Defective carbon nanotubes for single-molecule sensing

The sensing ability of metallic carbon nanotubes toward various gas species (NO2, NH3, CO, H2O, and CO2) is investigated via ab initio calculations and Nonequilibrium Green's Functions technique, focusing on the salient features of the interaction between molecules and oxygenated-defective tubes. As the adsorption/desorption of molecules induces modulations on the electrical conductivity of the tube, the computation of the electron quantum conductance can be used to predict gas detection. Indeed, the analysis of the conductance curve in a small energy range around the Fermi energy reveal that oxygenated-defective nanotubes are sensitive to NO2, NH3, CO, and H2O, but not to CO2. Molecular selectivity can also be provided by the nature of the charge transfer.