Zigzag Carbon Nanotubes Research Articles

Review on Molecular Dynamics Simulations of Effects of Carbon Nanotubes (CNTs) on Electrical and Thermal Conductivities of CNT-Modified Polymeric Composites

Due to the unique properties of carbon nanotubes (CNTs), the electrical and thermal conductivity of CNT-modified polymeric composites (CNTMPCs) can be manipulated and depend on several factors. There are many factors that affect the thermal and electrical conductivity of CNTs and CNTMPCs, such as chirality, length, type of CNTs, fabrication, surface treatment, matrix and interfacial interaction between the matrix and reinforcement (CNTs). This paper reviews the research on molecular dynamics (MD) simulations of the effects of some factors affecting the thermal and electrical conductivity of CNTs and CNTMPCs. First, the chirality dependence of the thermal and electrical conductivity of single-walled carbon nanotubes (SWNTs) was analyzed. The effect of chirality on the conductivity of short-length CNTs is greater than that of long-length CNTs, and the larger the chiral angle, the greater the conductivity of the CNTs. Furthermore, the thermal and electrical conductivity of the zigzag CNTs is smaller than that of the armchair one. Therefore, as the tube aspect ratio becomes longer and conductivity increases, while the effect of chirality on the conductivity decreases. In addition, hydrogen bonding affects the electrical and thermal conductivity of the CNTMPCs. The modeling of SWNTs shows that the thermal and electrical conductivity increases significantly with increasing overlap length. MD simulations can be effectively used to design highly conductive CNTMPCs with appropriated thermal and electrical properties. Since there are too many factors affecting the thermal and electrical conductivity of CNTMPCs, this paper only reviews the effects of limited factors on the thermal and electrical conductivity of CNTs and CNTMPCs based on MD simulations, and further detailed studies are required.

A density functional theory study of van der Waals interaction in carbon nanotubes

AbstractIn this article, we investigate the effect of van der Waals force in zigzag carbon nanotubes (CNTs) including single‐wall CNT (SWCNT) and double‐walled CNT (DWCNT) structures with several interaction configurations. The solid‐state density functional theory is employed to calculate the geometric optimization, normal mode frequencies, and IR and Raman spectra with the periodic boundary condition. For SWCNTs, we find that the Raman intensity is not affected by the tube diameter or the electronic structure. The IR absorption, however, increases with the tube diameter. We find that the close metallicity of the electronic structure has a significant impact on the IR simulations. When the van der Waals force is applied outside the CNTs at a distance longer than 3.0, the effect on Raman spectra is minimal but some effects can still be confirmed by IR absorption. When the van der Waals force acts inside the CNTs, the effect on the spectrum can be observed, especially at a distance of 2.8 Å, both IR and Raman can be significantly enhanced in many modes.

Numerical thermal analysis of armchair (6,6) and zig-zag (12,0) carbon nano-tubes (CNTs)

In this study, the thermal behaviour of small-sized single-atom CNTs was examined. CNTs are composed of crystals that form a nanostructure with different geometric shapes by arranging them in different ways according to the length-diameter ratio. Due to the mechanical, electrical, and thermal properties of CNTs, the thermal conduction of CNT materials is critical in controlling the performance and stability of CNTs. CNTs, which are low-dimensional materials with a single atomic layer thickness, have excellent thermal conductivity. According to the simulation technique in ANSYS, CNTs containing the same number of atoms and bonds were developed. The heat transfer of different structures of CNTs in armchairs (6,6) and zig-zag (12,0) were compared. A comparison of zig-zag and armchair CNTs thermal behaviour shows that zig-zag CNTs lattice structure has more advantages than armchair CNTs lattice structure by heat transfer. Highlights In this study, finite element-based thermal analysis of single and double-walled armchair and zig-zag carbon nano-tubes (CNTs) using the lattice method was investigated. A simulation technique was developed and applied in the ANSYS program for single and double-walled carbon nanotubes (CNTs). Armchairs (6,6) and zig-zag (12,0) CNTs in different lattice structures with equal atomic numbers and bond numbers are modelled according to different diameters and length ratios. The CNTs, which have the same material properties as the trays placed at both open ends of the pipes, are kept at different temperature values, and conduction heat transfer behaviour is investigated for certain temperature values. According to the investigated heat conduction behaviour of zig-zag and armchair CNTs, the lattice structure of the zig-zag carbon nano-tubes is more advantageous in terms of heat conduction than the cage structure of armchair CNTs, and it transmits heat faster than the armchair CNTs.

