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In this work we investigate the growth of diamond film on a porous single-wall carbon nanotubes (SWNT) paper by employing three different Chemical Vapour Deposition (CVD) systems: plasma-assisted hot filament, focused microwave plasma and linear antenna microwave plasma. We observe that the diamond growth is strongly affected by the different conditions in each of the CVD processes resulting in different SWNT/diamond composite structures. It is also found that only the linear antenna microwave plasma CVD process allows penetration of the activated growth species into the volume of the SWNT paper, whereas using the other methods, the diamond grains are formed on the SWNT paper surface only. Moreover, the growth of diamond structures within the substrate volume is strongly influenced by the CH4/CO2/H2 gas content ratio. A key factor influencing the formation of a compact SWNT/diamond composite is keeping the equilibrium between two competitive processes: establishing conditions where the diamond structure can grow while etching/damage of the SWNT paper is still kept at a minimum. The morphology and chemical composition of formed composite materials were characterized by scanning electron microscopy and Raman spectroscopy. [ABSTRACT FROM AUTHOR]

We report on single walled carbon nanotubes (SWCNTs) used as a filler material for polycarbonate (PC) composites in this paper. Thin flexible composite films were prepared by solvent casting with a viscous dispersion of SWCNTs in a polymer matrix. The interaction of SWCNTs with PC was studied by Raman spectroscopy. Our investigations focus on the electrical conductivity and thermopower of the carbon nanotube network formed within the matrix. In this paper, we demonstrate that the incorporation of carbon nanotubes in the polymer composite profoundly modifies the electrical properties of the polymer composite in proportion with the SWCNT concentration. Although, the electrical conductivity of the composite increases by 16 orders of magnitude upon adding 1 wt% of SWCNTs, the Seebeck coefficient, which characterizes the thermoelectric properties, appears to be dominated by the type of polymer matrix and decreased slightly throughout the tested filler loading. A reasonable Seebeck coefficient of 65 µV K−1 was determined for these SWCNT composite films and, thus, suggests that thermoelectric power generation would be a good application for them. We also demonstrated that both the electrical conductivity and the Seebeck coefficient of SWCNTs embedded in a polymer can be efficiently modified by means of chemical treatments. In this way, flexible composite films exhibiting positive and negative Seebeck coefficients were fabricated. Assembling these films into a sandwich structure with alternating p/n junctions should produce a higher potential difference when a temperature gradient is applied across a multilayer thermoelectric device. [ABSTRACT FROM AUTHOR]

Despite the intensive development of the terahertz technologies in the last decade, there is still a shortage of efficient room‐temperature radiation detectors. Carbon nanotubes (CNTs) are considered as a very promising material possessing many of the features peculiar for graphene (suppression of backscattering, high mobility, etc.) combined with a bandgap in the carrier spectrum. In this paper, we investigate the possibility to incorporate individual CNTs into devices that are similar to Schottky diodes. The latter is currently used to detect radiation with a frequency up to 50 GHz. We report results obtained with semiconducting (bandgap of about 0.5 eV) and quasi‐metallic (bandgap of few meV) single‐walled carbon nanotubes (SWNTs). Semiconducting CNTs show better performance up to 300 GHz with responsivity up to 100 V W−1, while quasi‐metallic CNTs are shown to operate up to 2.5 THz. [ABSTRACT FROM AUTHOR]

Chemical vapor deposition (CVD) enables the mass synthesis of high-quality nanotubes. There is a large number of synthesis process parameters that have an influence on the type and form of the final product. The aim of the paper is the optimization of the synthesis process of multiwalled carbon nanotubes (MWCNTs) with the CVD method. Three synthesis parameters were selected (temperature, process time, and hydrogen flow rate) influencing the form and quality of the material produced. The experiments were carried out using our own approach to the conditions of carbon multiwalled nanotubes synthesis. The following research techniques were applied to examine the influence of selected parameters of the MWCNTs synthesis process: transmission electron microscopy (TEM), atomic force microscopy (AFM), scanning electron microscopy (SEM), and Raman spectroscopy [ABSTRACT FROM AUTHOR]

The paper overviews experimental and theoretical studies of photogalvanic effects (PGEs) induced in graphene and carbon nanotubes (CNs) by polarized electromagnetic radiation. The following items are discussed: the helicity-dependent photon-drag and edge electric currents in graphene sheets, the circular PGEs in asymmetric graphene superlattices and chiral CNs, and pure valley currents generated in graphene by the interband absorption of linearly polarized light. [ABSTRACT FROM AUTHOR]

