Armchair Single-walled Carbon Nanotubes Research Articles

Cytotoxicity effects and ionic diffusion of single-wall carbon nanotubes in cell membrane

While carbon nanotubes have been put into massive practical industrial, environmental and biomedicine applications, the cytotoxicity effects or the effect to the ionic channels they bring into the living cells need to be thoroughly investigated. In this work, molecular dynamic simulations have been carried out to investigate the ionic diffusion through the single wall armchair carbon nanotube embedded right inside the cell membrane. By modeling a two-membrane system, we build a virtual cytoplasm environment including a cell chamber and an extracellular space, in which a certain amount of solute is dissolved. The system is first brought to its equilibrium by deployment of minimization and then simulated. The results suggested that carbon nanotubes (CNTs) with size less than (12, 12) shall be less cytotoxic since it does not bring any ionic diffusion through the CNT channel, so as to maintain active cytoplasm environment. Another phenomenon we observed is a notable shifting angle of the carbon nanotube which was normal to the surface of cell membrane initially. In general, the inclination angle of the carbon nanotube increases with its radius.

First Principles Investigation of NH3 and NO2 Adsorption on Transition Metal-Doped Single-Walled Carbon Nanotubes

Density functional theory calculations were carried out to investigate the binding ability of transition metals (TM = Cr, Mo, W, Mn, Tc, and Re) on (5,5) armchair single-walled carbon nanotubes (SWCNTs) and their adsorption ability with ammonia (NH3) and nitrogen dioxide (NO2). The geometric, electronic, and energetic properties of pristine SWCNT doping with TM and their NH3 and NO2 adsorptions were calculated to explore their potentials as gas adsorptions and sensors. The binding abilities of TMs to the SWCNT are found to be in the order: Cr > Mo > Tc > Re > W > Mn. According to the results, compared to the pristine SWCNT, TM atom doping can significantly increase gas adsorption ability in which W-SWCNT has the strongest interaction, and the ability to absorb NO2 is higher than NH3. The density of states and orbital distributions display that the band gaps and electron delocalizations of TM-SWCNTs are significantly changed upon gas adsorption. These observations suggest that the TM-doped SWCNTs can be introduced as promising candidates in gas adsorptions and sensor devices for storage and detecting NH3 and NO2 molecules.

Multistability of armchair single-walled carbon nanotubes: a molecular dynamics investigation

We report by molecular dynamics (MD) that the armchair single-walled carbon nanotubes (ACNTs) has a multistability rather than bistability as the diameters are above a threshold value of about 3.5 nm. The present work demonstrates that ACNTs have four stable states when the diameters are above the threshold value. The newly found stable states are caused by surface van der Waals forces. We also find the transformation between different stable states can be realized by external loading or temperature. These imply the ACNTs have a great potential application in the future nanoscale devices.

Geometry, Tautomerism, and Noncovalent Interaction of Bentiromide with a Carbon-Nanotube and γ-Fe2O3 Nanoparticles: A Quantum Mechanical Study

A doctor can find out how pancreas is working using bentiromide. This drug can exist as six possible tautomers. Herein, by density functional theory (DFT) and handling the solvent effects with the polarizable continuum model (PCM), the mechanism of its tautomerization, energies, and structural parameters of the tautomers are investigated. Also, the natural bond orbital analysis (NBO) is used for exploring the frontier molecular orbitals. The most stable tautomer of bentiromide has three carbonyl groups in its structure. The amount of other tautomers is negligible in the aqueous solution. The non-covalent interactions of the most stable tautomer of bentiromide with an armchair (5,5) single-wall carbon nanotube and a γ-Fe2O3 nanoparticle are explored. In each case, three possible forms are optimized. Their most stable form is determined. The intermolecular H bonds have a critical role in the energy behavior of the interaction between bentiromide and the γ-Fe2O3 nanoparticle.

