Role of defects on the gas sensing properties of carbon nanotubes thin films: experiment and theory

A gas sensor, fabricated by the simple casting of carbon nanotubes thin film on an interdigitated electrode, is presented for gas detection and its characteristics are analysed by means of experimental measurements and theoretical simulations. Our results show that topological defects may be responsible for the reported sensitivity of the electronic and transport properties to NO2. In particular, experimental findings show that when the nanotubes walls contain topological defects the sensor displays a high sensitivity to NO2 exposure with a poor recover of the base resistance value in absence of NO2 and the gas sensitivity measured on nanotubes may be strongly reduced by lowering the deposition temperature. Experimental results and theoretical calculations indicate that the adsorption and the uptake of the oxidizing gas are more likely to occur by the interaction between the NO2 molecule and defective sites into the hexagonal network of the nanotubes.