Covalent and Noncovalent Functionalization of Single-Walled Carbon Nanotubes: A MD/DFT Study

Carbon nanotubes (CNTs) have electronic and optical properties that depend on the chirality of the nanotube and can be tuned via covalent functionalization. The composition of these groups has been proven to affect the optical properties. We hypothesize that the geometric orientation of these groups has a larger impact on the electronic properties. Non-covalent functionalization by conjugated polymers affects the interaction between the CNT and covalently-attached groups, resulting in changes to the absorption and emission properties. Calculations have shown correlations between the tube chiralities and polymer wrapping morphology to pristine CNTs for the purposes of chirality separation. We extend this approach to covalently-functionalized CNTs to explore the CNT-polymer interactions and examine the impact on the optical properties. Our goal is to be able to understand and predict relative band gap values and emission energies for any given functionalization group and orientation. This will be achieved in two ways: (I) classical molecular dynamics to observe trends in binding energy of covalently-attached groups and (II) density functional theory (DFT) and time-dependent DFT to obtain the energy and intensity of optical transitions.