Amorphous carbon nanotubes (a‐CNT) with up to four walls and sizes ranging from 200 to 3200 atoms have been simulated, starting from initial random configurations and using the Gaussian Approximation Potential. The important variables (like density, height, and diameter) required to successfully simulate a‐CNTs were predicted with the machine learning random forest technique. The width of the a‐CNT models ranged between 0.55–2 nm with an average inter‐wall spacing of 0.31 nm. The topological defects in a‐CNTs were analyzed and new defect configurations were observed. The electronic density of states and localization in these phases were discussed and delocalized electrons in the π subspace were identified as an important factor for inter‐layer cohesion. Spatial projection of the electronic conductivity favors axial transport along connecting hexagons, while non‐hexagonal parts of the network either hinder or bifurcate the electronic transport. A vibrational density of states was calculated and is potentially an experimentally comparable fingerprint of the material. The appearance of a low‐frequency radial breathing mode was discussed and the thermal conductivity at 300 K was estimated using the Green‐Kubo formula. [ABSTRACT FROM AUTHOR]

The dynamics of the 1D array of single‐walled carbon nanotubes (CNTs), which interact by van der Waals forces, is considered. The molecular dynamics simulation shows that both the mutual displacements of the nanotubes and the deformations of their walls occur in the low‐frequency oscillations domain. The composite model taking into account both types of the nanotubes' motions is developed in the framework of the thin elastic shell theory. Such an approach allows us to reduce the problem to the dynamics of the linear lattice with contact interaction. The dispersion relations are represented analytically and the multichannel propagation that results in phonon interference (the acoustical analog of the Fano resonance) is observed in the presence of the array's irregularities. The latter can be formed with redundant nanotubes, which are placed over the array in the grooves between neighbor sites. The calculations of the transmittance have been performed by the transfer matrix method for several typical configurations. [ABSTRACT FROM AUTHOR]

Thermal conductance in helically coiled carbon nanotubes (HCCNTs) is calculated out of phonon dispersion relations: anharmonicity is included through Brenner interatomic potential and scattering rates of the three-phonon Umklapp processes are calculated exactly, for all allowed transport channels. Highlighted are the universal features of the quantized thermal conductance and crossover from the ballistic to the diffusive transport regime is studied in detail. Correlation between the geometrical parameters of HCCNTs and thermal conductance is investigated. Finally, the specific heat is calculated and compared to that of the other carbon materials. [ABSTRACT FROM AUTHOR]

The optical properties of armchair graphene nanoribbons (AGNRs) under the uniaxial strain are studied within a non-orthogonal tight-binding model. For 9-AGNR and 10-AGNR, the first transition energy [ABSTRACT FROM AUTHOR]

TiO2/WO3/Au/MWCNT composite materials were obtained using different commercial titanias (Aldrich Anatase, Aldrich Rutile, and Evonik Aeroxide P25) and Aldrich WO3. The gold nanoparticles were deposited on the semiconductor oxides' surface by chemical reduction using sodium borohydride, and the MWCNT's were combined with the composite (in different concentrations 0.1-10 wt%) by applying an ultrasonication method. The obtained nanocomposites were successfully characterized by means of X-ray diffraction, transmission electron microscopy, etc. The aim of the present work was to find the optimal composition (i.e. carbon nanotube content) of the composite for photocatalytic hydrogen production using oxalic acid as a sacrificial agent. [ABSTRACT FROM AUTHOR]

It is a challenging and application‐oriented goal to achieve the metal/semiconductor separation of large diameter single‐walled carbon nanotubes (SWCNTs) using a dextran‐based gel chromatograph. Herein, a study of the temperature effect on the metal/semiconductor separation of plasma torch SWCNTs through dextran‐based gel chromatograph is conducted. The temperature governs the interaction between SWCNTs and hydrogel, thus enabling the sorting of SWCNTs by electronic type. In addition, the temperature effect enables the metallic (m‐) and semiconducting (sc‐) fraction to be resolved and eluted using a single cosurfactant system, so that the process can be iterated easily. The fractions containing up to 99% of sc‐SWCNTs and 95% of m‐SWCNTs have been obtained after three times of iteration. The iteration process is not only applicable to sc‐SWCNTs and m‐SWCNTs, but also practicable for the cosurfactant system and circumvents additional preparation steps. [ABSTRACT FROM AUTHOR]

