School of Physics, CRANN and AMBER Research Centers, Trinity College Dublin, Dublin 2, Ireland
Liquid phase exfoliation (LPE) is a simple method to exfoliate layered crystals like graphite to give 2-dimensional nanosheets such as graphene. LPE can be achieved either by sonicating or shearing layered crystals in appropriate liquids and has been used to produce nanosheets of graphene, MoS2, BN, MoO3, Ni(OH)2, phosphorene and many other materials. The nanosheets produced by this method tend to be ~100-1000 nm wide, a few monolayers thick and relatively defect free. Using centrifugation, the dispersions can be easily size selected, solvent exchanged and concentrated to ~10 mg/ml, and are ideal for producing nanosheet networks. Here we show that, especially when combined with carbon nanotubes, such networks are of use in electrochemical devices such as supercapacitors, battery electrodes or electrocatalysts. In particular, composite films fabricated from combinations of Co(OH)2 nanosheet and carbon nanotube networks perform as state of the art oxygen evolution catalysts. When graphene nanosheet networks are combined with soft polymers, the resultant composite becomes an extremely sensitive electromechanical sensor. When mounted next to the skin, such sensors can detect pulse and even measure blood pressure. Alternatively graphene networks can be printed to act as electrodes. When combined in the correct architecture with networks of semiconducting (eg MoS2) and insulating (eg BN) nanosheets it is possible to produce all-printed, all-nanosheet field effect transistors.
Jonathan Coleman is the Professor of Chemical Physics in the School of Physics and the CRANN and AMBER Research centres, all at Trinity College Dublin. His research involves liquid exfoliation of layered compounds such as graphene, boron nitride and molybdenum disulphide. Exfoliation of these materials gives 2D nanosheets which can easily be processed into thin films or composites from applications from energy storage to sensing to electronics. He has published approximately 250 papers in international journals including Nature and Science, has a h-index of 72 and has been cited ~30000 times. He was recently listed by Thomson Reuters among the world’s top 100 materials scientists of the last decade and was named as the Science Foundation Ireland researcher of the Year in 2011. Prof Coleman has been involved in a number of industry-academic collaborative projects with companies including Hewlett-Packard, Intel, SAB Miller, Nokia-Bell Labs and Thomas Swan.