Papers by Keyword: Single-Walled Carbon Nanotube

Abstract: In this paper, (5,5) single-walled carbon nanotube was doped by substitutional nitrogen (N) atom forming bridgehead C-N bonds in the resulting C₃₉N armchair nanotube. It was then interacted with acetic acid to investigate its detection capability using first-principles calculations in the context of Density Functional Theory (DFT). As known, DFT is a very efficient and accurate method in calculating the properties of the atoms and molecules, and their interactions. Accordingly, the O-H bond of the acid has not undergone a heterolytic dissociation caused by the weak interaction of the materials. In the valence region of the C₃₉N-acid, the O atoms (2p) are the main causes of additional states as shown in the projected density of states (pDOS). Calculations of the charge density difference revealed the occurrence of charge redistribution and nonuniform charge transfer between the acid and the sidewalls of the C₃₉N. Further topological investigation of the system revealed no localized electrons between the interaction points indicating a physical binding mechanism. These electronic responses have shown the biosensing ability of C₃₉N to detect and capture acetic acid.

Abstract: This research investigated the Hydrogen doping of the single-walled carbon nanotube (HCNT) with encapsulated cellulose, (C₆H₁₀O₅)₂, and provide theoretical predictions on the properties of the resulting complex system. After full structural optimization, two different bond lengths and angles in the HCNT and (C₆H₁₀O₅)₂/HCNT system were calculated. Further, it was found that substitutional H atoms acted as charge acceptors and drove necessary rearrangements in the valence region. The (C₆H₁₀O₅)₂ caused some peaks at the valence band mainly caused by the p orbitals of the oxygen atoms. A bandgap decrease has been observed for the (C₆H₁₀O₅)₂/HCNT system. The results are consistent with the previous works which demonstrated the possibility of band gap engineering in CNTs.

Abstract: — Synthesized single-walled carbon nanotubes (SWCNTs) consist of a mixture of chiralities and therefore a post-synthesis separation is essential to separate them based on electronic type i.e., metallic (m-SWCNT) or semiconducting (s-SWCNT) for device applications. A key parameter to measure the effectiveness of separation process is the enrichment composition percentage between m-SWCNT and s-SWCNT, which can be estimated via several methods based on optical characterizations. In this paper, we compare the composition percentage estimations from 3 different methods based on Raman spectroscopy and UV-Vis optical absorption spectroscopy. The estimation methods are radial breathing mode (RBM) peak analysis, optical absorption area under curve (OUA) and first derivative amplitude of the optical absorption curve (FDA). Four different SWCNT sources were used in this study, which were subjected to post-synthesis separation process via agarose gel chromatography. Raman and UV-Vis spectroscopy measurements were carried out on all samples, before and after separation. From the estimations, we observed firstly that there are some variations on the estimated enrichment compositions between different methods, although the values are comparable. Secondly, for some SWCNTs samples, only a certain estimation method showed reliable composition percentage. The results presented in this work may provide viable options for characterizations of SWCNTs as there is no direct method to quantify the absolute composition percentage of SWCNTs based on electronic type. Keywords— single-walled carbon nanotube, separation, electronic type, optical characterization, purity percentage.

Abstract: Single-walled carbon nanotubes (SWCNTs) as a promising candidate in a wide range of applications have shown great potentials in optical, electronic, magnetic and mechanical fields. Precisely due to their excellent characteristics and performances, it has attracted widespread attention, and much progress has been made during recent decades. However, due to the huge challenge in controlled synthesis and purification, obtaining SWCNTs with consistent chirality has seriously limited their high-end industrial applications. In this article, we will review the approaches recently developed in chirality-controlled preparation of SWCNTs. Among them, we will introduce the mechanism of templated growth of SWCNTs from chiral affinities, including cloning and seeds designing strategies. The preparation of SWCNTs catalyzed by noble metal and assisted with weak oxidant have been illustrated as well. Meanwhile, we will also discuss some chirality-selective separation approaches, which pay more attention to post-processing strategies by purifying the chiral SWCNTs with functional reagents. We expect that these strategies in controlling the chirality of CNTs will shed more light on the mechanism and process for atomic structural control of CNTs, and may also be applicable in the controlled synthesis of other nanomaterials.

