First principles study of titanium-coated carbon nanotubes as sensors for carbon monoxide molecules

In this work, the electronic properties of the system composed by the CO molecules adsorbed on Ti-coated single-wall carbon nanotubes (SWNTs) are studied through first principles calculations. The changes in the electronic properties of the interaction of the CO molecules with a linear Ti wire covering an (8, 0) semiconductor SWNT are analyzed for different CO concentrations. A strong interaction between CO molecules and the SWCT/Ti system is observed, which decreases when the concentration of CO molecules increases. The resulting system are shown to be very sensitive to the CO concentration adsorbed on the tube/Ti system, making that the SWNT, which is originally semiconductor and becomes metallic after Ti covering, to recover the semiconductor behavior again when enough high concentrations of CO molecules is adsorbed on the SWNT/Ti system. These three distinct steps (semiconductor/metallic/semiconductor) constitute the basis for a feasible, flexible and efficient sensor device for CO molecule recognition.