Different Aspects of Single Wall Carbon Nanotube Functionalization by Aniline Adsorption; Quantum Mechanics/Molecular Mechanics Study

Abstract

In this research, kinetics and mechanism of aniline adsorption on different single-walled carbon nanotubes (SWCNT) was investigated, using 2-layer ONIOM (Our own N-layered Integrated molecular Orbital and molecular Mechanics) method at the ONIOM (B3LYP/6-31G (d);UFF) level. Various orientations of aniline relative to the carbon nanotube surface were investigated. To investigate the adsorption of aniline, three models including open-ended (model 1), cap-ended (model 2) and 1-cap-ended (model 3) SWCNT have been modeled. Calculated activation energies of adsorption showed that model 2 has the lowest activation energy of 40.8 kcal.mol-1. Natural bond orbital and frontier molecular orbital analysis confirmed the charge transfer from the aniline to the SWCNT. Density of states analysis showed that Fermi level is shifted towards the positive values after aniline adsorption which confirmed the effective interactions between the aniline and the SWCNT. According to the quantum theory of atoms in molecules studies, new bonds formed between the SWCNT and aniline which possess a covalence nature. Finally, based on the quantum reactivity indices, new linear correlations between the chemical hardness, charge transfer and activation energy and the inverse relationship of the electrophilic property and chemical electronic potential in the functionalized carbon nanotubes were obtained. Wiberg bond index calculations show that this reaction is carried out through an asynchronous concerted mechanism. Asynchronicity value in the case of model 2 is higher than other models.