional theory (DFT) method are used to investigate the adsorption properties of nerve agent DMMP on typical zigzag (semiconducting) and armchair (metallic) single wall carbon nanotubes (SWCNTs). The adsorption energies for DMMP molecule on different adsorption sites on SWCNTs are obtained. The results indicate that DMMP is weakly bound to the outer surface of both the considered SWCNTs and the obtained adsorption energy values and binding distances are typical for the physisorption. We find that DMMP adsorptive capability of metallic CNTs is about twofold that of semiconducting one. The adsorption of DMMP on the higher chiral angle nanotubes was also investigated and the results indicate that nanotube’s chirality increases the adsor...
Ferromagnetic semiconductor single wall carbon nanotube
2005-07-21
Possibility of a ferromagnetic semiconductor single wall carbon nanotube (SWCNT), where ferromagnetism is due to coupling between doped magnetic impurity on a zigzag SWCNT and electrons spin, is investigate. We found, in the weak impurity-spin couplings, at low impurity concentrations the spin up electrons density of states remain semiconductor while the spin down electrons density of states shows a metallic behavior. By increasing impurity concentrations the semiconducting gap of spin up electrons in the density of states is closed, hence a semiconductor to metallic phase transition is take place. In contrast, for the case of strong coupling, spin up electrons density of states remain semiconductor and spin down electron has metallic behavior. Also by increasing impurity spin magnitude, the semiconducting gap of spin up electrons is increased.
2003-01-01
We demonstrate that the total energy of finite, open-ended, single-walled carbon nanotubes is determined by a balance between the elastic energy due to the curvature of a tube and the chemical energy due to the dangling bonds at the open ends of a tube. The differences in total energy and radius between the most energetically stable zig-zag and armchair tubes, increases with increasing number of atoms in the tubes. Publisher: Elsevier Science BV Relation: Physics Letters A Vol. 310, Issue 2-3, p. 203-206; 10.1016/S0375-9601(03)00287-1 Other identifier: ISSN:1050-2947 Language:
Half metallicty in finite-length zigzag single walled carbon nanotube: A first-principle prediction
2008-01-01
We predict here from first-principle calculations that finite-length (n,0) single walled carbon nanotubes (SWCNTs) with H-termination at the open ends displaying antiferromagnetic coupling when n is greater than 6. An opposite local gating effect of the spin states, i.e., half metallicity, is found under the influence of an external electric field along the direction of tube axis. Remarkably, boron doping of unpassivated SWCNTs at both zigzag edges is found to favor a ferromagnetic ground state, with the B-doped tubes displaying half-metallic behavior even in the absence of an electric field. Aside of the intrinsic interest of these results, an important avenue for development of CNT-based spintronic is suggested. ©2008 American Institute of Physics Publisher: American Institute of Physics Coverage: 2008-08-18T00:00:00Z
Exohydrogenated single-wall carbon nanotubes
2001-08-15
An extensive first-principles study of fully exohydrogenated zigzag (n,0) and armchair (n,n) single-wall carbon nanotubes (C{sub n}H{sub n}), polyhedral molecules including cubane, dodecahedrane, and C{sub 60}H{sub 60} points to crucial differences in the electronic and atomic structures relevant to hydrogen storage and device applications. C{sub n}H{sub n}'s are estimated to be stable up to the radius of a (8,8) nanotube, with binding energies proportional to 1/R. Attaching a single hydrogen to any nanotube is always exothermic. Hydrogenation of zigzag nanotubes is found to be more likely than armchair nanotubes with similar radius. Our findings may have important implications for selective functionalization and finding a way of separating similar radius nanotubes from each other.
2008-01-01
The Rho(r) functions of (6,0)2, (6,0)3 and (6,0)4 zigzag single wall carbon clusters, SWCCs, were analyzed by quantum theory of atoms in molecules (QTAIM). Topological analysis of Rho(r) revealed the chemical bonds' nature and structure of cited species. It is found that molecular graph and classical frame derived from interatomic distances of clusters are in agreement and all topological rings are strain free. The direct information about the magnitude of electron density inside these clusters has been presented for the first time via the study of Laplacian of electron density. The Laplacian of Rho(r) revealed the zones of charge concentration and charge depletion. This analysis showed that inside the clusters are essentially empty space, they might be used for building a special type of ...
Random walks on finite lattice tubes
2003-05-10
Exact results are obtained for random walks on finite lattice tubes with a single source and absorbing lattice sites at the ends. Explicit formulae are derived for the absorption probabilities at the ends and for the expectations that a random walk will visit a particular lattice site before being absorbed. Results are obtained for lattice tubes of arbitrary size and each of the regular lattice types; square, triangular and honeycomb. The results include an adjustable parameter to model the effects of strain, such as surface curvature, on the surface diffusion. Results for the triangular lattice tubes and the honeycomb lattice tubes model diffusion of adatoms on single walled zig-zag carbon nano-tubes with open ends.
2007-03-28
In situ transmission electron microscopy studies have been carried out to determine the effect of temperature and pressure on the growth of carbon nanotubes by the Ni-catalyzed chemical vapour deposition of acetylene. The temperature range explored was 450-650 deg. C and the acetylene pressure range was 0.8-20 mTorr. Our observations show that straight, single-wall, carbon nanotubes tend to form at higher temperatures and lower pressures while bent, zigzag, multi-wall carbon nanotubes form at lower temperatures and higher pressures. These results can be understood as the result of competition between the arrival rate of carbon and the nucleation rate of carbon hexagons (which increases at high pressure and low temperature), and the annealing rate of the 5-ring and 7-ring defects that are responsible for the nanotube curvature.
2007-01-01
In situ transmission electron microscopy studies have been carried out to determine the effect of temperature and pressure on the growth of carbon nanotubes by the Ni-catalyzed chemical vapour deposition of acetylene. The temperature range explored was 450-650 deg. C and the acetylene pressure range was 0.8-20 mTorr. Our observations show that straight, single-wall, carbon nanotubes tend to form at higher temperatures and lower pressures while bent, zigzag, multi-wall carbon nanotubes form at lower temperatures and higher pressures. These results can be understood as the result of competition between the arrival rate of carbon and the nucleation rate of carbon hexagons (which increases at high pressure and low temperature), and the annealing rate of the 5-ring and 7-ring defects that are responsible for the nanotube curvature
Effects of boron nitride impurities on the elastic properties of carbon nanotubes
2008-01-01
The molecular dynamics method is used in this paper to investigate the effect of boron nitride (BN) impurities on the elastic properties of armchair (5, 5) (10, 10) and zigzag (9, 0) (18, 0) single-walled carbon nanotubes (SWCNTs). The results show the Young's moduli of armchair (5, 5) (10, 10) and zigzag (9, 0) (18, 0) SWCNTs with no impurities to be 948 GPa, 901 GPa and 804 GPa, 860 GPa, respectively. When the armchair SWCNTs are doped with BN, their Young's modulus decreases slightly. However, an increase in the doping ratio beyond a certain point does not cause any further reduction in the modulus, which continues to fluctuate at about 800 GPa and 760 GPa, respectively. The zigzag SWCNTs behave somewhat differently. When they are doped with BN, their Young's moduli drop quickly, and then rise as the doping ratio increases until it reaches 100% (i.e. boron nitride nanotubes are ...