Single-ion magnet behavior of Ln3+ encapsulated in carbon nanotubes: an ab initio insight.

Single-molecule magnets (SMMs) have attracted large interest owing to their capability to store information at the level of a single molecule, which has great potential for applications in information technology. The key characteristic required for SMM performance is the magnetization blocking barrier, and in the last decade, impressive efforts have been made to increase its height. Herein, we report an ab initio investigation of the SMM behavior of a series of lanthanide ions (Tb3+, Dy3+, Ho3+, Er3+, Tm3+ and Yb3+) encapsulated in zigzag carbon nanotubes (CNTs) of different diameters. The results show that despite the high symmetry of the Ln environment, none of the investigated systems, except for Er3+ encapsulated in the (7,0) CNT, exhibited any blocking behavior. This is mainly attributed to the strong competition between axial and equatorial contributions to the crystal field of these encapsulated ions, resulting in weak or lack of magnetic axiality. The presented results provide useful theoretical guidance for the design of high-performance SMMs via modulating the crystal field of the ligand environment.

Effect of CNT Parameter Variations on CNTFET Amplifier Performance

In this paper we propose a procedure to study the dependence of a CNTFET amplifier performance on CNT parameters that fully identify the geometrical properties of a regular CNT. In particular these parameters are the length and structural indices (n,m) of CNT. We analyse the effects on a linear common source amplifier using a N type CNTFET with a resistive gate polarization. We polarize at a fixed drain voltage and current, gradually changing the CNT parameters. As regards the indices, we present the analysis for a zig-zag CNT. However the proposed procedure can be applied to other types of CNT. We show the effect on gain, on the 3 dB cut off frequency, F3dB, on the input and output resistances, obtaining that F3dB has a clear inverse dependence on the length and that also decreases at higher structural indices for zig-zag CNT.

Correlated insulating states in carbon nanotubes controlled by magnetic field

Recent experiments have shown that nearly metallic nanotubes remain insulating throughout magnetic field sweeps, in which the magnetic flux through the nanotube is expected to pass through a critical point where the single-particle band gap closes in one valley. Here, the authors investigate correlated insulating states of zigzag carbon nanotubes, which emerge from the interplay of electron-electron interactions, magnetic flux, strain, and spin-orbit coupling. They find that the gap for charged excitations generically remains open near the critical flux value, and predict a novel mirror symmetry breaking phase that may arise in the experimentally relevant regime of spin-orbit coupling.

Nanofacet-density scaling on zig-zag carbon nanotubes within the kinetic 5-vertex growth model

Nanofacets density at the edge of a growing zig-zag single-walled carbon nanotube is investigated by means of a kinetic 5-vertex model. The model comprises, carbon atoms deposition and diffusion events that are assumed Markov processes. The nanotube synthesis temperature, the carbon atomic flux from the catalyst nanoparticles, and the diffusion length are the model physical parameters considered. The kinetic equation describing the nanotube growth is solved by Kinetic Monte Carlo simulations and the average nanofacet density at the nanotube edge is calculated. It is found that this quantity displays interesting behaviors, in particular a power-law behavior with the diffusion length and the growth time.

