Electronic Properties Of Carbon Nanotubes Research Articles

Carbon-chain inserting effect on electronic behavior of single-walled carbon nanotubes: a density functional theory study

Abstract

Chemical in situ modulation of doping interactions between oligoanilines and nanocarbon films

The electronic properties of carbon nanotubes are commonly customized through doping with various moieties, however, the modification is permanent as long as the dopant is present. Here we present a family of dopants that can be switched on and off while in place via environmental stimuli, in particular redox conditions and exposure to acids and bases. Aniline oligomers are firmly attached to the carbon nanotubes and are not easily displaced by other dopants or through rinsing with solvent in either oxidation state. As opposed to the reduced form of the aniline oligomers, their oxidized form causes p-doping of the carbon nanotubes. Similarly, the free base and chloride salt form of the aniline oligomers can be distinguished by their doping impact on the carbon nanotubes. The switching of the doping state can be followed by X-ray photoelectron spectroscopy, Raman spectroscopy and especially also electrically (film resistance), opening up applications as switches and sensors.

Extracting the Single-Particle Gap in Carbon Nanotubes with Lattice Quantum Monte Carlo

We show how lattice Quantum Monte Carlo simulations can be used to calculate electronic properties of carbon nanotubes in the presence of strong electron-electron correlations. We employ the path integral formalism and use methods developed within the lattice QCD community for our numerical work and compare our results to empirical data of the Anti-Ferromagnetic Mott Insulating gap in large diameter tubes.

Electronic properties of carbon nanotubes complexed with a DNA nucleotide.

Electronic properties of carbon nanotubes (CNTs) play an important role in their interactions with nano-structured materials. In this work, interactions of adenosine monophosphate (AMP), a DNA nucleotide, with metallic and semi-conducting CNTs are studied using the density functional tight binding (DFTB) method. The electronic structure of semi-conducting CNTs was found to be changed as they turned to metallic CNTs in a vacuum upon interaction with the nucleotide while metallic CNTs remain metallic. Specifically, the band gap of semi-conducting CNTs was decreased by 0.79 eV on average while nearly no change was found in the metallic tubes. However, our investigations showed that the presence of explicit water molecules prevents the metallicity change and only small changes in the CNT band gap occur. According to our charge analysis, the average negative charge accumulated on CNTs upon interaction with the AMP was determined to be 0.77 e in a vacuum while it was 0.03 e in solution. Therefore, it is essential to include explicit water molecules in simulating complexes formed by DNA nucleotides and CNTs which were ignored in several past studies performed using quantum mechanical approaches.

Electronic Properties of Carbon Nanotubes Intercalated with Li+ and Mg2+: Effects of Ion Charge and Ion Solvation

The influence of bare and solvated cations imbedded inside single-walled carbon nanotubes (SWCNTs) on the SWCNT electronic properties is studied by ab initio electronic structure calculations. The roles of ion charge and ion solvation are investigated by comparing Li+ vs Mg2+ and Li+ vs its solvatocomplex with two ethylene carbonate (EC) molecules, [Li(EC)2]+. Two achiral nanotubes with similar radii but different electronic structure are considered, namely, the metallic, (15,15) armchair, and semiconducting, (26,0) zigzag, SWCNTs. The intercalation process is energetically favorable for both CNT topologies, with all bare cations and the solvatocomplex under investigation, with the doubly charged Mg2+ ion exhibiting the highest energy gain. Insertion of the bare ions into the SWCNTs increases the electronic entropy. The electronic entropy changes because the ions introduce new energy levels near the Fermi level. Those initially empty levels of the cations accept electron density and generate electronic ho...