Bond Lengths of Single-Walled Carbon Nanotubes
2006-11-18
Results of the bond lengths for various chiralities of single-wall carbon carbon nanotubes (SWNTs) (armchair, zigzag and chiral) are obtained. We use modified helical and rotational symmetries to describe the structure of SWNTs and Tersoff potential to minimize the energy of these tubes. It emerges that in general, two bond lengths are required for obtaining minimum energy structure, in contrast to one bond length commonly used. The difference in bond lengths depends on chirality and radius of achiral tubes. Significantly, even a small deviation from zigzag or armchair character leads to interesting behavior of bond lengths. A reduction in diameter is responsible for difference in the bond lengths of achiral nanotubes. We also calculate the bond lengths under hydrostatic pressure. The behavior of bond lengths for armchair single-wall nanotubes when calculated under pressure shows that the larger bond length decreases faster with pressure in comparison to the shorter bond length. At some critical pressure (depending upon the radius of the tube), the two bond lengths become equal to each other, reversing their difference above this critical pressure. We suggest that this behavior can be exploited to experimentally determine the chirality and radius of the carbon nanotubes, for example by observing the presence and disappearance of modes typical of two different bond lengths. This change occurs only within a few GPa of pressure.
2007-01-01
The aim of this work was to develop a finite element model based on molecular mechanics to predict the ultimate strength and strain of single wallet carbon nanotubes (SWCNT). The interactions between atoms was modelled by combining the use of non-linear elastic and torsional elastic spring. In particular, with this approach, it was tried to combine the molecular mechanics approach with finite element method without providing any not-physical data on the interactions between the carbon atoms, i.e. the CC-bond inertia moment or Young's modulus definition. Mechanical properties as Young's modulus, ultimate strength and strain for several CNTs were calculated. Further, a stress-strain curve for large deformation (up to 70%) is reported for a nanotube Zig-Zag (9,0). The results showed that good agreement with the experimental and numerical results of several authors was ...
2010-01-01
Using molecular dynamic simulation (MDS), effects of chirality and Van der Waals interaction on Young's modulus, elastic compressive modulus, bending, tensile, and compressive stiffness, and critical axial force of double-walled carbon nanotube (DWCNT) and its inner and outer tubes are considered. Achieving the highest safety factor, mechanical properties have been investigated under applied load on both inner and outer tubes simultaneously and on each one of them separately. Results indicate that as a compressive element, DWCNT is more beneficial than single-walled carbon nanotube (SWCNT) since it carries two times higher compression before buckling. Except critical axial pressure and tensile stiffness, in other parameters zigzag DWCNT shows higher amounts than armchair type. Outer tube has lower strength than inner tube. Therefore, most reliable design of ...
Single Walled Carbon Nanotubes as Reporters for the Optical Detection of Glucose
This article reviews current efforts to make glucose sensors based on the inherent optical properties of single walled carbon nanotubes. The advantages of single walled carbon nanotubes over traditional...Full Text Available
Superconductivity in carbon nanotubes coupled to transition metal atoms
2002-08-19
The electronic structures of zig-zag and arm-chair single-walled carbon nanotubes interacting with a transitional-metal atomic nanowire of Ni have been determined. The Ni nanowire creates a large electron density of states (DOS)at the Fermi energy. The dependence of the enhanced DOS on the spin state and positioning of the transition-metal wire(inside or outside the nanotube) is studied. Preliminary estimates of the electron-phonon interaction suggest that such systems may have a superconducting transition temperature of $\\sim$ 10-50 K. The signs of superconductivity seen in ``ropes'' of nanotubes may also be related to the effect of intrinsic transition-metal impurities.
Silicon and III-V compound nanotubes: structural and electronic properties
2005-05-10
Unusual physical properties of single-wall carbon nanotubes have started a search for similar tubular structures of other elements. In this paper, we present a theoretical analysis of single-wall nanotubes of silicon and group III-V compounds. Starting from precursor graphene-like structures we investigated the stability, energetics and electronic structure of zigzag and armchair tubes using first-principles pseudopotential plane wave method and finite temperature ab-initio molecular dynamics calculations. We showed that (n,0) zigzag and (n,n) armchair nanotubes of silicon having n > 6 are stable but those with n 12. Furthermore, we identified stable tubular structures formed by stacking of Si polygons. We found AlP, GaAs, and GaN (8,0) single-wall nanotubes stable and semiconducting. Our results are compared with those of single-wall carbon nanotubes.
Endohedral terthiophene in zigzag carbon nanotubes: Density functional calculations
2006-06-27
The inclusion and encapsulation of terthiophene (T3) molecules inside zigzag single-walled carbon nanotubes (CNTs) is addressed by density functional calculations. We consider the T3 molecule inside five semiconducting CNTs with diameters ranging from 9.6 to 12.7 Ang. Our results show that the T3 inclusion process is exothermic for CNTs with diameters larger than 9.5 Ang. The highest energy gain is found to be of 2 eV, decreasing as the CNT diameter increases. This notable effect of stabilization is attributed to the positively-charged CNT inner space, as induced by its curvature, which is able to accommodate the neutral T3 molecule. The band structure of T3@CNT system shows that T3 preserves its electronic identity inside the CNTs, superimposing their molecular orbitals to the empty CNT band structure without hybridizes. Our results predict that the electronic states added by the T3 molecules would rise optical effects and nonradiative relaxation from excited states.
Analytical modeling of high performance single-walled carbon nanotube field-effect-transistor
2010-01-01
We present a novel analytical modeling of a zigzag single-walled semiconducting carbon nanotube field effect transistor (CNFET) by incorporating quasi-one-dimensional (Q1D) top-of-a-potential barrier approach. By implementing multimode carrier transport, we explore and compare the performance of a low- (360cm2/Vs) and high-mobility (7200cm2/Vs) CNFET model with experimental data from nanotube and 45nm MOSFET, respectively, as well as existing compact models. Mobility and carrier concentration models are also developed to obtain a good matching with physical data. For a high mobility CNFET, we found that a maximum of 120μA is obtained. In addition to this, a CNT-based inverter is also developed by constructing n-type and p-type CNFET in ORCAD’s analog behavioral model (ABM)....
Selective adsorption of first-row atoms on boron nitride nanotubes: the effect of localized states
2005-12-19
First-principles calculations reveal that the adsorption of representative first-row atoms with different electronegativity, such as lithium (Li), carbon (C) and fluorine (F), on zigzag single-walled boron nitride nanotubes (BNNTs) exhibits surprising selectivity. The adsorption energy and adsorption site are dependent upon the chemical activity of adsorbate with respect to the B and N atoms in the host tube. In detail, the F atom prefers to be adsorbed on the top of the B atom, the C atom is energetically favorable to stay on the bridge site which is perpendicular to the tube-axis, and the Li atom hardly adheres to the tube (an endothermal reaction). The adsorption behavior of these three types of elements on BNNTs is elucidated based on the frontier molecular orbital theory. In addition, the mechanism of modification of electronic structures of BNNTs by adsorption is probed, and a feasible approach is proposed to tailor the electronic properties of BNNTs.
Broken symmetry approach and chemical susceptibility of carbon nanotubes
2010-01-01
Constituting a part of odd electrons that are excluded from the covalent bonding, effectively unpaired electrons are posed by the singlet instability of the single-determinant broken spin-symmetry unrestricted Hartree-Fock (UBS HF) SCF solution. The correct determination of the total number of effectively unpaired electrons ND and its fraction on each NDA atom is well provided by the UBS HF solution. The NDA value is offered to be a quantifier of atomic chemical susceptibility (or equivalently, reactivity) thus highlighting targets that are the most favorable for addition reactions of any type. The approach is illustrated for two families involving fragments of arm-chair (n,n) and zigzag (m,0) single-walled nanotubes different by the length and end structure. Short and long tubes as well a...