Grasping the little things: Modeling and simulation of the electromechanical behavior of individual carbon nanotubes and nanotweezers

Nanotweezers are electromechanical nanosized devices with versatile applications. Due to the challenges for experiments on the nanoscale, the support of models and simulations is crucial to get a better insight into the operational mode of nanotweezers. In the current work, armchair and zigzag individual carbon nanotubes (CNTs) as well as nanotweezers are investigated with regard to their behavior under various prescribed electrostatic loads. The applied model is a combination of the model by Cox and Hill for the geometry, the modified molecular structural mechanics (MSM) model for the covalent bonds and the charge-dipole-model by Mayer for the electric field. Compared to the models based on the solution of the Schrdinger equation, the computational cost of the MSM model is much lower. A weak coupling is given between the mechanical and the electrical field through the application of the Coulomb forces on the mechanical model. The finite element software ABAQUS was used for the numerical simulation. It was shown that (i) the resulting strains and closing gaps are nearly identical for armchair and zigzag CNTs with the same diameter and that (ii) an increase in CNT length leads to greater strains for individual CNT and narrower closing gaps between the arms of the nanotweezers.

Research Paper: Investigation of the Effect of Uniaxial Strain on the Electrical Transport Properties of Zigzag Carbon Nanotube Joints

Research Paper: Investigation of the Effect of Uniaxial Strain on the Electrical Transport Properties of Zigzag Carbon Nanotube Joints

Influence of gradually vacating hexagonal patterns composition of C[sbnd]C bond in TWCNTs molecular structure using the FE method for vibrational analysis

The authors use the FE research to analyse and predict the oscillational performance of TWCNTs (Triple-Walled Carbone Nanotubes) in this work. Different types of nanotubes like chiral, zigzag, and armchair as well as different lengths and diameters are used for analysis purpose. The novelty is authors included the chiral structure which is difficult to model for simulation purpose. The approach employed here to account for the variation in length in atomic models produced by removing hexagonal patterns has either never been utilised or has very little evidence. As a result, this technique's use is distinct and novel. Moreover, the authors investigate the effect of gradually removing the hexagonal patterns which contain the Carbon-Carbon(CC) bond ring in triple-walled carbon nanotube models. Molecular structural mechanics methodology is used for developing and simulations of armchair, zigzag and chiral triple walled carbon nanotube (TWCNTs). The process of removing the Carbon-Carbon bond ring from the outside wall of TWCNTs by maintaining the inside walled unchanged. Authors analysed the resonant frequencies for different attached masses ranging from 10−16to 10−23gm on TWCNTs and different boundary conditions for TWCNTs.

Diameter-Change-Induced Transition in Buckling Modes of Defective Zigzag Carbon Nanotubes.

In general, the insertion of Stone-Wales (SW) defects into single-walled carbon nanotubes (SWNTs) reduces the buckling resistance of SWNTs under axial compression. The magnitude of reduction is more noticeable in zigzag-type SWNTs than armchair- or chiral-type SWNTs; however, the relation between the magnitude of reduction and aspect ratio of the zigzag SWNTs remains unclear. This study conducted molecular dynamics (MD) simulation to unveil the buckling performance of zigzag SWNTs exhibiting SW defects with various tube diameter. The dependencies of energetically favorable buckling modes and the SW-defect induced reduction in the critical buckling point on the tube diameter were investigated in a systematic manner. In particular, an approximate expression for the critical buckling force as a function of the tube diameter was formulated based on the MD simulation data.

Molecular Dynamics Simulation of Carbon and Boron Nitride nanotubes: Tensile and Compressive Behavior

In this paper, the mechanical properties of Carbon nanotubes (CNTs) and Boron Nitride nanotubes (BNNTs) are studied systematically by using molecular dynamics simulations. CNTs are considered semi-metallic, whereas the BNNTs, of the large band gap, are considered to be insulators, regarding the difference in the electrical properties of CNTs and BNNTs; comparing the mechanical properties of both nanotubes offers great scientific significance for their prospective applications. The simulations were carried out with the help of a Large-scale atomic/molecular massively parallel simulator (LAMMPS) and were based on the Airebo and Tersoffs force fields for C-C interaction in CNTs and B-N interaction in BNNTs, respectively. Failure behavior of armchair and zigzag CNTs and BNNTs under tensile and compressive loading has been predicted and observed that for both the nanotubes the armchair nanotubes showed higher tensile and compressive strength as compared to zigzag nanotubes. The maximum tensile and compressive strength for CNTs is 205 GPa and 35.62 GPa respectively and for BNNTs are 159 GPa and 24.81 GPa respectively. CNTs are identified as axially stronger and stiffer than BNNTs for the same diameter under identical loading conditions.

