A wireless, passive carbon nanotube-based gas sensor

摘要

A gas sensor, comprised of a gas-responsive multiwall carbonnnanotube (MWNT)-silicon dioxide (SiO2) composite layerndeposited on a planar inductor-capacitor resonant circuit is presentednhere for the monitoring of carbon dioxide (CO2), oxygen (On2), and ammonia (NH3). The absorption of differentngases in the MWNT-SiO2 layer changes the permittivity andnconductivity of the material and consequently alters the resonantnfrequency of the sensor. By tracking the frequency spectrum of thensensor with a loop antenna, humidity, temperature, as well as CO2n, O2 and NH3 concentrations can bendetermined, enabling applications such as remotely monitoring conditionsninside opaque, sealed containers. Experimental results show the sensornresponse to CO2 and O2 is both linear andnreversible. Both irreversible and reversible responses are observed innresponse to NH3, indicating both physisorption andnchemisorption of NH3 by the carbon nanotubes. A sensor array,ncomprised of an uncoated, SiO2 coated, and MWNT-SiO2n coated sensor, enables CO2 measurement to benautomatically calibrated for operation in a variable humidity andntemperature environment