Abstract: The dynamic free and forced axial vibrations subjected to moving exponential and harmonic axial forces of a single-walled carbon nanotube (SWCNT) embedded in an elastic medium, are studied in this paper. Two different boundary conditions of SWCNT, including clamped-clamped and clamped-free, are taken into account. Eringen’s nonlocal elasticity theory is used to show the nonlocality for the model. The constitutive equations and their boundary conditions are derived by Hamilton’s principle. Employing the general solution, the derived equations are analytically solved to obtain two items. Firstly, the axial natural frequencies, secondly, the time-domain axial displacements at the middle of the carbon nanotube (CNT), and then the maximum axial displacements. The responses are validated with previous works, and the results demonstrates good agreement to them to verify the influence of the nonlocal parameter on the nondimensional natural frequencies for three various mode numbers. In the time-domain section, the effects of the nonlocal parameter, length, nondimensional stiffness of the elastic medium, and velocity of the moving load on the axial displacement are investigated. Also, the influences of the excitation frequency to natural frequency for the harmonic moving load, as well as the time constant for the exponential moving load on the axial displacement, are illustrated. Finally, the effect of the nonlocal parameter on the maximum axial deflection versus velocity parameter is schematically indicated.

Abstract: Currently, composite materials composed of a matrix and reinforcing components are widely used as a structural material for various engineering devices designed to operate under extreme loads of different types. By modifying a composite with structure-sensitive inclusions, such as a single-wall carbon nanotube, the mechanical properties, especially elastic characteristics, of the resulting material can be significantly improved. The results of investigation of a single-walled carbon nanotubes chirality influence on its elastic properties are presented. Various configurations of nanotubes, such as zigzag and armchair are considered. The dependences of the nanotube bulk modulus and shear modulus of its diameter are shown.

Abstract: This paper aims to present an effective electromagnetic (EM) modelling approach for rectangular bundle of single-walled carbon nanotubes (RB-SWCNTs), based on the electrical conductivity, relative complex permittivity and linear distribution impedance by applying General Ohm’s law for this bundle. The equivalent single conductor material (ESCM) model for personification the RB-SWCNTs is present in this paper. The main target of this modeling approach is to estimate and investigate the EM properties of RB-SWCNTs using common EM engineering tool solver CST (MWS). For this purpose, the RB-SWCNTs and ESCM dipole antennas will be designed and implemented using CST (MWS). The equivalent conductivity model, relative complex permittivity and other parameters of the RB-SWCNTs will be derived in this paper and considered as an equivalent material parameters for the ESCM. This modeling technique is expected to provide new avenues for designing different antenna structures.

Abstract: Torsional buckling of single-walled carbon nanotubes filled with light weight molecular via molecular dynamics is reported. The model accounts for the deformation of CNTs, and interactions among gas molecules; between gas and carbon atoms. The effect of particle loading is predicted to significantly change CNT’s critical torsional moment and stiffness. This is therefore an approach by which the torsional mechanical properties and oscillation frequencies of carbon nanotubes may be tuned. Importantly, the predicted changes in torsional siffness are unique relative to conventional linear elastic materials and are indicative of nonlinear oscillations due to nonlinear mechanical effects. CNTs subjects to large deformations reversibly switch into different morphological patterns. Each shape change corresponds to an abrupt release of energy and a singularity in the stress-strain curve. At higher torsional angle, van der Waals (VDW: He, Ar, H₂) molecules reveal a stability effect on carbon nanotubes.

Abstract: In the paper are investigated the eigenfrequencies of single-walled carbon nanotubes (SWCNTs) by the analytical method based on nonlocal theory of beam bending. A continuum approach is applied for eigenfrequency computation of SWCNTs with four types of beam end conditions: clamped-free (C-F), simply-simply supported (S-S), clamped-simply supported (C-S) and clamped-clamped (C-C).

Abstract: Applying variation principle, the analytical nonlocal Euler-Bernoulli beam models for wave propagation in fluid-filled single-walled carbon nanotubes are established. The novel nonlocal governing equations are derived and used in wave propagation analysis. Comparing with partial nonlocal Euler-Bernoulli beam models used previously, the novel analytical nonlocal models predict stiffness enhancement of CNT and wave decaying at high wavenumber or high nonlocal effect area. Though the novel analytical model is less sensitive than partial nonlocal model when fluid velocity is high, it simulate much high nonlocal effect than the corresponding partial model in many cases.