Biomedical Engineering Reference
In-Depth Information
80.0
60.0
I
o
/
A
40.0
20.0
0
20.0
40.0
I
o
/
A
60.0
80.0
100.0
0.80
0.60
0.40 0.20
E/V vs SCE
0
0.20
0.40
FIGURE 15.3
Cyclic voltammetric curve of 5 mM dopamine in PBS (pH 7.4) at a CNT electrode at
20 mV s
1
. (Reprinted with permission from [16]. Copyright (1996) Elsevier.)
The aligned CNT-modifi ed electrode has added advantages to electrodes modifi ed with
a random tangle of CNTs (normally formed by drop coating) and CNT-composite elec-
trodes. For the preparation of this type of electrode, CNTs are vertically assembled on
the substrate surface; proteins and other electroactive species are then attached to the
end tip of the CNTs. The vertically aligned CNT-modifi ed electrode is helpful for under-
standing the electron transfer mechanism since proteins or other electroactive species
attached to the CNTs through a known and defi nite way (at the end tip). While in other
types of CNT-based electrodes, the electroactive species can either be attached to the
end tip or to the side wall which yields an unknown spatial geometry. Second, the verti-
cally aligned CNTs serve as molecular wires that facilitate the electron transfer between
the electrodes and redox centers of enzymes without the mediator. This feature simpli-
fi es the fabrication of electrochemical sensors using redox enzymes as sensing agents.
Third, vertically aligned CNTs can be used to make nano-electrode arrays.
Vertically aligned CNTs can be obtained through guided growth (physical method)
or self-assembly of modifi ed CNTs on certain substrates. In the fi rst case, CNTs are
synthesized in a controlled manner. One approach to achieve guided growth of CNTs
is by using a porous template (such as mesoporous silica, alumina nanoholes) in the
CVD method. For example, Li
et al.
[43] report the large-scale CVD growth of aligned
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