We Have Ignition! Carbon Nanotubes Ignite When Exposed to Flash
Troy, N.Y. — Researchers at Rensselaer have discovered a
surprising new property of single-walled carbon nanotubes
(SWCN). When exposed to a conventional photographic flash, the
nanotubes emit a loud pop and then ignite.
This discovery, reported in the April 26 issue of the journal
Science, could mean that SWCNs might be used in light sensors
or to remotely trigger explosives and combustion reactions,
although researchers say that more testing needs to be done to
realize these possibilities.
Pulickel Ajayan, associate professor, and Ganapathiraman
Ramanath, assistant professor, both of materials science,
explain that the loud popping sound heard after the flash is
actually a well-known phenomenon called the photo-acoustic
effect, known since Alexander Graham Bell’s time. This
phenomenon had not previously been associated with carbon
nanotubes. It occurs when porous black objects, such as
nanotubes, absorb a large amount of light, which results in the
expansion and contraction of the gas surrounding them,
What surprised the researchers even more was the fact that the
nanotubes then spontaneously ignited and burned upon
photographic flash exposure.
“The single-walled carbon nanotube samples in this situation
were just a jumble of tubes. They were not laid out in any
pattern, and because of that, the heat generated from the flash
could not dissipate, so the nanotubes just burned,” explained
The discovery was initially noted by Andres de la Guardia
while he took flash photographs of the nanotubes. De la
Guardia, currently an international graduate student from
Panama in operations research and statistics at Rensselaer, was
a first-semester freshman at the time of the discovery. De la
Guardia’s interest in carbon nanotubes was seeded by taking
“Chemistry of Materials” classes taught by Ajayan and Ramanath,
and led to an Undergraduate Research Project, which gives
undergraduates hands-on, real-world research experience.
“I was just in the right place at the right time,” de la
Guardia admitted. “I wasn’t even a materials sciences major,
but I was interested in carbon nanotubes and was asked to join
the research team. I’m glad I had the foresight to bring my
observations to Prof. Ajayan’s attention,” he added.
Since the discovery, the researchers have conducted a variety
of experiments to test how light exposure affects the
nanotubes. They found that while the tubes burn only when
oxygen is present, their atomic structure is altered even in
inert gas environments when exposed to the flash.
“While the initial surprise is that the nanotubes will ignite
upon exposure to a camera flash, perhaps most exciting is that
fact that the nanotubes are transformed into new carbon
structures in the absence of oxygen. It is an illustration of
how new behavior is observed at the nanometer scale, which
justifies the interest in nanosciences,” commented T.W.
Ebbesen, one of the co-authors of the paper, from the
Laboratoire des Nanostructures, Université Louis Pasteur.
“To the best of our knowledge, no other material emits such a
loud sound and ignites spontaneously when exposed to unfocused
low-power light; this adds to the long list of unique
properties of carbon nanotubes,” said Ramanath. “From an
applications perspective, our work opens up exciting
possibilities of using low-power light sources to create new
forms of nanomaterials, and will serve as a starting point for
developing nanotube-based actuators and sensors that rely on
remote activation and triggering,” he added.
The research is a collaborative effort between Rensselaer, a
French group headed by T.W. Ebbesen, and researchers in Mexico
Contact: Patricia Azriel
Phone: (518) 276-6531