Comparison study of CC and CH vibration frequencies and eelectronic properties for mono, Di, Tri, and tetra-rings layer of arm chair (SWCNTs)

Semi-empirical methods were applied for calculating the vibration frequencies and IR absorption intensities for normal coordinates of the {mono (C56H28), di (C84H28), tri (C112H28) and tetra (C140H28)} -rings layer for (7,7) armchair single wall carbon nanotube at their equilibrium geometries which were all found to have D7d symmetry point group.
 Assignment of the modes of vibration (3N-6) was done depending on the pictures of their modes by applying (Gaussian 03) program. Comparison of the vibration frequencies of (mono, di, tri and tetra) rings layer which are active in IR, and inactive in Ramman spectra. For C-H stretching vibrations, the results showed that vibration frequencies value increased with increased of length nano tube (rings layer SWCNT).
 The results include the relation for axial bonds, which are the vertical C-C bonds (annular bonds) in the rings and for circumferential bonds which are the outer ring bonds. Also include the assignment of puckering, breathing and clock-anticlockwise bending vibrations. They allow a comparative view of the charge density at the carbon atom too.

Geometry, tautomerism and non-covalent interaction of bentiromide with a carbon-nanotube and γ-Fe2O3 nanoparticles: A quantum mechanical study

A doctor can find out how pancreas is working using bentiromide. This drug can exist as six possible tautomers. Herein, by density functional theory (DFT) and handling the solvent effects with the polarizable continuum model (PCM), the mechanism of its tautomerization, energies, and structural parameters of the tautomers are investigated. Also, the natural bond orbital analysis (NBO) is used for exploring the frontier molecular orbitals. The most stable tautomer of bentiromide has three carbonyl groups in its structure. The amount of other tautomers is negligible in the aqueous solution. The non-covalent interactions of the most stable tautomer of bentiromide with an armchair (5,5) single-wall carbon nanotube and a γ-Fe2O3 nanoparticle are explored. In each case, three possible forms are optimized. Their most stable form is determined. The intermolecular H bonds have a critical role in the energy behavior of the interaction between bentiromide and the γ-Fe2O3 nanoparticle.

Environment and strain energy related micromechanics analysis for properties of carbon nanotubes

AbstractIn the present study, a theoretical prediction of the effect of thermal environment on elastic properties of single‐walled carbon nanotubes (SWCNTs) is reported, and a molecular structural mechanics model is proposed in which the covalent bonds are traded as a truss. The influences of the temperature and the coefficient of thermal expansion (CTE) on Young's modulus and shear modulus of both armchair and zigzag SWCNTs are investigated. When CTE is and remains constant, the surface Young's modulus and the normal Young's modulus are reduced, respectively, as compared with the normal temperature. With the change of CTE, its effect on the elastic constant is far greater than the temperature effect itself. According to the principle of elastic theory, a temperature‐dependent continuum shell model of strain energy is also established. The strain energy of single‐walled carbon nanotubes decreases with the increase of the temperature.

Subwavelength Coupling of Surface Plasmon Polaritons Along Parallel Armchair Single-Wall Carbon Nanotubes

In this paper, armchair single-wall carbon nanotubes (ASWCNTs) are considered as a plasmonic waveguide, and the propagation of surface plasmon polaritons is discussed extensively. The subwavelength coupling of plasmonic modes, in terahertz and infrared bands, is inspected for this waveguide configuration. The impact of the separation distance between nanotubes and the frequency of light on the coupling length and other characteristics of the presented waveguide structure are thoroughly investigated. Besides, the coupling lengths of the surface waves on ASWCNTs with various radii are compared which clarifies the influence of optical and structural characteristics of nanotubes on the coupling length. Extremely short coupling lengths and exceptional features, such as high-power confinement and long propagation lengths, exhibit promising features for the next-generation interconnects and optical circuits.

Ab initio study of the exo-hydrogenated single wall carbon nanotubes

Stability of the fully exo-hydrogenated zigzag (n,0) and armchair (n,n) single wall carbon nanotubes (CnHn) is studied using first-principles calculations. Zigzag and armchair carbon nanotubes (CNTs) were found to be different in electronic and atomic structures with respect to chemical hydrogenation. It was noted that the binding energy of hydrogenated carbon nanotubes revealed an approximately inverse proportionality behaviour with their diameter. Moreover, each single hydrogen atom was attached to nanotube by an exothermic process. The similar diameter exo-hydrogenated zigzag nanotubes were found to be energetically more favourable than armchair nanotubes. The calculated values of band gaps in small hydrogenated zigzag CNTs were found to be higher in both types of hydrogenated CNTs. These findings were important for particular functionalization of hydrogenated carbon nanotubes and improve the understanding to separate similar diameter zigzag and armchair nanotubes from each other through chemical functionalization.