The composite of FeNi nanocrystals (size of 10–100 nm) decorating reduced graphene oxide (rGO) sheets (FeNi@rGO) is prepared by hydrothermal reaction and hydrogen reduction. Compared with sole FeNi nanocrystals, the FeNi@rGO composite possesses a lower frequency of the optimal reflection loss (RL) and a greatly enhanced RL value. An optimal RL of −26.7 dB has been achieved at 4.8 GHz by measuring the composite with thickness of 4.55 mm, which is attributed to the combination of FeNi with excellent magnetic loss and rGO with outstanding dielectric loss, respectively. Obviously, the FeNi@rGO composite has an enormous potential as a microwave absorbing candidate due to its admirable microwave absorption performance. [ABSTRACT FROM AUTHOR]

The huge molecular cluster {Fe30Mo72} has been used as a source of catalyst nanoparticles in catalytic chemical vapour deposition (CCVD) process of carbon nanotubes (CNTs) synthesis. Thermal decomposition of {Fe30Mo72} in air is shown by X‐ray diffraction analysis to produce iron molybdate, which is converted to alloyed Fe‐Mo and Fe nanoparticles at elevated temperature and reduction environment. These nanoparticles supported on MgO, catalyse the growth of single‐walled, double‐walled and/or multi‐walled CNTs depending on the active metal loading and ratio of methane and hydrogen in the feedstock. The structural parameters of the products are studied by transmission electron microscopy and Raman spectroscopy. The best CNT samples are tested as field electron emitters. [ABSTRACT FROM AUTHOR]

The structure and electronic properties of the N‐doped bamboo‐like carbon nanotubes with different nitrogen content (N‐CNTs) are studied by the use of transmission electron microscopy, electron energy loss spectroscopy, Raman spectroscopy, and X‐ray photoelectron spectroscopy supplemented by measurements of the temperature dependence of conductivity. XPS data are used to estimate the content of nitrogen represented by pyridinic, pyrrolic, graphitic, and oxidized N species and encapsulated molecular nitrogen. The graphene blocks surrounded by borders containing hole defects and N‐species are considered as building blocks of N‐CNT walls. The intensity ratio of D, G, and 2D bands in Raman spectra and XPS data on the concentration of N‐species are used to analyze the size of defect‐free graphene blocks in N‐CNTs. The size of such blocks depends on the N‐defect content and is estimated to be 1–2 nm. The increase of N‐species content resulting in a decrease of graphene block size correlates with the decrease of current carrier concentration (nES) estimated within the Efros–Shklovskii model. [ABSTRACT FROM AUTHOR]

Phenol formaldehyde resin (PFR) based composites with multiwalled carbon nanotube (MWCNT) additives (2 and 5 wt.%) were prepared and their electromagnetic (EM) properties were investigated in Ka‐band frequency range (26–37 GHz). It was demonstrated that the combination of such materials in a double‐layered structure allows achievement of the significant attenuation of EM radiation. The electromagnetic response of considered double‐layered system was modeled by solving the electric field integral equation, utilizing the Green's function technique. Absorption up to 96% in the 26–37 GHz frequency band was both predicted and experimentally observed. [ABSTRACT FROM AUTHOR]

The growth of single-walled carbon nanotubes (SWCNT) inside host SWCNTs remains a compelling alternative to the conventional catalyst-induced growth processes. It not only provides a catalyst free process but also the ability to control the constituents of the inner tube if appropriate starting molecules are used. We report herein the growth of inner SWCNTs from 13C-enriched benzene or toluene and C60 fullerene with a natural isotopic distribution. The latter molecule is essentially a stopper which acts to retain the smaller toluene inside the tubes. The Raman spectrum of the inner nanotubes is anomalous as it contains a highly isotope shifted 'tail,' which cannot be explained by assuming a homogeneous distribution of the isotopes. Semi-empirical calculations of the Raman modes indicate that this unusual effect is explicable if small arrays of 13C are assumed. This indicates the absence of carbon diffusion during the inner tube growth. [ABSTRACT FROM AUTHOR]

