Effect of Stone-Wales Defects and Torsional Deformation on Oxygen Functionalization of MWCNTs

This study investigates the effect of nitrogen doping, Stone-Wales defects, and torsional deformation on the oxygen functionalization of multi-walled carbon nanotubes (MWCNTs). Structural defects and deformations significantly influence the chemical activity of MWCNTs; however, their combined impact on carboxyl functionalization remains insufficiently explored. The aim of this research was to establish the relationship between torsional deformation, crystalline lattice defects, and the efficiency of oxygen functionalization. Using the self-consistent charge density-functional tight-binding (SCC DFTB) method, we modeled the electronic and structural properties of pristine and torsionally deformed N-MWCNTs containing Stone-Wales defects. The analysis included charge redistribution, density of states calculations, repulsion energy, and activation energy barriers for the oxygen functional group attachment. Our results demonstrate that in twisted MWCNT regions, charge predominantly localizes near Stone-Wales defects, leading to an increase in the density of electronic states at the Fermi level and a decrease in its energy. Torsional deformation reduces the energy barrier for carboxyl functionalization from 0.14 eV/atom to 0.10 eV/atom, while the hydroxyl group attachment occurs barrier-free. These findings indicate that deformed MWCNT structures exhibit enhanced reactivity, making them promising candidates for applications in electrochemistry, catalysis, and biomedical nanomaterials. The obtained results contribute to the fundamental understanding of carbon nanomaterial functionalization mechanisms and provide a basis for developing new materials with tunable properties.