Pair Of Carbon Nanotubes Research Articles

Metallicity-Dependent Ultrafast Water Transport in Carbon Nanotubes.

Carbon nanotubes (CNTs) with hydrophobic and atomically smooth inner channels are promising for building ultrahigh-flux nanofluidic platforms for energy harvesting, health monitoring, and water purification. Conventional wisdom is that nanoconfinement effects determine water transport in CNTs. Here, using full-atomistic molecular dynamics simulations, it is shown that water transport behavior in CNTs strongly correlates with the electronic properties of single-walled CNTs (metallic (met) vs semiconducting (s/c)), which is as dominant as the effect of nanoconfinement. Three pairs of CNTs (i.e., (8,8)met , 10.85 Å vs (9,7)s/c , 10.88 Å; (9,8)s/c , 11.53 Å vs (10,7)met , 11.59 Å; and (9,9)met , 12.20 Å vs (10,8)s/c , 12.23 Å) are used to investigate the roles of diameter and metallicity. Specifically, the (9,8)s/c can restrict the hydrogen-bonding-mediated structuring of water and give the highest reduction in carbon-water interaction energy, providing an extraordinarily high water flux, around 250 times that of the commercial reverse osmosis membranes and approximately fourfold higher than the flux of the state-of-the-art boron nitrate nanotubes. Further, the high performance of (9,8)s/c is also reproducible when embedded in lipid bilayers as synthetic high-water flux porins. Given the increasing availability of high-purity CNTs, these findings provide valuable guides for realizing novel CNT-enhanced nanofluidic systems.

Pulling Simulations and Hydrogen Sorption Modelling on Carbon Nanotube Bundles

Recent progress in molecular simulation technology has developed an interest in modernizing the usual computational methods and approaches. For instance, most of the theoretical work on hydrogen adsorption on carbon nanotubes was conducted a decade ago. It should be insightful to reinvestigate the field and take advantage of code improvements and features implemented in contemporary software. One example of such features is the pulling simulation modules now available in many molecular dynamics programs. We conduct pulling simulations on pairs of carbon nanotubes and measure the inter-tube distance before they dissociate in water. We use this distance to set the interval size between adjacent nanotubes as we arrange them in bundle configurations. We consider bundles with triangular, intermediate and honeycomb patterns, and armchair nanotubes with a chiral index from n = 5 to n = 10. Then, we simulate low pressure hydrogen adsorption isotherms at 77 K, using the grand canonical Monte Carlo method. The different bundle configurations adsorb great hydrogen amounts that may exceed 2% wt at ambient pressures. The computed hydrogen capacities are considered large for physisorption on carbon nanostructures and attributed to the ultra-microporous network and extraordinary high surface area of the configured models.

On Adhesive and Buckling Instabilities in the Mechanics of Carbon Nanotubes Bundles

Many recently synthesized materials feature aligned arrays or bundles of carbon nanotubes (CNTs) whose mechanical properties are partially determined by the van der Waals interactions between adjacent tubes. Of particular interest in this paper are instances where the resulting interaction between a pair of CNTs often produces a forklike structure. The mechanical properties of this structure are noticeably different from those for isolated individual CNTs. In particular, while one anticipates buckling phenomena in the forked structure, an adhesion instability may also be present. New criteria for buckling and adhesion instabilities in forklike structures are presented in this paper. The criteria are illuminated with a bifurcation analyses of the response of the forklike structure to applied compressive and shear loadings.

Possible electric-field-induced one-dimensional excitonic insulators in pairs of carbon nanotubes

Recent experimental and theoretical works have shown that the Stark effect induced by the electric field from a scanning tunneling microscope (STM) can be used to reduce the gap of a boron nitride nanotube. In this paper, using density-functional theory calculations, we study the effect of an electric field on a pair of semiconducting carbon nanotubes and find that the application of an electric-field strength of $0.05\text{ }\text{eV}/\text{\AA{}}$ can close the Kohn-Sham gap of the system. Using a tight-binding formulation of the GW and Bethe-Salpeter methods we determine the quasiparticle and optical excitation spectrum of the system in an electric field and show that an electric-field strength of $0.06\text{ }\text{eV}/\text{\AA{}}$ fails to close the quasiparticle gap but closes the excitonic gap. This can cause a phase transition of the system into an excitonic phase where the ground state is populated with a quasi-one-dimensional repulsive gas of excitons. We discuss some of the properties of the resulting excitonic phase and the transition and also discuss how similar properties may be observed in experiments on nanotube bundles.

Plasma wave propagation in a pair of carbon nanotubes

Plasma waves which propagate in a pair of parallel metallic carbon nanotubes are studied within the framework of the classical electrodynamics. Electronic excitations over the each nanotube surface are modeled by an infinitesimally thin layer of free-electron gas which is described by means of the linearized hydrodynamic theory. An explicit form of plasmons dispersion in terms of interaction between the bare plasmon modes of the individual surfaces of the nanotubes is presented in this Letter.