Electronic and transport properties of carbon-nanotube (CNT) hybrid junction CNT(3, 3)/CNT(6, 0)/CNT(3, 3) are investigated and compared with substitutionally doped junction with transition metal atoms, iron, cobalt, and manganese; using density functional theory combined with nonequilibrium Green’s function formalism. Transmission coefficient and current–voltage (I–V) characteristics are calculated for all configurations. The results indicate a smooth increase of current with voltage in pristine junction up to 0.75V while in the case of higher voltages, the increase accelerates significantly and the conductance for the voltages between 1 and 1.5 becomes almost constant, about 40μAV. The replacement of carbon atoms with Fe, Co, and Mn in the scattering region causes rather substantial reduction of the transmission and conductance of the hybrid junction. It causes the current to reduce nearly 25% at the voltage of 1.5V compared to the pristine one. It also appears that, there is no serious difference in the I–V characteristics for different impurity atoms, except some deviation in manganese conductance from the other two impurities’ curves. These results can be useful for future CNTs based nano-electronic applications. [ABSTRACT FROM AUTHOR]

We report on quantum transport measurements of a carbon nanotube (CNT) quantum dot that is functionalized with magnetic {Mn4} complexes. The coupling between the spin-5/2 MnII ions within each {Mn4} complex is predominantly antiferromagnetic. Coulomb diamond measurements at T = 4 K reveal that the covalent attachment of the complexes to the CNT framework has only little influence on the carbon nanotube quantum dot. Surprisingly, a strong increase of noise is observed upon cooling the sample to T = 30 mK. Time traces of the current taken at a diamond edge reveal a random telegraph signal. We attribute this to fluctuations of molecular spin states of the attached {Mn4} complexes. [ABSTRACT FROM AUTHOR]

Hybrid materials composed of single walled carbon nanotubes (SWCNTs) as hollow containers and small molecules as fillers possess intriguing physical and chemical properties. Infrared spectroscopy is a useful method in most cases to characterize hybrid systems; however, regardless of the type of small molecule encapsulated in the SWCNT, the IR spectrum of the hybrid system remains silent. The possible explanation involves the highly polarizable [ABSTRACT FROM AUTHOR]

Recent experimental results based on Raman spectroscopy and mass spectroscopy showed that an appropriate heat treatment of small diameter carbon nanotubes filled with ferrocene molecules results in the formation of hydrocarbon molecules. However, the exact nature of these molecules is still unknown. In order to find possible candidates, we performed density functional theory calculations of the structure, electronic transition energies, and Raman spectrum for a large set of hydrocarbon molecules, including oligoenes and polyaromatic hydrocarbons. To follow the effect of deuteration in the Raman spectra we varied the mass of hydrogen atom from 1 to 2 by 0.1 steps. With increasing mass, the position of the lines red shifted as expected. However, in some rare occasions, the intensity of the red shifted line dramatically decreased and at the same time, an originally weak line gained large intensity at a nearby higher frequency. This can be interpreted in an experiment as an apparent blue shift. From a comparison of the calculations with experiments, based on molecular weight, excitation energy, and Raman spectrum (for both hydrogenated and deuterated forms) either quaterrylene (dimer of perylene) or the dimer of the 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) is the most likely product of the heat treatment. [ABSTRACT FROM AUTHOR]

Small diameter single-walled carbon nanotubes can be filled with carbon-rich molecules if the latter are small enough. For HiPco tubes ferrocene turned out to be appropriate. After filling and high temperature treatment (transformation) new Raman lines are observed. Here we show that these lines appear also for small diameter DIPS tubes after similar temperature treatment and that all new lines originate from one special molecule. This molecule has a C=C stretch vibration at 1597 cm [ABSTRACT FROM AUTHOR]

We performed resonance Raman spectroscopy on HiPCO-produced single-walled carbon nanotubes in the spectral region of 846 and [ABSTRACT FROM AUTHOR]

