Singled-walled carbon nanotubes are graphene sheets wrapped into tubes, and
are typically made up of various sizes and with different amounts of twist (also
known as chiralities). Each type of nanotube has its own electronic and optical
properties. Physicists at Osaka University in Japan used colored light to selectively
manipulate different types of carbon nanotubes. They found that some of nanotubes
displayed a tendency to cluster at the focal area of a focused laser beam.
Nanotubes are known for their strong color-dependant interactions with light.
By using an optical tweezer, a device that traps microscopic or nanoscopic objects
in laser beams, researchers were able to selectively pull only specific colors
of nanotube into focus.
Their results are the first experimental evidence demonstrating that colored
light drives the clustering of nanotubes in a laser tweezer. Moreover, this
color dependence can be exploited to select one type of nanotube over another.
The study is a significant step towards developing optical methods for sorting
and purification of nanotubes, a process that remains a major challenge for
the application of nanotubes to engineering.
Source: Tweezers Trap Nanotubes by Color
T. Rodgers, S. Shoji, Z. Sekkat and S. Satoshi Kawata
Physical Review Letters
http://link.aps.org/abstract/PRL/v101/e127402
Posted September 26th, 2008
