Exploring the Electronic Topology and Binding Mechanism of Acetic Acid Adsorption on Nitrogen and Boron Co-Doped (5, 5) SWCNT

Chemical inertness of pristine carbon nanotubes (CNTs) poses challenges on their biocompatibility. In this paper, surface modification of pristine (5, 5) single-walled carbon nanotube (SWCNT) was explored through substitutional Boron (B) and Nitrogen (N) doping forming a C38NB isomer. The electronic topology and binding mechanism of acetic acid adsorption on the isomer was then examined in the context of first-principles Density Functional Theory (DFT). Accordingly, high abundance of localized electrons between the substitutional doping sites indicates chemical binding of the substitutional atoms with the SWCNT. These are further supported by the calculated bond angles. When the acid was adsorbed on the C38NB isomer, spontaneous charge redistributions were observed which are attributed to the oxidation caused by the O atoms and the charge acceptance of the C atoms. Topological analyses revealed that the net charge transfers for all considered configurations were towards the acid. In addition, the Lowest Unoccupied Molecular Orbital (LUMO) and Highest Occupied Molecular Orbital (HOMO) revealed the nonuniform distribution of electronic charges near the Fermi level. Finally, calculations of the electron localization function (ELF) showed that there was no orbital hybridization between the acid and the isomer. Further, the absence of localized electrons between their interaction points implied a physical binding mechanism. The results of the study could be used for future opto-electronic experiments and electrochemical biosensing applications of CNTs.