Structural,Vibrational and Electronic Properties of Defective Single‐Walled Carbon Nanotubes Functionalised with Carboxyl Groups: Theoretical Studies

Covalent sidewall functionalisation of defective zigzag single‐walled carbon nanotubes SWCNTs(10,0)] with COOH groups is investigated by using DFT. Four types of point defects are considered: vacancy (V), divacancy V₂(5‐8‐5), V₂(555‐777)], adatom (AA) and Stone–Wales (SW). The energetic, structural, electronic and vibrational properties of these systems are analysed. Decreasing reactivity is observed in the following order: AA>V>V₂(555‐777)>V₂(5‐8‐5)>SW. These studies also demonstrate that the position in which a carboxyl group is attached to a defective SWCNT is of primary importance. Saturation of two‐coordinate carbon atoms in systems with the vacancy V‐7 and with the adatom AA‐1(2) is 3.5–4 times more energetically favourable than saturation of three‐coordinate carbon atoms for all studied systems. Vibrational analysis for these two systems shows significant redshifts of the ν(C?O) stretching vibration of 96 and 123 cm^?1 compared to that for carboxylated pristine systems. Detailed electronic‐structure analysis of the most stable carboxylated systems is also presented.