Interaction of Lactic Acid and Silicon-doped Single-walled Carbon Nanotubes: A Density Functional Theory Study

In this study, we investigate the adsorption of lactic acid (LA) on the outer surface, inside, and at the edge of Si-doped single-walled carbon nanotubes (SWCNTs) with different chiralities using dispersion-corrected hybrid density functional theory. For this propose, the adsorption of LA through its hydroxyl and carboxylic acid groups on Si-doped carbon nanotubes (Si/CNTs) with (4,4), (5,5), and (6,6) chirality is investigated. The geometries of all the studied aggregates have been fully optimized. The results show that the adsorption of LA on the outer surface of Si/CNTs is thermodynamically favored. The adsorption energies for Si/CNTs with (4,4), (5,5), and (6,6) chiralities, calculated at the density functional theory-D level, were in the range −5.17 to −18.62, −5.12 to −16.55, and −5.23 to −26.80 kcal/mol, respectively. Total density of states and projected density of states analysis showed the electronic states related to SWCNTs. The influence of diameter on different electronic properties has been analyzed. In addition, global reactivity descriptors were calculated for Si/CNTs and the modified ones and were compared.