Precise unzipping of flattened carbon nanotubes to regular graphenenanoribbons by acid cutting along the folded edges

Abstract

Precise unzipping of carbon nanotubes (CNTs) is achieved using flattened carbon nanotubes (F-CNTs) as the starting material and using acid to cut along the folded edges, as these high energy sites are preferentially attacked to yield regular graphene nanoribbons (GNRs). All-bilayer GNRs with narrow uniform width (8–12 nm) and straight edges are fabricated by unzipping flattened double-wall CNTs (F-DWCNTs) using mixed acids of H₂SO₄ and KMnO₄. Transmission electronic microscopy observations confirm the localized and directional unzipping of the F-DWCNTs and the formation of regular bilayer GNRs. The oxidation temperature and acid concentration control the degree of oxidation, the extent of unzipping, and the exfoliation of F-DWCNTs from their bundles. Under certain conditions, assemblies of interconnected GNRs are formed by unzipping F-DWCNT bundles and partial exfoliation. The precise unzipping of flattened CNTs provides a reliable and scalable process for fabricating regular GNRs with controlled structures and morphologies, as demanded for applications that use them as structural, functional and electronic materials.