Double-walled Carbon Nanotubes Research Articles

Screen-Printed Carbon Electrodes Modified with Double-Walled Carbon Nanotubes Functionalized with Polypyrrole and Their Electrochemical Processes in the Presence of Folic Acid.

In this work, the electrochemical polymerization of pyrrole in the presence of H₃PMo12O40 onto the screen-printed carbon electrodes (SPCE) modified with double-walled carbon nanotubes (DWNTs) is reported. The influence of the pyrrole and H₃PMo12O40 concentration as well as a scan rate used to recording of cyclic voltammograms that describe the electrochemical synthesis of polypyrrole (PPY) onto the DWNTs surface is assessed. Using scanning electron microscopy (SEM) we demonstrate that the electrosynthesis of PPY doped with H₃PMo12O40 heteropolyanions (PPY-PMo12) results in the generation of a globular morphology. Considering the variations induced of DWNTs in the IR and Raman spectra of PPY doped with H₃PMo12O40 heteropolyanions, a functionalization process of carbon nanotubes with macromolecular compound is invoked. According to SEM investigations, DWNTs allow the realization of connections between the globular structures of the macromolecular compound. The changes induced of folic acid (FA) during the oxidation-reduction processes at the interface of the DWNTs functionalized with PPY doped with H₃PMo12O40 heteropolyanions (SPCE-DWNT/PPY-PMo12) with electrolyte solution are reported.

Dynamic analysis of wave propagation and buckling phenomena in carbon nanotubes(CNTs)

The present study focuses on analysing the behaviour of wave propagation in carbon nanotubes along with the characterization of the buckling phenomenon. The carbon nanotubes are modelled as continuum shells that utilize the nonlocal theory of elasticity as these consider the small effects of the nano structures. The expression for the dispersion relation of the wave propagation in single-walled carbon nanotube (SWCNT) and the double-walled carbon nanotubes (DWCNTs) are achieved using a suitable mathematical treatment. For the case of SWCNT, a combined effect of uniform external lateral pressure, uniform axial pressure, stretching of middle surface, the shearing force due to the torque applied, scaling effect are considered, which presents a new concept. The van der Waals (vdW) interaction, additionally, is regarded for the case of DWCNTs. Moreover, the expression for the buckling phenomenon of the DWCNTs and the triple-walled carbon nanotubes (TWCNTS) taking account of the effect of stretching of middle surface, the shearing force due to torque applied, scaling effect, vdW interaction, and net pressure due to vdW interaction has been established. As a special case of the problem, the deduced results of the present study are found to be well-matched with the pre-existing results, hence, validates the undertaken study. The phase velocity and buckling load curves are manifested graphically using numerical data of two distinct kinds of DWCNTs and TWCNTs depending on the armchair configuration. The influence of various affecting parameters the phase velocity and buckling load curves are noted and are illustrated in tabular form. The study may find its potential application for some engineering problems dealing with the characterization of CNTs and wave propagation through them under the combined effect.

Pullout Force and Inlet Oscillation in Telescopic Carbon Nanotubes: A Quantum Study

The noncovalent interaction energy as a function of the core extension in double-walled carbon nanotubes (DWCNT) was accurately calculated in the frame of density functional theory, considering dis...

Effects of light-ion low-fluence implantation on the pressure response of double-walled carbon nanotubes

Low-fluence light-ion $(^{11}\mathrm{B}^{+})$ medium-energy (150 keV/ion) implantation preprocessing of double-walled carbon nanotubes (DWCNTs) has been effected to ``decorate'' them with defects. These are intended to serve as nucleation sites for potential $s{p}^{3}$ interlinking between tube walls in close proximity, following on strong deformation of the tube cross sections under cold compression to 20--25 GPa in diamond anvil cells. The pressure response of such implanted DWCNTs has been monitored in situ using Raman spectroscopy, and compared with those of unimplanted reference DWCNTs. Pressure dependences of the ${G}^{+}$ mode frequency and D to ${G}^{+}$ band intensity ratio, and radial breathing modes, have been monitored. These Raman signatures show that some degree of mechanical softening occurs in the implanted tube bundles, without major disruption to tube integrity in both samples. Consequently, the collapse pressure to racetrack or peanut shaped cross-sectional profiles is lowered substantially, from ${P}_{\mathrm{c}}\ensuremath{\sim}18\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$ in the reference tube bundles to ${P}_{\mathrm{c}}\ensuremath{\sim}11\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$ in the implanted case. Defect structures also proliferate more readily in the implanted sample under pressure. Therefore, the light-ion low-fluence implantation lowers the threshold pressure for deformation of tube cross sections to high-curvature profiles decorated with defects. Considerations of whether irreversible $s{p}^{3}$ interlinking at low volume fractions is discerned in the Raman data from implanted tube bundles under compression, and the stability of such bonding is discussed.

