Zigzag Carbon Research Articles

Zigzag graphene nanoribbons separated by F/O as interconnects for all-carbon integrated circuits: A DFT investigation

Adsorbing atom is a promising technology for graphene nanoribbons separation. Using a combination of density functional theory (DFT) and non-equilibrium Green's function (NEGF), we investigated stability and electronic transport properties of zigzag graphene nanoribbons (ZGNRs) that adsorb a row of fluorine or oxygen atoms on the central zigzag carbon chain. Results indicate that all ZGNRs after adsorption can exist stably. Adsorbing separation has excellent current work in comparison with the results of mechanical separation. Transmission pathways of electrons and local density of states (LDOS) reveal that fluorinated carbon chain can prevent electrons moving. Two sections on the ZGNR are separated by the row of fluorine atoms that are shown to function as a transport boundary between them. However, the row of oxygen atoms cannot separate ZGNR. Electrons tend to move around oxygen atoms and the lone-pair electrons of oxygen atoms participate in the transport of electrons, resulting in an improvement of carrier mobility. Realizing this adsorbing separation of ZGNR will provide new ideas for interconnects wiring in all-carbon integrated circuits.

Synthesis, aromatization and cavitates of an oxanorbornene-fused dibenzo[de,qr]tetracene nanobox.

Oxanorbornene-fused double-stranded macrocycles, represented by kohnkene, are not only synthetic precursors toward short segments of zigzag carbon nanotubes but also typical cavitands processing an intrinsic cavity. However, their capability to bind guest molecules in solution remained unexplored. Herein we report a new member of oxanorbornene-fused double-stranded macrocycles, which is named a nanobox herein because of its shape. Reductive aromatization of this oxanorbornene-fused nanobox leads to observation of a new zigzag carbon nanobelt by high resolution mass spectroscopy. The fluorescence titration and NMR experiments indicate that this nanobox encapsulates C70 in solution with a binding constant of (3.2 ± 0.1) × 106 M−1 in toluene and a high selectivity against C60 and its derivatives. As found from the X-ray crystallographic analysis, this nanobox changes the shape of its cross-section from a rhombus to nearly a square upon accommodating C60.

Phenylene segments of zigzag carbon nanotubes synthesized by metal-mediated dimerization.

Well-studied cycloparaphenylenes (CPPs) correspond to the simplest segments of armchair CNTs, whereas the corresponding macrocyclic oligophenylene strip of zigzag CNTs is still missing. Herein, we present two series of conjugated macrocycles (CM2PP and CN2PP) containing two meta-phenylene or 2,7-naphthylene units facing each other in the strip. CM2PP and CN2PP can be regarded as the shortest cyclic primitive segments of zigzag CNTs. They were synthesized by gold-mediated dimerization and unambiguously characterized. They adopted the tubular structures and can further pack into one-dimensional supramolecular nanotubes. In particular, the supramolecular nanotube of CM2P4P mimics the CNT(9, 0) structure. Structural analysis and theoretical calculation accounted for the reduced ring strain in CM2PPs and CN2PPs. CM2PPs and CN2PPs exhibited a large optical extinction coefficient and high photoluminescence quantum yield. CN2P8P can accommodate fullerene C60, forming a Saturn-like C60@CN2P8P complex, a mimic structure of zigzag CNT peapods.

Theoretical study of the chemical interactions between carbon fiber ultramicroelectrodes and the dihydroxybenzene isomers for electrochemical sensor understanding

Herein we present a study using the density functional theory in periodic systems to describe the interaction of carbon fiber ultramicroelectrodes during the detection of the dihydroxybenzene isomers: catechol (CT), resorcinol (RS), and hydroquinone (HQ). We used graphene as the surface model in the conformations: carbon basal plane, zig-zag, and armchair edges. We modeled the surface models functionalized with oxygenated groups. We predicted chemisorption for the oxidized form of RS when the COOH group is present in the armchair edge. Also, the susceptibility of the RS to form dimers and trimers bonded to the electrode surface. Experimentally, the electrooxidation of RS showed inactivation of the ultramicroelectrode, which can be explained considering the chemisorptions mentioned above and the formation of no-electroactive polymers. In the case of the other two molecules (CT and HQ), the model describes favorable interaction energies with the electrode; none of them as strong as RS, thus, experimentally, we did not see affections to the electrochemical responses, and we could measure a well-defined steady-state current at different concentrations of these molecules. Furthermore, the characteristic half-wave potential (E1/2) of the isomers ensured their detection and quantification in single or mixed solutions in concentrations from 40 μM to 1 mM.