2005-11-11
The elasticity and piezoelectricity of zinc oxide (ZnO) crystals and single layers are investigated from the first-principles calculations. It is found that a ZnO thin film less than four Zn-O layers prefers a planar graphite-like structure to the wurtzite structure. ZnO single layers are much more flexible than graphite single layers in the elasticity and stronger than boron nitride single layers in the piezoelectricity. Single-walled ZnO nanotubes (SWZONTs) can exist in principle because of their negative binding energy. The piezoelectricity of SWZONTs depends on their chirality. For most ZnO nanotubes except the zigzag type, twists around the tube axis will induce axial polarizations. A possible scheme is proposed to achieve the SWZONTs from the solid-vapor phase process with carbon nanotubes as templates.
2009-01-01
Density functional theory (DFT) is used to determine chemical-shielding isotropic (CSI) and nucleus-independent chemical shift (NICS), an index of local aromaticity, for the composing of finite length (6, 0) and (4, 4) single-wall boron nitride nanotubes (BNNTs) as a function of their length for the first time. One of the highlights of the study is different CSI values of middle layers for both zigzag and armchair BNNTs, whereas the values do not change much for the middle layers with increase of the nanotube lengths. So the computed CSI values may spread and apply to the longer nanotubes. The NICS variations beside zigzag BN nanotubes are more significant within armchair BNNTs with increase of nanotube length.
2010-01-01
We have used density functional theory (DFT) at the B3LYP/6-31G level to calculate Raman and IR spectra of zigzag (n,0) single-walled carbon nanotubes (SWNTs) and (n,0) and (2n,0) double-walled carbon nanotubes (DWNTs), for n ranging from 6 to 19 and 6 to 8, respectively. In the low frequency RBM region, calculated Raman spectra of SWNTs indicate that there are three vibrational modes, with symmetries A1g, E1g and E2g, whose frequencies depend strongly on nanotube diameter. The E2g mode is not only diameter dependent, but also depends on whether the number of hexagons formed in the circumference direction of the CNT is even or odd. Two IR spectral modes (of A2u and E1u symmetries) are found in calculated IR spectra that show strong diameter dependence. Also, three Raman bands with E1g, A1g...
Nose-Hoover thermostat length effect on thermal conductivity of single wall carbon nanotubes
2010-01-01
Non-equilibrium molecular dynamics simulations are used to determine the thermal conductivities of single wall carbon nanotubes. By fixing opposing ends of an armchair single wall carbon nanotube with a Nose-Hoover thermostat, the length dependence of thermal conductivities of single wall carbon nanotubes were studied in a vacuum. Specifically, single wall carbon nanotubes of 12.3nm, 24.6nm, and 36.9nm lengths with varying fixed end temperatures were analyzed to determine thermal conductivities. In addition, the fixed end temperature lengths of single wall carbon nanotubes were varied to see convergence of the temperature profiles.
40 CFR 721.10156 - Single-walled carbon nanotubes (generic).
...2009-07-01 false Single-walled carbon nanotubes (generic). 721.10156 Section...721.10156 Single-walled carbon nanotubes (generic). (a) Chemical substance...generically as single-walled carbon nanotubes (PMN P-08-328) is subject...
Water Soluble Single-Walled Carbon Nanotubes Inhibit Stimulated Endocytosis in Neurons
2008-10-01
We report the use of chemically-functionalized water soluble single-walled carbon nanotube (SWNT) graft copolymers to inhibit endocytosis. The graft copolymers were prepared by the functionalization...Full Text Available
2007-07-11
Amine functionalized soluble single walled carbon nanotubes (SWNTs) were derivatized with cisplatin prodrug conjugates as a delivery system by which to internalize multiple prodrug centers....Full Text Available
Single-Walled Carbon Nanotubes Induces Oxidative Stress in Rat Lung Epithelial Cells
2007-07-01
Single-walled carbon nanotubes (SWCNT) show unique properties find applications in micro devices; electronics to biological systems specially drug delivery and gene therapy. However the manufacture...Full Text Available
2009-07-01
Significant shifts of the frequency of the Raman spectra of the tangential mode of single walled carbon nanotubes (SWNTs) and fluorinated tubes (FSWNTs) in composites of polybutadiene (PB) were...Full Text Available
Magnetic Property Measurements on Single Wall Carbon Nanotube-Polyimide Composites
Temperature and magnetic field dependent magnetization measurements were performed on polyimide nanocomposite samples, synthesized with various weight percentages of single wall carbon nanotubes. It was ...
A black body absorber from vertically aligned single-walled carbon nanotubes
2009-04-14
Among all known materials, we found that a forest of vertically aligned single-walled carbon nanotubes behaves most similarly to a black body, a theoretical material that absorbs all incident light....Full Text Available
Simulated Stress and Stretch of SWCNT
2004-01-01
We have studied the mechanical stability of open single wall carbon nanotubes (SWCNT) under axial stress, stretch, and twist. SWCNTs with different chiralities and number of atoms have been simulated with a classical molecular dynamics method employing the many-body empirical Tersoff-Brenner potential. Stress and stretch have been achieved by enforcing constant linear velocity on the edge atoms from both sides of the SWCNT as suggested by Srivastava and Barnard. We find opposite trends in scaling at fast (1/10 of v_sound, the sound velocity in the carbon tube), and slow (1/20 v_sound) stretch. Another finding is that at fast stretch short zigzag (10, 0) tubes transform from perfect to a plastic state before they break in the middle, while longer tubes (containing above 2000 carbon atoms) break-up directly in the elastic state. Thus, short tubes behave like metals or ionic solids, while long tubes resemble ceramics or glasses under the conditions studied. All tubes form spiral-like structures when twisted. Gentle, periodic twist of the tubes is a promising way for creating dynamical adsorbing centers for various gases. Keywords: Molecular Dynamics simulations, elasticity and inelasticity, single-wall carbon nanotubes, nanoscale pattern formation, constant-composition solid-solid phase transformations, pressure treatment PACS: 02.70.Ns, 81.30.Hd, 81.40.Jj, 81.40.Vw
First principles study of magnetism in nanographenes
2007-06-07
Magnetism in nanographenes (also know as polycyclic aromatic hydrocarbons, or PAHs) are studied with first principles density functional calculations. We find that an antiferromagnetic (AFM) phase appears as the PAH reaches a certain size. This AFM phase in PAHs has the same origin as the one in infinitely long zigzag-edged graphene nanoribbons, namely, from the localized electronic state at the zigzag edge. The smallest PAH still having an AFM ground state is identified. With increased length of the zigzag edge, PAHs approach an infinitely long ribbon in terms of (1) the energetic ordering and difference among the AFM, ferromagnetic (FM), and nonmagnetic (NM) phases and (2) the average local magnetic moment at the zigzag edges. These PAHs serve as ideal targets for chemical synthesis of nanographenes that possess magnetic properties. Moreover, our calculations support the interpretation that experimentally observed magnetism in activated carbon fibers originates from the zigzag edges of the nanographenes.
