Optical Unzipping of Carbon Nanotubes in Liquid Media

Abstract

Optical unzipping of carbon nanotubes (CNTs) in liquid media is one of the most awaited technologies as it promises instant material transformation from CNTs to graphene nanoribbons (GNRs) and also an easy transfer of GNRs to arbitrary subsirates. In the present article, we report the laser-induced optical unzipping of CNTs, dispersed in dimethylformamide (DMF) solvent. In a nutshell) laser unzipping, of CNTs dispersed in liquid solvent is a photophysicochemical process where: molecular interactions between CNTs and solvent are tuned by the laser irradiation and results in the formation of GNRs in a scalable manner. The proposed mechanism includes the creation of defects together with vacancies upon laser irradiation, followed by their migration toward the energetically favorable axis of the CNT-the longitudinal direction-finally leading to the unzipping/fragmentation of the nanotube. Distinct laser thresholds have been observed for each of the three events, namely, (a) the formation of the first defect, (b) vacancy migration along the longitudinal direction, and (c) fragmentation of CNTs into graphene nanosheets. Our experimental findings of the unzipping process have further been supported by the density functional theory (DFT) and density functional tight binding (DFTB) calculations performed on both single-walled and multiwalled CNTs.