Large-scale surfactant exfoliation of graphene and conductivity-optimised graphite enabling wireless connectivity

Graphene and other graphitic materials are suggested as a route to cheap, high-performance, environmentally-sustainable electronic devices owing to their almost unique combination of properties. Liquid-phase exfoliation is a family of shear-based techniques that produce dispersions of nanosheets from bulk layered material crystallites. High-quality nanosheets of graphene can be produced in solvents or surfactant dispersions; however the lateral size of these sheets limits the network transport properties observed in printed films. A high-throughput, industrially-scalable aqueous process for the production of graphene and related layered nanomaterials is presented. By considering not only the exfoliation process, but also the size selection and deposition processes, printable graphitic nanoparticulate materials with conductivities up to 50 000 S m-1 are demonstrated. This value is ten times larger than is typically obtained for few-layer graphene produced by liquid-phase exfoliation. The size selection process is critical to obtaining the maximum conductivity of deposited films, with an optimized nanographite having greater performance than few-layer graphene or graphite that is processed and used without size selection. Building on these results a radio-frequency antenna application is demonstrated, which is competitive with the state-of-the-art, and a route to recycling of such printed short-lifetime electronic devices to lower the environmental impact is discussed.