Computer Simulation of Sorption Interactions of L-Arginine and L-Lysine with Carbon Nanotubes

Abstract

Carbon nanotubes (CNTs) are a new class of nanomaterials with a high potential for different technological applications. The prospects of using them in biomedicine is associated with the ability of CNTs to cross the cell’s membrane without being impaired, which determines the significance of the study of the interactions of CNTs with biologically active substances, especially amino acids. This work presents a computer simulation of the structure and characteristics of arginine (lysine) – single-wall carbon nanotube (CNT) systems using the B3LYP/6-31G(d,p) density functional theory with GD3 dispersion correction. We calculated the energies of adsorption, dipole moments, total charge on the amino acid and nanotube atoms, and the smallest distances from the amino acid atoms to the CNT. Taking into account the dispersion correction, which is almost absent in scientific literature, allows more accurate calculations of the energies of adsorption of amino acids on CNT to be obtained as compared to the existing calculations due to the high polarizability of CNTs. We considered scenarios with the amino acid position on the open end and on the external and internal lateral surfaces of the CNT. The calculated series of adsorption energies satisfies the conditions Eend > Einside > Elateral. This is due to the fact that when the amino acid is placed on the external lateral surface of a CNT the sorbate interacts with a part of the lateral surface of the tube. When it is placed inside the CNT the sorbate interacts with the whole surface through van der Waals forces and when the sorbate is placed on the end of the sorbent a covalent bond is formed between them. The formation of the covalent bond on the open end of the CNT is due to the higher electron density near the ends of the nanotube as compared to the external and internal lateral surfaces of the tube. An explanation is given of the mechanisms of adsorption and enhancement of the antibacterial action of the CNT functionalised by arginine and lysine, as compared to nonfunctionalised CNTs.

Keywords

• carbon nanotubes
• amino acids
• computer simulation