C<Subscript>60</Subscript> fullerene decoration of carbon nanotubes

A new fully carbon nanocomposite material is synthesized by the immersion of carbon nanotubes in a fullerene solution in carbon disulfide. The presence of a dense layer of fullerene molecules on the outer nanotube surface is demonstrated by TEM and XPS. Fullerenes are redistributed on the nanotube surface during a long-term action of an electron beam, which points to the existence of a molecular bond between a nanotube and fullerenes. Theoretical calculations show that the formation of a fullerene shell begins with the attachment of one C₆₀ molecule to a defect on the nanotube surface.     

Nanotube bundle oscillators: Carbon and boron nitride nanostructures

In this paper, we investigate the oscillation of a fullerene that is moving within the centre of a bundle of nanotubes. In particular, certain fullerene–nanotube bundle oscillators, namely C₆₀-carbon nanotube bundle, C₆₀-boron nitride nanotube bundle, B₃₆N₃₆-carbon nanotube bundle and B₃₆N₃₆-boron nitride nanotube bundle are studied using the Lennard–Jones potential and the continuum approach which assumes a uniform distribution of atoms on the surface of each molecule. We address issues regarding the maximal suction energies of the fullerenes which lead to the generation of the maximum oscillation frequency. Since bundles are also found to comprise double-walled nanotubes, this paper also examines the oscillation of a fullerene inside a double-walled nanotube bundle. Our results show that the frequencies obtained for the oscillation within double-walled nanotube bundles are slightly higher compared to those of single-walled nanotube bundle oscillators. Our primary purpose here is to extend a number of established results for carbon to the boron nitride nanostructures.     

Encapsulation of small fullerenes into nitrogenated holey nanotubes: a density functional theory study

Encapsulation of fullerene into nanotubes based on a C₂N sheet, known as nitrogenated holey graphene, was investigated using density functional theory. The structural and electronic properties of these carbon hybrid materials, consisting of nitrogenated holey nanotubes and a small C₂₀ fullerene, were studied. The formation energies showed that encapsulation of the fullerene into the nitrogenated holey nanotube is an exothermic process. To characterise the electronic properties, the electronic band structure and density of states of armchair and zigzag nitrogenated holey nanotubes were calculated. Filling these nanotubes with the C₂₀ fullerene resulted in a p-type semiconducting character. The energy band gap of the nitrogenated holey nanotubes decreased with fullerene encapsulation. The results are indicative of the possibility of band gap engineering by encapsulation of small fullerenes into nitrogenated holey nanotubes.     

Unravelling low lying phonons and vibrations of carbon nanostructures: The contribution of inelastic and quasi-elastic neutron scattering

We illustrate the contribution of inelastic neutron scattering to the understanding of the vibrations and lattice excitations of fullerenes and carbon nanotubes, through some significant experimental results. Particular emphasis is placed on the study of intra and inter-molecular modes of fullerene C₆₀, as well as on the order/disorder transition characteristic of these molecules. In addition, a significant part of this article is dedicated to various intercalation compounds of fullerenes and carbon nanotubes, such as the co-crystal ??fullerene-cubane?? consisting of an arrangement of molecules of spherical and cubic shapes, or the compound called ??peapods??, in which fullerene C₆₀ are inserted inside carbon nanotubes.     

The Influence of the Geometric Shape of Carbon Nanoparticles on the Strength Properties of Nanocomposite Materials Obtained by Filling an Epoxy Matrix

Abstract

The effects of filling an epoxy matrix modified with “Viniflex” with carbon nanotubes, fullerene C₆₀, or graphene on the mechanical properties, surface morphologies and glass transition temperatures of the composite materials obtained after curing were studied. It was shown that the largest decrease in glass transition temperature and an increase in impact strength was achieved by the introduction of 0.1 mass% graphene. Filling with graphene and carbon nanotubes increased the bending strength while filling with C₆₀ fullerenes provided the greatest compressive strength and elasticity modulus. An explanation of the results was based on ideas about the relationship of the geometrical shape of the nanofiller to the load direction and features of the phase composition of the composite materials. It is suggested that the carbon nanomaterials had a template effect on the packing of the epoxy matrix chains.     

