Biomedical Engineering Reference
In-Depth Information
(a)
O
O
O
SWCNT
SWCNT
O
DCC
C
C
+
NH
2
(CH
2
)
2
SH
C
C
OH
HO
SH(CH
2
)
2
NH
NH(CH
2
)
2
SH
(b)
SWCNT
C
C
NH
O
O
NH
CH
2
CH
2
CH
2
CH
2
S
S
SWCNT
SWCNT
O
C
+
OH
Au(111)
Au(111)
FIGURE 14.6
(a) Scheme for the thiolization reaction of ca rboxyl-ter m inated cysteam ine (NH
2
CH
2
-
CH
2
SH)
and (b) schematic diagram of the assembling structure of SW CNTs on gold. (From Liu, Z.F, Shen, Z.Y., Zhu,
T., Hou, S.F., Ying, L.Z., Shi, Z.J., and Gu, Z.N.,
Langmuir
, 16, 3569, 2000. With permission.)
pipes and thiol derivatized at the open ends. The ordered assembly of SWCNTs was made by spon-
taneous chemical adsorption to gold through Au-S bonds. Tapping mode atomic force micros-
copy (AFM) images clearly show that the nanotubes have been organized on gold, forming a
self-assembled (SA) monolayer structure with a perpendicular orientation. This kind of chemical
manipulation has great versatility and is not limited to the present system. One can design the
terminal functionality of nanotubes and assemble them on various substrates by a predesigned
bonding nature.
An alternative to self-assembling aligned nanotubes on an electrode surface is to grow aligned
nanotubes directly on to an electrode surface. Sotiropoulou and Chaniotakis [186] performed it
using the CVD method on a platinum electrode.
14.2.1.1.3 Attaching Individual or Microbundles of MWCNTs to the End of Wires
Nugent et al. [187] used arc-derived MWCNT microbundles to fabricate electrodes. The bundle
that forms on the electrode during the electric arc discharge is broken open, and a microbundle of
nanotubes is picked out and attached to the end of a copper electrode wire using a conductive silver
paint. The electrodes show Nernstien behavior and fast electron-transfer kinetics for electrochemi-
cal reactions of Fe(CN)
3
−
/4
−
.
Boo et al. reported of an interesting needle-type nanobiosensor based on individual MWCNT
[188]. The nanoneedles were fabricated by attaching a MWCNT to an etched tungsten tip using a
nanomanipulator in a high-vacuum chamber. This attachment process was carried out in a fi eld
emission scanning electron microscope (JEOL, JSM-6700F) equipped with two piezoelectric
nanomanipulator [189]. The nanoelectrodes can serve analytical functions as reliable as electro-
chemical nanosensors to detect electroactive species.