In this study, a buckypaper (BP), a foil of carbon nanotubes, with covalently bonded graphene leaves is prepared as a scaffold of pseudocapacitors. The capacitive electrodes are fabricated by an in situ growth of graphene on BP followed by electrochemical deposition of MnO2. The specific capacitance, energy/power-density, and cycle stability of the hybrid electrodes are explored by means of electrochemical impedance analysis, cyclic voltammetry measurements, and galvanostatic charge-discharge analysis. Due to the graphene interconnection between carbon nanotubes, the internal resistances of the electrodes decrease by a factor of ∼2. The MnO2/graphene/BP (MnO2/g-BP) hybrid electrode delivers a specific capacitance as high as 1022 F g−1 at a scan rate of 5 mV s−1, based on the mass of MnO2. It exhibits excellent rate capability and cycle stability. The critical role of the covalently bonded graphene leaves in enhancing charge transport is further clarified by comparison with the electrodes without them. Therefore, this study provides a new understanding for improving the performance of metal oxide-based electrochemical supercapacitors and can be generalized for designing next-generation high-performance energy-storage devices. [ABSTRACT FROM AUTHOR]

In this work, we present the analysis of adsorption properties of CO2 on Ag nanoparticle/carbon nanotube nanocomposites compared to those of N2 and O2. We observe for all gases an identical kinetic behavior, indicating that the nonwetting properties of CO2 on a carbon surface do not influence the gas adsorption. We perform the analysis in conditions of low pressure and temperature to better observe the physical properties of the system. We observe a first kinetic order for all gases, indicating the absence of gas-gas interactions on the composite surface. The desorption curves for all gases present several desorption temperatures, indicating the presence of different kinds of adsorption sites. [ABSTRACT FROM AUTHOR]

The effect of laser wavelength on single-wall carbon nanotubes synthesis yield and their properties was studied. A double-pulse Nd:YAG laser, working at a wavelength of 355 or 1064 nm, was used for carbon nanotubes production. The synthesized carbon nanotubes (CNTs) were investigated using the SEM/STEM microscopy and Raman spectroscopy. The results show that the useful range of UV laser radiation fluence is narrower and the properties of synthesized CNTs depend much more on the laser fluence than in the case of infrared laser radiation. [ABSTRACT FROM AUTHOR]

The dielectric/electric properties of polyurethane composites filled with carbon nanotubes (CNT), onion-like carbon (OLC), and mixed OLC/CNT are compared across a wide frequency range from hertz to terahertz. The dielectric/electric properties of composites filled with OLC are very attractive and can be improved by addition of small amounts of CNTs due to a strong synergism between the two carbon allotropes. Moreover, in composites with mixed OLC/CNT inclusions, the value of the percolation threshold is lower than the value predicted by the excluded-volume theory. In composites with mixed OLC/CNT inclusions, the dielectric permittivity and electrical conductivity increase due to a decrease in the average distance between nanocarbon clusters. [ABSTRACT FROM AUTHOR]

The magnetoresistance and electrical resistivity of nitrogen-doped multi-walled carbon nanotubes (N-MWCNTs) were studied in the temperature range of 1.6-100.3 and 1.6-286 K, respectively, using a standard four-probe technique. The possible mechanisms of the observed effects are discussed in detail. [ABSTRACT FROM AUTHOR]

The frequency axis of Fig. 3 is corrected. [ABSTRACT FROM AUTHOR]

We performed a thorough multifrequency Raman spectroscopy study to access the entire spread of all traces of chirality species and confirm the absence of metallic species in metallicity and single chirality sorted single-walled carbon nanotubes. On the bulk scale the diameters of all detectable species fall within 1.43 nm [ABSTRACT FROM AUTHOR]

A theoretical study of the first-order resonance Raman optical activity (ROA) of a single-walled carbon nanotube (SWCNT) is presented for the first time. Tight-binding (TB) Raman and ROA scattering tensors are combined with precise first principles harmonic vibrational modes to obtain scattering intensities. This computational protocol for Raman and ROA spectra has been tested previously for chiral fullerenes, such as C [ABSTRACT FROM AUTHOR]

We present a theoretical study on the molecule-substrate interaction within the porphyrin-functionalized graphene. Recent experiments on porphyrin-functionalized carbon nanotubes have revealed an extremely efficient energy transfer from the adsorbed molecules to the carbon substrate. To investigate the energy transfer mechanism, we have characterized the hybrid structure within the density functional theory including the calculation of the molecular transition dipole moment, which allows us to determine the Förster coupling rate. We find a strongly pronounced Förster-induced energy transfer in the range of fs [ABSTRACT FROM AUTHOR]