Electrostatic charge distribution in armchair and zigzag carbon nanotubes: a numerical comparison of CNT charge models

In engineering—especially in mechanics, lightweight engineering, aerospace engineering, electrical engineering as well as bioengineering—there is a desire of developing materials enabling an excellent performance with respect to mechanical, thermal, and electrical properties. One of the most promising materials are carbon nanotubes (CNTs), as they show excellent mechanical and electrical properties. To improve the understanding of the electrical behavior, i.e., the charge distribution in single-walled carbon nanotubes, both open ended armchair and zigzag types are investigated. In the present research, three different modeling approaches, a classic electrostatic model, the model by Li and Chou and the model by Mayer, are analyzed and compared with respect to their further applicability. In the numerical investigations, different test cases are performed: (i) the carbon nanotubes are charged with an overall charge, (ii) the CNTs are exposed to an external electric field, and (iii) the test cases (i) and (ii) are combined. Furthermore, the influence of different geometric parameters is investigated. It is shown that the charge applied to the CNTs distributes over the whole CNT having maxima at the ends of the tubes. These maxima can be influenced by both, the geometric parameters and the electric field strength.

Optical and NLO properties of zigzag carbon nanobelt compounds

• Photophysical properties of CNBs were firstly studied. • The electron transition properties of CNBs were assigned. • The relation between substitutions and photophysical properties was established. • CNBs that introduce substituents from the perspective of breaking centrosymmetric may become potential second-order NLO materials with excellent performance. Zigzag carbon nanobelts (CNBs) attracted great attention from researchers with their potential applications in materials science and supramolecular chemistry. Photophysical properties of the reported CNB and five new designed substituted CNBs are investigated with the aid of density functional theory. Studies show that different substituents have different effects on the electronic structure, electronic transition and first hyperpolarizability. The introduction of electron donors and electron acceptors in a way like CNB 6 is an feasible way to obtain the smallest band gap and cause obvious charge separation in FMOs, and the introduction of different substituents makes the low-energy absorption band produce a significant red shift, and the insertion of substituents from the perspective of breaking centrosymmetric is the most effective method to enhance second-order NLO properties. In view of strong second-order NLO response of CNBs 5 and 6 , they may have the probability to be candidates used as excellent second-order NLO materials. Photophysical properties of the studied CNBs were studied with the help of the DFT calculations.

Influence of temperature variation on the electrical conductivity of zigzag carbon nanotubes under homogeneous axial dc field

We present theoretical framework investigations of the influence of temperature variation on the electrical conductivity of zigzag carbon nanotubes (CNTs) under the applied homogeneous axial dc field. This study was done semiclassically by solving Boltzmann transport equation to derive the current density of zigzag CNT as a function of homogenous axial dc field and temperature. Plots of the normalized current density versus homogeneous dc field applied along the axis of semiconducting zigzag CNTs as room temperature increases from 293 to 299 K revealed a significant increase in electrical conductivity, whereas in metallic zigzag CNTs, almost constant or a negligible decrease in electrical conductivity is observed. The study predicts semiconducting zigzag CNT as a potential material for temperature sensors since it exhibits a faster response and a substantially higher sensitivity to room temperature changes than the metallic counterpart. The electrical conductivity of metallic zigzag CNTs increases immensely as the temperature is reduced to a very low value which could probably lead to a potential superconductivity property that usually occurs at very low temperatures. These potential temperature sensors and superconductors of nanomaterial have vast applications in current-day science and technology.