Molecular Dynamics Simulations and Theoretical Model for Engineering Tensile Properties of Single-and Multi-Walled Carbon Nanotubes.

To apply carbon nanotubes (CNTs) as reinforcing agents in next-generation composites, it is essential to improve their nominal strength. However, since it is difficult to completely remove the defects, the synthesis guideline for improving nominal strength is still unclear, i.e., the effective strength and the number of nanotube layers required to improve the nominal strength has been undermined. In this study, molecular dynamics simulations were used to elucidate the effects of vacancies on the mechanical properties of CNTs. Additionally, the relationships between the number of layers and effective and nominal strengths of CNTs were discussed theoretically. The presence of extensive vacancies provides a possible explanation for the low nominal strengths obtained in previous experimental measurements of CNTs. This study indicates that the nominal strength can be increased from the experimentally obtained values of 10 GPa to approximately 20 GPa by using six to nine nanotube layers, even if the increase in effective strength of each layer is small. This has advantages over double-walled CNTs, because the effective strength of such CNTs must be approximately 60 GPa to achieve a nominal strength of 20 GPa.

Impacts from the stacking morphology on the tensile performance of double-walled carbon nanotube bundles

Carbon nanotube (CNT) based fibers/films are envisioned as the building blocks for next generation high-performance composite materials. However, the mechanical performance of the as-synthesized or as-prepared CNT bundles are still well below their constituent CNTs. Here, we systematically assessed the influence from the stacking morphology on the tensile properties of double-walled CNTs (DWNTs)-based bundles through molecular dynamics simulations. We found that the bundles containing zigzag DWNTs exhibit higher Young’s modulus, but lower yielding strength (and yielding strain) compared with that of the pure armchair DWNT-based bundles. In particular, an initial off-axial angle perturbation in one of the constituent DWNTs induces evident misalignments in other constituent DWNTs, which remarkably degrades the yielding strength and yielding strain of the bundle structures. Following the Hooke’s law, the impacts from the stacking morphology on the overall tensile properties of DWNT bundles can be quantitatively predicted by approximating each DWNT as an elastic column approximation. Overall, this work establishes a comprehensive understanding of the influence from the stacking morphology, which not only provides a perspective explanation of the unexpected low performance of as-synthesized CNT bundles, but also shed light on the design of high-performance CNT based bundles.

Slime molds response to carbon nanotubes exposure: from internalization to behavior

Carbon nanotubes (CNTs) offer attractive opportunities due to their physical, electrical, mechanical, optical, and thermal properties. They are used in a wide range of applications and are found in numerous consumer products. On the downside, their increasing presence in the environment poses potential threats to living organisms and ecosystems. The aim of this study was to evaluate the toxicity of double-walled carbon nanotubes (DWCNTs) on a new model system: the acellular slime mold Physarum polycephalum. Despite its ecological significance, its simplicity of organization, and its behavioral complexity, exposure of such organisms to nanoparticles has been poorly investigated. Slime molds were exposed to DWCNTs using three routes of exposure (topical, food, environment). We first demonstrated that DWCNTs were rapidly internalized by slime molds especially when DWCNTs were mixed with the food or spread out in the environment. Secondly, we showed that a 6-week exposure to DWCNTs did not lead to bioaccumulation nor did it lead to persistence in the slime molds when they entered a resting stage. Thirdly, we revealed that 2 days following exposure, DWCNTs were almost entirely excreted from the slime molds. Lastly, we uncovered that DWCNTs exposure altered the migration speed, the pseudopods formation, and the expansion rate of the slime molds. Our results extend our current knowledge of CNTs cytotoxicity and introduce P. polycephalum as an ideal organism for nanotoxicology.

