Single-wall carbon nanotubes are formed by Nd:YAG laser vaporization of a graphite/(1 at. % Ni, 1 at. % Co) target into flowing argon (500 Torr) within a quartz tube furnace (1000 °C). Here, this process is investigated for the first time with time-resolved laser-induced luminescence imaging and spectroscopy of Co atoms, C2 and C3 molecules, and clusters. These measurements under actual synthesis conditions show that the plume of vaporized material is segregated and confined within a vortex ring which maintains a ˜1 cm3 volume for several seconds. Using time-resolved spectroscopy and spectroscopic imaging, the time for conversion of atomic and molecular species to clusters was measured for both carbon (200 μs) and cobalt (2 ms). This rapid conversion of carbon to nanoparticles, combined with transmission electron microscopy analysis of the collected deposits, indicate that nanotube growth occurs during several seconds of time from a feedstock of mixed nanoparticles in the gas-suspended plume. Using these in situ diagnostics to adjust the time spent by the plume within the high-temperature zone, single-walled nanotubes of controlled length were grown at an estimated rate of 0.2 μm/s.

In a recent publication we have described the synthesis of multiwalled carbon nanotubes (MWNTs) by the reaction of a hydrocarbon vapor over a dispersed iron catalyst that is deposited in situ on quartz substrates. Our system configuration involves entraining a mixture of xylene and ferrocene into an inert gas stream. Decomposition of the ferrocene at temperatures in the range 625-775 °C, and at atmospheric pressure, produces a coating of iron nanoparticles on the quartz surfaces, and these metal sites function as catalysts for the formation and growth of MWNTs. In this study, we report the influence of operating conditions on MWNT purity and yield. These parameters include the feed injection temperature, furnace temperature, hydrocarbon partial pressure, reaction time, space velocity, and iron to carbon ratio in the feed. We observed that the quality of the MWNTs dependc sensitively on the growth parameters and a window for the operating conditions is identified for the growth of high purity aligned MWNTs. Characterization of the MWNTs by electron microscopy has shown that there is a relationship between metal particle size and MWNT diameter.

We have recently discovered self-assembled chains of C60 molecules contained within single wall carbon nanotubes (SWNTs). Using in situ transmission electron microscopy studies, we show a route by which such ‘peapod’ structures can be synthesized. The results indicate that exterior C60 molecules arrive at the nanotubes from the vapor phase and subsequently enter, presumably through open ends or sidewall defects. The methods discussed in this work provide a means for the bulk production of these molecular assemblies.

Boron nitride (BN) multi-walled (MWNT) or single-walled (SWNT) nanotubes were synthesized from carbon MWNT and SWNT templates, respectively, under heating of C nanotubes together with boron trioxide in a flowing nitrogen atmosphere. B and N atom substitution for C atoms in the nanotubular shells during C oxidation by the B2O3 vapor in the N2 flow is thought to underlie the formation mechanism. Structural and chemical BN MWNT/SWNT analyses were performed by means of high-resolution electron microscopy (HRTEM) and electron energy loss spectroscopy (EELS), respectively. In particular, BN MWNT shell structure and defects, and electron irradiation stability were studied. Finally, the prospects of using the substitution technique for the synthesis of other advanced nanostructures made of BN (nanorods, nanoplates and nanocones) are discussed.

Bundles of single-walled carbon nanotubes produced by laser ablation are often seen twisted in morphology, forming nanoropes which would better suit the function for improvement of structural stability in mechanical applications. The rope-like configuration is explained with a model that relates the twisting morphology to the helicity difference between the neighboring nanotubes. This selfassembly phenomenon is attributed to the fact that a twisted structure has lower total energy compared with the raft-like parallel bundles when the helicities of neighboring nanotubes are different.

Aligned multi-wall carbon nanotubes have been grown on silicon substrates by microwave plasma enhanced chemical vapor deposition using methane/ammonia mixtures. The concentration ratio of methane/ammonia in addition to substrate temperature was varied. The morphology, structure and alignment of carbon nanotubes were studied by scanning electron microscopy and transmission electron microscopy. Both concentric hollow and bamboo-type multi-wall carbon nanotubes were observed. Growth rate, size distribution, alignment, morphology, and structure of carbon nanotubes changed with methane/ammonia ratio and growth temperature. Preliminary results on field emission properties are also presented.

