Carbon nanotube functionalization with carboxylic derivatives: a DFT study

Abstract

Chemical functionalization of a single-walled carbon nanotube (CNT) with different carboxylic derivatives including –COOX (X = H, CH₃, CH₂NH₂, CH₃Ph, CH₂NO₂, and CH₂CN) has been theoretically investigated in terms of geometric, energetic, and electronic properties. Reaction energies have been calculated to be in the range of −0.23 to −7.07 eV. The results reveal that the reaction energy is increased by increasing the electron withdrawing character of the functional groups so that the relative magnitude order is −CH₂NO₂ >−CH₂CN >−H >−CH₂Ph >−CH₃ >−CH₂NH₂. The chemical functionalization leads to an increase in HOMO/LUMO energy gap of CNT by about 0.32 to 0.35 eV (except for −H). LUMO, HOMO, and Fermi level of the CNT are shifted to lower energies especially in the case of −CH₂NO₂ and ₋CH₂CN functional groups. Therefore, it leads to an increment in work function of the tube, impeding the field electron emission.