Stereoselectivity in spontaneous assembly of rolled incommensurate carbon bilayers

The periodicity of two-dimensional entities can be manipulated by their stacking assembly, and incommensurate stacks of bilayers are attracting considerable interest in materials science. Stereoisomerism in incommensurate bilayers was first noted with incommensurate double-wall carbon nanotubes composed of helical carbon networks, but the lack of structural information hampered the chemical understanding such as the stereoselectivity during bilayer formation. In this study, we construct a finite molecular version of incommensurate carbon bilayers by assembling two helical cylindrical molecules in solution. An outer cylindrical molecule is designed to encapsulate a small-bore helical cylindrical molecule, and the spontaneous assembly of coaxial complexes proceeds in a stereoselective manner in solution with a preference for heterohelical combinations over diastereomeric, homohelical combinations. The rational design of incommensurate bilayers for material applications may be facilitated by the design and development of molecular versions with discrete structures with atomic precision.

Observation of a superparamagnetic breakdown in gadolinium chloride filled double-walled carbon nanotubes

In this article, the magnetic properties of gadolinium chloride-filled double-walled carbon nanotubes (GdCl3@DWNTs) in the temperature range 2-300 K are explored. The temperature-dependent phonon frequencies of the G-band were studied from 80-300 K to investigate the effect of temperature on the magnetic ordering. Temperature-dependent susceptibility measurements show that the GdCl3@DWNTs sample has a pronounced superparamagnetic phase from 83 K. The temperature dependence of the G-band frequency for filled tubes exhibited a distinct difference compared to pristine nanotubes, where a sharp phonon hardening at low temperatures was observed. A correlation between the onset temperature of superparamagnetism and the abrupt G-band phonon hardening in the filled tubes was verified. GdCl3@DWNTs were characterized by a finite remnant magnetization at 300 K which decreased as the temperature was lowered because of the presence of the discontinuous magnetic nanoparticles, providing a superparamagnetic contribution characterized by an S-shaped non-saturating hysteresis loop at 2 K. Remarkably, the onset of superparamagnetism, marked by the bifurcation point, occurred at roughly the same temperature where the G-band phonon frequency showed a pronounced hardening at approximately 80 K, indicating a close correlation between phonon modes and spin clusters.

Optical properties of double walled carbon nanotubes

Density functional theory was utilized to simulate the electronic band structure and optical spectra of double walled (4, 4) @ (8, 8) carbon nanotubes. The dielectric constants and dielectric function were calculated for the perpendicular and parallel to the tube axis polarizations. The output indicates that for the DWCNTs, the effect of the 2pz orbitals overlapping on the static refractive index in the parallel to the tube axis polarization outweighs that of the perpendicular to the tube axis polarization. The real part of the dielectric functions shows that for the z polarization of DWCNTs (4, 4) @ (8, 8), the optical refraction (n) for the most of the allowed energies is higher compare to the n of the SWCNTs (4, 4) and SWCNTs (8, 8). E11(eV), E22(eV), E12(eV) and E21(eV) optical band gap of DWCNTs (4, 4) @ (8, 8) are equal to 1.41 eV, 1.92 eV, 1.47 eV and 0.12 eV respectively. The first optical absorption’s maximum of the SWCNTs (4, 4) and SWCNTs (8, 8) also happens at 2.1 eV and 1.2 eV respectively for the x and y polarization.

N-decane diffusion in carbon nanotubes with vibration.

Carbon nanotubes (CNTs) have a wide range of applications in nanotechnology engineering. This research aims to quantify the effect of wall vibration on n-decane molecules' diffusion in double-walled CNTs (DWNTs) with different diameters and determine the diffusion mechanisms behind it. Molecular dynamics simulations are performed to generate mass density profiles of confined n-decane molecules. The root mean square fluctuation and mean squared displacement analyses show that the confinement suppresses n-decane molecules' fluctuations. A self-diffusion coefficient of n-decane molecules in a 13.6 Å-diameter DWNT is the largest. However, the vibration enhancement of the n-decane molecules' diffusion in a 27.1 Å-diameter DWNT is 207%, more extensive than that in 13.6 Å-diameter and 10.8 Å-diameter DWNTs. The n-decane-CNT attractive interactions, extreme confinement, and surface friction affect the n-decane molecules' diffusion in CNTs with vibration.

