Molecular and Nano-Material Architectures

Single-walled Carbon Nanotube-based Materials

Carbon nanotubes are hexagonal networks of carbon atoms that are rolled up to make cylinders. The cylinder is a nanometer across but can be tens of microns long. Each tube is capped at both ends with half of a fullerene molecule.

Single-walled carbon nanotubes (SWNT) have exceptional electrical, mechanical, optical, and chemical properties that make them attractive for many applications. In collaboration with internal and external partners, we are engaged in developing molecular devices for biomedial applications and new composite materials, understanding gas adsorption inside nanotubes, and verifying whether carbon nanotubes can yield better fuel cells.

Adequate supply is central in developing these applications. Currently, we are pursuing two approaches: one is laser-based, the other, for large-scale production, is based upon chemical vapor decomposition (CVD). We have developed a unique approach to laser-based synthesis of SWNT capable of producing samples of high purity with good total yield. The upcoming installation of a new higher power carbon dioxide laser promises to improve our production rates even further. We think that this method and its derivatives can be applied to synthesize nanotubes with tailored band gap structures.

Continuous and unsupported gas phase synthesis through CVD could lead to fully scalable synthesis methods. Our method relies on the in-situ synthesis of catalytic metallic nanoparticles. The catalyst solution is sprayed in an oven at high temperatures (800-1200ºC), under an inert or reducing atmosphere. We have investigated many source designs and configurations, and have produced a variety of carbonaceous nanostructures, such as multi-walled nanotubes, nanobamboo, nanofibres, and others.

Many processes are competing in the reaction conditions, and it is crucial to control the source parameters in order to deliver a narrow distribution of the catalyst particles. We are now working to favour the production of SWNT.

Our long-term objective in the area of synthesis is to arrive at methods capable of controlling the diameters and chirality.

Hydrogen storage in SWNT has been drawing attention from the world community, but the results are very controversial. Gas uptakes ranging from 0 to 60 wt% have been reported. In collaboration with researchers from Defence Research Development Canada (Dr. S. Desilets), the Hydrogen Research Institute (Dr. R. Chahine), and the Functional Materials Program, we investigated hydrogen uptake in several SWNT samples originating from various sources. Our measurements yield uptakes of less than 1 wt% at room temperature. However, this result could be highly dependent on processing and metal doping, and we are currently investigating these effects.

We are also interested in understanding adsorption of other gases in and on SWNT. Confinement of a fluid in nanopores substantially affects its properties. SWNT are perfectly suited for this type of studies. We are investigating confinements effects using various gases.

Many of the applications listed above require developing new functionalization , purification and characterization strategies. We are engaged in developing the necessary expertise to develop these capabilities.

For more information, please contact Benoit Simard or visit
Benoit Simard's personal Web site.