Theoretical insights into chirality-controlled SWCNT growth from a cycloparaphenylene template

A self-assembly mechanism for low-temperature SWCNT growth from a [6]cycloparaphenylene ([6]CPP) precursor via ethynyl (C₂H) radical addition is presented, based on non-equilibrium quantum chemical molecular dynamics (QM/MD) simulations and density functional theory (DFT) calculations. This mechanism, which maintains the (6,6) armchair chirality of a SWCNT fragment throughout the growth process, is energetically more favorable than a previously proposed Diels-Alder-based growth mechanisms [E. H. Fort, et al., J. Mater. Chem. 2011, 21, 1373]. QM/MD simulations and DFT calculations show that C₂H radicals play dual roles during SWCNT growth, by abstracting hydrogen from the SWCNT fragment and providing the carbon source necessary for growth itself. Simulations demonstrate that chirality-controlled SWCNT growth from macrocyclic hydrocarbon seed molecules with pre-selected edge structure can be accomplished when the reaction conditions are carefully selected for hydrogen abstraction by radical species during the growth process. Exquisite control: A self-assembled, C₂H-radical-mediated low-temperature SWCNT formation mechanism starting from an organic [6]CPP template is proposed based on nonequilibrium QM/MD simulations (see picture). This bottom-up organic approach may potentially yield chirality- and diameter-controlled SWCNT growth.