Encapsulation of lamivudine into single walled carbon nanotubes: A vdW-DF study

To explore a suitable carrier for lamivudine drug, the incorporation of lamivudine inside the single walled carbon nanotubes (SWCNTs) has been investigated by using first-principles van der Waals density functional (vdW-DF) calculations. The obtained binding energies reveal that lamivudine prefers to be encapsulated into the metallic nanotubes with diameter of about 13 Å. Semiconducting SWCNTs exhibit slightly weaker interaction strength with the lamivudine in comparison with the metallic counterparts. However, the calculated binding energies for both considered nanotubes are typical for the physisorption. The influence of nanotube length on the lamivudine incorporation inside the various considered nanotubes has also been investigated and the results show that it plays an important role in the encapsulation process. The electronic structures analysis for the energetically most favorable complexes reveal that incorporated lamivudine changes slightly the electronic properties of SWCNTs. This indicates that there is no considerable hybridization between the corresponding orbitals and the weak interaction obtained quantitatively in terms of binding energies.     

Adsorption of nonpolar benzene derivatives on single-walled carbon nanotubes

The adsorption of benzene, toluene, and chlorobenzene on single-walled carbon nanotubes (SWCNTs) with and without acid oxidation was conducted to investigate the influences of derivative groups on benzene rings and functional groups from SWCNTs on adsorption by SWCNTs. The SWCNTs of high purity were chosen and moderate acid oxidation was performed so that the surface physical properties remained unchanged after acid oxidation and the influences of acid oxidation on adsorption were only contributed from the modification of the surface chemistry of SWCNTs. The oxygen-containing surface groups introduced by acid oxidation obstructed the interactions between functional groups of nonpolar benzene derivatives and C-rings of SWCNTs significantly. The dispersive interaction between the partially positive H⁺ of the methyl group and the oxygen-containing surface groups slightly increased the adsorption of toluene on oxidized SWCNTs at high solution pH. The thermodynamic of adsorption was also studied at different temperatures.     

Electronics and Structural Properties of Single-Walled Carbon Nanotubes Interacting with a Glucose Molecule：ab initio Calculations

The adsorption of glucose molecule on single-walled carbon nanotubes (SWCNTs) is investigated by density functional theory calculations. Adsorption energies and equilibrium distances are evaluated, and glucose binding to the typical semiconducting and metallic nanotubes with various diameters and chirality are compared. We also investigated the role of the structural defects on the adsorption capability of the SWCNTs. We could observe larger adsorption energies for the larger diameters semiconducting CNTs, while the story is paradoxical for the metallic CNTs. The obtained results reveal that the adsorption energy is significantly higher for nanotubes with higher chiral angles. Finally, the adsorption energies are calculated for defected nanotubes for various configurations such as glucose molecule approaching to the pentagon, hexagon, and heptagon sites in the tube surface. We find that the respected defects have a minor contribution to the adsorption mechanism of the glucose on SWNTs. The calculation of electron transfers and the density of states supports that the electronic properties of SWCNTs do not change significantly after the gluycose molecular adsorption. Consequently, one can predict that presence of glucose would neither modify the electronic structure of the SWCNTs nor direct to a change in the conductivity of the intrinsic nanotubes.     

Electronics and Structural Properties of Single-Walled Carbon Nanotubes Interacting with a Glucose Molecule: ab initio Calculations

The adsorption of glucose molecule on single-walled carbon nanotubes(SWCNTs)is investigated by density functional theory calculations.Adsorption energies and equilibrium distances are evaluated,and glucose binding to the typical semiconducting and metallic nanotubes with various diameters and chirality are compared.We also investigated the role of the structural defects on the adsorption capability of the SWCNTs.We could observe larger adsorption energies for the larger diameters semiconducting CNTs,while the story is paradoxical for the metallic CNTs.The obtained results reveal that the adsorption energy is significantly higher for nanotubes with higher chiral angles.Finally,the adsorption energies are calculated for defected nanotubes for various configurations such as glucose molecule approaching to the pentagon,hexagon,and heptagon sites in the tube surface.We find that the respected defects have a minor contribution to the adsorption mechanism of the glucose on SWNTs.The calculation of electron transfers and the density of states supports that the electronic properties of SWCNTs do not change significantly after the gluycose molecular adsorption.Consequently,one can predict that presence of glucose would neither modify the electronic structure of the SWCNTs nor direct to a change in the conductivity of the intrinsic nanotubes.     

