Iron oxide and oxygen plasma functionalized multi-walled carbon nanotubes for the discrimination of volatile organic compounds

Oxygen plasma functionalized multiwall carbon nanotubes and iron oxide decorated multiwall carbon nanotubes are studied for detecting volatile organic compounds (VOCs) at room temperature. Alumina substrates with interdigitated gold electrodes are employed as transducers and the air-brushing method is used to coat them with a thin film of the differently treated carbon nanotube samples. The electrical characterization of the sensors in the presence of benzene, toluene, acetone, methanol and ethanol vapors is carried out. The different treatments allow for tuning the response of carbon nanotubes and it is found that combining the responses of two sensors (i.e., one decorated with iron oxide and the other treated in an oxygen plasma) enables discriminating the aromatic hydrocarbons from the other VOCs tested. Additionally, discriminating benzene from toluene also appears to be possible. Sensors as the ones presented here, which are operated at room temperature, may led to a new generation of affordable, mass produced portable/wearable detectors with important applications in the selective detection of benzene.