Nanotubes are hot, and might be made to act like tiny filamentary light
bulbs, a nanometric equivalent of the carbon filament light sources
of a hundred years ago.
A group of physicists at the University of Claude Bernard in Lyon,
France sends currents through carbon nanotubes. The electrons, when
they arrive at the end of the tube will, if the voltage is high enough,
fly forward toward an anode. Such a "field emission" (FE)
effect could someday be a component in flat-panel displays.
In the meantime, the researchers have observed a number of interesting
and useful properties. The nanotubes can be thought of as nanometric
filaments, emitting, in this case, electrons, light, and heat. From
the spectrum of the emitted electrons, they have deduced the temperature
at the end of the nanotube, the first time this has been done.
They are also the first to measure simultaneously the electrical resistance
of the nanotube (by way of the field emissions process) and find it
to obey Ohm's law. The heating of the nanotube as current flows through
it is therefore simply Joule heating. Above a temperature of about 1500
K, the nanotube emits light.
Stephen Purcell (firstname.lastname@example.org) and his colleagues from
the FE group of Prof. Vu Thien suggest that the emitted light is an
example of incandescence and not fluorescence. Owing to the very tiny
size of nanotubes (only nm wide) and because of this newfound control
over heating, nanotubes might be ideal spot sources of heat, light,
et al., Physical Review Letters, 11 March 2002.)