A computational prediction of total carbo-merization on single-walled carbon nanotubes

The total carbo-mer of single-walled carbon nanotubes (C-SWCNTs) are constructed by inserting two sp carbon atoms into each C-C bond in pristine single-walled carbon nanotubes (SWCNTs). The geometric, mechanical and electronic properties for these novel structures are investigated by self-consistent-field crystal calculations. The calculated zigzag and chiral C-SWCNTs are all small gap semiconductors, whereas the metallic property is still kept in the armchair C-SWCNT. The calculated Young's moduli of C-SWCNTs are smaller than those of SWCNTs. Our calculations show that the zigzag C-SWCNTs have higher mobility than the corresponding SWCNTs. Moreover, the calculated mobility of the C-SWCNTs has a periodic change with the change of the tube diameters.     

Electrochemical functionalisation of SWNTs with poly(3,4‐ethylenedioxythiophene) evidenced by anti‐Stokes/Stokes Raman spectroscopy

The capability of anti‐Stokes/Stokes Raman spectroscopy to evaluate chemical interactions at the interface of a conducting polymer/carbon nanotubes is demonstrated. Electrochemical polymerisation of the monomer 3,4‐ethylenedioxythiophene (EDOT) on a Au support covered with a single‐walled carbon nanotube (SWNT) film immersed in a LiClO₄/CH₃CN solution was carried out. At the resonant optical excitation, which occurs when the energy of the exciting light coincides with the energy of an electronic transition, poly(3,4‐ethylenedioxythiophene) (PEDOT) deposited electrochemically as a thin film of nanometric thickness on a rough Au support presents an abnormally intense anti‐Stokes Raman spectrum. The additional increase in Raman intensity in the anti‐Stokes branch observed when PEDOT is deposited on SWNTs is interpreted as resulting from the excitation of plasmons in the metallic nanotubes. A covalent functionalisation of SWNTs with PEDOT both in un‐doped and doped states takes place when the electropolymerisation of EDOT, with stopping at +1.6 V versus Ag/Ag⁺, is performed on a SWNT film deposited on a Au plate. The presence of PEDOT covalently functionalised SWNTs is rationalised by (1) a downshift by a few wavenumbers of the polymer Raman line associated with the symmetric C C stretching mode and (2) an upshift of the radial breathing modes of SWNTs, both variations revealing an interaction between SWNTs and the conjugated polymer. Raman studies performed at different excitation wavelengths indicate that the resonant optical excitation is the key condition to observe the abnormal anti‐Stokes Raman effect. Copyright © 2010 John Wiley & Sons, Ltd.     

X-ray absorption investigation of the electronic structure of the CuI@SWCNT nanocomposite

The Cu 2p, I 3d, and C 1sX-ray absorption spectra of the CuI@SWCNT nanocomposite prepared by filling single-walled carbon nanotubes (SWCNTs) with the CuI melt by the capillary technique have been measured with a high-energy resolution using the equipment of the Russian-German beamline at the BESSY electron storage ring. In order to characterize the electronic structure of the nanocomposite and possible changes in the atomic and electronic structures of CuI and SWCNTs in the CuI@SWCNT nanocomposite, the spectra obtained have been analyzed in the framework of the quasi-molecular approach by comparing with the spectra of the pristine (CuI and SWCNT) and reference (CuO) systems. It has been revealed that the encapsulation of the CuI compound inside SWCNTs is accompanied by changes in the electronic structure of CuI and SWCNTs due to the chemical interaction between the filler and carbon nanotubes and the change in the atomic structure of CuI.     

