Professor Jonathan Coleman is internationally known for developing liquid phase exfoliation (LPE), a scalable process for converting layered materials into two-dimensional (2D) nanosheets. Since first producing LPE-graphene, Coleman’s team has demonstrated exfoliation of more than 25 layered compounds, building LPE into one of the standard methods for producing 2D nanosheets. Access to this material set has allowed Coleman’s team to develop new characterisation and processing methods and to pioneer applications of 2D materials in areas including nanocomposites, sensors, printed electronics and energy storage.

Inspired by the obvious demand for large quantities of defect-free graphene, in 2008 Coleman’s team demonstrated LPE, whereby applying ultrasound or high shear in liquids could be used to exfoliate defect-free graphene nanosheets from graphite. Focusing on the physics of the LPE process, Coleman combined theory and experiment to prove that surface-energy-matching solvents facilitate exfoliation with minimal energy input. Coleman subsequently showed LPE could be achieved in aqueous surfactant solutions, avoiding toxic solvents and paving the way for scaleup to the production of 700 litre batches of graphene using shear exfoliation. This process was patented, licenced to Thomas Swan and Samsung, and has resulted in multiple commercial products.

Realising the generality of this exfoliation process, Coleman demonstrated liquid exfoliation of boron nitride, molybdenum disulphide and tungsten disulphide in 2011. The subsequent realisation that certain solvents form protecting layers at the liquid–nanosheet interface allowed Coleman’s group to demonstrate ambient exfoliation of oxidatively unstable layered materials such as phosphorene, titanium disulphide and germanium sulphide. To date, Coleman’s group has used LPE to produce over 25 distinct 2D materials.

Coleman’s group has highlighted the processability of LPE-produced dispersions, demonstrating size selection and monomer enrichment. Size-selected suspensions are ideal for spectroscopic characterisation, permitting Coleman’s team to probe fundamental relationships between absorption and scattering spectral features, and nanosheet size and thickness. Coleman’s group has also used nanosheet suspensions to fabricate nanocomposites and to print patterned films and coatings. This has allowed the team to demonstrate a range of novel applications of 2D materials including the most sensitive piezoresistive nanocomposite sensors ever made, battery electrodes with superlative capacity and the first all-printed, all-nanosheet transistors.

This work has had significant impact. LPE is now a pillar method of 2D materials production and widely used by hundreds of groups globally. LPE-based materials are the basis of a wide range of applications, patents and products. According to IDTechEx, the family of exfoliation techniques that are descended from LPE constitute over 60% of global graphene production capacity.