Nanomechanics model for properties of carbon nanotubes under a thermal environment

This paper proposes a modified molecular mechanics model in which the covalent bond is treated as a beam element, and a theoretical prediction of the thermal environment effect on the elastic properties of single-walled carbon nanotubes (SWCNTs) is reported. The influence of the temperature on Young’s modulus of both armchair and zigzag SWCNTs is investigated. The study shows that the moduli decrease with the increase in temperature, but Poisson’s ratio is not dependent on the temperature. The temperature-dependent Young’s modulus increases with the increase in tube diameter. According to the principle of elasticity theory and energy consistent theory, a temperature-dependent continuum shell model of strain energy is also established. It is found that the deviation between the potential energy of carbon nanotubes and the strain energy of a continuum shell is significantly reduced based on the molecular mechanics model proposed in this study.

Electronic, Thermochemistry and Vibrational Properties for Single-walled Carbon Nanotubes

Background: The Single-wall Carbon Nanotubes (SWCNTs) represent one of the most active classes of nanostructures, and they have been widely used as active materials for important applications. In this study, the electronic, thermochemistry and vibrational properties of zigzag and armchair SWCNTs were investigated. Objective: Using these investigations, it is possible to obtain much more data to apply SWCNTs in medical science, industrial technologies and nanosensors applications. Methods: All the calculations are based on the Density Functional Theory (DFT) at the B3LYP/6-31G level through the Gaussian 09W program package. Results: The optimized structures, diameter, contour plots for electronic states (HOMO and LUMO), energy gaps, thermochemistry functions and vibrational intensities were performed and discussed. Conclusion: This study clarified the properties of SWCNTs are dependent on the diameter of the tube, i.e. the chrial vector (n, m). An addition, these results could help to design more efficient functional SWCNTs, and these properties play a key role for many applications.

Theoretical Study of Chemisorption of Hydrogen and Fluorine Atoms on the Sidewalls Armchair Single-walled Carbon Nanotubes with Two Carbon Ad-dimer Defects

Single-walled carbon nanotubes with two carbon ad-dimer defect and the chemisorption of hydrogen and fluorine on the surface of these nanotubes were studied through density functional theory method. The results indicate that nanotubes with two carbon ad-dimers defect exhibit a higher reactivity than perfect ones. Moreover, side-wall reactions of H2 and F2 are thermodynamically feasible. The reaction energy for per F2 chemisorption is more exothermic than for per H2 chemisorption.

Interaction of HF, HBr, HCl and HI Molecules with Carbon Nanotubes.

The present work applies the density functional theory (DFT) to study the interactions between armchair (n,n) single walled carbon nanotubes (SWCNTs) and hydrogen halides confined along the nanotube axis and perpendicular to it. Calculations are performed using the CAM-B3LYP functional. According to the hydrogen halides orientation and the internal diameter of CNTs hollow space, HF, HCl, HBr and HI behave differently. The nanoconfinement alters the charge distribution and the dipolar moment. The encapsulated hydrogen fluoride (HF) molecule is stable along and perpendicular to the nanotubes (5,5) and (6,6) axis. The hydrogen chloride (HCl), hydrogen bromide (HBr) and hydrogen iodide (HI) form stable systems inside the nanotube (6,6) only at the perpendicular orientation. In addition, other phenomena are observed such as leaving the nanotube or decreasing the bond length of the molecule and even the creation of covalent bind between the guest molecule and the host nanotube.

