Process for the preparation of graphene
The present invention provides a process for the preparation of graphene or graphene-like fragments of another layered structure, said process comprising the step of mixing and grinding graphite or said other layered structure with at least one ionic liquid. The invention also provides the use of grinding in ionic liquids in such a process and products formed or formable by such methods.
1. A process for the preparation of graphene or graphene-like fragments of another layered structure, said process comprising the step of mixing and grinding graphite or said other layered structure with at least one ionic liquid, wherein the process does not comprise a sonication step.
2. A process of claim 1 having a yield of at least one of graphene nanosheets and graphene nanodots of greater than 10% relative to the starting weight of the graphite or other layered material.
3. A process as claimed in claim 1 , wherein mixing and grinding occurs for a time period of between 0.5 and 4 hours.
4. A process as claimed in claim 1 , wherein the graphite is natural graphite.
5. A process as claimed in claim 1 , wherein the graphene is in the form of graphene nanosheets or graphene nanodots.
6. A process as claimed in claim 5 , wherein the graphene nanosheets comprise 2 to 4 layers of graphene.
7. A process as claimed in claim 5 , wherein the graphene nanodots have a height of 1 to 3 nm.
8. A process as claimed in claim 5 , wherein the graphene nanodots have a diameter of less than 10 nm.
9. A process as claimed in claim 1 , wherein the ionic liquid comprises an organic salt containing one more cations selected from the group consisting of ammonium, imidazolium and pyridinium ions.
10. A process as claimed in claim 9 , wherein the organic salt contains an imidazolium ion.
11. A process as claimed in claim 10 , wherein the ionic liquid is 1-butyl-3-methyl-imidazolium hexafluorophosphate.
12. A process as claimed in claim 1 , wherein the oxygen content of the graphene is less than 5 at %.
13. A process as claimed in claim 1 , wherein the process does not include the use of a reducing agent or an oxidising agent.
14. A process as claimed in claim 1 further comprising separating the ionic liquid from the graphene.
15. A process as claimed in claim 14 further comprising separating the ionic liquid from the graphene by means of addition of a solvent followed by centrifugation.