OVERVIEW ON THE MAJOR RESEARCH ACTIVITIES ON CARBON NANOTUBES BEING DONE IN AMERICA, EUROPE AND ASIA - Carbon Nanotubes: From Bench Chemistry to Promising Biomedical Applications - page 264

relatively low density gradient ultracentrifugation (DGU) technique and
long centrifugation times. UV-vis-NIR absorption and photoluminescence
(PL) peaks of these quasi zero-dimensional SWCNTs showed a blue shift up
to ∼ 30 meV compared with long nanotubes, owing to quantum coninement
effects along the length of ultra-short SWCNTs. On the whole, these carbon
“capsules” corresponded to SWCNT quantum dots.
9.2.3 USA
Mark HERSAM
@ Northwestern University-Illinois
Website: http://www.hersam-group.northwestern.edu/index.html
Expertise: CNT “sorting” for electronics and single-molecule
manipulation
The Hersam Research Group at Northwestern University joins materials
science and engineering, with the purpose of applying organic molecules
to inorganic substrates for a better functionality of the resulting hybrid
system. This unique combination is enabled by a successful integration of
advanced techniques and sophisticated instruments ranging from ultra-
high-vacuum (UHV) scanning tunneling microscopy (STM) to atomic force
microscopy (AFM). Research projects involve mainly fundamental studies
(e.g., single-molecule manipulation with UHV STM) and applied technology
(e.g., optimisation of CNT materials for electronic and optical devices). On
the whole, this highly interdisciplinary research group has been promoting
worldwide impact in the ields of information technology, bionanotechnology
and alternative energy.
9.2.3.1 CNT sorng
In order to achieve optimal performance in all conceivable applications,
SWCNTs need to be monodisperse in their diameter, electronic behaviour
and chiral handedness. This is because SWCNTs with extremely similar (but
not identical) diameters can show diverse chiral vectors and thus different
electronic characteristics. On the other hand, although sharing the same
chiral vectors, CNTs might differ for chiral handedness, which means that
they will interact with circularly polarised light differently. Hence, there is
the need for an effective SWCNTs sorting strategy, which should incorporate
a few crucial aspects: (i) scalability (to respond to an anticipated increase in
demand), (ii) compatibility of dimensions as raw material, (iii) durability, (iv)
reproducibility, (v) affordability. 83