Influence of intermolecular interactions on the properties of carbon nanotubes

This study is aiming at theoretical and experimental confirmations of the deposition of oligothiophene dyes (OT) on structurally and chemically diverse surfaces of carbon materials, especially carbon nanotubes (CNTs). This study is a contribution to the wide search and design of novel hybrid materials for light-sensitive (dye solar cells) and light-emitting (LEDs) structures. The obtained materials containing OTs embedded in the pores of a carbon matrix were analysed by means of microscopic and spectroscopic techniques as well as low-temperature adsorption of nitrogen, together with an investigation of the surface area by the BET method. Confocal microscopy was employed to confirm the immobilization of oligomers on the surface of CNTs. Raman spectra, XRD and HTEM microscopies allowed to judge the quality of the carbonaceous material and to compare the test material before and after the introduction of OT. Additionally, the elemental content and elemental surface species were determined by means of XPS and combustion elemental analyses. The explanation of thiophene; 2,2 $$^\prime $$ :5 $$^\prime $$ ,2 $${^{\prime \prime }}$$ -terthiophene and $$\alpha $$ -sexithiophene molecular interactions with single wall armchair CNTs was supported by theoretical calculations. In computational investigations, CNTs were modelled by tubules of different sizes, lengths and hydrogenated open ends.

Structural parameters, electronic properties, and band gaps of a single walled carbon nanotube: A pz orbital tight binding study

Single walled carbon nanotube (SWCNT), an emerging one-dimensional carbon nanostructure, have several unique attributes and amazing properties that offers a great potential for interconnects, nanoelectronic and optoelectronic devices. For the first time, the pz orbital tight binding study on structural parameters, electronic properties, and band gaps of a SWCNT have been presented and analyzed in this paper. The analytical values of different parameters regarding the overall unit cell and molecular structure of a SWCNT have been verified using the simulation approach, therefore, proved the validation of both the simulation as well as analytical values. It has been observed that the total number of unit cells, carbon atoms, and hexagons within the overall unit cell and molecular structure of a SWCNT at different chirality values and lengths obtained using the simulation matches with the analytical values. Further, the metallic and semiconducting properties of a SWCNT can be investigated with the help of different simulated electronic band structures obtained for different chirality combinations. First, it has been found that all armchair SWCNTs are metallic with a very small constant band gap of 10.88 meV whereas the zigzag SWCNTs show metallic as well as semiconductor behavior with zero and larger than zero band gap values. Second, it has been observed that the total number of subbands in each electronic band structure of a SWCNT (both armchair and zigzag) is chirality dependent and equal to the total number of carbon atoms present in their overall unit cell structure. Furthermore, the reported band gap values have been compared with the already published calculation as well as experimental values which show excellent agreement between them. Finally, it has been observed that the metallic SWCNTs are best suited for interconnects and the semiconducting SWCNTs are best suited for novel channel materials of a field effect transistor.

Benchmark study of ionization potentials and electron affinities of armchair single-walled carbon nanotubes using density functional theory

The intrinsic parameters of carbon nanotubes (CNTs) such as ionization potential (IP) and electron affinity (EA) are closely related to their unique properties and associated applications. In this work, we demonstrated the success of optimal tuning method based on range-separated (RS) density functionals for both accurate and efficient prediction of vertical IPs and electron affinities (EAs) of a series of armchair single-walled carbon nanotubes C20nH20 (n = 2–6) compared to the high-level IP/EA equation-of-motion coupled-cluster method with single and double substitutions (IP/EA-EOM-CCSD). Notably, the resulting frontier orbital energies (–εHOMO and –εLUMO) from the tuning method exhibit an excellent approximation to the corresponding IPs and EAs, that significantly outperform other conventional density functionals. In addition, it is suggested that the RS density functionals that possess both a fixed amount of exact exchange in the short-range and a correct long-range asymptotic behavior are suitable for calculating electronic structures of finite-sized CNTs. Next the performance of density functionals for description of various molecular properties such as chemical potential, hardness and electrophilicity are assessed as a function of tube length. Thanks to the efficiency and accuracy of this tuning method, the related behaviors of much longer armchair single-walled CNTs until C200H20 were studied. Lastly, the present work is proved to provide an efficient theoretical tool for future materials design and reliable characterization of other interesting properties of CNT-based systems.

Thermal and Small-Scale Effects on Vibration of Embedded Armchair Single-Walled Carbon Nanotubes

The non-local Timoshenko beam theory has been implemented to investigate the free vibration of armchair single-walled carbon nanotubes embedded in elastic medium including the thermal effects. The mechanical properties of nano-composite (carbon nanotubes and polymer matrix) are treated as functions of temperature change and the analytical solution is derived according to the governing equations of non-local Timoshenko beam models. The equivalent Young’s modulus and shear modulus for armchair single-walled carbon nanotubes are derived using an energy-equivalent model. Influence of small-scale coefficient, vibrational mode number, matrix of nano-composite and aspect ratio on the frequency ratio of the armchair single-walled carbon nanotubes including the thermal effect are studied and discussed. The research work reveals the significance of the small-scale coefficient, the vibrational mode number, the elastic medium and the aspect ratio on the frequency ratio. It is also demonstrated that some properties of free vibrations of single-walled carbon nanotubes are dependent on the change of temperature.

