Biomedical Engineering Reference
In-Depth Information
[54]. Hence, we may find that our relamination process, and the
accompanying cascades indicative of the sp
2
2 +
x
2 +
x
to sp
and sp
to
3
sp
transitions, may also depend on temperature, and may alter in
the presence of excess induced charge.
(a)
(b)
Figure 7.6
(a) The “pyramid configuration” for the adsorption of gas atoms
or molecules the carbon nanotubes (consistent with Figs. 7.3
and 7.4 at 25%), and (b) the “ring configuration” for the
adsorption of gas atoms or molecules on the hexagonal lattice
of the carbon nanotubes. These configurations are denoted as
3(P) and 3(R), respectively. Reproduced with permission from
Ref. [5]. Copyright American Chemical Society, 2005.
7.2.2
Adsorption and Rehybridization on Carbon
Nanotubes
Based on these results for the relamination of a graphene layer
over a diamond surface, one may be forgiven for expecting that
the continuous, random impingement of atomic hydrogen on
CNTs may eventually give rise to hollow sp
2 +
x
3
-bonded
tubular hydrocarbons, which have never been observed. However,
depending on the environment or the application, continuous
random impingement is rather unlikely. Exposure of CNTs to
gases usually results in sporadic adsorption and/or more ordered
adsorption configurations. Indeed, this is the premise behind some
CNT-based gas sensor devices, which provide predictable responses
to interactions with particular (individual) gaseous species.
As mentioned briefly above, the individual adsorption of gases
on the outer walls of CNTs introduce defects, that have been shown
to promote the nucleation (and subsequent growth) of diamond
nanoparticles by hydrogen plasma treatment [35, 37]. These
or sp
