▎ 摘　　要

We introduce a facile fabrication process for obtaining graphene nanoribbon (GNR) thin films on any substrate from solution-exfoliated graphene flakes with wrinkles or ridges. Copper nanoparticles (Cunp's) grown on graphene films by radio-frequency sputtering adhere well on flat graphene surfaces, but not on graphene wrinkles and ridges. By etching the Cu-np's in nitric acid, we can remove the largest portions of flat graphene flakes, leaving behind only ridges and wrinkles as individual GNRs. The resulting GNRs are remarkably long and straight and, different from those obtained from graphene with other methods, are not oxidized. Two classes of GNRs are formed in our films: wide GNRs from planar ridges and narrow and straight GNRs from vertical wrinkles. Our GNR still retain the excellent electrical conductivity of pristine graphene. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.