Biomedical Engineering Reference
In-Depth Information
Figure 9.15
(a) Schematic diagram of the chemically modified carbon
nanotubes, which have COOH groups attached along the
sidewall of the MWCNTs. (b) The proposed mechanism for
alcohol vapor detection using f-CNT-sensors. The COOH
groups tend to form hydrogen bonding with the ethanol
molecules at room temperature. This figure is adapted as
referenced by Sin
et. al
. [172].
[173, 174] developed SWCNTs with
covalently attached functional groups of poly
In addition, Bekyarova
et al.
-aminobenzene
sulfonic acid (PABS) to sidewalls exhibiting improved sensor
performance for NH
m
detection. SWCNTs produced by arc discharge
(P2-SWNT) were dispersed in DMF by sonication to obtain
dispersions of 0.2 mg/ml. SWNT-PABS (1 mg/ml) with attached
functional groups were produced by Carbon Solution Inc. and
prepared by sonication. Both dispersions were deposited on an
array of gold interdigitated (IDE), with a gap between the fingers of
~
3
µ
m. The deposition was performed by spraying the dispersions
with air brush in several steps until the desired resistance ranging
from 0.2 to 20 k
80
Ω
was obtained. Figure 9.16 shows the sensor device,
the typical responses toward NH
, the comparison of the ammonia
response exhibited by the different SWCNTs, with and without PABS
functional groups attached to sidewalls, and the scheme of the
interaction of SWNT-PABS with NH
3
. Compared to purified SWNTs,
devices fabricated with SWNT-PABS have shown more than two
times higher change of resistance upon NH
3
exposure. Importantly,
the SWNT-PABS sensors rapidly recover their resistance when NH
3
is
3
replaced with nitrogen. Exposure to NH
induces significant changes
in the electronic structure of the SWNT-PABS, which allow detection
of ammonia at concentrations as low as 5 ppm. Thin film deposited
3