It is well established that the structural characteristics of graphite nanofibers can be controlled by several factors including, the chemical nature of the catalyst, the composition of the reactant gas mixture and temperature at which the growth process is performed. In the current investigation we have endeavored to modify the behavior of the catalyst by dispersing the active metals on different support media. We have found that the strength of the metal-support interaction exerts a significant impact not only on the average size of the nanofibers generated by such a procedure, but also results in major changes in the architecture of the carbon materials. The support imposes certain geometrical constraints on the metal particles and these features are manifested in modifications in the degree of crystalline perfection and arrangement of the graphite sheets constituting the nanofibers. In addition, there is also the possibility that the support can induce electronic perturbations in the metal particles, a feature that will be most pronounced with a conductive carrier.

Single-wall carbon nanotubes (SWNTs) have been synthesized by laser ablation of Ni/Co catalyzed graphite target at 1200°C in argon gas. Raman spectroscopy has been used to study the effect of target position in the furnace and flow rate of argon gas on the diameter distribution of SWVNTs. It was found that yield of smaller diameter SWNTs relatively increases as target is placed away from the hot zone of the furnace. The relative yield of smaller diameter SWNTs decreases with increase in flow rate of the argon gas.

We present an ab–initio molecular dynamics study of the modifications induced on fullerite by the irradiation with ultrashort very intense laser pulses. We identified the threshold for the non–thermal cage–opening of the C60 molecules which is the analogue of the laserinduced non–thermal melting observed in semiconductors and graphite. The new phase formed by the non–thermal coalescence of the C60 molecules is fluid–like and mainly formed by small chains of 2–fold coordinated carbon atoms.

The Langmuir-Blodgett (LB) film formation behavior of the endohedral metallofullerene Dy@C82 was studied at the air/water and Ar/water interfaces. The LB film constructed at the Ar/water interface (2-4 layers) was found to be thinner and more uniform than at the air/water interface (4-6 layers). Particulate aggregates were observed in the LB films, which contrasts the extended wire networks formed by direct evaporation of the metallofullerene solution on a quartz plate. The UV-Vis absorption peaks are blue-shifted for the LB film deposited in air, which is attributed to the partial oxidation of the metallofullerene balls. They are red-shifted, however, for the LB film at the Ar/water interface presumably due to the interaction between the pristine metallofullerenes.

The problem of nanotube growth macrokinetics is viewed within the framework of the continuum surface diffusion equation combined with step-flow growth kinetics. The differences in incorporation rates of adatoms approaching the growth steps from “upper” or lower" terraces are taken into account. These differences can lead to the onset of surface island nucleation in front of a propagating step. This effect is able to cause formation of defects in the growing layer and even to inhibit stable step-flow modes of nanotube growth. The segregation effect of a second phase (BN) in front of the propagating of C layer step is considered, suggesting that it may cause increase in BN concentration and nucleation of islands leading to BN inclusions in C layers or the propagation of a BN layer over C layer.

Nanostructured carbon films have been grown by deposition of supersonic cluster beams. A novel pulsed microplasma cluster source allows to obtain cluster beams of high intensity and stability. Cluster growth and beam formation have been charaterized. Separation effects typical of supersonic expansions cause inhomogeneities of cluster distribution in the beam, depending on their masses. This effect, observed for the first time, has been carefully characterized. The deposited films have a low density porous structure based on nanometer-size grains. The coordination is essentially three-fold with a large number of defects. Film density, morphology and surface roughness can be controlled by varying the precursor cluster mass distribution. Applications of cluster-assembled carbon films will be presented.

Nanoporous carbons have been synthesised through a selective etching reaction, performed by halogenisation of metal carbides. The structures obtained can be controlled by choice of starting materials and reaction parameters, and here one example, chlorination of aluminium carbide at 700 °C, is given. The produced material is nanotube-like with agglomerates of short and wide interconnected tubular structures, which are here described as nanobarrels. The synthesis process gives a pure product with high-yield, and may be scaled up to produce bulk amounts.

New preparative methods for the synthesis of nanoporous carbons using silica particles as templates will be presented. Gellation of resorcinol and formaldehyde in the presence of silica sol particles generated RF gel-silica nanocomposite. Carbonization followed by HF etching of silica templates generated nanoporous carbons with pore size ranging 10 ∼ 100 nm. When silica particles stabilized with surfactant were used as templates, uniform ∼ 10 nm pore-sized carbons have been formed. These nanoporous carbons exhibited excellent adsorption capacity for dyes.