Enhancement of semiconducting single-wall carbon nanotubes photoluminescence
2010-01-07
Photoluminescence properties of semiconducting single wall carbon nanotubes (s-SWNT) thin films with different metallic single wall carbon nanotubes (m-SWNT) concentrations are reported. s-SWNT purified samples are obtained by polymer assisted selective extraction. We show that a few m-SWNT in the sample generates a drastic quenching of the emission. Therefore, highly purified s-SWNT films are a strongly luminescent material and a good candidate for future applications in photonics, such as near infrared emitters, modulators and detectors.
A single wall carbon nanotube double quantum dot
2006-06-14
We report on two top-gate defined, coupled quantum dots in a semiconducting single wall carbon nanotube, constituting a tunable double quantum dot system. The single wall carbon nanotubes are contacted by titanium electrodes, and gated by three narrow top-gate electrodes as well as a back-gate. We show that a bias spectroscopy plot on just one of the two quantum dots can be used to extract the addition energy of both quantum dots. Furthermore, honeycomb charge stability diagrams are analyzed by an electrostatic capacitor model that includes cross capacitances, and we extract the coupling energy of the double quantum dot.
Characterizing SWCNT Dispersion in Polymer Composites
The new wave of single wall carbon nanotube (SWCNT) infused composites will yield structurally sound multifunctional nanomaterials. The SWCNT network requires thorough dispersion within the polymer matrix in ...
2009-01-01
We theoretically study effects of substitute nitrogen-doping on linear optical properties of zigzag carbon nanotubes using tight-binding model and gradient approximation. It is found that, generally, nitrogen-doping reduces the value of absorption peaks and creates a number of new absorption peaks. In addition, near the low energy range, linear optical absorption spectra of nitrogen-doped (m,0) zigzag tubes are remarkably dependent on whether m mod 3 (the remainder of dividing m by 3) is equal to 0, 1 or 2
The unique chemical reactivity of a graphene nanoribbon's zigzag edge
2007-04-01
The zigzag edge of a graphene nanoribbon possesses a unique electronic state that is near the Fermi level and localized at the edge carbon atoms. We investigate the chemical reactivity of these zigzag edge sites by examining their reaction energetics with common radicals from first principles. A "partial radical? concept for the edge carbon atoms is introduced to characterize their chemical reactivity, and the validity of this concept is verified by comparing the dissociation energies of edge-radical bonds with similar bonds in molecules. In addition, the uniqueness of the zigzag-edged graphene nanoribbon is further demonstrated by comparing it with other forms of sp2 carbons, including a graphene sheet, nanotubes, and an armchair-edged graphene nanoribbon.
2010-01-01
The structures of zigzag-zigzag, armchair-zigzag, zigzag-chiral, armchair-armchair, armchair-chiral, and chiral-chiral pair connections produced by single-walled carbon nanotubes 1.55.0 diameter with the use of the combined 57 and 48 topological defects have been calculated by molecular mechanics methods. It has been established that the use of the combined 57 topological defect makes it possible to produce connections between pairs of single-walled carbon nanotubes with any conductivities, chiralities, and diameters, whereas the use of the combined 48 topological defect provides a means for forming connections between nanotubes only with the same type of conductivity. The angles between the axes of nanotubes connected by the combined 57 and 48 topological defects lie ...
Infinite single-walled boron-nitride nanotubes studies by LGTO-PBC-DFT method
2009-01-01
Localized Gaussian type orbital-periodic boundary condition-density functional theory (LGTO-PBC-DFT) method was used to determine the electronic and detailed geometrical structures of (n, 0) zigzag type for n=633 and (n, n) armchair type for n=315 single-walled boron-nitride (BN) nanotubes with infinite tubular lengths. The calculations reveal that the calculated Eg (band gap between HOCO and LUCO) increases with increasing tubular diameter and eventually converge to 5.03eV for BN nanotubes of larger tubular diameter. According to the calculated Egs, the BN nanotubes are semi-conductor and their conductivities are not sensitive to the tubular diameter. Theoretically, the calculated bond length decreases with increasing tubular diameter. Based on our calculations, the bond length an...
Synthesis and characterization of chitosan–carbon nanotube composites
2009-03-15
Acid functionalized single walled carbon nanotubes were covalently grafted to chitosan by first reacting the oxidized carbon nanotubes with thionyl chloride to form acyl-chlorinated carbon nanotubes...Full Text Available
Miniature Arcs for Synthesis of Carbon Nanotubes in Microgravity
Although many methods are available for producing single-walled carbon nanotubes (SWNTs), the conventional carbon arc process remains the most popular due to its simplicity and large production rate. In the carbon ...
Small angle neutron scattering study of isolated single wall carbon nano tubes in water
2007-07-01
As an effort to provide more practical approaches to a wide range of potential applications of carbon nano tubes, we report a new type of noncovalently functionalized isolated single-walled carbon nano tube(SWNT) which is easily dispersible in water by only ten minutes of mild vortex mixing. The structure and quality of dispersion have been investigated using small angle neutron scattering (SANS) technique.
Single-walled carbon nanotubes as a multimodal — thermoacoustic and photoacoustic — contrast agent
2009-01-01
We have developed a novel carbon nanotube-based contrast agent for both thermoacoustic and photoacoustic tomography. In comparison with de-ionized water, single-walled carbon nanotubes exhibited...Full Text Available
2006-11-27
We present a systematic study of the electronic and magnetic properties of transition-metal (TM) atomic chains adsorbed on the zigzag single-wall carbon nanotubes (SWNTs). We considered the adsorption on the external and internal wall of SWNT and examined the effect of the TM coverage and geometry on the binding energy and the spin polarization at the Fermi level. All those adsorbed chains studied have ferromagnetic ground state, but only their specific types and geometries demonstrated high spin polarization near the Fermi level. Their magnetic moment and binding energy in the ground state display interesting variation with the number of $d-$electrons of the TM atom. We also show that specific chains of transition metal atoms adsorbed on a SWNT can lead to semiconducting properties for the minority spin-bands, but semimetallic for the majority spin-bands. Spin-polarization is maintained even when the underlying SWNT is subjected to high radial strain. Spin-dependent electronic structure becomes discretized when TM atoms are adsorbed on finite segments of SWNTs. Once coupled with non-magnetic metal electrodes, these magnetic needles or nanomagnets can perform as spin-dependent resonant tunnelling devices. The electronic and magnetic properties of these nanomagnets can be engineered depending on the type and decoration of adsorbed TM atom as well as the size and symmetry of the tube. Our study is performed by using first-principles pseudopotential plane wave method within spin-polarized Density Functional Method.
Single-Wall Carbon Nanotube Anodes for Lithium Cells
In recent experiments, highly purified batches of single-wall carbon nanotubes (SWCNTs) have shown promise as superior alternatives to the graphitic carbon-black anode materials heretofore used in rechargeable ...
Single-Wall Carbon Nanotube Anodes for Lithium Cells
In recent experiments, highly purified batches of single-wall carbon nanotubes (SWCNTs) have shown promise as superior alternatives to the graphitic carbon-black anode materials heretofore used in rechargeable ...
Single-Wall Carbon Nanotube Anodes for Lithium Cells
In recent experiments, highly purified batches of single-wall carbon nanotubes (SWCNTs) have shown promise as superior alternatives to the graphitic carbon-black anode materials heretofore used in rechargeable ...
