Biomedical Engineering Reference
In-Depth Information
of several tens of nanometers. They appear coated by CdA host matrix
and randomly distributed in tangled nets of nanotubular chains
densely aggregated. The sensing characteristics for acoustic devices
indicated that sensitivity to polar and nonpolar tested VOCs of the
SWCNT-CdA composite increased with the SWCNT filler content.
. [180] demonstrated that HiPco SWCNTs-CdA
nanocomposite was deposited onto a distal end of an optical fiber
for optochemical detection of VOCs at room temperature. Different
xylene and ethanol sensitivities have been measured for pure HiPco
SWCNTs and CdA/SWCNT-based fiber probes with the higher
sensitivities of the nanocomposite-based sensor being attributed
to its higher refractive index. In addition, the different response
dynamics observed on xylene and ethanol exposure has been
ascribed to the different chemophysical properties of the analytes
under test, such as the higher volatility (lower boiling point) and/or
the higher polarity (higher dipole moment) of the alcohol against
the aromatic hydrocarbon.
Cusano
et al
. [181] developed novel multifunctional chemical sensors
based on vertically aligned MWCNTs and polymer composites. The
sensors were fabricated by partially coating perpendicularly aligned
MWCNTs with polymers, such as poly(vinyl acetate), polyisoprene,
and then sputtering with gold electrodes. Rapid and reversible
sensing of high concentrations of a variety of volatile organic
solvents was demonstrated. The sensing mechanism was attributed
to the charge transfer interaction with gas molecules and/or the
intertube distance change induced by polymer swelling during gas
adsorption.
Wei
et al
9.4.3
Purified CNTs
The CNTs are usually grown by different synthesis techniques
(laser ablation, arc discharge, CVD, pyrolysis), as reported in
the Section 1.3, forming tangled nets of nanotubules or mats of
aggregated nanochains or bundles of roped nanocylinders, or
individual nanotubes. Most approaches in general produce raw
powders containing not only nanostructured material as CNTs
but also other carbonaceous particles such as amorphous carbon,
fullerenes, nanocrystalline graphites, and transition metals (Fe, Ni,
Co) that were used as catalysts for the growth. This non-nanotube
