First Principles Calculations of Alanine Radicals Adsorbed on Pristine and Functionalized Carbon Nanotubes

Abstract

The structural and electronic properties of alanine radicals adsorbed on pristine and carboxyl-functionalized (5,5) single-walled carbon nanotubes (SWCN) are investigated through ab initio calculations based on density functional theory. We find that the bonds between the alanine radicals and pristine SWCNs are stronger when the interaction occurs via the amine group. In particular, the strongest bond occurs for a structure where all C atoms belonging to the SWCN keep sp 2 -like hybridization. Interestingly, this is the only case where the system remains metallic. In all other cases, the systems result in a semiconductor or semiconductor with a half-filled level in the gap, depending on how the alanine radical is adsorbed. On the other hand, for carboxyl-functionalized SWCNs the properties of the systems do not significantly depend on how the alanine radical is absorbed.

Molecules with Biological Interest Adsorbed on Carbon Nanostructures

“…For the pristine SWCNTs, the strongest bond was observed where all C atoms from the tubes exhibited sp 2 -like hybridisation and remained a metallic system. In contrast, for functionalised SWCNTs with carboxyl groups, the properties of the resulting systems were independent of the alanine adsorption site [32].…”

“…Similarly, Carneiro et al [32] employed DFT to investigate the adsorption of the amino acid alanine on pristine and functionalised (5,5) single-walled carbon nanotubes (SWCNTs), showing that the interaction occurred via the amine group. For the pristine SWCNTs, the strongest bond was observed where all C atoms from the tubes exhibited sp 2 -like hybridisation and remained a metallic system.…”

“…The charge density plots illustrate the same behaviour as that found for SWCNTs, with a concentration of charge on the fullerene surface for the conduction level, and in the fullerene and the -SH group for the valence level. As discussed earlier, a number of studies have investigated the interaction of different amino acids with pristine and functionalised CNs, mainly aimed at the development of biosensor applications [29,[31][32][33][34][35][36][37]. From a theoretical point of view, the binding energies and electronic properties of the three functional groups of cysteine, when interacting with different pristine CNs (graphene, CNTs and fullerene), reflect physical adsorption.…”

“…From a theoretical point of view, the binding energies and electronic properties of the three functional groups of cysteine, when interacting with different pristine CNs (graphene, CNTs and fullerene), reflect physical adsorption. Functionalisation is an effective method with which to increase the interaction between the CN and the adsorbed molecules, especially for biosensor applications [31][32][33][34][35][36][37].…”

Interaction of single‐walled carbon nanotubes and saxitoxin: Ab initio simulations and biological responses in hippocampal cell line HT‐22

“…Based on this idea, the potential interactions of pristine and carboxylated SWCNTs with molecules of biological interest can be analyzed in silico. In the same way, a density functional simulation was used to investigate the adsorption of the amino acid alanine (ALA) with pristine and functionalized SWCNTs, indicating that the interaction occurred through the amine group . With the pristine SWCNTs, the interaction was observed homogenously with all carbon atoms of the tube to the sp 2 hybridization, and remained a metal system.…”