An Immunologically Modified Nanosystem Based on Noncovalent Binding Between Single-Walled Carbon Nanotubes and Glycated Chitosan.

Functionalized single-walled carbon nanotubes are currently being explored as novel delivery vehicles for proteins and therapeutic agents to treat various diseases. In order to maximize treatment efficacy, a strong binding between single-walled carbon nanotubes and their functionalized molecules is necessary. Glycated chitosan, a polymer with potent immunostimulatory properties for cancer treatment, has been used as a surfactant of single-walled carbon nanotubes to form an immunologically modified nanosystem for biomedical applications. In this study, we investigated the binding characteristics of single-walled carbon nanotube and glycated chitosan using molecular dynamics simulations. The mean square displacement, radius of gyration, interaction energy, and radial distribution function of the single-walled carbon nanotube-glycated chitosan system were analyzed. The results from the simulations demonstrated that glycated chitosan was bound to single-walled carbon nanotubes by a strong, noncovalent interaction. The stability of glycated chitosan on the single-walled carbon nanotubes surface was enhanced by the length of glycated chitosan, and the binding energy of the 2 molecules was closely related to the diameter and chirality of single-walled carbon nanotubes, with the most stable single-walled carbon nanotube-glycated chitosan system being formed by the combination of long polymer, large single-walled carbon nanotube, and armchair single-walled carbon nanotube. The understanding of the interactions between single-walled carbon nanotube and glycated chitosan and the structure of single-walled carbon nanotube-glycated chitosan allows the modifications of the novel nanosystem for disease diagnostics and therapeutics.

Geometry, tautomerism and non-covalent interactions of the drug halofuginone with the carbon-nanotube and γ-Fe2O3 nanoparticles: A DFT study

Halofuginone is a potential anti-malarial drug, which could exist as three possible tautomers. Herein, using density functional theory (DFT), and handling the solvent effects with the PCM model, the tautomerism of halofuginone was investigated. Intramolecular H-bonds play an important role in the stability of the tautomers. The conformer H1a is the most stable. Noncovalent interactions of the H1a conformer with the armchair (5,5) single-wall carbon nanotubes and ?-Fe2O3 nanoparticles were explored in several manners. The most stable form of them was determined. The intermolecular H-bonds play a substantial role in the energy behavior of the interaction between ?-Fe2O3 nanoparticles and halofuginone.

$$\hbox {N}_{2}$$ N 2 adsorption on the inside and outside the single-walled carbon nanotubes by density functional theory study

The adsorption energies, bond order, atomic charge, optical properties, and electrostatic potential of nitrogen molecules of armchair single-walled carbon nanotubes (SWCNTs) and nitrogen-doped single-walled carbon nanotubes (N-SWCNTs) were investigated using density functional theory (DFT). Our results show that adsorption of the $$\hbox {N}_{2}$$ molecules on the external wall of a nanotube is more effective than on the internal wall in SWCNTs. The results show that $$\hbox {N}_{2}$$ molecule(s) are weakly bonded to SWCNTs and N-SWCNTs through van der Waals-type interactions. The interaction of $$\hbox {N}_{2}$$ molecules with SWCNTs and N-SWCNTs is physisorption as the adsorption energy and charge transfer are small, and adsorption distance is large. The electronic transitions from the highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular orbital (LUMO) ( $$\hbox {H}\rightarrow \hbox {L}$$ ) have the maximum wavelength and the lowest oscillator strength. The potential sensor on the surface of pristine SWCNTs and N-SWCNTs for the adsorption of $$\hbox {N}_{2}$$ molecule(s) is investigated. The N-loaded single-walled carbon nanotube is introduced as a better $$\hbox {N}_{2}$$ molecule(s) detector when compared with SWCNTs.