We performed first-principle calculations of the covalent functionalization of metallic (6,0) and semiconducting (10,0) single-walled carbon nanotubes (SWCNTs) with aromatic diisocyanate molecules, namely, 4,4 '-methylene diphenyl diisocyanate (MDI) and toluene-2,4-diisocyanate (TDI). The corresponding binding energies of the attached molecules were scrutinized. We analyzed the changes in the electronic band structure of SWCNTs caused by the amide bond formation after the functionalization process. Furthermore, the MDI-MDI and TDI-TDI mutual interactions on the nanotube surface were investigated. (C) 2014 Elsevier B.V. All rights reserved.