On the encapsulation of azafullerenes inside the single-walled carbon nanotubes: Density-functional theory based treatments

We theoretically studied the encapsulation of azafullerene (C₅₉N) inside the single-walled carbon nanotubes (SWCNTs) from the first-principles. Adsorption energy is calculated, and the azafullerene affinities for the typical semiconducting and metallic nanotubes are investigated and compared with those of pure C₆₀ fullerene. It has been found that the azafullerene as well as the fullerene affinity for the semiconducting nanotubes is stronger than that for the metallic ones, and the energy values and binding distances are typical for the physisorption. Our first-principles results indicate that the interaction between SWCNTs and azafullerenes is comparable with the nanotubes-C₆₀ system. The charge analysis shows, however, that the charges have been transferred from the cage to the tube in the azafullerene peapods, while in the fullerene peapods the charges were found to be transferred from the tube to the fullerene nanocage. Furthermore, it was found that the interaction between the considered fullerenes and host nanotubes strongly depends on the tube diameters.     

Near-Field Optical Identification of Metallic and Semiconducting Single-Walled Carbon Nanotubes

Single-walled carbon nanotubes(SWCNTs),due to their outstanding electrical and optical properties,are expected to have extensive applications,such as in transparent conductive fims and ultra-small field-effect transistors(FETs).However,those applications can only be best realized with pure metallic or pure semiconducting SWCNTs.Hence,identifying and separating metallic from semiconducting SWCNTs in as-grown samples are crucial.In addition,knowledge of the type of an SWCNT is also important for f...     

Study on the electronic structure and hydrogen adsorption by transition metal decorated single wall carbon nanotubes

The ground state geometry and electronic structure of various 4d transition metal (TM) atom (Y, Zr, Nb and Mo) decorated single wall carbon nanotubes (SWCNTs) are obtained using density functional theory and the projector augmented wave (PAW) method. We found a systematic change in the adsorption site of the transition metal atom with increasing number of d electrons. We also predicted that Y and Zr decorated SWCNTs are metallic whereas Nb and Mo decorated SWCNTs are semiconducting. From detailed electronic structure and Bader charge analysis we found that the systematic variation of the adsorption site with the number of d electrons is related to the decreasing amount of charge transfer from the TM atom to the SWCNT along the 4d series. We have also studied the hydrogen adsorption capabilities of these decorated SWCNTs to understand the role of transition metal d electrons in binding the hydrogen molecules to the system. We found that metallic SWCNT + TM systems are better hydrogen adsorbers. We showed that the hydrogen adsorption by a TM decorated SWCNT will be maximum when all the adsorptions are physisorption and that the retention of magnetism by the system is crucial for physisorption.     

Strange non-chaotic attractors in a state controlled-cellular neural network-based quasiperiodically forced MLC circuit

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.     

单壁碳纳米管电子输运特性的稳定性分析

基于变形单壁碳纳米管能量色散关系,计算了碳纳米管最低导带的电子速度及有效质量随形变系数变化的各种曲线,以此推测碳纳米管输运性质的稳定性问题.计算结果表明：对于特定类型的碳纳米管,只当其形变发生在某特定方向、且处于低形变（形变系数ε≤002 ）区时,电子平均速度v_mean及平均有效质量m^*_mean随形变改变才会很小（相对改变量≤2%）,这意味着此时的碳纳米管低偏压电子输运性能是基本稳定的.而其他形变情形,电子平均速度v_mean或电子平均有效质量m^*_mean或两者随形变变化明显,甚至有跃变,这意味着其低偏压电子输运性能是不稳定的,甚至极不稳定. 关键词： 变形单壁碳纳米管 电子速度 电子有效质量 输运性能稳定性     

From metal/semiconductor separation to single‐chirality separation of single‐wall carbon nanotubes using gel

