Insights into the adsorption of simple benzene derivatives on carbon nanotubes

Exploring the adsorption characteristics of small molecules on carbon nanotubes (CNs) is important for rational design of CN-based materials for many applications. In this work, we construct a quantitative structure-activity relationship (QSAR) model to predict the adsorption of 25 simple benzene derivatives on CNs, and investigate the molecule-SWCN interactions by density functional theory (DFT) calculations, with the M062X functional at the 6-31G(d) basis set. The QSAR model exhibits a regression correlation coefficient (R-rm(2)) of 0.986 and a cross-validated coefficient (Q(cv)(2)) of 0.968. A total of more than 200 optimizations are carried out to determine preferential interaction modes, binding conformations, and underlying driving forces of the molecule-SWCN systems. We show the bridge configuration is the preferred molecule-SWCN interaction mode, which is mainly governed by pi-pi stacking; the molecules have experienced a significant electron rearrangement whereas the SWCNs have a weak one due to the molecule-SWCN mutual forces; and the substituents play dual effects on the adsorption in two ways, i.e., indirectly affecting pi-pi stacking by altering the electron density of the benzene ring and directly interacting with the nanotube surface. This work provides insights into noncovalent functionalization of CNs, and adsorption and desorption of simple organic molecules on CNs.