Electrical transport in single-walled carbon nanotube bundles embedded in Langmuir–Blodgett monolayers

Langmuir films consisting of single-walled carbon nanotubes and surfactant molecules were deposited on substrates with lithographically defined electrode arrays. Atomic force microscopy revealed a different matrix structure of the Langmuir–Blodgett monolayers compared to monolayers on bare substrates. Electrical transport measurements were performed on individual thin bundles at room temperature and 4.2 K. At low temperatures, the current/voltage characteristics show a non-linear dependence with step-like features, which are critically discussed in the frame of Coulomb charging theory and electron tunneling through discrete energy levels.     

Spectroscopic ellipsometry characterization of amorphous carbon and amorphous, graphitic and fullerene-like carbon nitride thin films

Carbon nitride (CN_x) and amorphous carbon (a-C) thin films are deposited by reactive magnetron sputtering onto silicon (001) wafers under controlled conditions to achieve amorphous, graphitic and fullerene-like microstructures. As-deposited films are analyzed by Spectroscopic Ellipsometry in the UV-VIS-NIR and IR spectral ranges in order to get further insight into the bonding structure of the material. Additional characterization is performed by High Resolution Transmission Electron Microscopy, X-ray Photoelectron Spectroscopy, and Atomic Force Microscopy. Between eight and eleven resonances are observed and modeled in the ellipsometrically determined optical spectra of the films. The largest or the second largest resonance for all films is a feature associated with C-N or C-C modes. This feature is generally associated with sp³ C-N or sp³ C-C bonds, which for the nitrogen-containing films instead should be identified as a three-fold or two-fold sp² hybridization of N, either substituted in a graphite site or in a pyridine-like configuration, respectively. The π→π? electronic transition associated with sp² C bonds in carbon films and with sp² N bonds (as N bonded in pyridine-like manner) in CN_x films is also present, but not as strong. Another feature present in all CN_x films is a resonance associated with nitrile often observed in carbon nitrides. Additional resonances are identified and discussed and moreover, several new, unidentified resonances are observed in the ellipsometric spectra.     

空心富勒烯纳米MoS2和WS2

空心富勒烯纳米MoS2 和WS2 具有优异的摩擦学性状 ,这归结于它们独特的空心富勒烯结构和化学反应性能。预计这种固体润滑剂在空间技术、超高真空技术和汽车运输业将发挥重要作用。     

Al-induced fullerene-like nanostructures in C-Al-N thin films

The role of aluminium incorporated into growing carbon nitride (CN_x) films prepared by reactive dc-magnetron sputtering was investigated using X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and high-resolution transmission electron microscopy (HRTEM). XPS analyses revealed the formation of Al-N bonding besides C-C and C-N bonds. With increasing Al concentrations above 11.8 at.%, a structural transformation from essentially amorphous (a-) (CN_x, AlN) phase to locally ordered microstructure comprising of fullerene-like (FL-) CN_x nanostructures surrounded by a-(CN_x, AlN) matrices was evidenced by Raman and HRTEM. The effect of aluminium in triggering FL-CN_x nanostructures was elucidated from thermodynamic considerations.     

Evidences of Rubber Grafting on Activated Carbon Surfaces Containing Fullerene-like Structures

It is shown that graphite is converted into an high disordered carbon black by prolonged ball milling. The kinetics of this transformation has been followed by powder x-ray diffraction, measurements of the crystallinity and of the surface area. Ball milling is able to introduce an high concentration of defective sites in the pristine graphite including the fullerene-like structures. By mixing with natural rubber both the pristine and the ball-milled graphite, it is shown by bound rubber measurements that the amount of rubber grafted (chemically linked) on the pristine graphite surface is negligible but reaches a very high level in the ball-milled graphite. Similarly, ball-milling of N660 carbon black causes a deep activation of its surface activity which can be measured by a significant increase in the bound rubber level and in the amount of grafted rubber in comparison to the pristine N660 sample. The bound rubber measurement has been performed also on a natural rubber masterbatch with extracted fullerene carbon black (EFCB). Also in this case extremely high levels of rubber grafting have been achieved in comparison to graphite. It is discussed and demonstrated that the fullerene-like nanostructures in carbon blacks play a key role in the formation of bound rubber phenomenon and in grafting natural rubber on carbon black surface.     