In the present work, a review of the metallic (M) and semiconducting (S) separation of single‐wall carbon nanotubes (SWCNTs) using polysaccharide gels is presented. First, the progress of the M/S separation is described, including the following: the discovery of high‐yield separation using agarose gel electrophoresis, the separation of SWCNTs without an electric field, such as through the use of the freeze and squeeze method, the development of continuous separation using column chromatography, and the single‐chirality separation of SWCNTs using a multicolumn with dextran‐based gel. Next, the separation mechanism using gel is discussed, in which separation is achieved by selective adsorption of S‐SWCNTs by gel with a specific combination of surfactant and gel. Lastly, future directions for the separation of SWCNTs and for the use of the separated SWCNTs are discussed.

     

Interaction between methanol and single-walled carbon nanotubes: Density functional theory study

Density functional calculations have been performed to investigate the dependence of methanol interaction with the side walls of single-walled carbon nanotubes (SWCNTs) on the nanotube's type, curvature and chirality. The author's results show that methanol prefers to be physically adsorbed on semiconducting CNTs in comparison with the metallic one. It was found that the binding energy of methanol is increased for adsorption on larger-diameter nanotubes. Furthermore, we find that when a methanol molecule was adsorbed on higher chiral angle nanotubes the binding energy was increased. The study of the electronic structures and Mulliken analysis indicate that the methanol and CNT are interacting rather weakly, consistent with recent experimental observation.     

Structural, curvature and electronic properties of Rh adsorption on armchair single-walled carbon nanotube

This paper systematically studies the rolling effects of the (n, n) single-wall carbon nanotubes (SWCNT) with different curvatures on Rh adsorption behaviours by using density functional theory. The outside charge densities of SWCNTs are found to be higher than those inside, and the differences decrease with the increase of the tube radius. This electronic property led to the discovery that the outside adsorption energies are higher than the inside ones, and that the differences are reduced with the increase of the tube radius. Partial density of states and charge density difference indicate that these strong interactions induce electron transfer between Rh atoms and SWCNTs.     

Theoretical studies on the geometrical and electronic structures of supramolecule bis(2,2′-bipyridine)-5-amino-1,10-phenanthroline ruthenium(II)/functionalized SWCNT dyads

Functionalization of carbon nanotube (CNT) with multiple redox and photo active entities is one of the extensive processes due to its importance in building molecular or supramolecular electronic devices, solar energy storage and conversion systems. Thus, to have better understanding about structural aspects and correct electronic structure of these large systems, the quantum studies have gained increased popularity. In present study, we have investigated the structural and electronic properties of functionalized CNTs (fCNTs) with [Ru(bpy)₂(5-NH₂-1,10-phen)]⁺², (Ru-bpy-phen)⁺², supramolecule based on DFT calculations. Main attention has been applied to obtain stable configuration, binding energies and effect of functionalization on electronic behavior of the selected supramolcule. We also evaluate the effect of nanotube’s diameter and chirality on electronic properties of considered supramolecule. Calculated binding energies show that interaction between the (Ru-bpy-phen)⁺² and the host CNTs depends on the tube diameter while the chirality doesn’t affect significantly on the binding nature of respected complex. We have also investigated the influence of non-local dispersion interactions (vdW) and temperature on the stability and electronic structure of the considered system. Results obtained from the ab initio MD simulations showed that increasing the temperature can affect the distance between C and N atoms in the linkage position. The charge analysis indicates the existence of remarkable charge transfer between (Ru-bpy-phen)⁺² as donor and fCNTs as acceptor moieties in the isolated molecule. In the presence of vdW forces and at higher temperature, the charge transfer was decreased but the direction of transferred charge remains unchanged.     

