Quantum chemical modeling of the surface modification of an “armchair” carbon nanotube with cobalt oxide

In this work the adsorption of the cobalt oxide on the surface of the “armchair” carbon nanotube (CNT) in three positions of the adsorption was investigated by quantum chemical modeling with methods of the density functional theory on the B3LYP/3-21G level. The values of the band gap of the pure CNT(6,6) and CNT(6,6)/Co3O4 composites with different adsorption positions were calculated and the mechanisms of its change were determined, the charge distribution in the obtained structures was analyzed. The conducted study permitted the establishment of the possibility of surface modification of CNT(6,6) with cobalt oxide in any of the considered adsorption positions, as evidenced by the observation of a process of chemical adsorption in all the given cases. Such modification leads to a decrease in the band gap, which is associated with an increase in the top of the valence band and a decrease in the bottom of the conduction band. The maximum decrease of the band gap is observed for the adsorption of cobalt oxide to a position where the cobalt atom of the cobalt oxide is located above the center of the CNT hexagon. The electron density shifts from the cobalt oxide to the surface of the CNT, while the cobalt atom of the cobalt oxide charges positively, and the carbon atoms nearby it charge negatively. The obtained results can be useful for the development of new nanoelectronics devices, gas sensors and biosensors.