Interfacial interaction of parallel carbon nanotubes under external electric field: A first-principles study

Carbon nanotubes (CNTs) are widely used in high-quality and high-performance nanoscale devices. Using first-principles calculations, we studied the interaction at the interface between parallel CNTs with different electrical properties under applied transverse electric fields. Typical metallic armchairs (6,6) and semiconducting zigzag (10,0) CNTs were considered. The effect of axial moving of one of the CNTs on the interface electronic structure and interaction energy for different interface types was analyzed. Our calculations revealed that interfacial adhesion of CNTs increased with the increase of the external electric field. At this, the interface charge redistribution for (6,6) and (10,0) CNTs showed different polarization responses. By analyzing the density of states (DOS), a correlation between the semiconductor-to-metal transition in parallel (10,0) CNTs and interface interaction under applied external electric field was demonstrated. Obtained results provide a theoretical background for the application of the adhesion properties of CNTs in future nanoscale devices.

Structure and Dynamics of Adsorbed Dopamine on Solvated Carbon Nanotubes and in a CNT Groove.

Advanced carbon microelectrodes, including many carbon-nanotube (CNT)-based electrodes, are being developed for the in vivo detection of neurotransmitters such as dopamine (DA). Our prior simulations of DA and dopamine-o-quinone (DOQ) on pristine, flat graphene showed rapid surface diffusion for all adsorbed species, but it is not known how CNT surfaces affect dopamine adsorption and surface diffusivity. In this work, we use molecular dynamics simulations to investigate the adsorbed structures and surface diffusion dynamics of DA and DOQ on CNTs of varying curvature and helicity. In addition, we study DA dynamics in a groove between two aligned CNTs to model the spatial constraints at the junctions within CNT assemblies. We find that the adsorbate diffusion on a solvated CNT surface depends upon curvature. However, this effect cannot be attributed to changes in the surface energy roughness because the lateral distributions of the molecular adsorbates are similar across curvatures, diffusivities on zigzag and armchair CNTs are indistinguishable, and the curvature dependence disappears in the absence of solvent. Instead, adsorbate diffusivities correlate with the vertical placement of the adsorbate’s moieties, its tilt angle, its orientation along the CNT axis, and the number of waters in its first hydration shell, all of which will influence its effective hydrodynamic radius. Finally, DA diffuses into and remains in the groove between a pair of aligned and solvated CNTs, enhancing diffusivity along the CNT axis. These first studies of surface diffusion on a CNT electrode surface are important for understanding the changes in diffusion dynamics of dopamine on nanostructured carbon electrode surfaces.

Experimental and theoretical evaluation of the clonazepam adsorption onto carbon nanotubes

• Electronic properties of zigzag CNTs are sensitive to CLNP. • CLNP adsorption energy on CNTs is about −5.6 kJ/mol. • The conductivity of CNTs does not change by CLNP adsorption. • CNTs have good sorption ability to CLNP. This work illustrates the evaluation of the clonazepam interaction (CLNP) with zigzag carbon nanotubes (CNTs) through voltammetric, FT-IR, and UV–Vis spectrometry, and density functional theory (DFT) assays. The primary purpose was to evaluate the CNTs' ability in the effective adsorption of CLNP molecules. Experimental funding demonstrated noticeable physical interactions between CLNP molecules and CNTs, which leads to their adsorption on the surface of CNTs. The CLNP redox reaction occurred more facile in the presence of CNTs, resulting in voltammograms with sharper peaks with lower overvoltages. The electronic features of the used semiconductive CNTs were responsive to the CLNP and its reduction products, but their electrical conductivity was not altered. The average CLNP adsorption energy by CNTs ≈ −4.8 kJ/mol indicates the effective interaction of the CLNPs molecules and the CNTs. The findings of this study indicate the suitability of CNTs for the fabrication of sensitive sensors for trace analysis of CLNP or effective adsorbents for CLNP removal from contaminated specimens.