Band structures of carbon nanotube with spin-orbit coupling interaction

We explore the band structures of single-walled carbon nanotubes (SWCNTs) with two types of spin-orbit couplings. The obtained results indicate that weak Rashba spin-orbit coupling interaction can lead to the breaking of four-fold degeneracy in all tubes even though without the intrinsic SO coupling. The asymmetric splitting between conduction bands and valence bands is caused by both SO couplings at the same time. When the ratio of Rashba spin-orbit coupling to the intrinsic spin-orbit coupling is larger than 3, metallic zigzag nanotube is always metallic conductor, on the contrary it becomes semiconducting properties. However, only when this ratio is equal to about 3 or the intrinsic spin-orbit coupling is much weak, the metallic armchair nanotube still holds the metallic behavior in transport.     

Composite Cathodes Containing SWCNT@S Coaxial Nanocables: Facile Synthesis,Surface Modification,and Enhanced Performance for Li‐Ion Storage

The arrangement and construction of 1D carbon nanotubes (CNTs) into frameworks with two or more levels of structures is an essential step to demonstrate their intrinsic properties and promising applications for energy storage. Single‐walled CNTs (SWCNTs) are considered to have more excellent properties compared with multiwalled CNTs (MWCNTs), however, how to appropriately use SWCNTs as building blocks for nanocomposite electrodes is not well understood. Here, a composite cathode containing SWCNT@S coaxial nanocables for Li‐S battery is fabricated by a facile melt‐diffusion strategy. Beneficial from its sp² carbon nanostructure, higher specific surface area, larger aspect ratio, and interconnected electron pathway, the SWCNT@S cathode have reversible capacities of 676, 441 and 311 mAh g^?1 for the first discharging at 0.5 C, 100^th discharging at 1.0 C, and discharging at 10.0 C, respectively. These capacities are much higher than the corresponding capacities of the MWCNT@S cathode. By introducing polyethylene glycol (PEG) as a physical barrier to trap the highly polar polysulfide species, the PEG modified SWCNT@S cathode afforded improved reversible capacities. The cycling stability of the reversible capacities is expected to be further improved. The SWCNTs can serve as scaffolds for Li‐S battery with much improved energy storage performance.     

Effects of various defects on the electronic properties of single-walled carbon nanotubes: A first principle study

The geometries,formationenergies and electronic band structures of （8, 0） and （14, 0） singlewailed carbon nanotubes （SWCNTs） with various defects, inehlding vaeaney, Stone-Wales defect, and octagon pentagon pair defect, have been investigated within the framework of the density- huictional theory （DFT）, and the influence of the concentration within the same style of deflect on the physical and chenfical properties of SWCNTs is also studied. The results suggest that the existeilcc of vacancy and octagon-pentagon pair deflect both reduce the band gap, whereas the SW- defect induces a band gap opening in CNTs. More int, erestingly, the band gaps of （8, 0） and （14, 0） SWCNTs eonfigurations with two octagon pentagon pair defect presents 0.517 eV and 0.163/eV, which arc a little smaller than the perfectt CNTs. Furthermore, with the concentration of defects increasing, there is a decreasing of band ga.p making the two types of SWCNTs change from a semiconductor to a metallic conductor.     

Ionic liquid based on 6‐amino‐6‐deoxy hexopyranose cation and BF4¯, PF6¯, and ClO4¯ as anions: A DFT study on the structural and electronic properties

In this study, the structural and electronic properties of a carbohydrate‐based (6‐amino‐6‐deoxy hexopyranose [ADHP]) ionic liquid were explored. The interactions among 3 anions (BF₄^¯, PF₆^¯, and ClO₄^¯) and ADHP as cation were investigated at B3LYP/6‐311++G(d,p) level. Based on the calculated interaction energy, it was found that PF₆^¯ anion has the highest interaction energy with ADHP. It was found that the hydrogen bonds play an important role in the interaction of ion pairs. The nature of hydrogen bonds in the optimized ion pars was analyzed by using natural bond orbital analysis and the quantum theory of atoms in molecules. The linear relationship between electron density at the bond critical points of hydrogen bonds and the interaction energy values was checked.