A study of carbon nanosystems using the Hubbard model

The Hubbard model is used as a framework for analyzing carbon nanosystems: the fullerenes C₆₀ and C₈₀ and open-ended carbon nanotubes with chiralities (5, 5) and (10, 10) of various lengths. In the strong-correlation limit, the model predicts that open carbon nanotubes have a lower energy per atom as compared to C₆₀ and C₈₀ fullerenes. This finding contradicts the conventional view that dangling bonds increase the energy of a system. However, the increase, if any, is due to the presence of five-member carbon rings in fullerenes. The energy per atom should be higher for the five-member carbon ring compared to the six-member one, because the former cannot exist in a lower energy singlet state. Carbon nanotube growth is explained. The ionization energies and electron affinities of C₆₀ and C₈₀ fullerenes are calculated and found to agree well with experimental data.     

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.     

Optical properties of fullerene and non-fullerene peapods

Single-wall carbon nanotubes (SWNTs) encapsulating fullerenes, so-called fullerene peapods, were synthesized in high yield by using diameter-selected nanotubes as pods. Transmission electron microscopy revealed high-density fullerene chains inside the nanotubes. X-ray-diffraction measurements indicate 85% filling for C₆₀ and 72% filling for C₇₀ molecules as a total yield. Interestingly, C₆₀ peas do not show any thermal expansion while C₇₀ peas show normal behavior. Room-temperature Raman spectra show one-dimensional photopolymerization of C₆₀ inside nanotubes by blue-laser irradiation, suggesting molecular rotation inside them. In C₇₀ peapods, no photopolymerization was observed but the relative Raman intensity of each peak is different from the C₇₀ 3D crystal. This is probably caused by mixing of two different crystal structures in C₇₀ peas. Furthermore, we synthesized Zn-diphenylporphyrin peapods. Optical absorption and Raman spectra suggest that the encapsulated molecules are deformed by interaction with the SWNT. Received: 12 November 2001 / Accepted: 3 December 2001 / Published online: 4 March 2002     

Electronic and optical properties of fullerene nanostructures

Two new types of molecular/electronic fullerene nanostructures are considered: 1) highly stable hydrated clusters (I _h symmetry group) and microcrystals (T _h symmetry group) of fullerene C₆₀ in water solution and 2) the single-walled carbon nanotube from C₆₀ fullerenes. The vibrational spectra of these fullerene nanostructures are calculated using molecular dynamics. The electronic properties of a single-walled fullerene nanotube are investigated using the tight-binding method. The theoretical results obtained were compared with available experimental data. Fiz. Tverd. Tela (St. Petersburg) 41, 885–887 (May 1999) Published in English in the original Russian journal. Reproduced here with stylistic changes by the Translation Editor.     

Nanoemitter of giga- and terahertz ranges based on a carbon peapod: Numerical simulation

A mathematical model of a nanoemitter for the giga- and terahertz ranges based on a carbon nanopeapod formed by a (10, 10) nanotube with encapsulated C₆₀ fullerenes has been proposed. The fundamental possibility of the generation of giga- and terahertz radiation by a charged free fullerene oscillating in the potential well created by the atomic framework of the nanotube and several fullerenes polymerized with its walls and with each other has been proven. The radiation frequency is controlled by means of an external electric field. The dependence of the amplitude and frequency of oscillations on the charge of C₆₀ and on the external field strength has been revealed by the molecular dynamics method. If the fullerene has a charge of +1e or +2e, it emits electromagnetic waves only in the gigahertz range in strong external fields. At the same time, the physical conditions under which the frequency of radiation can be 0.36 GHz have been established: the charge of the fullerene must be +3e, the tube should be oriented strictly along the external field lines, and the strength should be 0.1 V/nm.     

Vibrational spectra of lanthanide endofullerenes with different symmetries of molecular structure

Quantum-chemical calculations of the geometric structure and vibrational spectra of lanthanide endofullerenes have been carried out. The vibrational frequencies of lanthanide atoms depend substantially on the symmetry of the molecular structure of the endofullerene and on the distance between the metal atom and the carbon cage. The infrared spectra of the endofullerenes M@C₆₀ contain vibrations that are forbidden by symmetry for the empty fullerene C₆₀. A change in the vibrational spectra due to the encapsulation of a metal atom in fullerenes with a C₆₀ cage is considerably more pronounced than that of the higher fullerenes. In the vibrational spectra, there are lines not characteristic of C₆₀, which indicates the presence of M@C₆₀ endofullerenes in a mixture with C₆₀ fullerenes.     