Miniature Arcs for Synthesis of Carbon Nanotubes in Microgravity
Although many methods are available for producing single-walled carbon nanotubes (SWNTs), the conventional carbon arc process remains the most popular due to its simplicity and large production rate. In ...
Laser ablation for the synthesis of carbon nanotubes
Single walled carbon nanotubes are produced in a novel apparatus by the laser-induced ablation of moving carbon target. The laser used is of high average power and ultra-fast pulsing. According to various preferred ...
Laser ablation for the synthesis of carbon nanotubes
Single walled carbon nanotubes are produced in a novel apparatus by the laser-induced ablation of moving carbon target. The laser used is of high average power and ultra-fast pulsing. According to various ...
Laser ablation for the synthesis of carbon nanotubes
Single walled carbon nanotubes are produced in a novel apparatus by the laser-induced ablation of moving carbon target. The laser used is of high average power and ultra-fast pulsing. According to various ...
Laser ablation for the synthesis of carbon nanotubes
Single walled carbon nanotubes are produced in a novel apparatus by the laser-induced ablation of moving carbon target. The laser used is of high average power and ultra-fast pulsing. According to various ...
Laser ablation for the synthesis of carbon nanotubes
Single walled carbon nanotubes are produced in a novel apparatus by the laser-induced ablation of moving carbon target. The laser used is of high average power and ultra-fast pulsing. According to various preferred ...
Laser ablation for the synthesis of carbon nanotubes
Single walled carbon nanotubes are produced in a novel apparatus by the laser-induced ablation of moving carbon target. The laser used is of high average power and ultra-fast pulsing. According to various preferred ...
Laser ablation for the synthesis of carbon nanotubes
Single walled carbon nanotubes are produced in a novel apparatus by the laser-induced ablation of moving carbon target. The laser used is of high average power and ultra-fast pulsing. According to various ...
Laser ablation for the synthesis of carbon nanotubes
Single walled carbon nanotubes are produced in a novel apparatus by the laser-induced ablation of moving carbon target. The laser used is of high average power and ultra-fast pulsing. According to ...
Laser ablation for the synthesis of carbon nanotubes
Single walled carbon nanotubes are produced in a novel apparatus by the laser-induced ablation of moving carbon target. The laser used is of high average power and ultra-fast pulsing. According to various preferred ...
Iron Catalyst Chemistry in High Pressure Carbon Monoxide Nanotube Reactor
The high-pressure carbon monoxide (HiPco) technique for producing single wall carbon nanotubes (SWNT) is analyzed using a chemical reaction model coupled with properties calculated along streamlines. Streamline ...
Iron Catalyst Chemistry in High Pressure Carbon Monoxide Nanotube Reactor
The high-pressure carbon monoxide (HiPco) technique for producing single wall carbon nanotubes (SWNT) is analyzed using a chemical reaction model coupled with properties calculated along streamlines. Streamline ...
Iron Catalyst Chemistry in High Pressure Carbon Monoxide Nanotube Reactor
The high-pressure carbon monoxide (HiPco) technique for producing single wall carbon nanotubes (SWNT) is analyzed using a chemical reaction model coupled with properties calculated along streamlines. Streamline ...
Improvements in Production of Single-Walled Carbon Nanotubes
A continuing program of research and development has been directed toward improvement of a prior batch process in which single-walled carbon nanotubes are formed by catalytic disproportionation of carbon ...
2007-06-15
Exposure of mice to single walled carbon nanotubes (SWCNTs) induces an unusually robust pulmonary inflammatory response with an early onset of fibrosis, which is accompanied by oxidative stress...Full Text Available
2005-11-08
An oxygen-assisted hydrocarbon chemical vapor deposition method is developed to afford large-scale, highly reproducible, ultra-high-yield growth of vertical single-walled carbon nanotubes (V-SWNTs)....Full Text Available
Transverse electric field–induced deformation of armchair single-walled carbon nanotube
The deformation of armchair single-walled carbon nanotube under transverse electric field has been investigated using density functional theory. The results show that the circular cross-sections of...Full Text Available
2009-01-01
It is demonstrated that an optically transparent and electrically conductive polyethylene oxide (PEO) film is fabricated by the introduction of individualized single-walled carbon nanotubes (SWNTs). The incorporated SWNTs in the PEO film sustain their intrinsic electronic and optical properties and, in addition, the intrinsic properties of the polymer matrix are retained. The individualized SWNTs with smaller diameter provide high transmittance as well as good electrical conductivity in PEO films.
Thermal ablation of tumor cells with antibody-functionalized single-walled carbon nanotubes
2008-06-24
Single-walled carbon nanotubes (CNTs) emit heat when they absorb energy from near-infrared (NIR) light. Tissue is relatively transparent to NIR, which suggests that targeting CNTs to tumor cells, followed...Full Text Available
Single Wall Carbon Nanotube Weak Links
2007-03-13
We have reproducibly contacted gated single wall carbon nanotubes (SWCNT) to superconducting leads based on niobium. The devices are identified to belong to two transparency regimes: The Coulomb blockade and the Kondo regime. Clear signature of the superconducting leads is observed in both regimes and in the Kondo regime a narrow zero bias peak interpreted as a proximity induced supercurrent persist in Coulomb blockade diamonds with Kondo resonances.
2003-10-15
The exposure of as-produced HiPCo single-walled carbon nanotubes (SWNTs) to a camera flash causes ignition, (oxidation) and subsequent coalescence of the Fe catalyst particles, while purified SWNTs do not respond to flashing. TEM and electron energy loss spectroscopy (EELS) analysis attribute the phenomena to the pyrophoric oxidation of Fe nanoparticles.
2008-09-01
BackgroundSingle-wall carbon nanotubes (SWCNTs), with their unique physicochemical and mechanical properties, have many potential new applications in medicine and industry. There...Full Text Available
Raman study of bromine-doped single-walled carbon nanotubes under high pressure
2002-11-11
Raman results for different single-walled carbon nanotube bundles doped with Br{sub 2} were studied both at ambient pressure and under high pressure up to 6 GPa. Our study indicates that bromine resides in the interstitial channel of nanotube bundles as a form of polymer.
Raman study of bromine-doped single-walled carbon nanotubes under high pressure
2002-01-01
Raman results for different single-walled carbon nanotube bundles doped with Br2 were studied both at ambient pressure and under high pressure up to 6 GPa. Our study indicates that bromine resides in the interstitial channel of nanotube bundles as a form of polymer
Raman study of bromine-doped single-walled carbon nanotubes under high pressure
Raman results for different single-walled carbon nanotube bundles doped with Br sub 2 were studied both at ambient pressure and under high pressure up to 6 GPa. Our study indicates that bromine resides in the interstitial channel of nanotube bundles as a form of polymer.
LDRD final report on carbon nanotube composites
Carbon nanotubes and their composites were examined using computational and experimental techniques in order to modify the mechanical and electrical properties of resins. Single walled nanotubes were the focus of the first year effort; however, sufficient quantities of high purity single walled nanotubes could not be obtained for mechanical property investigations. The unusually high electrical conductivity of composites loaded with <1% of multiwalled nanotubes is useful, and is the focus of continuing, externally funded, research.
LDRD final report on carbon nanotube composites
1997-04-01
Carbon nanotubes and their composites were examined using computational and experimental techniques in order to modify the mechanical and electrical properties of resins. Single walled nanotubes were the focus of the first year effort; however, sufficient quantities of high purity single walled nanotubes could not be obtained for mechanical property investigations. The unusually high electrical conductivity of composites loaded with <1% of multiwalled nanotubes is useful, and is the focus of continuing, externally funded, research.
