Interaction mechanism between serine functional groups and single-walled carbon nanotubes

Abstract

The adsorption of serine (Ser) on the (8, 8) and (10, 0) single-walled carbon nanotubes (CNTs) was studied by density-functional tight-binding calculations. For Ser, the two most stable configurations were chosen to research the interactions with the CNT. It found that the most stable Ser/(8, 8) and Ser/(10, 0) complexes have similar structures, in which the amino group, carboxyl, and side chain of serine directly interact with the CNT. The binding energies, charge transfer properties, the shortest distance (d1) between the H atom and the corresponding benzene ring, distance (d2) between the H atom and the center of benzene ring (HCB), and the angle (α) between the HCB line and the corresponding benzene ring plane were analyzed to explain the interactions. Because of the interaction, the CH of the main chain runs away from the surface of CNT, and the angles between the CH bond of the main chain and the carboxyl, the amino group, and the side chain of the Ser become small. The strain energies and changes of angles and dihedral angles of the serine after adsorption were analyzed to illustrate the deformation. The interactions of Ser with the CNT were further illustrated by calculating the molecular orbitals and the partial density of states of the stable complexes. We further compared the binding energies of armchair (n, n) and zigzag (n, 0) CNTs to investigate the diameter dependence of binding energies.