Powerful greenhouse gas nitrous oxide adsorption onto intrinsic and Pd doped Single walled carbon nanotube

Density functional studies on the adsorption behavior of nitrous oxide (N2O) onto intrinsic carbon nanotube (CNT) and Pd-doped (5,5) single-walled carbon nanotube (Pd-CNT) have been reported. Introduction of Pd dopant facilitates in adsorption of N2O on the otherwise inert nanotube as observed from the adsorption energies and global reactivity descriptor values. Among three adsorption features of N2O onto CNT, the horizontal adsorption with Eads=−0.16eV exhibits higher adsorption energy. On the other hand the Pd-CNT exhibit strong affinity toward gas molecule and would cause a huge increase in N2O adsorption energies. Chemical and electronic properties of CNT and Pd-CNT in the absence and presence of N2O were investigated. Adsorption of N2O gas molecule would affect the electronic conductance of Pd-CNT that can serve as a signal of gas sensors and the increased energy gaps demonstrate the formation of more stable systems. The atoms in molecules (AIM) theory and the natural bond orbital (NBO) calculations were performed to get more details about the nature and charge transfers in intermolecular interactions within adsorption process. As a final point, the density of states (DOSs) calculations was achieved to confirm previous results. According to our results, intrinsic CNT cannot act as a suitable adsorbent while Pd-CNT can be introduced as novel detectable complex for designing high sensitive, fast response and high efficient carbon nanotube based gas sensor to detect N2O gas as an air pollutant. Our results could provide helpful information for the design and fabrication of the N2O sensors.

Tuning electronic properties of carbon nanotubes by Boron and Nitrogen doping

The electronic properties of pure and doped carbon nanotubes and NC3-, BC3-, NC- and BC-nanotubes are investigated by using tight binding theory. It was found that applying the external fields and doping change the band gap. The energy gap is reduced by B/N-doping and the reduction value is sensitive to the several parameters such as nanotube diameter and chirality, external field strength, electric field direction, impurity type and concentration. The direct N (B) substitution creates a new band above (below) the Fermi level and leads to creation of n-type (p-type) semiconductor. The external fields modify the band structure and convert the doped nanotube into metal. For both XC and XC3 nanotubes (X=B/N), the gap energy reduction shows identical dependence to electric field and the XC3 nanotubes show more sensitive behavior to electric field rather than XC nanotubes.

Quantum Monte Carlo calculations for carbon nanotubes

We show how lattice Quantum Monte Carlo can be applied to the electronic properties of carbon nanotubes in the presence of strong electron-electron correlations. We employ the path-integral formalism and use methods developed within the lattice QCD community for our numerical work. Our lattice Hamiltonian is closely related to the hexagonal Hubbard model augmented by a long-range electron-electron interaction. We apply our method to the single-quasiparticle spectrum of the (3,3) armchair nanotube configuration, and consider the effects of strong electron-electron correlations. Our approach is equally applicable to other nanotubes, as well as to other carbon nanostructures. We benchmark our Monte Carlo calculations against the two- and four-site Hubbard models, where a direct numerical solution is feasible.

Anomalous electrostatic potential properties in carbon nanotube thin films under a weak external electric field

Using density functional theory, we studied the electronic properties of carbon nanotube (CNT) thin films under an electric field. The carrier accumulation due to the electric field depends strongly on the CNT species forming the thin films. Under a low electron concentration, the injected electrons are distributed throughout the CNTs, leading to an unusual electric field between CNTs, the direction of which is opposite to that of the applied field. This unusual field response of CNT thin films to an external electric field is ascribed to the internal electric field arising from the electrostatic potential difference between the constituent CNTs.

Electronic properties of carbon nanotubes linked covalently with iron phthalocyanine to determine the formation of high-valent iron intermediates or hydroxyl radicals