Water adsorption on lubricated fullerene-like CNx films

Humidity influences the tribological performance of the head-disk interface in magnetic data storage devices. In this work we compare the uptake of water of amorphous hydrogenated carbon (a-CH_y) and carbon nitride (a-CN_x) films, widely used as protective overcoats in computer disk drive systems, with two types of amorphous non-hydrogenated carbon (a-C and a-C_sp²) films, and fullerene-like carbon nitride (FL-CN_x) films. Carbon films were deposited on quartz crystal substrates by reactive dc magnetron sputtering in Ar/N₂ discharges. After deposition, some of the films were coated with a 2-nm-thick layer of Z-tetraol, a lubricant used in hard disk devices. A quartz crystal microbalance placed in a vacuum chamber was used to measure the adsorption of water at room temperature and at pressures of water corresponding to relative humidities in the range RH = 0 to 90%. Water adsorption and desorption is fast, indicating that equilibrium with ambient humidity is reached on time scales of minutes, much faster than the time scales for fluctuations in ambient humidity. The amount of water adsorbed on the non-lubricated amorphous carbon films is significantly higher than that on the fullerene-like films. The presence of the lubricant influences water adsorption but its impact differs on different carbon films.     

Fullerenic-topological tools for honeycomb nanomechanics. Toward a fullerenic approach to brain functions

Fullerenic structures equipped with Stone-Wales transformations have been successfully utilized in the study of macromolecular assemblies. Here we show that this approach could be useful in the assessment of issues from a far-flung research area, i.e., neuroscience. Indeed, the basic morphological and functional unit of the brain, called the human microcolumn, is a tubular structure that can be flattened in the guise of a fullerene-like two-dimensional lattice. We describe this procedure in order to build a fullerene-like microcolumn, in which neuronal firing and electric signal propagation are assessed in terms of topological neural network modifications, instead of the canonical logic circuits. Every node represents a neuron, where neural computations take place. This means that nervous activity, other than logic circuits, could instead depend on topological changes and symmetry constraints dictated by Stone-Wales transformations occurring in the upper cortical layers. A two-dimensional fullerene-like lattice not only simulates the real microcolumn's microcircuitry, but also makes it possible for us to build artificial networks equipped with robustness, plasticity and fastness. In this note, electric signal propagation is investigated in terms of pure topological modifications of the neural honeycomb network.     

Possible Role Played by the Fullerene-like Structures of Interstellar Carbon Dust in the Formation of Molecular Hydrogen in Space

After a general introduction to the problem of formation of molecular hydrogen from atomic hydrogen in the interstellar medium and in the dense molecular clouds in particular, and after the explanation of the key role played by the surfaces on this process, it is proposed that the most suitable carbon surface for the formation of molecular hydrogen (from the radiative association process of atomic hydrogen) can be represented by carbon black rather than by graphite. Furthermore, it is proposed that the fullerene-like structures present in the carbon black graphene sheets are the reaction sites where molecular hydrogen may be formed.     

Spray drying process to synthesize multiple fullerene-like MoS2 particles

Multiple inorganic fullerene-like (IF) molybdenum disulfide hollow spheres were synthesized through spray drying method. The molybdenum trisulfide precursor, which was prepared by the mixed solution of ammonium molybdate ((NH₄)₂MoO₄) and ammonium disulfide ((NH₄)₂S) with a spray drying method, was desulfurized at 850 °C in a mixture of hydrogen and argon, and subsequently multiple fullerene-like molybdenum disulfide hollow spheres were obtained. The samples were identified and characterized by X-ray powder diffraction (XRD), field-emission scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM), and the mechanism of formation is also discussed based on the experimental result. The spray drying process would be an effective method to synthesize large-scale of inorganic fullerene-like materials.