Structural, electronic, and optic properties of Se nanotubes

A new category of tubular nanostructures solely composed of selenium was explored by using the density functional theory. Similar to those in carbon nanotubes, the armchair and zigzag tube-like structures formed as a roll-up α-Se nanoribbon. The zigzag (n ≤ 16, 0) nanotubes exhibit decreasingly narrow direct band gap, and the armchair (n, n) possess decreasingly moderate indirect gap. The strain energy of nanotubes is inversely proportional to the second power of the nanotube diameter. With increasing tube diameter, an initial rise and consequent decrease occurred in the effective masses to the limit value of α-Se monolayer. The carrier mobility of nanotubes is comparable with that of its monolayer with orders of 103 and 102 cm2V−1s−1 for electron and hole, respectively. The optical absorption spectra of α-Se nanotubes exhibit high absorbance in energy window cover the entire visible light spectrum. Therefore, α-Se nanotubes hold great potential for future applications in high-performance optoelectronics.

Computational Modelling of SO2 and H2S gas interacting with small diameter Au-doped (5, 0) zig-zag single-walled carbon nanotubes

An ab initio density functional theory (DFT) is employed to explore the effect of adsorption of SO2 and H2S gases on gold-doped small diameter (5,0) zig-zag single-walled carbon nanotubes. Au-SWCNT nanostructures are extremely sensitive to the presence of both SO2 and H2S gases. Charge is transferred from the Au-SWCNT to the SO2 upon the adsorption of the gas molecules onto the Au-SWCNTs surface. There is a decrease in the energy bandgap of the Au-SWCNT. As a consequence, the electrical conductivity of Au-SWCNTs/SO2 is extremely enhanced. On the contrary, the adsorption of H2S gas onto the surface of the gold-doped nanotube provokes charge transfer from H2S to the Au-SWCNT. Another interesting observation is that the energy bandgap of AuSWCNT increases upon the adsorption of the H2S gas molecules onto the Au-SWCNT surface, thereby decreasing the electrical conductivity of the Au-SWCNT/H2S nanostructure. Citation: Elloh, V. W., Boadu, E. O., Ofosuhene, D. F. and Arhin, I. (2021). Computational Modelling of SO2 and H2S gas interacting with small diameter Au-doped (5, 0) zig-zag single-walled carbon nanotubes.International Journal of Technology and Management Research (IJTMR), Vol. 6 (2): Pp.87-95. Received: March 20, 2021Accepted: September 1, 2021

Mechanical and thermal stability of armchair and zig-zag carbon sheets using classical MD simulation with Tersoff potential

In this work, the molecular dynamics method is implemented to study the temperature and edge effects on the atomic crack's growth in graphene nanosheet. Graphene nanosheets with armchair and zig-zag edges are simulated to this mechanical procedure. In our calculations, the atomic interactions of simulated carbon atoms are based on Tersoff potential. Simulation results show that nanosheets' edge is an important parameter in crack growth. Physically, graphene with armchair edge shows more resistance against atomic cracking in atomic simulations. In this structure, the final length of crack is 23.60 Å which is smaller than the zig-zag one at 300 K. Furthermore, the effects of temperature on the atomic crack of graphene nanosheets are studied. Our results show that by increasing the temperature from 300 K to 350 K, the atomic movements of carbon atoms increase; so, we concluded that the atomic stability of graphene nanosheets decreases by temperature increasing. Numerically, by 50 K temperature increasing in armchair/zig-zag graphene nanosheet, the crack length in this structure reaches to 28.32 Å/30.34 Å from 23.60 Å/28.91 Å value.