2008-12-04
The adsorptions of a glycine molecule as well as dehydrogenated radicals on the side walls of both intrinsic and boron-doped (B-doped) single-walled (8,0) carbon nanotubes (SWCNTs) were investigated...Full Text Available
Single-walled carbon nanotubes (SWCNTs), which were commercial grade containing 60–70 wt% impurity, were treated in a mild poly(phosphoric acid) (PPA). The purity of PPA treated SWCNTs...Full Text Available
2008-12-10
A novel single-walled carbon nanotube (SWNT)-based tumor-targeted drug delivery system (DDS) has been developed, which consists of a functionalized SWNT linked to tumor-targeting modules as...Full Text Available
DNA-wrapped single-walled carbon nanotube hybrid fibers for supercapacitors and artificial muscles
2008-02-04
DNA-single-walled carbon nanotube (SWNT) hybrid fibers are fabricated. Partial debundling and alignment of the nanotubes reduces junction resistances leading to high conductivities. The DNA is effective, as a mechanical binder and for debundling the SWNTs, even when immersed in liquid electrolytes. Therefore, the DNA-SWNT Fibers show excellent supercapacitor behavior and superior actuation performance. (Abstract Copyright [2008], Wiley Periodicals, Inc.)
We present a new thin-film solar cell structure in which the traditional transparent conductive oxide electrode (ZnO) is replaced by a transparent conductive coating consisting of a network of bundled single-wall carbon nanotubes. Optical transmission pro...
2010-01-01
High purity single walled carbon nanotubes (SWCNTs) were prepared from arc discharge produced cloth-like soot by a new purification strategy, in which liquid oxidation and steam oxidation were combined with a freeze-drying process to remove the metallic and carbonaceous impurities. The process gives a product of
A dihydroxotin(IV) porphyrin functionalized single-walled carbon nanotubes (SWNTs) nanohybrid is obtained. Solubility of the nanohybrid in organic solvents is determined by UV-Vis-NIR absorption spectroscopy....Full Text Available
Electron-electron interaction effects on the photophysics of metallic single-walled carbon nanotubes
2009-01-01
Single-walled carbon nanotubes are strongly correlated systems with large Coulomb repulsion between two electrons occupying the same pz orbital. Within a molecular Hamiltonian appropriate for correlated pi-electron systems, we show that optical excitations polarized parallel to the nanotube axes in the so-called metallic single-walled carbon nanotubes are excitons. Our calculated absolute exciton energies in twelve different metallic single-walled carbon nanotubes, with diameters in the range 0.8-1.4 nm, are in nearly quantitative agreement with experimental results. We have also calculated the absorption spectrum for the (21, 21) single-walled carbon nanotube in the E22 region. Our calculated spectrum gives an excellent fit to the experimental absorption spectrum. In all cases our calculated exciton binding energies ...
2009-09-01
Raw single-walled carbon nanotubes produced by arc discharge were oxidized in the air to eliminate amorphous carbon, and then dispersed in the aqueous solution of sodium taurocholate supersonically. Thus obtained stable dispersion was subjected to centrifugation, and the metal catalysts and varying carbon impurities were separated with carbon nanotubes. The efficiency of the above procedure was confirmed by scanning electron microscope observation, thermogravimetry, and optical absorption and Raman spectroscopic analyses. The advantage of this procedure lies in easiness, high purity, and no pollution to environment.
2009-01-01
Raw single-walled carbon nanotubes produced by arc discharge were oxidized in the air to eliminate amorphous carbon, and then dispersed in the aqueous solution of sodium taurocholate supersonically. Thus obtained stable dispersion was subjected to centrifugation, and the metal catalysts and varying carbon impurities were separated with carbon nanotubes. The efficiency of the above procedure was confirmed by scanning electron microscope observation, thermogravimetry, and optical absorption and Raman spectroscopic analyses. The advantage of this procedure lies in easiness, high purity, and no pollution to environment
Single walled carbon nanotube network electrodes for dye solar cells
2010-10-15
The photovoltaic properties of a new working electrode for dye sensitised solar cells, consisting of networks of covalently bound single walled carbon nanotubes on indium tin oxide, have been investigated. Following covalent sensitisation of the carbon nanotube networks with a ruthenium dye an appreciable cathodic photocurrent is measured upon illumination with simulated sunlight. Significant increases in photocurrent density are observed by building up sequential layers of carbon nanotube cross-linked with ethylenediamine to form a three-dimensional dye sensitised single walled carbon nanotube network. Such electrodes are promising for the future fabrication of low cost, minimal material use solar cells. (author)
Single walled carbon nanotube network electrodes for dye solar cells
2010-01-01
The photovoltaic properties of a new working electrode for dye sensitised solar cells, consisting of networks of covalently bound single walled carbon nanotubes on indium tin oxide, have been investigated. Following covalent sensitisation of the carbon nanotube networks with a ruthenium dye an appreciable cathodic photocurrent is measured upon illumination with simulated sunlight. Significant increases in photocurrent density are observed by building up sequential layers of carbon nanotube cross-linked with ethylenediamine to form a three-dimensional dye sensitised single walled carbon nanotube network. Such electrodes are promising for the future fabrication of low cost, minimal material use solar cells.
Alignment enhanced photoconductivity in single wall carbon nanotube films
2009-01-01
In this paper we report, for the first time, the alignment enhanced photoconductivity of single wall carbon nanotube films upon laser illumination. The photoconductivity exhibited an increase, decrease or even 'negative' values when the laser spot was on different positions between contact electrodes, showing a 'position' dependent photoconductivity of partially aligned films of carbon nanotubes. Photon induced charge carrier generation in single wall carbon nanotubes and subsequent charge separation across the metal-carbon nanotube contacts is believed to cause the photoconductivity changes. A net photovoltage of approx4 mV and a photocurrent of approx10 muA were produced under the laser intensity of approx273 mW with a quantum efficiency of approx7.8% in vacuum. The photocurrent was observed to be ...
Synthesis and Characterization of Carbon Nanotubes for Reinforced and Functional Applications
Many efforts have been engaged recently in synthesizing single-walled and multi-walled carbon nanotubes due to their superior mechanical, electrical and thermal properties, which could be used for numerous ...
Synthesis and Characterization of Carbon Nanotubes for Reinforced and Functional Applications
Many efforts have been engaged recently in synthesizing single-walled and multi-walled carbon nanotubes due to their superior mechanical, electrical and thermal properties, which could be used to enhance ...
Strain Dependence of Photoluminescense of Individual Carbon Nanotubes
We have investigated strain dependence of photoluminescense (PL) spectra of single wall carbon nanotubes (SWNT). Nanotubes were sparsely dispersed in a thin PMMA film applied to acrylic bar, and strained in both ...
Strain Dependence of Photoluminescense of Individual Carbon Nanotubes
We have investigated strain dependence of photoluminescense (PL) spectra of single wall carbon nanotubes (SWNT). Nanotubes were sparsely dispersed in a thin PMMA film applied to acrylic bar, and strained in both ...
Strain Dependence of Photoluminescense of Individual Carbon Nanotubes
We have investigated strain dependence of photoluminescense (PL) spectra of single wall carbon nanotubes (SWNT). Nanotubes were sparsely dispersed in a thin PMMA film applied to acrylic bar, and strained ...
