Amino acids interacting with defected carbon nanotubes: ab initio calculations

Abstract

The adsorption of a number of amino acids on a defected single-walled carbon nanotube (SWCNT) is<br />investigated by using the density-functional theory (DFT) calculations. The adsorption energies and<br />equilibrium distances are calculated for various configurations such as amino acid attaching to defect<br />sites heptagon, pentagon and hexagon in defective tube and also for several molecular orientations<br />with respect to the nanotube surface. The results showed that amino acids prefer to be physisorbed on<br />the outer surface of the defected nanotube with different interaction strength following the hierarchy<br />histidine > glycine > phenylalanine > cysteine. Comparing these findings with those obtained for<br />perfect SWCNTs reveals that the adsorption energy of the amino acids increase for adsorption onto<br />defected CNTs. The adsorption nature has also been evaluated by means of electronics structures<br />analysis within the Mulliken population and DOS spectra for the interacting entities