Liquid-Phase Exfoliation of Graphene Materials

Liquid-phase exfoliation (LPE) offers a versatile route to produce graphene nanosheets by dispersing bulk graphite in a liquid medium and applying mechanical energy to separate individual layers. Key techniques include ultrasonication, high-shear mixing, ball milling and microfluidisation, each invoking mechanisms such as cavitation and shear forces to overcome interlayer van der Waals interactions. Choice of solvent or dispersant—ranging from organic solvents and ionic liquids to water with polymeric or surfactant additives—governs exfoliation efficiency, flake quality and colloidal stability. Recent advances have focused on replacing toxic media with green alternatives, boosting monolayer yield, increasing concentration and enabling additive-free dispersions. These developments have broadened applications in printable electronics, energy storage, composite materials and coatings. Ongoing challenges include scaling to industrial throughput, maintaining high monolayer purity, and integrating graphene suspensions into functional devices with minimal environmental impact.

Research from Nature Portfolio

Recent studies have demonstrated scalable exfoliation methods that yield exceptionally high monolayer content. A ball-milling approach assisted by a viscous polymer liquid achieved over 97 per cent monolayer yield at 78 per cent mass efficiency, not only for graphite but also for a range of layered materials. A separate non-dispersion water-phase strategy produced highly crystalline graphene slurries at concentrations up to 50 mg mL^–1 without organic solvents, which can be stored long-term and directly used in 3D printing, aerogels and polymer composites. These techniques represent significant strides towards cost-effective, eco-friendly manufacture of graphene nanosheets at scale.

Liquid-Phase Exfoliation of Graphene Materials publication trend

The graph below shows the total number of articles in liquid-phase exfoliation of graphene materials across all publications each year (not limited to Nature Index journals).

Technical terms

Liquid-phase exfoliation (LPE): A top-down method for producing two-dimensional nanosheets by dispersing layered materials in a liquid and applying mechanical energy to separate layers.

Cavitation: Formation and collapse of microbubbles during ultrasonication, generating localised high shear and pressure that aid exfoliation.

High-shear mixing: Application of intense turbulent flow to a suspension, using rotor–stator systems to delaminate layered materials into thin flakes.

Monolayer: A single atomic or molecular layer of a material; in graphene, one layer of sp²-hybridised carbon atoms.

Surfactant: A surface-active agent that adsorbs onto newly exposed sheet surfaces, imparting electrostatic or steric stabilization to prevent reaggregation.

References

1. Liquid-Phase Exfoliation of Graphene: An Overview on Exfoliation Media, Techniques, and Challenges. Nanomaterials (2018).
2. Microfluidization of Graphite and Formulation of Graphene-Based Conductive Inks. ACS Nano (2017).
3. An eco-friendly solution for liquid phase exfoliation of graphite under optimised ultrasonication conditions. Carbon (2023).
4. Scalable high yield exfoliation for monolayer nanosheets. Nature Communications (2023).
5. A non-dispersion strategy for large-scale production of ultra-high concentration graphene slurries in water. Nature Communications (2018).
6. Sustainable graphene production for solution-processed microsupercapacitors and multipurpose flexible electronics. Nano Energy (2024).
7. Graphene in Water is Hardly Ever Neutral. Advanced Science (2024).