Carbon-rich fillers like ferrocene can be transformed into an inner tube with extremely small diameter if they are filled into HiPco tubes. For ferrocene@HiPco three new Raman bands appear in the D-band region during this transformation. These bands do not show dispersion and exhibit a strong resonance for red laser excitation. The observed resonance is for the outgoing phonon at 1247 cm [ABSTRACT FROM AUTHOR]

We present a high-pressure optical spectroscopy study on single-walled carbon nanotubes (SWCNTs) doped with bromine using nitrogen as pressure transmitting medium. Bromine-doped SWCNTs (Br-SWCNTs) with different doping levels were prepared by the gas phase method and characterized by optical and Raman spectroscopy. The absorption and Raman spectra clearly reveal the effects of charge doping by bromine. Like for pristine SWCNTs, the absorption bands of Br-SWCNTs show a red shift under pressure. Anomalies in the pressure-induced relative frequency shift indicate structural changes in the nanotubes. The results are compared with those for empty nanotubes. [ABSTRACT FROM AUTHOR]

We present electrochemical Raman measurements on energy transfer complexes formed by combining single-walled carbon nanotubes and dye molecules. The presence of the dye molecules in the proximity of the nanotubes impacts the nanotubes' charging behavior, leading to changes in the position of the charge neutrality point and the maximum achievable doping strength. We compare these results to spectra acquired in solution and determine the corresponding Fermi energy shifts, which are found to be similar in the energy transfer complexes and a reference sample. Our results have implications for the photoluminescence enhancement/quenching previously observed in these energy transfer complexes. Electrochemical G-mode Raman spectra at a gate voltage of −1.1 V showing much larger doping strength for the reference sample than for the energy transfer complexes, as seen in the higher-frequency and narrower peak. [ABSTRACT FROM AUTHOR]

Effect of Peierls instability on the electronic band structure of carbon nanotubes (CNTs) under torsional strain is studied by tight-binding approximation. When Kekulé structure with two different bond lengths is introduced, armchair (5,5) and zigzag (9,0) CNTs become semiconducting indicating by a small band gap opening at the Fermi level. Numerical calculations show that the increasing of shear strain leads to reduce the band gap of armchair (5,5) carbon nanotube. Shear strain threshold for a semiconductor-metal phase transition depends on the difference in the bond lengths. In the metal state, the torsional strain induces the Fermi wavenumber of (5,5) carbon nanotube deviated from the center of the first Brillouin zone. Under the torsional strain, a semiconductor-metal-semiconductor phase transition appears for (9,0) CNT with Kekulé structure as well. [ABSTRACT FROM AUTHOR]

The structural and electronic properties of end-capped carbon nanotubes (CCN) functionalized by carboxyl, amine, amide, and hydroxyl chemical groups under the action of electric fields are investigated through first-principles simulations based on density functional theory. Changes in the original properties of the functionalized capped nanotubes are observed due to the application of external electrical fields and the responses for different intensities are shown to be nonlinear. It is demonstrated that there are optimum values for the electric field to obtain the most stable binding energies for the studied systems. In all cases, the energy levels are rearranged to stabilize the systems and electric dipole moments are induced toward the incident electric field. It is also shown that these electric dipole moments generate polarized nanotubes and the previously weak physical interactions between molecules with the tube surface would become stronger and, by binding chemically, allow the manipulation of the intrinsic properties of the nanotubes. The structural and electronic properties of end-CCN pristine and functionalized by carboxyl, amine, amide, and hydroxyl chemical groups under the action of electric fields are investigated through first-principles simulations based on the density functional theory. [ABSTRACT FROM AUTHOR]

Although the possibility of using metallocenes acting as n-type dopants for metallicity mixed and separated single-walled carbon nanotubes (SWCNT) has been proven, the question of usability for real-life applications still needs to be addressed. The most important factor for their applicability is the stability of the doping outside a vacuum environment. To clarify this issue we have conducted a long-term study on purely metallic SWCNTs after being filled with ferrocene and compared it to results after prolonged exposure to air, demonstrating a decomposition of about half of the filling material leaving a lower but stable doping state. The successful conversion to double-walled carbon nanotubes by high-temperature annealing yielding p-type doped hybrid structures is evidenced additionally. These results let us conclude that SWCNTs filled with metallocenes are an ideal n, or p-type doped starting material for applied electronics based on graphitic structures. [ABSTRACT FROM AUTHOR]

