Functionalization of SingleWalled Carbon Nanotubes with DNA

1
Functionalization of Single-Walled Carbon
Nanotubes with DNA Patrick Gasda, Mark
Ellison Ursinus College, Department of Chemistry
Nanotube Applications
Carbon nanotubes were discovered in 1991 by
Japanese researchers looking for applications of
C60 (bucky balls). Ever since, many applications
of nanotubes have been either discovered or
proposed (see right). Nanotubes are graphite
sheets that are rolled into a tube in three
different configurations armchair, zigzag, and
chiral (see figure), each of which have slightly
different conductivities. They are rolled up
using different techniques such as laser ablation
or high pressure CO (HiPCO) that use metal
catalysts. The nanotubes we use are HiPCO, and
we purify them by forcing hot and moist air over
them. When nanotubes are synthesized, they
arrive as a bundle of fibers called ropes.
Nanotubes are so small that they cannot be
manipulated by machines (average diameter is 2 nm
and lengths on the order of 500 nm) so the best
way to free up the ropes is to add functional
groups. Adding functional groups increases the
nanotube reactivity, solubility or conductivity.4
There are a number of methods to use such as
radical chemistry. We use a covalent
functionalization using a diazonium reaction. We
want to eventually attach nanotubes to DNA. DNA
is a well characterized molecule that would allow
the product to be applied to make nano circuits
or nanoparticle arrays. DNA also has some
interesting properties that let it selectively,
strongly, and reversibly link to other molecules
or surfaces.

• Super-strong/ultra-light materials
• The C-C bond is one of the strongest bonds. For
  its weight, nanotubes are much stronger than
  steel and would have applications in advanced
  carbon fiber materials or nanotube cables.
• Nano-sized electronic systems such as circuits or
  transistors
• Nanotubes are electron rich and can be conductors
  or semiconductors depending on their structure.
  The conductivity also changes depending on what
  functional groups are on the nanotubes.
• Bio-transport systems
• Nanotubes are mostly impervious to the
  environment inside the human body so they would
  be ideal for the transport of drugs to specific
  targets in the body.
• Quantum dot arrays
• Quantum dots are small metal particles that can
  be used in LEDs, and when arranged in a lattice,
  their fluorescence increases. Nanotubes could
  possibly be the structure for these lattices.

Introduction
Results
4-Step Reaction Scheme
Interpretations

• The IR spectrum of the product has peaks
  associated with the absorptions of nitro groups.
  The peaks for amino groups are absent.
• UV/Vis The small absorptions for A are the
  various transitions of the surface orbitals.
  Since this is not present for B, the surface has
  somehow been changed.
• Agrees with literature data so we can assume that
  we obtained a similar product

• Other results
• Increased solubility in DMF
• Color change

SMCC contains aliphatic and aromatic carbons as
well as carbonyl groups. The spectrum to the
left has peaks that indicate that the
cross-linker is present.
Reduction data agrees with literature results and
all subsequent reductions resulted in a
flat-lined graph. Therefore, the reduction was
carried out successfully.
Conclusions

• We have successfully purified Nanotubes using
  warm, moist air (Step 1).
• We have successfully functionalized the
  nanotubes with p-nitroaniline (Step 2).
• We reduced the nitro group to an amino group and
  attached the SMCC cross-linker (Step 3 and 4a).

References and Acknowledgements
1) Baker, S. E. et al. Nano Letters 2002, 2,
1413. 2) Bahr, J. L. et al. J. Am. Chem. Soc.
2001, 123, 6536. 3) Dyke, C. A. and Tour, J. M.
J. Am. Chem. Soc., 2003, 125, 1156. 4) Lee, C.-S.
et al. Nano Letters, 2004, 4, 1713. 5) White, C.
T. and Mintmire, J. W. J. Phys. Chem., 2005, 109,
52. Ursinus College and The American Chemical
Society Petroleum Research Fund Special Thanks
Steve Morris, the UC Chemistry Department