2008-12-17
A series of self-assembling multidomain peptides have been designed, synthesized, and tested for their ability to individually suspend single-walled carbon nanotubes (SWCNTs) in water while...Full Text Available
Radio frequency analog electronics based on carbon nanotube transistors
2008-02-05
The potential to exploit single-walled carbon nanotubes (SWNTs) in advanced electronics represents a continuing, major source of interest in these materials. However, scalable integration of SWNTs into...Full Text Available
Broad applications of single-walled carbon nanotubes (SWCNT) dictate the necessity to better understand their health effects. Poor recognition of non-functionalized SWCNT by phagocytes is prohibitive...Full Text Available
Very high purity single-walled carbon nanotubes (SWNTs) were obtained from HiPco SWNT samples containing Fe ... acid treatment to remove the metal, filtration, ... available activated carbons ($1000 m2/g) while ...
2008-09-01
An optimized noninvasive Raman microscope was used to evaluate tumor targeting and localization of single walled carbon nanotubes (SWNTs) in mice. Raman images were acquired in two groups of...Full Text Available
Li, Jing - NASA Technical Reports Server
Enclose terms in double quotation marks (") to search for exact phrases, ... Carbon Nanotube Based Chemical Sensors for Space and Terrestrial Applications ... Characterizations of Enriched Metallic Single-Walled Carbon Nanotubes in ...
Enclose terms in double quotation marks (") to search for exact phrases, ... Carbon Nanotube Based Chemical Sensors for Space and Terrestrial Applications ... Development of Metal-impregnated Single Walled Carbon Nanotubes for Toxic Gas ...
Interaction of D-Amino Acid Oxidase with Carbon Nanotubes: Implications in the Design of Biosensors
2009-02-01
We have investigated the interaction of D-amino acid oxidase (DAAO) with single walled carbon nanotubes (CNT) by spectroscopic ellipsometry. Dynamic adsorption experiments were performed at...Full Text Available
Electronic Properties of Carbon Nanotubes and Junctions
Metallic and semiconducting Single Wall Carbon Nanotubes (CNT) have recently been characterized using scanning tunneling microscopy (STM) and the manipulation of individual CNT has been demonstrated. These developments make ...
Drug delivery with carbon nanotubes for in vivo cancer treatment
2008-08-15
Chemically functionalized single-walled carbon nanotubes (SWNTs) have shown promise in tumor targeted accumulation in mice and exhibit biocompatibility, excretion and little toxicity. Here,...Full Text Available
Cross-polarized excitons in carbon nanotubes
2008-05-13
Polarization of low-lying excitonic bands in finite-size semiconducting single-walled carbon nanotubes (SWNTs) is studied by using quantum-chemical methodologies. Our calculations elucidate properties...Full Text Available
Many applications of single wall carbon nanotubes (SWCNT), especially in microelectronics, will benefit from use of certain (n,m) nanotube types (metallic, small gap semiconductor, etc.) Especially fascinating ...
Conductivity of a single DNA duplex bridging a carbon nanotube gap
2008-03-01
We describe a general method to integrate DNA strands between single-walled carbon nanotube electrodes and to measure their electrical properties. We modified DNA sequences with amines on either...Full Text Available
2008-02-05
Carbon nanotubes are promising new materials for molecular delivery in biological systems. The long-term fate of nanotubes intravenously injected into animals in vivo is currently unknown,...Full Text Available
Characterizations of Enriched Metallic Single-Walled Carbon Nanotubes in Polymer Composite
Using different processing conditions, we disperse the single-walled carbon nanotube (SWNT) into the polymethyl methacrylate (PMMA) to form composites. In the melt-blended sample, the SWNTs originally semiconducting - became ...
Characterizations of Enriched Metallic Single-Walled Carbon Nanotubes in Polymer Composite
Using different processing conditions, we disperse the single-walled carbon nanotube (SWNT) into the polymethyl methacrylate (PMMA) to form composites. In the melt-blended sample, the SWNTs originally semiconducting - ...
Characterizations of Enriched Metallic Single-Walled Carbon Nanotubes in Polymer Composite
Using different processing conditions, we disperse the single-walled carbon nanotube (SWNT) into the polymethyl methacrylate (PMMA) to form composites. In the melt-blended sample, the SWNTs originally semiconducting - ...
Characterizations of Enriched Metallic Single-Walled Carbon Nanotubes in Polymer Composite
Using different processing conditions, we disperse the single-walled carbon nanotube (SWNT) into the polymethyl methacrylate (PMMA) to form composites. In the melt-blended sample, the SWNTs originally semiconducting - became ...
Characterizations of Enriched Metallic Single-Walled Carbon Nanotubes in Polymer Composite
Using different processing conditions, we disperse the single-walled carbon nanotube (SWNT) into the polymethyl methacrylate (PMMA) to form composites. In the melt-blended sample, the SWNTs originally semiconducting - became ...
Characterizations of Enriched Metallic Single-Walled Carbon Nanotubes in Polymer Composite
Using different processing conditions, we disperse the single-walled carbon nanotube (SWNT) into the polymethyl methacrylate (PMMA) to form composites. In the melt-blended sample, the SWNTs originally semiconducting - became ...
Carbon nanotube screening effects on the water-ion channels
2008-07-28
A self-consistent tight-binding method is used to investigate the screening effects of semiconducting and metallic single-wall carbon nanotubes (SWCNTs) when the water molecules and various charged...Full Text Available
Carbon Nanotube Amplification Strategies for Highly Sensitive Immunodetection of Cancer Biomarkers
2006-08-30
We describe herein the combination of electrochemical immunosensors using single-wall carbon nanotube (SWNT) forest platforms with multi-label secondary antibody-nanotube bioconjugates for highly...Full Text Available
Nucleation and growth of single wall carbon nanotubes
2005-09-15
The nucleation and growth of single wall carbon nanotubes from a carbon-saturated catalytic particle surrounded by a single sheet of graphene is described qualitatively by using a very restricted number of elementary processes, namely Stone-Wales defects and carbon bi-interstitials. Energies of the different configurations are estimated by using a Tersoff energy minimization scheme. Such a description is compatible with a broad variety of size or helicity of the tubes. Several mechanisms of growth of the embryos are considered: one of them is made more favourable when the tubes embryos are arranged in an hexagonal network in the graphene plane. All the proposed mechanisms can be indefinitely repeated for the growth of the nanotubes.
Chemical vapour deposition of single walled carbon nanotubes freely suspended over nanotube supports
2007-04-04
Single walled carbon nanotubes (SWNTs) suspended above the substrate can be fabricated simply and rapidly by chemical vapour deposition growth over pre-grown multi-walled carbon nanotubes (MWNTs). SWNTs are suspended either on a randomly organized carbon nanotube network on an unpatterned substrate, or between organized pillars made from vertically aligned nanotube forests on a patterned substrate. All nanotubes are produced during a single growth run using a two step growth technique. This approach enables the fabrication of laterally suspended SWNT networks which are well suited for optical applications.