Preparation and water flow velocity measurement of a large diameter single-wall carbon nanotube

To fill the gap in the measurement of large diameter single-wall carbon nanotube (SWCNT) and further predict the variation rule of mass flux versus diameter, this work measured the water flow velocity and mass flux coefficient in an individual SWCNT with a 3.07 nm diameter. A mechanical method is used to obtain the large diameter SWCNT by removing the internal tube of a double-wall carbon nanotube, and then the water flow velocity through this SWCNT was measured by an electrical method. The water flow velocity of large diameter SWCNT can reach to 146.1 ± 32.5 μm s−1, and the enhancement factor compared with no-slip Hagen–Poiseuille relation is about 14.5. A mass flux coefficient is defined to describe the mass flow ability through SWCNT and calculated by the experiment data. Although the enhancement factor decreased to ∼1/4 of the normal size SWCNT (∼1.5 nm), the mass flux coefficient in the large diameter SWCNT increased efficiently, and which is about 5.7 times to the normal size SWCNT. Based on the above measurement result, a reported simulation result can be revised and then verified to describe the enhancement factor versus diameter, and the mass flux coefficient of the SWCNT can be further predicted. According to the prediction result, in the bulk-like liquid region, the mass flux of an individual SWCNT can reach to maximum when the diameter is around 2.9 nm, which would provide a new idea for the design of the SWCNT-based nanodevices in the future.

Enhanced mechanical properties of double-walled carbon nanotubes reinforced silica aerogels: An all-atom simulation study

To enhance the mechanical properties of highly porous low strength and stiffness silica aerogel, we proposed double-walled carbon nanotubes (DWCNTs) of different length to diameter ratios as reinforcement material for the silica aerogel matrix using molecular dynamics (MD) simulations. It is found that a small amount of DWCNTs (2.06%) in the silica aerogel resulted in a significant improvement in the tensile strength and elastic modulus, which is mainly due to random distribution of strong and stiff DWCNT fibers. Moreover, the elastic modulus values of nanocomposites increase quadratically with respect to the weight percentage (wt %) of DWCNT fibers. Furthermore, in compression simulations, as the wt % of DWCNT fibers increases, the initial stiffness also increases, and early densification occurs. The presented work helps to design a new composite material for a specific application.

Stability analysis of double-walled and triple-walled carbon nanotubes having local curvature

In this study, stability loss research has been made for composite material containing a locally curved one double-walled carbon nanotube and one triple-walled carbon nanotube separately. The research has been made within the scope of piecewise-homogenous body model by the use of three-dimensional linearized theory of stability (TDLTS). The carbon nanotubes are resistant to tension, but as they contain large gaps in their structure, their resistance to compression is very low. For this reason, searching the behaviors of nanotubes under compression is very important. The van der Waals forces between the walls of the carbon nanotube have been considered. It has been thought that the referred composite material is under the effect of uniformly distributed normal forces in the direction of carbon nanotube at infinity. In the model, ideal contact conditions have been used between the nanotube and the matrix. In addition, the effect of increasing the number of layers of the nanotube on the critical load has been investigated. The results obtained from this study will be able to guide in the implementations relevant to modeling of mechanical behaviors of the addressed composite material. Thus, the limits required to be considered in the production of composite material containing double-walled and triple-walled nanotubes with local curvature have been obtained.

Calculation of the Green's function in the scattering region for first-principles electron-transport simulations

We propose a first-principles method of efficiently evaluating electron-transport properties of very long systems. Implementing the recursive Green's function method and the shifted conjugate gradient method in the transport simulator based on real-space finite-difference formalism, we can suppress the increase in the computational cost, which is generally proportional to the cube of the system length to a linear order. This enables us to perform the transport calculations of double-walled carbon nanotubes~(DWCNTs) with 196,608 atoms. We find that the conductance spectra exhibit different properties depending on the periodicity of doped impurities in DWCNTs and they differ from the properties for systems with less than 1,000 atoms.

