Particular attention will be focused on efficient self-assembly pyrolytic routes to large arrays (<2.5 cm2) of aligned C, CNx and BxCyNz nanotubes (15-80 nm od and < 100 microns length). In general, these 'hollow' fibres do not easily break upon bending and may behave as shock absorbing fillers in the fabrication of robust composites. The electronic and field emission properties, as well as the density of states (DOS) of CNx and BCx nanotubes using scanning tunneling spectroscopy (STS) will be presented. We further demonstrate that the presence of N and B are responsible for introducing donor and acceptor states near the Fermi Level. Novel applications of these doped materials will also be discussed. Finally, it will be shown that high electron irradiation during annealing at 700 - 800 °C, is capable of coalescing and joining single-walled nanotubes (SWNTs). Vacancies induce the merge via a zipper-like mechanism, imposing a continuous reorganization of atoms on individual tube lattices within the adjacent tubes. Other topological defects induce the polymerization of tubes and creation of 'Y', 'T' and 'X' nanotube junctions. The latter results pave the way to the fabrication of nanotube contacts, nanocircuits and strong 3D composites using irradiation doses under annealing conditions.
Controlling carrier transport in light emitting polymers is a crucial factor for their efficient use in any organic opto-electronic device. In this work, we demonstrate a novel method of utilizing the interactions between single wall carbon nanotubes (SWNTs) and conjugated polymers to modify the overall mobility of charge carriers within nanotube- polymer nanocomposites. Using a unique, double emitting- organic light emitting diode (DE-OLED) structure, we characterize the hole transport within electroluminescent nanocomposites (nanotubs in poly (m-phenylene vinylene-co- 2,5-dioctoxy-p-phenylene) (PmPV)) and show that devices with chromic tunability can be achieved. This leads naturally to a model for hole transport in SWNT - PmPV blends that provides fundamental insights into the formation of discrete hole traps and the modification to hole mobility. Perhaps more importantly however, these results are suggestive of the significant role that SWNT nanocomposites can play in future organic-based photonic systems such as fully organic optical amplifiers, transistors, and color displays.
Organic - Inorganic matrix nano composites have been created using an acid catalyzed, tetraethyl orthosilicate-based sol- gel technique with SWNTs. By utilizing nanotubes functionalized with the dendron methyl 3,5- di(methyltrigycoloxy)benzylic alcohol, ultrasonication blending in the sol phase prior to gelation yields excellent dispersion characteristics of the nanotube phase. Further, glasses could easily be dried by heating to 600 degrees C yielding 80 percent of theoretical density wit little change in the nanotube content. These materials exhibited intrinsic Rayleigh scattering, suggesting near ideal dispersion. Nonlinear optical transmissivity was observed for 1064 and 532 nm light suggesting that the matrix has a strong broad band coupling to the optical field. Such composites allow for a host of applications based on the novel confinement properties of carbon nanotubes in a robust host.