Buckminsterfullerene, higher fullerenes, and their endohedral and fluorine derivatives

This paper presents an overview of recent works concerned with determination of the electron affinity (EA) and the ionization energy (IE) for higher fullerenes and their endohedral and fluorine derivatives. The numerical values of the electron affinity are analyzed for higher fullerenes up to C₁₀₆ and lanthanum, gadolinium, and scandium endohedral fullerenes, including Sc₃N@C₈₀. Most attention is concentrated on two methods for producing fluorofullerenes, namely, direct fluorination of fullerenes with molecular fluorine in a manganese difluoride matrix and solid-phase reactions between fullerenes and fluorinating agents capable of donating fluorine to fullerene. The structures of three fluorofullerenes (C₆₀F₁₈, C₆₀F₂₀, and C₆₀F₄₈) characterized by a distortion of the carbon cage due to attachment of functional groups are discussed.     

A theoretical study on the interaction between well curved conjugated systems and fullerenes smaller than C60 or larger than C70

A large body of data exists about the interaction between curved π systems and C₆₀ or C₇₀. However, little is known about the interaction with fullerenes smaller than C₆₀ or larger than C₇₀. To fill that gap, we studied, by means of density functional theory (M06‐2X), the interaction between corannulene, pentaindenocorannulene, C₆₀H₂₈ buckycatcher and the following fullerenes: C₄₄, C₅₀, C₈₀, C₉₀, C₁₀₀, C₁₈₀ and C₂₄₀. For fullerenes smaller than C₆₀, their high reactivity facilitated the covalent addition to the hosts assayed. Yet, the reaction energies determined for the covalent addition were comparable to those calculated for the formation of supramolecular complexes. Thus, the receptor may host a fullerene and at least have another one attached. As expected, for fullerenes larger than C₇₀, supramolecular complexes were preferred over covalent assemblies. The binding energies with bowls increased with the size of the fullerenes in a non‐monotonic fashion since they depended on the shape of the fullerene. Indeed, for one C₈₀ isomer, it is possible to find a region which forms a complex with corannulene that is stronger than C₆₀@corannulene, while another region exists whose interaction with corannulene is weaker. As the size of the fullerene becomes larger, ball–socket interactions are weakened, and CH–π interactions become important, accounting for the large interaction determined for corannulene and graphene. Finally, for the buckycatcher, the maximum encapsulation energy among the fullerenes assayed was displayed by C₉₀. The fullerenes C₈₀, C₉₀ and C₁₀₀ formed complexes with the buckycatcher which are stronger than in C₆₀@buckycatcher. Copyright © 2014 John Wiley & Sons, Ltd.     

Transmission electron microscopy imaging of individual functional groups of fullerene derivatives

Mobility and reactivity of the functionalized fullerenes with pyrrolidine (C60-C3NH7) incorporated in single-wall carbon nanotubes were examined by high-resolution transmission electron microscopy. An individual functional group attached to each fullerene cage is unambiguously visualized. This provides a direct evidence for the functionalized structure on a single-molecular basis. A rotational motion of the incorporated molecules tends to occur during the observation and, consequently, each fullerene molecule is likely to stand facing its functionalized group towards the nanotube wall. A fine structure analysis of electron energy-loss spectra for the nitrogen K(1s) edge shows a considerable change in the nitrogen chemical state and suggests a strong tube-fullerene interaction.     

Effect of C60 fullerene, fullerene-containing soot, and other carbon materials on the sliding edge friction of metals

A comparative study of different carbon materials (C₆₀ fullerene; soot, both with and without fullerenes; graphite; and industrial carbon black) as additives to industrial lubricating oils has been carried out for copper-steel and steel-steel sliding couples. The soot containing fullerene and the powder of pure fullerene produce a noticeable improvement in the antifriction and antiwear properties of steel-steel and steel-copper couples, especially under heavy loads and pressures at the contact. The greatest improvement was observed for the steel-steel couple. Structural-mechanical studies were carried out for copper riders and it has been demonstrated by several methods that the addition of the C₆₀ fullerene (pure fullerene or as a fullerene-containingsoot) creates a fullerene-polymer film on the frictional surface about 1000 Å thick, which has a protective effect.     

