Polymer structure and solvent effects on the selective dispersion of single-walled carbon nanotubes.

Combinations of different aromatic polymers and organic solvents have been studied as dispersing agents for preparing single-walled carbon nanotubes solutions, using optical absorbance, photoluminescence-excitation mapping, computer modeling, and electron microscopic imaging to characterize the solutions. Both the polymer structure and solvent used strongly influence the dispersion of the nanotubes, leading in some cases to very high selectivity in terms of diameter and chiral angle. The highest selectivities are observed using toluene with the rigid polymers PFO-BT and PFO to suspend isolated nanotubes. The specific nanotube species selected are also dependent on the solvent used and can be adjusted by the use of THF or xylene. Where the structure has more flexible conformations, the polymers are shown to be less selective but show an enhanced overall solubilization of nanotube material. When chloroform is used as the solvent, there is a large increase in the overall solubilization, but the nanotubes are suspended as bundles rather than as isolated tubes which leads to a quenching of their photoluminescence.

Direct spectroscopic evidence of energy transfer from photo-excited semiconducting polymers to single-walled carbon nanotubes.

Single-walled carbon nanotubes have been efficiently dispersed in an organic solvent using the semiconducting polymers MEHPPV and PFO. It has been found that energy is transferred to the carbon nanotubes when the polymer is photo-excited across its minimum energy gap. This is shown using photoluminescence excitation mapping in the range of both the polymer's and the nanotube's optical absorbance. Possible mechanisms for the energy transfer are discussed.

Highly selective dispersion of single-walled carbon nanotubes using aromatic polymers.

Solubilizing and purifying carbon nanotubes remains one of the foremost technological hurdles in their investigation and application. We report a dramatic improvement in the preparation of single-walled carbon nanotube solutions based on the ability of specific aromatic polymers to efficiently disperse certain nanotube species with a high degree of selectivity. Evidence of this is provided by optical absorbance and photoluminescence excitation spectra, which show suspensions corresponding to up to approximately 60% relative concentration of a single species of isolated nanotubes with fluorescence quantum yields of up to 1.5%. Different polymers show the ability to discriminate between nanotube species in terms of either diameter or chiral angle. Modelling suggests that rigid-backbone polymers form ordered molecular structures surrounding the nanotubes with n-fold symmetry determined by the tube diameter.

Right ventricular disarticulation. An 18-year single centre experience.

OBJECTIVE: Right ventricular disarticulation (RVD) is an accepted procedure in the treatment of ventricular tachycardia of right ventricular origin. We set out to review the long-term outcomes with RVD at our institution for patients with arrhythmogenic right ventricular dysplasia (ARVD) or refractory tachycardia. A renewed interest in this operation has come about in patients unable to tolerate implantable cardioverter defibrillators. METHODS: Seventeen patients had RVD carried out between 1985 and 2003. There were 15 males and 2 females. The age range was 14-72 (median: 34). Six patients had partial RVD and 11 a complete RVD. ARVD was confirmed in 15 patients at histology. Biventricular pacing was used post-operatively in the two most recent patients. RESULTS: The follow-up was complete in 94% (16/17). The median follow-up was 13 years (0-18). The overall hospital mortality was 6% (1/17). Over the follow-up period there were three deaths 9, 11 and 17 years post-surgery. Heart transplantation due to biventricular failure was required in two patients. In the group followed up for more than 10 years the over all event free survival at 10 years was 77% (3/13). CONCLUSIONS: In cases of refractory ventricular tachycardia, where multiple antiarrhythmic medication, repeated catheter ablation and ICD insertion are unsuccessful at symptom control, RVD is an excellent antiarrhythmic procedure. In the long term, signs of biventricular failure present, possibly, dependent on the natural history of ARVD. The long-term effect of biventricular pacing on the disarticulated right ventricle is yet to be defined.

Computer aided design of nano-structured materials with tailored ionic conductivities.

We show, using simulation techniques, that the high ionic conductivity in BaF2/CaF2 heterolayers is because the interfaces reduce the activation energy barriers to mobility and increase the number of charge carriers.

Synthesis, structure and ionic conductivity in nanopolycrystalline BaF2/CaF2 heterolayers.

Atomistic simulations have shown that the calculated conductivity of nano-polycrystalline BaF2/CaF2 heterolayers is considerably higher than the component bulk materials and we predict that grain-boundary diffusion is the key to fast ionic conductivity in these systems.