The production of multi-layer graphene nanoribbons from thermally reduced unzipped multi-walled carbon nanotubes

An easy and scalable approach is reported for the production of multi-layer graphene nanoribbons (GNRs) from thermally treated unzipped multi-walled carbon nanotubes (MWCNTs) by controlled oxidation and intercalation. The prepared GNRs are characterized using transmission and scanning electron microscopy, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. AFM studies show that the thickness of the unzipped MWCNTs lies in the range of 100–124 nm, which correspond to ∼150–185 GNRs, whereas the width is in the ranges of 500–700 nm. This could be due to the displacement of loose individual graphene layers in the solvent during sonication process. The irregular edges of the multi-layer GNR appeared due to the presence of functional groups attached at the edges, is confirmed by XPS. The XPS studies reveals that the amount of defects present on the nanoribbons after heat treatment at 1000 °C is almost same as that of as synthesized MWCNTs. However, on heat treatment at 2500 °C, defects are reduced and the quality of ribbon is improved. Also, Raman spectroscopy has confirmed that on heat treatment at 2500 °C the quality of GNRs is improved and I(D)/I(G) ratio decreases from 0.92 to 0.44.