We have performed polarization-dependent ultrafast pump-probe spectroscopy of a film of aligned single-walled carbon nanotube bundles. By taking into account imperfect nanotube alignment as well as anisotropic absorption cross sections, we quantitatively determined distinctly different photobleaching dynamics for polarizations parallel and perpendicular to the tube axis. For perpendicular polar...

Electron-electron interactions are significantly enhanced in one-dimensional systems, and single-walled carbon nanotubes provide a unique opportunity for studying such interactions and the related many-body effects in one dimension. However, single-walled nanotubes can have a wide range of diameters and hundreds of different structures, each defined by its chiral index (n,m), where n and m are ...

A 0.4 mm long semiconducting single-walled carbon nanotube is doped into n type by potassium ~K! vapor. Electrical measurements of the doped nanotube reveal single-electron charging at temperatures up to 160 K. The K-doped sample manifests as a single quantum dot or multiple quantum dots in series depending on the range of applied gate voltage. This is explained by an inhomogeneous doping profi...

We demonstrate the efficient chemical vapor deposition synthesis of single-walled carbon nanotubes where the activity and lifetime of the catalysts are enhanced by water. Water-stimulated enhanced catalytic activity results in massive growth of superdense and vertically aligned nanotube forests with heights up to 2.5 millimeters that can be easily separated from the catalysts, providing nanotub...

The role of water in carbon feed on the surface-guided growth of horizontally aligned single-walled carbon nanotubes (HA-SWCNTs) was investigated. It is shown that the amount of water can be optimized to favor HA-SWCNT growth, which is proposed to be due to selective etching of carbon deposits at carbon–metal interface. Without water, nanotube–nanotube interaction and carbon accumulation at the...

We demonstrate a fully tunable diode structure utilizing a fully suspended single-walled carbon nanotube. The diode's turn-on voltage under forward bias can be continuously tuned up to 4.3 V by controlling gate voltages, which is ∼6 times the nanotube band gap energy. Furthermore, the same device design can be configured into a backward diode by tuning the band-to-band tunneling current with ga...

Rayleigh scattering spectra were obtained from individual single-walled carbon nanotubes with the use of a laser-generated visible and near-infrared supercontinuum. This diagnostic method is noninvasive and general for nanoscale objects. The approach permits clear identification of excited states in arbitrary metallic and semiconducting nanotubes. We analyzed spectral lineshapes in relation to ...

first principles calculations were carried out for investigation the novel 7-hydroxycoumarinyl gallates derivatives in gas and liquid phases using density functional theory (dft) method. computational chemistry simulations were carried out to compare calculated quantum chemical parameters for gallates derivatives. all calculations were performed using dmol3 code which is based on dft. the doubl...

the interaction between some heavy metal ions such as of pb(ii), cd(ii) and cu(ii) ions from aqueous solution adsorbed by single walled carbon nanotube (swcnts) and carboxylate group functionalized single walled carbon nanotube (swcnt-cooh) surfaces were studied by atomic absorption spectroscopy. the effect of contact time, ph, initial concentration of ion, ionic strength and temperature on the...

carbon nanotubes (cnts) are specific structures with valuable characteristics. in general, the structure of each nanotube is defined by a unique chiral vector. in this paper, different structures of short single-walled cnts are simulated and their mechanical properties are determined using finite element method. for this aim, a simple algorithm is presented which is able to model the geometry o...