Distortion of yttrium bisphthalocyanine (YPc2) upon noncovalent interaction with carbon nanotubes: A DFT study

We performed a DFT analysis of the changes in geometry and some electronic properties of yttrium bisphthalocyanine YPc2 when forming noncovalent hybrids with two single-walled carbon nanotube models, having armchair (ANT) and zigzag (ZNT) chiralities. The Perdew-Burke-Ernzerhof functional in combination with a long-range dispersion correction by Grimme (PBE-D) and the double numerical basis sets of variable size (DN, DND and DNP) was used. We found that YPc2 molecule suffers binding distortion in order to increase the area of contact with nanotube sidewall, which enhances interaction between the two components. YPc2 bonding is stronger with ZNT nanotube, of −43.8 kcal/mol, vs. −37.1 kcal/mol for YPc2 + ANT complex (as calculated with DNP basis set). The height of bisphthalocyanine molecule in the dyads dramatically increases compared to that calculated for isolated YPc2, whereas the calculated N-Y-N angles in YN4 coordination change very insignificantly. In all cases, a minor HOMO-LUMO gap narrowing is observed. For YPc2 + ANT the gap tends to match the one for isolated YPc2, whereas for YPc2 + ZNT it is much closer to the band gap of ZNT. The calculated HOMO, LUMO and spin density plots are analyzed.

Chemical Synthesis of Carbon Nanorings and Nanobelts

ConspectusThe discovery and creation of new forms of carbon have always transformed the scientific landscape. For example, the discoveries of fullerenes, carbon nanotubes (CNTs), and graphenes have opened doors to the science of nanometer-sized carbon allotropes, otherwise known as nanocarbons. Since then, researchers worldwide have unveiled their outstanding physical and chemical properties, and a number of applications and technologies have arisen in not only materials science but also biological research fields. The synthesis and study of this privileged class of “single-molecule” compounds has become one of the most engaging subjects in chemistry and holds huge promise to establish new fields in molecular science. However, there have been huge gaps between established small-molecule chemistry and nanocarbon science. In the particular case of CNTs, it is still not possible to access structurally uniform CNTs. Although a wide range of synthetic methods have been reported, CNTs are generally accessed as a mixture of various structures. One logical strategy to achieve full synthetic control over CNTs is to build up from a template molecule with structural precision (the so-called “growth-from-template” strategy), where a short CNT segment molecule represents an initial synthetic target. To this end, organic synthesis techniques are our most powerful tools to synthesize short CNT segments such as carbon nanorings and carbon nanobelts. This Account highlights our 16-year campaign in the synthesis and application of carbon nanorings and carbon nanobelts. The first topic is the synthesis of carbon nanorings (cycloparaphenylenes) as substructures of CNTs. The second topic is the synthesis of armchair and zigzag carbon nanobelts, which consist solely of fully fused hexagonal rings and provide a continuous double-stranded cylindrical framework. The third topic is the synthesis of methylene-bridged cycloparaphenylene, an aromatic belt containing nonhexagonal rings, in which the cyclic paraphenylene chain is ladderized by methylene bridges. This nonalternant aromatic belt can be regarded as segments of nonconventional CNTs. During our extensive investigation, we found that the careful design of strainless macrocyclic precursors is crucial to the success of the synthesis of these curved π-conjugated nanorings and nanobelts. In the final section, some of the representative size-dependent properties of these nanorings/belts, including their HOMO–LUMO energies, strain energies, and photophysical properties, are summarized. In addition to basic properties, the utilization of these compounds as supramolecular hosts and organic materials is also briefly introduced. We hope this Account will inspire the development of new forms of nanocarbon molecules that would open doors to new fields and applications.

Achieve 100% transmission via grafting hydroxyl groups on CNT nanomotors

Nanomotors are essential in nanorobots and nanoenergy. The critical issues include stability and efficiency. Here, we have investigated the influence of hydroxyl groups on the transmission behavior of carbon nanotube based nanomotors using molecular dynamic simulations. The results showed that 100% transmission efficiency occurred in kinetic energy transmission, irrespective to the diameters and chiral angles of carbon nanotubes. Such stable and efficient transmission was attributed to the hydrogen bonds formed between hydroxyl groups on motor and rotor. The fastened responses were observed in the systems with zigzag and armchair carbon nanotube motor. Our results provide atomic insights into improving stability and efficiency in nanomotors.