Chemical vapour deposition of single walled carbon nanotubes freely suspended over nanotube supports
2007-01-01
Single walled carbon nanotubes (SWNTs) suspended above the substrate can be fabricated simply and rapidly by chemical vapour deposition growth over pre-grown multi-walled carbon nanotubes (MWNTs). SWNTs are suspended either on a randomly organized carbon nanotube network on an unpatterned substrate, or between organized pillars made from vertically aligned nanotube forests on a patterned substrate. All nanotubes are produced during a single growth run using a two step growth technique. This approach enables the fabrication of laterally suspended SWNT networks which are well suited for optical applications
Zigzag carbon nanotubes with generic electron-electron interactions
2009-01-01
A Hamiltonian is derived for a zigzag carbon nanotube with an arbitrary number of weak electron-electron charge and spin interactions, which become significant in ultraclean systems. The renormalization group and bosonization are used to determine the ground-state phase diagram. Our phase diagram contains some exotic phases which have not previously been predicted in carbon nanotubes with physically possible interaction profiles. Phases of the undoped case include Mott insulators and a variety of density wave states. In the doped case a Tomanaga-Luttinger liquid is possible. Publisher: Research Online Format: application/pdf Source: Faculty of Informatics - Papers
Selective growth of single-wall carbon nanotubes and the fabrication of devices on their basis
2010-01-01
Single-wall carbon nanotubes were synthesized on specified parts of oxidized silicon substrates by single acetylene burst CVD and studied with high-resolution scanning electron and scanning probe micro-scopes. The resistance of individual nanotubes and nanotube series was measured using devices fabricated by the deposition of Pd and Pd/Al electrodes on the obtained single-wall nanotubes. The contact potential difference between Pd electrodes and carbon nanotubes was measured in the Kelvin mode of a scanning probe microscope.
2010-01-01
Spray drying was investigated as a strategy for producing single wall carbon nanotube (SWCNT)/polymer composites. The spray-drying method produced SWCNT/poly(3-hydroxybutyrate) and SWCNT/poly(3-hydroxyoctanoate) composite particles in which the SWCNTs have been trapped in a well-dispersed state throughout the polymer matrix. Increasing SWCNT content in the composite led to a change in particle morphology from spherical and smooth to rosette shape with angular distortions. The technique shows potential for bulk carbon composite fabrication.
Molecular dynamics of single wall carbon nanotube growth on nickel surface
2006-01-01
Growth mechanism of a single wall carbon nanotube on the surface of a nickel nanoparticle in the CVD method has been investigated by classical molecular dynamics method. Using first principles methods, we have first constructed a classical potential to describe the interaction between a carbon atom and the nickel surface. The important ingredient in this potential is its coordination number dependence, which also provides the key to the growth mechanism of the nanotube. From the simulations, it is proposed that the growth of an armchair nanotube takes place via attachment of dimers to its end which is in contact with the nickel surface. The effect of nickel nanoparticles radius on the attachment barrier is also discussed.
Direct and Heterodyne Detection of Microwaves in a Metallic Single Wall Carbon Nanotube
2006-04-21
This letter reports measurements of microwave (up to 4.5 GHz) detection in metallic single-walled carbon nanotubes. The measured voltage responsivity was found to be 114 V/W at 77K. We also demonstrated heterodyne detection at 1 GHz. The detection mechanism can be explained based on standard microwave detector theory and the nonlinearity of the DC IV-curve. We discuss the possible causes of this nonlinearity. While the frequency response is limited by circuit parasitics in this measurement, we discuss evidence that indicates that the effect is much faster and that applications of carbon nanotubes as terahertz detectors are feasible.
2006-03-18
Exploring the synthesis of novel molecular nanostructures has been in the forefront of material research in the last decade. One of the most interesting nanostructures are single wall carbon nanotubes (SWCNTs). Their catalyst free growth, however, remains an elusive goal. Here, we present the growth of single wall carbon nanotubes from organic solvents such as benzene and toluene in a confined environment, inside a host SWCNT. The solvents encapsulated in SWCNTs are transformed to an inner tube when subject to a heat treatment under dynamic vacuum at 1270 $^{\\circ}$C. We used isotope labeling of the different carbon sources to prove that the source of the inner tubes is indeed the solvent. Our results put constraints on the models explaining the inner tube growth and provides a simple alternative for the fullerene based inner tube growth. It also provides the possibility to study a completely new field of in-the-tube chemistry.
A route to brightly fluorescent carbon nanotubes for near-infrared imaging in mice
2009-11-01
Full Text Available.The near-infrared photoluminescence intrinsic to semiconducting single-walled carbon nanotubes is ideal for biological imaging owing to the low autofluorescence and deep tissue penetration in the near-infrared region beyond 1 µm. However, biocompatible single-walled carbon nanotubes with high quantum yield have been elusive. Here, we show that sonicating single-walled carbon nanotubes with sodium cholate, followed by surfactant exchange to form phospholipid–polyethylene glycol coated nanotubes, produces in vivo imaging agents that are both bright and biocompatible. The exchange procedure is better than directly sonicating the tubes with the phospholipid–polyethylene glycol, because it results in less damage to the nanotubes and improves the quantum yield. We show whole-animal in vivo imaging using an InGaAs camera in the 1–1.7 µm spectral range by detecting the intrinsic near-infrared photoluminescence of the ‘exchange’ single-walled carbon nanotubes at a low dose (17 mg l
Vibrational modes of carbon nanotubes and nanoropes
1999-09-01
The vibrational modes of carbon nanotubes and nanoropes are studied. The Raman and infrared active modes are determined for armchair, zigzag, and chiral nanotubes. High-energy Raman and infrared modes exhibit distinct characteristic patterns for armchair, zigzag, and chiral tubes. In the nanorope the intertube interactions shifts the energy of certain vibrational modes dramatically. This has implications when using the vibrational spectra to identify tubes. In the nanorope we find Raman modes exhibit shifts under a change in pressure which differ from the corresponding shifts found in graphite. [copyright] [ital 1999] [ital The American Physical Society]
2007-05-02
Single wall carbon nanotubes (SWNTs) bind strongly to sapphyrins, quintessential pentapyrrolic “expanded porphyrin” macrocycles, through π-stacking interactions. The...Full Text Available
Penn researchers introduce a new nanotube-laced gel, create new means of aligning nanotubes
2004-03-01
Penn researchers have devised a new method for aligning isolated single wall carbon nanotubes and, in the process, have created a new kind of material with liquid crystal-like properties, which they call nematic ...
Nanotube/Quantum Dot-Polymer Solar Cells
Single wall carbon nanotubes used or this study were synthesized using the pulse laser vaporization technique. The as-produced SWNTs were collected from the condensed region on the quartz tube outside ...
Nanotube/Quantum Dot-Polymer Solar Cells
Single wall carbon nanotubes used or this study were synthesized using the pulse laser vaporization technique. The as-produced SWNTs were collected from the condensed region on the quartz tube outside the furnace and ...
Empirical Nanotube Model for Biological Applications
2005-06-16
An empirical model is developed to capture the electrostatics of finite-length single-walled armchair carbon nanotubes for biological applications. Atomic partial charges are determined to match...Full Text Available
2009-01-01
Electrochemical immunosensors based on single wall nanotube (SWNT) forests and 5 nm glutathione-protected gold nanoparticles (GSH-AuNP) were developed and compared for the measurement of human...Full Text Available
DETECTION OF PROTEIN ADSORPTION WITH SINGLE WALL CARBON NANOTUBE DEVICE. (R829623)
The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...
Conductive Single-Walled Carbon Nanotube Substrates Modulate Neuronal Growth
2009-01-01
We used conductive nanotube films as substrates with which we could systematically vary the conductance to see how this property affects neuronal growth. Here we show that nanotube substrates...Full Text Available
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