A novel methane sensor based on porous SnO2 nanorods: room temperature to high temperature detection.

We report for the first time a novel room temperature methane (CH(4)) sensor fabricated using porous tin oxide (SnO(2)) nanorods as the sensing material. The porous SnO(2) nanorods were synthesized by using multiwall carbon nanotubes (MWCNTs) as templates. Current versus time curves were obtained demonstrating the room temperature sensing capabilities of the sensor system when exposed to 0.25% CH(4) in air. The sensor also exhibited a wide temperature range for different concentrations of CH(4) (25-500 °C), making it useful in harsh environments as well.

Surface oxidation study of single wall carbon nanotubes.

Functionalization of single wall carbon nanotubes (SWCNTs) is desirable to enhance their ability to be incorporated into polymers and enhance their bonding with the matrix. One approach to carbon nanotube functionalization is by oxidation via a strong oxidizing agent or refluxing in strong acids. However, this approach can damage the nanotubes, leading to the introduction of defects and/or shorter nanotubes. Such damage can adversely affect the mechanical, thermal, and electrical properties. A more benign approach to nanotube functionalization has been developed involving photo-oxidation. Chemical analysis by XPS revealed that the oxygen content of the photo-oxidized SWCNTs was 11.3 at.% compared to 6.7 at.% for SWCNTs oxidized by acid treatment. The photo-oxidized SWCNTs produced by this method can be used directly in various polymer matrices or can be further modified by additional chemical reactions.

Field Emission and Radial Distribution Function Studies of Fractal-like Amorphous Carbon Nanotips.

The short-range order of individual fractal-like amorphous carbon nanotips was investigated by means of energy-filtered electron diffraction in a transmission electron microscope (TEM). The nanostructures were grown in porous silicon substrates in situ within the TEM by the electron beam-induced deposition method. The structure factor S(k) and the reduced radial distribution function G(r) were calculated. From these calculations a bond angle of 124 degrees was obtained which suggests a distorted graphitic structure. Field emission was obtained from individual nanostructures using two micromanipulators with sub-nanometer positioning resolution. A theoretical three-stage model that accounts for the geometry of the nanostructures provides a value for the field enhancement factor close to the one obtained experimentally from the Fowler-Nordheim law.