Expanding Graphene Through Chemistry

C arbon used to be so plain, so ordinary, so common. In its two atomic forms based on chemical bonding, graphite (sp 2) and diamond (sp 3), it certainly has its charms, but it was largely ignored in its unalloyed states for high-tech applications until the discovery of stable, nanoscale structures starting with buckyballs (C 60) in 1985. However, how to cheaply mass produce C 60 , also known as fullerene, remained a mystery. Then, when another even more usable form, nanotubes, was discovered in 1991, interest began to pick up again as the phenomenal properties of these atomic forms of carbon became apparent. Researchers began to speculate that if 1D layers of graphite appeared in balls and tubes, then a flat layer, which they dubbed graphene, must also be attainable. This was achieved in 2004, and since then, the race has been on to produce graphene in quantity at costs that would make it economically feasible for industrial applications. Chemically modified graphene (CMG) has emerged as a new form of graphene that can be manipulated to display some remarkable qualities previously unattainable in pure graphene. NRL researchers have developed a way to cheaply produce large-area, ultra-thin CMG films through which they can test its properties and also produce prototype electrical and mechanical devices. CMG can be fine-tuned to its specific application and has been used to produce sensors of extraordinary sensitivity, illustrating its potential as a key material for tomorrow's commercial and defense-oriented marvels. C hemically modified graphene (CMG) has emerged as a new material whose many attractive properties complement those of pure graphene. Graphene, a single atomic sheet of carbon bonded in a honeycomb lattice, has remarkable physical properties ranging from near-ballistic electron conduction to extremely high mechanical stiffness (more than five times that of steel). Such extreme properties motivate researchers to investigate these materials for use in applications ranging from high-frequency, low-power electronics, to flexible displays, chemical/biological sensors, and high-frequency electromechanical devices. We have developed a process to form large-area, ultra-thin CMG films that enable us to investigate CMG properties and to explore prototype devices. Using these films we have fabricated state-of-the-art chemical sensors and nanomechanical resonators. For chemical sensors, we have increased the sensitivity and reduced the level of noise by tuning the CMG film chemistry. These optimized sensors are capable of real-time detection of explosives and the three main classes of chemical-warfare agents at parts-per-billion …