Biomedical Engineering Reference
In-Depth Information
14.12
Radical addition yielding functional groups (-CH
3
, -CN, -OH,
-NH
2
,...)covalently attached to CNT sidewall (Bystrzejewski
et al.
, 2009).
resulting in diminution of their diameter with destruction of the outer wall,
the forming of onion-like structures, or even their complete destruction.
Plasma post-discharge treatment of carbon nanotubes
To prevent the unwanted effects of plasma functionalization, a solution was
proposed by Ruelle et al. (2007). These authors proposed avoiding the
functionalization of CNTs directly inside the plasma where the density of
high energy ions is very high, and instead, placing the CNTs outside the
discharge production zone to reduce the detrimental effects associated with
ion bombardment and irradiation. In this approach, radicals are the most
important reactive species to graft functional groups onto the CNT surface.
In this case, the application of microwave discharge sources for the
production of intense beams of atomic, radical and metastable species is well
established. For example, carbon nanotubes have been hydrogenated by
atomic hydrogen generated in a H
2
microwave plasma (Wu et al., 2007). In
this type of functionalization, the exact location of the sample and its
distance from the plasma discharge zone become a key factor in determining