Two different nanomaterial-based metallophthalocyanine catalysts were synthesized by immobilizing iron trinitrophthalocyanine with amino (FeMATNPc) covalently on multi-walled carbon nanotubes (MWCNTs) by deamination-synthesized MWCNTs-FeTNPc and on oxidized MWCNTs by amidation-synthesized MWCNTs–CONH–FeTNPc. The resulting hybrid structure was confirmed and characterized by X-ray photoelectron spectroscopy and attenuated total reflection Fourier transform infrared spectra. Catalytic activity tests showed that the introduction of MWCNTs resulted in a marked enhanced catalytic activity of FeMATNPc. A series of designed experiments proved that large amounts of hydroxyl radicals accompanied by some peroxy radicals and seldom by high-valent iron intermediates were formed in a MWCNTs-FeTNPc/H2O2 system. In a MWCNTs–CONH–FeTNPc/H2O2 system, much more high-valent iron intermediates with fewer hydroxyl radicals were formed. Conduction electron spin resonance and cyclic voltammetry was used to investigate the intrinsic difference between the two catalysts. More conducting electrons fill MWCNTs and electron transfer between MWCNTs and iron phthalocyanine is faster than that for MWCNTs–CONH–FeTNPc. This special electronic property may influence the formation of active species.

Dendrimer assisted dispersion of carbon nanotubes: a molecular dynamics study.

Various unique physical, chemical, mechanical and electronic properties of carbon nanotubes (CNTs) make them very useful materials for diverse potential application in many fields. Experimentally synthesized CNTs are generally found in bundle geometry with a mixture of different chiralities and present a unique challenge to separate them. In this paper we have proposed the PAMAM dendrimer to be an ideal candidate for this separation. To estimate the efficiency of the dendrimer for the dispersion of CNTs from the bundle geometry, we have calculated potential of mean forces (PMF). Our PMF study of two dendrimer-wrapped CNTs shows lesser binding affinity compared to the two bare CNTs. PMF study shows that the binding affinity decreases for non-protonated dendrimer, and for the protonated case the interaction is fully repulsive in nature. For both the non-protonated as well as protonated cases, the PMF increases gradually with increasing dendrimer generations from 2 to 4 compared to the bare PMF. We have performed PMF calculations with (6,5) and (6,6) chirality to study the chirality dependence of PMF. Our study shows that the PMFs between two (6,5) and two (6,6) CNTs respectively are ∼-29 kcal mol-1 and ∼-27 kcal mol-1. Calculated PMF for protonated dendrimer-wrapped chiral CNTs is more compared to the protonated dendrimer-wrapped armchair CNTs for all the generations studied. However, for non-protonated dendrimer-wrapped CNTs, such chirality dependence is not very prominent. Our study suggests that the dispersion efficiency of the protonated dendrimer is more compared to the non-protonated dendrimer and can be used as an effective dispersing agent for the dispersion of CNTs from the bundle geometry.

Influence of defects on carrier injection in carbon nanotubes with defects

Based on density functional theory, we study the electronic properties of carbon nanotubes (CNTs) with divacancy, C2 adatom, and Stone–Wales defects under an electric field. These defects intrinsically induce an internal electric field in CNTs because of the modulation of the electrostatic potential arising from the defects. According to the internal electric field induced by the defects, the threshold gate voltage required to accumulate electrons and holes strongly depends on the defect species and their relative positions in the CNTs with respect to the electrode. The results suggest that the defects result in large gate voltage variations for both electron and hole injection, causing the degradation of CNT-based electronic devices.

Threshold voltage variation for charge accumulation in carbon nanotube owing to monatomic defect arrangement

We report the electronic properties of carbon nanotubes (CNTs) with monovacancy under an electric field on the basis of density functional theory (DFT) with effective screening medium methods. Our DFT calculations show that the electronic structures of CNT under the electric field show their ridged band nature with respect to the carrier accumulations by the electric field. However, an internal electric field induced by the monovacancy leads to a variation in the gate voltage for carrier accumulations. The accumulated carriers are mainly localized at the electrode side of CNTs and are sparsely distributed around the defect sites because of the internal electric field.