The synthesis of single-walled carbon nanotubes (SWCNTs) with the narrowest possible diameter distribution is a challenging undertaking in carbon nanoscience, which can be overcome through the fabrication of monodisperse catalytic nanoparticles. A technique is presented here to approach the diameter control of SWCNTs using a chemisorbed nickel acetylacetonate monolayer at the surface of silica. We show by Fourier transform infrared spectroscopy and thermogravimetry coupled with mass spectroscopy that a monolayer of nickel acetylacetonate is anchored with the silanol groups at the surface of the substrate. After thermal decomposition, the nickel remains bonded with these silanol groups, resulting in a good dispersion of the nickel over the silica surface. Using this catalyst, SWCNTs with a narrow diameter distribution were synthesized at moderate temperature. This opens new perspectives for the fabrication of uniform-diameter carbon nanotubes. [ABSTRACT FROM AUTHOR]

We present local magnetoresistance measurements on carbon nanotubes contacted with the ferromagnetic alloy Co50 Pd50. A sample with contacts of [ABSTRACT FROM AUTHOR]

Photoluminescence (PL) properties of CdS nanoparticles were studied depending on spacing between the nanoparticles and carbon nanotube (CNT) surface. Using a chemical bath deposition procedure the nanoparticles were grown directly on CNT arrays or arrays covered by a polystyrene layer. The polymer thickness was changed by varying the polystyrene concentration in a solution and the duration of CNT immersing. Transmission electron microscopy and atomic force microscopy were used for estimation of CdS nanoparticle size. An increase in the separation between CdS and CNTs was found to enhance the PL intensity and contribute to the exciton lifetime. PL spectra of CdS nanoparticles grown on a CNT surface and polystyrene layer coating the CNTs. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs) can be used as nanoreactors due to their unique hollow nanostructures. In order to prepare linear carbon chains inside CNTs, eDIPS single-wall carbon nanotubes were annealed at high temperatures from 1300 to 1500 [ABSTRACT FROM AUTHOR]

In this review, I trace the development of dielectrophoresis (DEP) for the directed assembly of carbon nanotubes (CNTs) and graphene. DEP involves driving a nanoparticle in an alternating current (AC) electric field, whereby the particles migrate towards or away from the direction of high-field gradient depending on the relative polarizability of the particle and medium. DEP offers a scalable and controllable route for integration of various kinds of nano-carbon devices, such as field-effect transistors, nano-electromechanical resonators and sensors. DEP utilizes nano-carbons in solution phase and is compatible with the various CNT and graphene sorting methods which have been developed, allowing for instance the large-scale integration of single-chirality CNTs. False-colour scanning electron micrograph of an array of semiconducting single-wall carbon nanotube devices assembled by alternating-current dielectrophoresis. [ABSTRACT FROM AUTHOR]

Conduction in thin random networks of single-walled carbon nanotubes (SWNTs) is typically dominated by metallic SWNT segments and limited by variable-range hopping (VRH) in disordered junction regions. However, in our surfactant-free networks, we show that in parallel with VRH there is another mode of conduction involving both semiconducting and metallic SWNTs. This second process showing activated behavior makes a substantial contribution to conductance at higher temperatures, with similar activation energies in different samples despite a large variation in overall magnitude of the conductivity. From the magnitude of the activation energy (0.160.05\,eV), we ascribe this additional term to activation across Schottky barriers between metallic and semiconducting SWNTs in conducting paths involving a small number of semiconducting SWNTs. The Mott parameters for VRH are also independent of the overall conductivity, indicating that the local structure of intertube contacts between metallic SWNTs in the most conductive paths is also similar in samples of different overall conductivity. [ABSTRACT FROM AUTHOR]

The magnetic response of electrons in a zigzag carbon nanotube (CN) threaded by an Aharonov Bohm flux φ is carefully analyzed by using a Hartree Fock approximation. The ground state energy as a function of the magnetic field, B, and the electron-electron repulsion strength, U, are obtained for Ne interacting electrons confined in short (∼100 nm) and long (∼1 μm) CNs. The spin and orbital magnetization responses to the magnetic field variations are discussed. The CN transport properties are investigated and periodic field dependent oscillations are predicted for both longitudinal ballistic and persistent currents. The behavior of persistent current is investigated as a function of U and a significant suppression in current amplitude is observed when the strength of the electron-electron repulsion increases. [ABSTRACT FROM AUTHOR]

