Chemical methods for producing graphene

Fig. 1. Intercalated graphite layers can be easily separated from each other ^[1]

One of the methods for the chemical production of graphene consists in the intercalation of graphite with surface-active substances (surfactants), which have a higher energy of interaction with graphene layers than the van der Waals forces between the layers. After intercalation, the distance between the layers increases, which allows mechanical separation ( sonication and centrifugation ) on graphite to separate the layers. Use the same substances as surfactants that are used to separate bundles of carbon nanotubes: N-polymethylpyrrolidone (NMP), N, N-dimethylacetamide (DMA), g-butyrolactone (GBL), 1,3-dimethyl-2-imidazolidinone (DMEU ) ^[2] .

Using strong oxidizing agents, it is possible to oxidize the inner layers of graphite, after which the distance between the layers increases. Such graphite oxide is mechanically separated by ultrasound in an aqueous solution, since due to the hydrophilicity of graphite, water molecules penetrate inward, and the interlayer distance increases even more. At the last stage, the resulting oxidized graphene sheets are reduced in an aqueous solution of a mixture of hydrazine and ammonia , then the reaction products are removed and the solution is filtered ^[3] .

In any case, the quality of the resulting mixture of monolayers does not allow their use in technologies that require medium mobility and uniformity of the material.

In articles ^{[4] [5]} another chemical method for the production of graphene embedded in a polymer matrix is ​​described.