Changing in Electron Properties of Carbon Nanotube on Molecular Adsorption

Abstract

As the solution to air pollution of the exhaust gas of Plants and cars, an exhaust amount of air contaminants is strictly controlled now. From the environmental criteria about air contaminants, it demands the gas sensors that can reach up to ppb(gm-3) of magnitude in detecting the gas is subject to control. In some recent works, it is shown that an electroconductivity of semiconductive carbon nanotubes (CNTs) is increased due to the adsorption of NO2 molecules on the CNT surface. It is expected that the mechanisim enables us to develop a new CNT-based sensor to defect NO2 molecules in the exhaust fume. In this study, we used first-principles calculation to investigate the mechanism of increasing in conductivity of NO2-adsorbed CNT. As the result, the local density of states (LDOS) distribution shows that the contribution of π orbitals to the electron conductivity is larger than that of α orbitals. Additionallly, in the LDOS of the NO2-adsorbed (7,0)CNT, the density of states around the energy of π orbitals of CNT is increased. It is consider that this leads to increasing of the conductivity of CNT.