In this contribution, we apply a hierarchical fibre bundle model (HFBM), previously developed to estimate the mechanical properties of multiscale carbon nanotube (CNT)-based structures, to the case of graphene macroscopic cables. The nonlinear elastic properties of graphene and its exceptional intrinsic strength, with mean Young's modulus of 1 TPa, third-order elastic stiffness of −2.0 TPa and intrinsic strength of 130 GPa, are drawn from recent experimental studies. The model allows to derive macroscopic characteristics like strength, stiffness, toughness as a function of hierarchical structure, starting from statistically distributed properties at the nanoscale and without the introduction of additional ad hoc parameters. The influence of the presence of defects in the graphene bundles is evaluated. We also analyse the properties of graphene-reinforced composites, including the influence of the volume fraction of a ductile polymeric matrix. We show that the composite properties can be engineered to optimize strength and/or stiffness, and that the present model can be a useful tool to help pursue this objective [ABSTRACT FROM AUTHOR]

In situ measurements of the resistance changes of carbon nanotube bundles irradiated by 60Co γ-quanta at room temperature are presented. The peculiarity of our study consists in providing the sample irradiation in a hermetic cell filled with different gases at atmosphere pressure. Here we demonstrate the results for irradiation in hydrogen, deuterium, helium and argon media. The obtained dependences of the resistance change versus irradiation dose in vacuum are presented, too. We have developed a novel two-stage mechanism, which implies defect introduction by energetic intermediate particles that are gas atoms. Preliminary calculations for Compton electrons (0.85 MeV) and atmospheric gas pressure show the high efficiency of this two-stage mechanism in comparison to conventional one-stage mechanism. It is shown that the defect introduction rate in the developed two-stage mechanism is strongly dependent on the gas atomic mass and coincides well with our experimental results. [ABSTRACT FROM AUTHOR]

This work gives data on the stability of dispersions of single wall carbon nanotubes stabilized by sodium dodecylbenzenesulfonate in binary polar solvents 'water + antifreeze' (glycerol, polyethyleneglycole) with eutectic compositions. The absorption spectra of the suspensions demonstrate no changes during 1-year storage with temperature spanning from −40 to +40 °C. The systems provide relevant optical power limiting properties, the one with glycerol showing good resistance to optical bleaching effects. We also demonstrate that aqueous dispersions of nanotubes exhibit considerable enhancement of optical limiting parameters alongside an increase of the bundled material populace. [ABSTRACT FROM AUTHOR]

We have investigated the efficiency of scattering processes through acoustic phonons in semiconducting nanotubes. Based on the density matrix formalism we obtain Boltzmann scattering equations, which give us a microscopic access to the time- and momentum-resolved relaxation dynamics of optically excited carriers. In agreement with a recent experiment [see Dyatlova et al., Nano Lett. 12, 2249 (2012)], we obtain relaxation times on the picosecond time scale. Here we study the importance of carrier-phonon interaction as a function of probe energy and initial temperature for the exemplary (8,7) nanotube. Furthermore, we calculate the relaxation dynamics for nanotubes with different diameters focusing on the change in the relaxation time with the curvature of the corresponding energetically lowest conduction subband. [ABSTRACT FROM AUTHOR]

Bucky gel actuators are one of the most promising type of electrochemical actuators based on carbon nanotubes (CNTs). They are lightweight, they are able to work in air without any liquid electrolyte and require just few volts to operate. In order to find real world applications where bucky gel actuators can outperform conventional motors, there are still some issues to be addressed. One key aspect in CNT-based electrochemical actuators is that their actuation speed is limited by the ability of charging and discharging the device without exceeding the electrochemical stability window of the electrolyte. This speed is macroscopically related with the product of the resistance and the capacitance of the equivalent circuit (circuit time constant), and with the ion diffusion speed inside the active electrodes. To enhance the actuator performance it is necessary to increase the ion drift current in the electrolyte avoiding to significantly raise the voltage at the electrodes and shorten the ion path necessary to charge the bucky gel electrodes. By proper material processing, we have successfully addressed this issue. A reduced thickness of the actuators to one third of the original size results in a one order of magnitude increase both of the strain at higher frequencies and of the maximum operating frequency. [ABSTRACT FROM AUTHOR]