Comparative studies on acid and thermal based selective purification of HiPCO produced single-walled carbon nanotubes

We report a comparative study on gas and liquid phase oxidative treatments of SWNTs, using a HiPCO produced raw material with a broad distribution of nanotube diameters. The effects of these two processes were correlated using absorption and Raman spectroscopy (radial breathing and G modes) and TEM. We conclude that liquid phase oxidation is a continuous diameter-selective process eliminating narrower SWNTs through oxidizing sidewalls of SWNTs. Gas phase oxidation is a more discrete process requiring high activation energy for diameter-selective purification. Unlike liquid phase oxidation the gas phase process preferentially oxidizes SWNTs without introducing sidewall defects. © 2003 Elsevier B.V. All rights reserved

Controlled orientation of ellipsoidal fullerene C-70 in carbon nanotubes

In single walled carbon nanotubes (SWNT), controlled orientation of ellipsoidal fullerenes C70 using density functional theory was discussed. The effect of nanotube diameter on the orientation of the ellipsoidal fullerenes was demostrated by using (10,10) nanotubes of 13.6 diameter for longitudinal orientation and (11,11) nanotubes of 14.9 diameter for transverse orientation. Raman spectroscopy and high resolution transmission electron microscopy (HRTEM) were used to examine SWNT of these diameters filled by C70 fullerenes. It was observed that all fullerenes in a given nanotube have the same transverse and longitudinal controlled orientation

Ordering and interaction of molecules encapsulated in carbon nanotubes

A clear understanding of the interactions between the building blocks of self-assembled molecular materials is essential for rational design of functional nanostructures. Intermolecular interactions have been investigated for three different classes of fullerenes in single-walled carbon nanotubes (SWNTs); van der Waals molecule - molecule and molecule - SWNT interactions control the geometry of the molecular arrays inside nanotubes; electrostatic intermolecular forces influence the alignment of polar endohedral fullerenes M@C82; and hydrogen bonding between functionalised fullerenes has a significant effect on the selectivity of insertion of functionalised fullerenes into SWNTs

Growth of InAs/GaSb strained layer superlattices by MOVPE .3. Use of UV absorption to monitor alkyl stability in the reactor

InAs/GaSb strained layer superlattices have been grown by atmospheric pressure MOVPE and the growth conditions optimised by observing, in real time, the in-situ UV absorption of the alkyls in the growth chamber. The Raman scattering of folded longitudinal acoustic phonons in the superlattices has been used as a probe of the periodicity of the superlattice. Atomic force microscopy has also been used to give information about the final surface morphology and RMS roughness of the superlattices. By combining all three techniques, optimum conditions have been found for the growth of short period InAs/GaSb superlattices. These have been used to sandwich a long period superlattice designed for transport measurements. The use of the short period superlattices eliminated additional conducting layers at each end of the semimetallic superlattice and produced structures where the hole and electron densities are equal. Such structures exhibit a dramatic new quantum transport effect where the Hall resistance goes to zero at high pressures and low temperatures