Quantitative evaluation of orbital hybridization in carbon nanotubes under radial deformation using π-orbital axis vector

When a radial strain is applied to a carbon nanotube (CNT), the increase in local curvature induces orbital hybridization. The effect of the curvature-induced orbital hybridization on the electronic properties of CNTs, however, has not been evaluated quantitatively. In this study, the strength of orbital hybridization in CNTs under homogeneous radial strain was evaluated quantitatively. Our analyses revealed the detailed procedure of the change in electronic structure of CNTs. In addition, the dihedral angle, the angle between π-orbital axis vectors of adjacent atoms, was found to effectively predict the strength of local orbital hybridization in deformed CNTs.

On the Compton clock and the undulatory nature of particle mass in graphene systems

In undulatory mechanics the rest mass of a particle is associated to a rest periodicity known as Compton periodicity. In carbon nanotubes the Compton periodicity is determined geometrically, through dimensional reduction, by the circumference of the curled-up dimension, or by similar spatial constraints to the charge carrier wave function in other condensed matter systems. In this way the Compton periodicity is effectively reduced by several order of magnitudes with respect to that of the electron, allowing for the possibility to experimentally test foundational aspects of quantum mechanics. We present a novel powerful formalism to derive the electronic properties of carbon nanotubes, in agreement with the results known in the literature, from simple geometric and relativistic considerations about the Compton periodicity as well as a dictionary of analogies between particle and graphene physics.

Tuning electronic properties of carbon nanotubes by nitrogen grafting: Chemistry and chemical stability

Plasma-based methods were used to graft nitrogen atoms to the hexagonal lattice of vertically aligned carbon nanotubes (v-CNTs). The nitrogen grafting (as pyridinic, pyrrolic and graphitic) was mediated by the creation of defects induced by energetic species present in the nitrogen plasma. We investigated the effect of adding nitrogen atoms via plasma treatment on the electronic properties of both v-CNT tips and sidewalls using ultraviolet and X-ray photoemission spectroscopy and spectromicroscopy. Site selective nitrogen grafting near the tips, up to a depth of 4μm, was evaluated, beyond which the properties of the v-CNTs remain unperturbed. The N 1s XPS spectra recorded on the v-CNT tips showed three components related to nitrogen grafted as pyridinic, pyrrolic or graphitic. During thermal heating, we observed variations in the intensity ratio of these components due to the different thermal stability of the nitrogen grafting configurations; the most stable were the sp2 pyridinic and graphitic nitrogen. The area ratio variation of these components was accompanied by a change in the density of states at the Fermi energy level, thus suggesting that the nitrogen functionalization strategy employed can be used to activate the v-CNT tips allowing the tuning of electronic properties by controlling the grafting of different nitrogen species.

Electronic structures of carbon nanotubes with monovacancy under an electric field

We report the electronic properties of carbon nanotubes (CNTs) with monovacancy under an electric field, based on density functional theory. The threshold gate voltage required to accumulate electrons and holes strongly depend on the relative positions of the defects on the CNTs, with respect to the electrode. Additionally, the defects induce an internal electric field in the nanotubes, causing the the threshold gate voltage variation for the carrier accumulation. Furthermore, the defects cause the field to concentrate around them.

ChemInform Abstract: Substitutional Doping of Carbon Nanotubes with Heteroatoms and Their Chemical Applications

AbstractReview: [72 refs.

Chemical basis of interactions between engineered nanoparticles and biological systems.

Chemical basis of interactions between engineered nanoparticles and biological systems.

Substitutional Doping of Carbon Nanotubes with Heteroatoms and Their Chemical Applications

The electronic properties of carbon nanotubes (CNTs) can be tuned by substitutional doping with heteroatoms (mainly B and N) to expand the applications of CNTs. Based on the comprehensive understanding of the substitutional doping of CNTs, it should be possible to deliberately design doped CNTs for specific purposes. Thus, relevant experimental and theoretical works are reviewed herein in an attempt to correlate the synthetic methods, electronic properties, and applications of heteroatom-doped CNTs. The distribution and arrangement of heteroatoms in the graphitic lattice of CNTs can be modulated through the choice of synthetic conditions, which would further lead to different electronic properties of CNTs for their chemical applications.