The effect of localized strain on the electrical characteristics of curved carbon nanotubes

Carbon nanotubes (CNTs) are the emerging alternative for silicon for developing miniatured electromechanical devices in the More than Moore's era. But, the inconsistent pitch distances among the aligned CNTs have limited their outstanding performances. Except for the intertube overlapping, the curved morphology is an important but often ignored factor for the attractive CNTs under van der Waals interaction. Here, we have synthesized a clean and curved CNT structure with a definite curvature radius by introducing micro perturbation. Electrical measurement has demonstrated that the curved structure will limit the on/off ratio by orders of magnitude but can maintain a high output delivery in transistors. This is attributed to the resistance induced by the localized strain and the extra current delivery capability of the inner walls, which can be well explained by the energy band diagram model. Among the curved CNTs, incommensurate double walled CNTs of higher diameter difference are the optimal candidates for delivering a high current output by limiting intertube charge transfer. Our demonstrations and analysis have highlighted the importance of controlling both the chiral structures and morphology of CNTs for the applications of high-performance carbon-based electronics.

The transport of a charged peptide through carbon nanotubes under an external electric field: a molecular dynamics simulation.

The study of interactions between biomolecules and carbon nanotubes (CNTs) is of great importance in CNT-based drug delivery systems and biomedical devices. In this work, the transport of polyarginine (R8) peptide through CNTs under an external electric field was investigated via all-atom molecular dynamics (AAMD) simulation. It was found that the electric field can assist the R8 peptide to overcome the resistance and make the transport smooth. Moreover, the efficiency of transport was improved with the increasing intensity of the electric field in a suitable range. In addition, we also investigated the effects of different types of CNTs on the transport of the R8 peptide and found that the single-walled carbon nanotube (SWCNT) was more suitable for transporting the R8 peptide than the double-walled carbon nanotube (DWCNT) due to its lower energy barrier to the R8 peptide. All these findings shed light on the role of the electric field on the transport of the R8 peptide through CNTs and also gave some valuable insights into the effects of CNT types on the transport process of the peptide.

Simulation of different carbon structures on significant mechanical and physical properties based on MDs method

In this research, the nanocomposite boxes are simulated using polyurethane (PU) as a thermoplastic polymer with various reinforcements including carbon nanoparticles (CNPs), graphene platelets (GPLs), single-walled carbon nanotubes (SWCNTs), and double-walled carbon nanotubes (DWCNTs), which are as biocompatible and biodegradable. To predict the mechanical and physical properties of each nanocomposite boxes, the molecular dynamics (MDs) method with Materials studio software has been applied. Ultimately, all properties including mechanical and physical properties (Young's modulus, shear modulus, bulk modulus and Poisson's ratio of nanocomposite from CNPs to DWCNTs approximately becomes 5.7, 10.25, 28.63, 96 and 1.39 times, respectively. Then, the stiffness matrix are obtained by Materials studio software. Moreover, the obtained results from this research are validated with the results of the literature. Also, the mechanical and physical properties of nanocomposite are recommended before fabrication. The manufacturing of this nanocomposite is used for biomedical cases such as artificial vessels and piping.

Effect of strain engineering on superlubricity in a double-walled carbon nanotube.

Double-walled carbon nanotubes (DWCNTs) have received a great deal of attention due to their great potential in the field of superlubricity. However, this superlubricity is susceptible to failure in practical applications due to the introduction of various defects. Here, a novel method based on strain engineering is employed for achieving superlubricity in the DWCNT using molecular dynamics simulations. The DWCNT exhibits a superlow friction force when an inner tube slides against a stretched outer tube even with a low content of defects. However, strain engineering shows its limitation on superlubricity in the case of a large magnitude of strain or a high content of point defects. The mechanism of superlubricity in the DWCNT could be explained by the analysis of the energy barrier.

The potential application of carbon nanotubes in water Treatment: A state-of-the-art-review

Abstract Sustainability of the human race is dependent on the availability of clean water. Human race cannot be flourished without availability of clean water. Scientists and researchers are always in search of better and new technology for the treatment of waste water. Carbon Nanotubes has extensive range of applications in various fields of science and technology. Carbon Nanotubes nowadays are widely utilized for cleaning water. Carbon Nanotubes have emerged as a lucrative, effective and eco-friendly alternative in relation to that of existing water treatment facilities for the removal of various water pollutants. This review article comprehensively focuses on the major nanomaterials, how the single and double walled CNTs are acting differently. The highlighted features of the chapter covers CNTs as Sorbents, remediation of various pollutants organic and inorganic, factors effecting adsorption of organic molecule and inorganic molecules. It also postulates developments in the field to CNTs. To complement futures aspects have also been discussed. Attempts have been made to describe several aspects of water treatment using carbon nanotubes because of the immense importance of water quality.