Biomedical Engineering Reference
In-Depth Information
gas concentrations were measured from 2 ppb to 5 ppm. A detection
limit was measured as 5 ppb NO at a relative humidity of 30%. Cross-
sensitivity to CO
was measured as well, modeling human
breath conditions. Compared to chemiluminescence methods for
monitoring NO, this sensor offers the advantages of low cost, compact
size, and simplicity for self-diagnostics and home care, as claimed by
the authors.
and O
2
2
. [273] demonstrated the improvement of CNTFET
performances by chemical tuning of the nanotube/substrate and
nanotube/electrode interfaces. This method is based on a selective
placement of individual SWNTs by patterned aminosilane monolayer
and its use for the fabrication of self-assembled nanotube transistors.
This method brings a relevant solution to the problem of systematic
connection of self-organized nanotubes. The aminosilane monolayer
reactivity can be used to improve carrier injection and doping
level of the SWNT as well. The authors showed that the Schottky
barrier height at the nanotube/metal interface can be diminished
in a continuous fashion down to an almost ohmic contact through
these chemical treatments. Moreover, sensitivity toward 20 ppb of
triethylamine was demonstrated for self-assembled CNTFETs, thus
opening new prospects for gas sensors taking advantages of the
chemical functionality of the aminosilane used for assembling the
CNTFETs.
Auvray
et al
. [278] demonstrated electrically refreshable CNT-
based gas sensors with a FET structure. They found that the sensors
can be refreshed by applying a negative gate voltage pulse in NO
Chang
et al
2
gas and a positive gate voltage pulse in NH
gas. Furthermore, the
temporal response of the conductance to the gate voltage pulse was
observed to be dependent on the gas species, but independent of gas
concentration. These results, as claimed by the authors, showed the
possibility of distinguishing gas species using CNTFET sensors.
3
. [211] demonstrated a new, versatile class of nanoscale
chemical sensors based on single-stranded DNA (ss-DNA) as the
chemical recognition site and single-walled carbon nanotube field
effect transistors (swCN-FETs) as the electronic read-out component.
swCN-FETs with a nanoscale coating of ss-DNA respond to gas odors
that do not cause a detectable conductivity change in bare devices.
Responses of ss-DNA/swCNFETs differ in sign and magnitude for
different gases and can be tuned by choosing the base sequence of the
ss-DNA. ss-DNA/swCN-FET sensors detected a variety of odors (e.g.,
propionic acid, trimethylamine, methanol, dinitrotoluene, dymethyl
Staii
et al