Nanotube nanoscience: A molecular-dynamics study

Carbon nanotubes, fullerenes, and other nanostructured carbon materials are now the most important material phases in the field of nanoscience and nanotechnology. We study the structural stabilities and the interconversion of carbon nanotubes and various other carbon nanostructured phases at elevated temperatures as well as under high pressure using the molecular dynamics method combined with a newly parametrized transferable tight-binding model. The model can deal with not only sp² and sp³ covalent bonds but also the interaction between sp² layers, which plays an important role in the structural and electronic properties of carbon nanostructured materials. It is found that, during a thermal transformation process of carbon nanotubes with C₆₀ fullerenes trapped inside into double-walled carbon nanotubes, the outer carbon-nanotube wall is chemically active and forms covalent bonds with inner carbon atoms, and that most vacancies on the initially imperfect outer tube wall are eventually filled with atoms migrated from inner fullerenes. It is also found that external pressure of about 20 GPa induces a variety of structural transformations in carbon nanostructures. On the other hand, pressure of 30 GPa or higher usually results in sp³-rich amorphous carbon materials. Finally, the rotational interlayer friction force in double-walled carbon nanotubes is studied for the system of (4,4)@(9,9), and the torque of the friction force per unit area acting on each nanotube of the system is found to be as small as . This small value indicates the importance of carbon nanostuctured materials not only for nanoelectronics but also for nanometer-scale machines in the future.     

First-principle study of the electronic transport properties of a new dumbbell-like carbon nanocomposite

Using a first-principle density functional theory and non-equilibrium Green's function formalism for quantum transport calculation, we have investigated the electronic transport properties of a new dumbbell-like carbon nanocomposite, in which one carbon nanotube segment is capped with two C₆₀ fullerenes. Our results show that the current–voltage curve reveals a highly nonlinear feature. A negative differential resistance (NDR) behavior is obtained at a very low bias, which is expected to be helpful for the development of low bias NDR-based molecular devices. Moreover, the carbon nanotube length and fullerene type can affect the NDR behavior strongly. The electronic transport is analyzed from the transmission spectra and the molecular projected self-consistent Hamiltonian states under different applied biases.     

Phase states and magnetic properties of iron nanoparticles in carbon nanotube channels

The structure, phase composition, and magnetic properties of carbon nanotubes filled with iron nanoparticles and obtained by thermolysis of a mixture of ferrocene and C₆₀ fullerene or ferrocene and orthoxylene at a temperature of 800°C are investigated. Electron microscopy, X-ray diffraction, and Mössbauer spectroscopy data lead to the conclusion that carbon nanotubes are multilayer systems partially filled with iron nanoparticles and/or nanorods. Metallic inclusions in nanotube channels form α-Fe, γ-Fe, and Fe₃C phases. The concentration of each phase in the samples is determined. It is shown that 10–20-nm iron clusters in nanotubes exhibit magnetic properties typical of bulk phases of iron. High elasticity of carbon nanotube walls facilitates stabilization of the high-temperature γ-Fe phase; the relative concentration of this phase in a sample can be increased by lowering the concentration of ferrocene in the initial reaction mixture.     

Molecular dynamics simulation of the low-energy interaction between Cu<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript>@C<Subscript>60</Subscript> endofullerenes and the surface of a copper crystal

A molecular dynamics simulation of the low-energy interaction of C₆₀ fullerenes and Cu₁@C₆₀, Cu₆@C₆₀, and Cu₁₃@C₆₀ endofullerenes with a Cu(100) surface was performed. The effects of a copper cluster encapsulated in a fullerene and of a fullerene’s translational motion and rotation energy on its penetration into a surface were investigated. It was shown that the presence of an encapsulated cluster has a positive effect on fullerene penetration into a surface with preservation of the fullerene’s structure. The optimal conditions for fullerene penetration into a copper crystal surface were determined.     

Comparison of the photosensitivity and bacterial toxicity of spherical and tubular fullerenes of variable aggregate size

Nanomaterials such as fullerene C₆₀, carbon nanotubes (CNTs), and other fullerenes show unique electrical, chemical, mechanical, and thermal properties that are not well understood in the context of the environmental behavior of this class of carbon-based materials. In this study, aqueous suspensions of three fullerenes nanoparticles, C₆₀, single-wall (SW) and multi-wall (MW) CNTs were prepared by sonication and tested for reactive oxygen species (ROS) production and inactivation of Vibrio fischeri, a gram-negative rod-shaped bacterium, under ultraviolet (UV)-A irradiation. We show that ROS production and microbial inactivation increases as colloidal aggregates of C₆₀, SWCNT, and MWCNT are fractionated to enrich with smaller aggregates by progressive membrane filtration. As the quantity and influence of these more reactive fractions of the suspension may increase with time and/or as the result of fractionation processes in the laboratory or the environment, experiments evaluating photo-reactivity and toxicity endpoints must take into account the evolution and heterogeneity of nanoparticle aggregates in water.