Putting a Wrapper on Nanotubes Increases Luminescence

A University of Connecticut team from the school’s Nanomaterials Optoelectronics
Laboratory at the Institute of Materials Science has discovered a nifty
way to increase the photoluminescence of single-walled carbon nanotubes
by wrapping the tubes with a sleeve made from a Vitamin B₂
analog. The wrapping prevents defects caused by oxygen and renders them
much more useful for nanotech applications. Their research is published
in a recent edition of Science.

The problem they are addressing has to do with SWNTs and their
tendency to be poor emitters of light because of spotty, “bumpy”
1,4-endoperoxide defects on the surface of nanotubes longer than 94 nm.

The group, led by Fotios Papadimitrakopoulos,
is using a helical wrap of a flavin mononucleotide to “smooth” the SWNT
surface and increase photoluminescence efficiency as high as 20
percent, a 40-fold increase.

The luminescence property is aroused in SWNTs when they are
subjected to infrared irradiation or electrical excitation. On the
applications side, researchers are hopeful because nanotube emissions
are extremely sharp and are in a spectral region where little
absorption or scattering takes place by soft tissue. For example, a
patient could be injected with wrapped nanotubes – instead of using
X-rays or radioactive dyes – to detect internal problems. The
patient could then be passed through an infrared lightsource/scanner that would record a high-resolution image of the luminescence of the
nanotubes in problem areas.

Other apps could include near-infrared emitters (which could find
their way into medicine and homeland security as bio-reporting agents
and nano-sized beacons), nano-scaled LEDs and photo detectors.

This animation is the work of Xiao-Ming Xu, a graduate student in
the Department of Pharmaceutics under the supervision of professor
Diane Burgess.