First-principles investigation of the electronic and optical properties of As2GeTe nanotubes

In this paper, the electronic and optical properties of the armchair and zigzag As2GeTe nanotubes are investigated. Calculations have been performed using QUANTUM-ESPRESSO computational package, which is based on the density functional theory and pseudopotential technique. The strain and formation energies computed for the equal diameter of the two armchair and zigzag systems are almost the same and converge to the reference As2GeTe monolayer by increasing the diameter of the nanotubes. For each diameter, the calculated strain energies are lower than the corresponding armchair and zigzag carbon nanotubes. The electronic calculations indicate that for both armchair and zigzag systems, As2GeTe nanotubes have a semiconductor characteristic with a direct band gap of approximately 1.0 eV within the generalized gradient approximation. Based on the phonon dispersion curve at ambient pressure, nanotube structures are dynamically stable. The optical band gap derived from the imaginary part of the dielectric function also verifies the electronic results. All types of nanotubes, except the armchair (4.4) nanotube, have an equal and very low optical reflectivity (~0.05) in the far-ultraviolet frequencies, which is an interesting problem for the reflectivity application. Apart from the first diameter of the armchair structure, the values of Plasmon energies calculated for both armchair and zigzag As2GeTe nanotubes are almost identical. The nearly identical electronic and optical properties of different diameters of the As2GeTe nanotubes make them attractive from an application point of view.

Interaction mechanism between gaseous arsenic and the unburned carbon in coal-fired fly ash: A DFT combined thermodynamics study

Based on the density functional theory (DFT) combined thermodynamics method, the flue gas arsenic forms from the coal-fired power plants were successfully confirmed at different temperature ranges, and the interaction mechanism of the fly ash unburned carbon (UBC) components on different gaseous arsenic species were also investigated. The content of trivalent arsenic (As3+) is the highest in flue gas, and its morphological distribution is significantly affected by the flue gas temperature. When the flue gas temperature is lower than 900 K, the As2O3 molecules are dominant in the trigonal bipyramid type. While when the temperature exceeds 900 K, the priority structure of As2O3 is chain type > horn type > trigonal bipyramid type in turn. This paper has verified the feasibility for the adsorption of flue gas arsenic via the unburned carbon in fly ash, and the performance of the zigzag carbon surface is always better than the armchair surface. This paper provides theoretical support for arsenic removal in coal-fired power plants, and also provides some new ideas for the secondary utilization of fly ash and the development of carbon-based arsenic removal adsorbent.

Radius dependence of the electrical conductivity of zigzgag carbon nanotubes

The radius dependence of the electrical conductivity of metallic and semiconducting zigzag carbon nanotubes (CNTs) is theoretically studied. The investigation was done semiclassically by solving the Boltzmann transport equation to derive current density as a function of a homogenous axial dc field and radius of the tube. The analysis was numerically carried out by varying the radius of the materials at a constant temperature. Plots of the normalized current density versus dc field applied along the axis of both materials are presented. We observed that in the case of the metallic zigzag CNTs as the radius increases, the electrical conductivity decreases. On the other hand, in the semiconducting zigzag CNT there was an increase as radius increases. This research shows that thinner metallic zigzag CNTs and thicker semiconducting zigzag CNTs are better conductors of electricity. This investigation therefore offers way of obtaining higher electrical conductivity in both materials without doping. This study therefore shows applications in the development of current conducting nano-devices for scientific systems.

