High-throughput, ultrafast synthesis of solution- dispersed graphene via a facile hydride chemistry

Graphene is a single-atom-thick two-dimensional macromolecule with sp-bound carbon atoms arranged in a honeycomb lattice. Recently, graphene has emerged as an attractive candidate for several applications, including ultrafast nanoelectronic devices, tunable spintronics, ultracapacitors, transparent conducting electrodes, single-molecule chemical sensors, ultrasensitive biodevices, and nanomechanical devices. These applications have evolved from its atypical properties, such as weakly scattered ballistic transport of charge carriers behaving as massless fermions at room temperature, magneto-sensitive transport, tunable bandgap, quantum Hall effect at room temperature, tunable optical transitions, exceptional mechanical strength, megahertz characteristic frequency, carrier collimation, and ultrahigh stiffness. Graphene can be 1) synthesized on-substrate, 2) deposited on-substrate via mechanical processes, or 3) deposited onsubstrate from solution. On-substrate synthesis includes hightemperature (>1000 8C) epitaxial growth on SiC, ruthenium or chemical vapor deposition on nickel and copper, while mechanical deposition includes adhesive-tape exfoliation of highly oriented pyrolytic graphite (HOPG) and the ensuing transfer. The third process, which is based on onsubstrate deposition from a graphene suspension, has several advantages including the large-scale production of reduced graphene oxide (RGO) and easy-to-apply chemical and physical manipulations for functionalization and directed deposition. Graphene suspension synthesis methods include 1) p–p intercalation or graphite intercalation compound (GIC)-based exfoliation of graphite flakes into graphene sheets, and 2) in-solution reduction of graphite oxide prepared by Hummers method with hydrazine. The p–p intercalation and GIC-based methods produce highquality graphene; however, the yield is low with relatively low stability of the graphene solution, in which the graphene sheets have a tendency to settle down. The graphene suspension