The phonon density of states of single-wall carbon nanotubes (SWNT) was measured by inelastic neutron scattering (INS) in a large energy range (0 to 120 meV). New information on the vibrational dynamics of SWNT is reported and compared with calculated density-of-sates. At lower frequencies (< 12 meV) we observe a peculiar energy dependence which we attribute to contributions from inter-tube modes in the 2D lattice of SWNT bundles, and also from effects of intertube coupling on the intra-tube excitations.

Raman scattering is used to study the structure and electronic properties of bundles of single wall carbon nanotubes. A relation between the tube diameter and the radial breathing mode frequency is derived by combining a description of the covalent bonds inside each nanotube via force constant model with a pair-potential approach to deal with the van der Waals interaction between nanotubes. In the framework of this approach a good agreement is evidenced between the diameter distribution derived from the A1g radial breathing mode frequencies and the one obtained from the analysis of the neutron diffraction spectrum. On the other hand, an investigation of the intermediate frequency range (600-1100 cm-1) of the Raman spectrum is reported. A dependence of the frequency of the modes with the excitation energy is clearly evidenced and assigned to a mode coupling.

Multi-walled carbon nanotubes synthesized by the carbon arc in hydrogen gas have very thin core channels. We have measured resonance Raman scattering of some samples synthesized in different conditions, and have observed radial breathing mode (RBM) peaks from 200 to 500 cm−1. Resonance effect of each peak is similar to that of single-walled nanotube. However, the peak frequencies are about 5 % higher than those of single-walled nanotubes, which is probably due to the inter-layer interaction. Further, the highest RBM peak splits in three peaks. The result on the resonance effect and the zone-folding band calculation suggest that the thinnest core nanotube is (4,3) that have four candidates of second outer nanotubes. This suggests that the different outer nanotube gives different degree of the interlayer interaction.

In this contribution, we report on a mechanical method to cut and open single walled carbon nanotubes. This technique is based on using an abrasive material (diamond powder) without any chemical treatments or oxidation in air at high temperature. We present highresolution transmission electron microscopy micrographs, which show firstly that the tubes are unambiguously opened and secondly, that the nanotubes have not suffered the treatment. x-ray diffraction pattern confirms a well-defined bundle organisation. A breaking mechanism of the nanotube bundles is proposed. Nitrogen adsorption measurements at 77K reveal the presence of new microporosities ranging in the average nanotube diameter, which confirm the opening of some tubes.

Single-walled carbon nanotubes (SWNTs) were purified and cut into short length by the liquid phase oxidation using the typical oxidants such as HNO3, H2SO4 and their mixture. The SWNTacid solutions were refluxed at high temperature, filtered on poly tetra-fluoro ethylene (PTFE) filter paper. rinsed with distilled water, and then dried at room temperature. In order to find optimum purifying condition, acid solutions were made by mixing nitric / sulfuric acid by the different volume ratio. The reaction time was also varied from 1h to 6h. Through this method, purified SWNTs with the length of less than 2μm were successfully obtained, which was confirmed by scanning electron microscopy (SEM). From transmission electron microscopy (TEM) analysis, it was verified that SWNTs were purified with little damage on surface and metal catalysts were efficiently removed when sulfuric acid was mixed, which was also confirmed by energy disperse spectrum analysis (EDS). Moreover, size distribution of the purified SWNTs was characterized with Field Flow-Fractionation (FFF) method.

The Z-contrast scanning transmission electron microscopy (STEM) imaging technique has been used to study dopant atoms and catalyst particles in single wall carbon nanotubes (SWNT). Iodine and bromine have been doped respectively in arc-grown SWNTs. We have directly observed the dopant sites and distributions. Both dopants appear to be incorporated linearly within the SWNT bundles. SWNT were also grown by pulsed laser ablation with mixed Ni and Co catalyst, and the size and distribution of catalytic particles was studied. By using Z-contrast imaging, we found that the size distribution of the catalyst particles varied over a large range, but even the smallest were larger than the diameter of an individual SWNT. Furthermore, electron energy loss spectroscopy (EELS) is used to determine the composition of individual nanocatalyst particles, and were found to consist of a uniform alloy of Co and Ni.