Modulation of electric field on low-frequency plasmons of carbon nanotubes

Abstract The electric-field-dependent plasmons of armchair and zigzag carbon nanotubes (ACNTs and ZCNTs) are calculated by the pz-orbital tight-binding model including curvature effect and random-phase-approximation. As electric field increases, ZCNTs undergo a zero-gap transition, whereas ACNTs remain metallic. Band structures of CNTs in electric field can exhibit many local minima and maxima leading to more transition channels. The position and amplitude of the peak-dip structures in the dielectric functions have strong dependence on field strength and nanotube's geometry. For ACNTs and narrow-gap ZCNTs, plasmon frequency at zero field increases with increasing transferred momentum, but plasmon peak is enhanced and then reduced. With increasing field strength, plasmon frequency is lowered and the critical momentum causing a vanish of plasmon becomes smaller. Moreover, temperature provides more electronic excitation states leading to a higher plasmon frequency. There is no plasmon at zero field for moderate-gap ZCNTs, but it can be induced by applying electric field. With increasing temperature, low-frequency plasmon with THz could be further enhanced.

Vibrational and electronic properties of (5,0) zigzag and (5,5) armchair carbon and SiC nanotubes using density functional theory

We have performed optimization of (5,0) zigzag and (5,5) armchair single-walled carbon nanotube and SiC nanotube using density functional theory at zero spin and high spin values. Further, Infrared and Raman spectra, highest occupied and lowest unoccupied molecular orbitals and their gap and natural bond orbital analysis were carried out at optimized structures of these materials. Three different exchange and correlation functionals PBE, LSDA and HCTH along with cc-pVDZ basis set were used. For conspicuous normal modes assignments of both the (5,0) zigzag and (5,5) armchair single-walled carbon nanotube and SiC nanotube, potential energy distributions of the normal modes were calculated using normal coordinate analysis. The diameter of carbon nanotube and SiC nanotube in (5,0) zigzag form were optimized at 4.0 Å and 5.0 Å respectively and in (5,5) armchair form were optimized at 7.0 Å and 8.0 Å respectively at all the three level of theories.

RKKY interaction in spin polarized doped zigzag carbon nanotube in Holstein model

We have theoretically studied the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction in zigzag gapped graphene nanotube in the presence of Holstein phonons . We investigate the effect of quantities such as the gap parameter, intensity of the electron-phonon interaction, nanotube diameter, next nearest neighbor hopping parameter, chemical potential, etc. on the spatial behavior of the RKKY interaction. Since the RKKY interaction can be obtained from the static spin susceptibility function, we first need to calculate this function. The spin susceptibility is calculated using Green's function approach via computing the correlation function of spin density operators for the Holstein model Hamiltonian. We also exploit the random phase approximation (RPA) to correct the spin susceptibility function using the self energy due to the electron-phonon interaction. The results indicate an oscillating behavior for the spatial dependence of the RKKY interaction. It is also clear that the mentioned quantities listed above affect the spatial behavior of RKKY interaction. • Using Holstein model Hamiltonian, the excitation spectrum of electrons on nanotube has been found. • To obtain RKKY interaction, the spin susceptibility has been calculated using Green's function approach in Holstein model. • We have the effects of diameter, electron-phonon coupling and electron doping on the RKKY interaction in zigzag nanotube. • Results show an oscillating behavior for spatial dependence of coupling exchange constant between two local impurities.

Free Transverse Vibration of Nickel Coated Carbon Nanotubes

Transverse vibration of nickel coated carbon nanotubes is investigated by using molecular dynamics simulations. The simulations are carried out for armchair and zig-zag carbon nanotubes with various lengths. Uncoated and nickel coated carbon nanotubes having same lengths are analyzed and their vibrational behaviors are compared. Free transverse vibrations of nickel coated carbon nanotubes are modelled by using a two-phase local–nonlocal Euler–Bernoulli beam model and solved by finite element method. Nonlocal parameter of the beam model is calibrated based on molecular dynamics simulation results. It is seen that for the same length diameter ratio, the nickel coated carbon nanotubes have similar vibrational characteristics with the uncoated carbon nanotubes but their natural frequencies are smaller than the uncoated ones. Also, it is shown that by using proper nonlocal parameters for each radius length ratio, the two-phase local–nonlocal Euler–Bernoulli beam model can successfully predict the natural frequencies of both short and long nanotubes. Besides natural frequencies and mode shapes, the clustering of nickel atoms depend on simulation temperature which is discussed during oscillation of nickel coated carbon nanotubes.