Separating carbon sheets: Mechanical and chemical exfoliation of graphite to produce graphene

Abstract

Mechanical exfoliation of highly-oriented pyrolytic graphite (HOPG) via the "scotch-tape method" was used to produce graphene. HOPG flakes peeled using 3M Magic Tapeâ„¢ were deposited on Si (111)/SiO₂ (<315 nm) to give films as thin as ~0.822 nm. The adhesive tape was effectively removed by annealing at 400°C for 1 h. Using modified Hummer's method, ordinary pyrolytic graphite can be chemically oxidized to graphene oxide (GO). Washing GO with ammonia dispersed the sheets further and made it more difficult to centrifuge into a pellet. The layers that remained dispersed in solution were dried at 70°C under vacuum to give a brown powder, in dark contrast to the gray-black color of the graphite used, indicating that oxidation occurred.