Theoretical study on detection of harmful molecules for designing carbon-nanotube-based sensors

We present the electronic transport of pyridine-type and pyrrole-type nitrogen-doped semiconducting carbon nanotubes (N-doped CNTs) and the adsorption effects of harmful molecules on transport properties of periodically aligned N-doped CNTs based on our first-principles quantum transport study. By using the N-doped CNTs with not a single defect but periodically aligned defects, harmful molecules (CO, NO and NO${}_2$) are found to be selectively detectable in air by measuring the variation of the conductance without any applied bias voltages. Therefore, the pyridine-type and the pyrrole-type N-doped CNTs are found to be useful materials for designing low-power sensors. Moreover, we also discuss how the dopant-defect density affects the transport properties. It is revealed that the pyridine-type and pyrrole-type N-doped CNTs could act as a highly sensitive quantum sensor material to detect even a single molecule.