Interaction of O2, CO2, NO2 and SO2 on Si- doped Carbon Nanotube

We report reactivity of silicon doped single walledcarbon nanotube (Si-CNT) towards the small atmospheric gasmolecules O2, CO2, SO2 and NO2 using density functionaltheory based on the numerical basis set method. The reactivityof gas molecules is explained with binding energy, bandstructure, charge density, and density of states. We found thatthe substitutional doping of silicon atom in CNT increases thebinding energy as compared with pure CNT. The chargedensity analysis reveals the formation of sigma ( sigma ) bondsbetween silicon and carbon atoms. Further, the band structureand density of states clearly illustrate the creation of extra statenear the Fermi level and reduction in the band gap, which actsas a reactive center for adsorption of the molecules on Si-CNT.We have observed that the large value of adsorption energyshows the chemisorption between molecules and Si-CNT.Mulliken population analysis clearly reveals the charge-induceddipole interactions between the Si-CNT and molecules, whichare responsible for chemisorption for gas molecules. The donorlike impurity state generated in energy gap almost disappearsafter adsorption of all gas molecules excluding NO2. We furthernote that molecules accept the electronic charge from nanotubesand have significant influence on electronic structure near theFermi level and are responsible for the increase in the p-typeconductivity of tubes.