Ultra-large single-layer graphene obtained from solution chemical reduction and its electrical properties

Graphene is a promising candidate for making next-generation nanoelectronic devices. Developing methods to produce large sized graphene with high yield is the key for graphene applications. Here, we report a simple method for large-scale production of ultra-large single-layer graphene sheet (up to 50 μm) reduced from graphene oxides by hydrazine in the presence of aromatic tetrasodium 1,3,6,8-pyrenetetrasulfonic acid (TPA) which efficiently disperse the resulting graphene sheet in aqueous solutions. Field-effect transistors can be readily fabricated using such large reduced graphene oxide sheets. It was found that the mobility of the reduced graphene oxide increases with the temperature of subsequent thermal reduction and reaches 3.5 cm² V^-1 s^-1 after reduction at 1000 °C. Such solution-processable method is of great potential in printable fabrication of graphene-based devices.