DFT Study of Adsorption of Methyl Red on the Surface of Pure, Pyrrolidine-Functionalized, Silicon- and Germanium-Doped Zigzag (6, 0) Carbon Nanotubes

DFT Study of Adsorption of Methyl Red on the Surface of Pure, Pyrrolidine-Functionalized, Silicon- and Germanium-Doped Zigzag (6, 0) Carbon Nanotubes

The Influencing of Toxic Gases on Structural, Electronic and Optical Features of CNTs Molecules: Computation Study

The electronic properties of carbon nanotubes CNTs, such as ionization potential (IP), electron affinity (EA), energy gap (Eg), Fermi energy (Ef), binding energy (Eb), the density of state (DOS), and IR spectral properties, investigated after substituted the OH, SO, SiO2, H2O, and N2 groups on the optimization structure of CNT (3,3). The lengths of C=C for zigzag CNT (3,3) slight altered with substituted the mention groups and given the depress in bond length during the substituted –OH, -SO, and –SiO2 that attitude to bond orders for these substituted groups and different in electronegativity power for an oxygen atom in these groups. Moreover, the C-C bond for zigzag CNT (3,3) changed also, and gave a slight increase during the substituted OH group, but decreased during substituted So and SiO2 groups. The substituted of –SO and –SiO2 on the structure of CNT (3,3) demonstrated, fewer values of total energies that will increase the stability of CNT. The CNTS-SiO2 has a less value for bandgap compared with other substituted materials, this behaver has given it a good electronic conductivity. The B3LYP functional theory has been used to conduct the DFT approach. The analyzed Nano species agree well with the experimental results based on the measured values of HOMO and LUMO energies. The Gaussian 09 program was used to calculate all feature values.

Effect of defects and boundary conditions on the vibrational behavior of carbon nanotube and graphene: A molecular dynamics perspective

The presence of defects has a significant effect on the mechanical and vibrational properties of carbon nanotubes (CNTs) and graphene. The vibrational properties of single-layered graphene sheets (SLGS) and single-wall carbon nanotubes (SWCNT) have been investigated in this research. Molecular dynamics simulations have been conducted on pristine and defective zigzag and armchair CNTs, with clamped-free (C-F) boundary conditions as well as pristine and defective armchair graphene sheets with different boundary conditions to investigate the effect of various parameters such as chirality, aspect ratio, boundary conditions, and types and number of defects on the longitudinal and transverse vibrational behavior of CNTs and graphene sheets. It was observed that for the cantilever boundary condition, shorter tubes give better vibrational sensitivity as compared to the larger ones for a constant diameter of the tube. The chirality has not a considerable effect on the natural frequency of CNTs. Regarding graphene sheets, it was observed that increasing the size of the graphene sheet decreased the fundamental natural frequency of SLGS. As compared to Stone-Wales defects, the vacancy defects were found to have more impact on the degradation of the natural frequency of CNTs and GS.

Molecular structure based study on the elastic properties of carbon nanotubes in a thermal environment

In this investigation, a modified mechanical model considering the environmental temperature is established based on a method of molecular structural mechanics. It is assumed that the covalent bonds are traded as a truss, and the boundary condition range is taken into account. The relations of Young's modulus and shear modulus with different diameters of carbon nanotubes are also predicted. Moreover, according to the principle of elastic theory, the Young's modulus, Poisson's ratio and strain energy of both zigzag and armchair carbon nanotubes are also investigated. The influences of temperature and nanotube diameter on elastic properties are significant, and the elastic modulus of multi-walled carbon nanotubes is not only sensitive to the number of layers, but also sensitive to the tube wall thickness.

Zigzag Carbon Nanotube Segments from Gold Rings

Zigzag Carbon Nanotube Segments from Gold Rings