Functionalization of Carbon Nanotubes
The carbon atoms in nanotubes are great at forming covalent bonds
with many other types of atoms for several reasons:
- Carbon atoms have a natural capacity to form covalent bonds with
many other elements because of a property called electronegativity.
Electronegativity is a measure of how strongly an atom holds onto
electrons orbiting about it. The electronegativity of carbon (2.5)
is about in the middle of the range of electronegativity of various
substances from potassium (0.8) to fluorine (4). Because carbon has
an electronegativity in the middle of the range, it can form stable
covalent bonds with a large number of elements.
- All the carbon atoms in nanotubes are on the surface of the
nanotube and therefore accessible to other atoms.
- The carbon atoms in nanotubes are bonded to only three other
atoms, so they have the capability to bond to a fourth atom.
These factors make it relatively easy to covalently bond a variety of
atoms or molecules to nanotubes, which changes the chemical properties
of the nanotube. (This method is called functionalization).
Taking this bonding thing further, if the molecules attached to the
carbon nanotubes also attach to carbon fibers, the functionalized carbon
nanotubes can bond to the fibers in a composite, producing a stronger
Excerpted from Nanotechnology For Dummies (2nd edition), from Wiley Publishing