Journal of Sensors / 2009 / Article / Tab 1 / Review Article
Conductometric Gas Nanosensors Table 1 CNT-based nanosensor properties and performances. Sensors generally operate at RT. In several cases some sort of conditioning process is used for improving device characteristics. Recovery is obtained with quite empirical approaches.
Material Chemical species detected (carrier) Range Recovery Conditioning notes Ref. SWCNT NO2 (N2 ) 10s to 100s ppb Yes, slow, better with UV light No [32 ] Nitrotol. (N2 ) SWCNT (Pd charged) CH4 (air) 10–100 ppm Yes, slow, better with UV light Yes Operated at 40°C [33 ] CNT CH4 (vacuum) 0.01–12 mbar No No [34 ] O2 (vacuum) SWCNT NO2 50 ppb Not Available (NA) No Carrier data NA [35 ] MWCNT NO2 (dry air) 100 ppb Yes, slow No Operated at
[36 ] NH3 (dry air) 5 ppm SWCNT NO2 ; NH3 in Ar diluited in air 100 ppt Yes with UV light No Selectivity obtained with polymer coating [37 ] 100 ppm Commercial SWCNT NH3 (N2 ) 30% in aqueous solution Yes with electrostatic perturbation Yes Sensitivity depends on gate voltage. NH3 reduces the conductivity; NOx induces an opposite effect [38 ] NOx (N2 ) 13.5 ppm PANI-SWCNT network NH3 50 ppbv Yes, with argon Yes At room temperature sensor response is completely reversible [39 ] SWCNT NH3 (N2 ) 5 ppm Yes, increasing the carrier flow or heating during the desorption Yes Annealing pretreatment increased the sensor sensitivity. Sensitivity diminished when NH3 concentration reached 40 ppm [40 ] MWCNT (SnO2 particles coated) LPG 100–1000 ppm Yes (few seconds) Yes Working temperature 325°C. Sensor response is linear with gas concentrations [41 ] C2 H5 OH in 50% RH 10–200 ppm MWCNT (thiol funct.) CH3 OH C2 H5 OH 1 ppm NA NA Resonant freq. Shift. Freq. response is due to the binding between Thiol group and ionic hydrocarbon [42 ] C3 H7 OH C4 H9 OH (DI water) SWCNT NO2 3–10 ppm No NA Dispersion of SWCNT powder into dimethylformamide [44 ] Commercial SWCNT H2 (air) 0.05–1% Yes No Pd-functionalized [45 ] Commercial SWCNT alcohol 1–21 ppm Yes No Recovery by current injection [46 ] Commercial SWCNT NH3 and H2 0.01–1000 ppm NA NA Composite with conducting polymers [47 ]
