▎ 摘　　要

NOVELTY - Preparing a free or transferrable graphene sheet comprises: (a) pre-treating surface of polycrystalline copper substrate with a hydrogen-containing plasma to enhance the relative proportion of (101) and (111) facets relative to (100) facets; (b) depositing graphene onto the substrate by contacting the surface of substrate with a plasma comprising a carbon source gas for a deposition period; and (c) decoupling graphene from substrate by exposing the graphene and substrate to a polar liquid to instantly decouple the graphene from the substrate to provide a free or transferrable graphene sheet. USE - The method is useful for preparing a free or transferrable graphene sheet (claimed), which is used in high performance flexible, transparent and UV nano-devices, or sensors for detecting nitrogen dioxide. ADVANTAGE - The method: provides free or transferrable graphene sheet in an easily isolated and low defect form; provides new forms of vertical graphene that exhibit desirable controllable electronic, optical, or mechanical properties; is carried out at mild reaction temperatures and is suitable for industrial use; avoids the use of wet chemistry or a polymeric transfer material; and provides graphene in cost-effective and environmental friendly manner, which exhibits excellent sensing properties in dry environments for hazardous nitrogen dioxide gas. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for: (1) a free or transferrable graphene sheet prepared by the method; and (2) a graphene structure comprising many stacked planar carbon layers, where at least one layer of the structure comprises integrated horizontal and vertical nanosheet portions.