Chemical modification Graphene chemistry

photograph of single-layer graphene oxide undergoing high temperature chemical treatment, resulting in sheet folding , loss of carboxylic functionality, or through room temperature carbodiimide treatment, collapsing star-like clusters.

soluble fragments of graphene can prepared in laboratory through chemical modification of graphite. first, microcrystalline graphite treated acidic mixture of sulfuric acid , nitric acid. series of oxidation , exfoliation steps produce small graphene plates carboxyl groups @ edges. these converted acid chloride groups treatment thionyl chloride; next, converted corresponding graphene amide via treatment octadecylamine. resulting material (circular graphene layers of 5.3 angstrom thickness) soluble in tetrahydrofuran, tetrachloromethane , dichloroethane.

refluxing single-layer graphene oxide (slgo) in solvents leads size reduction , folding of individual sheets loss of carboxylic group functionality, 20%, indicating thermal instabilities of slgo sheets dependent on preparation methodology. when using thionyl chloride, acyl chloride groups result, can form aliphatic , aromatic amides reactivity conversion of around 70–80%.

boehm titration results various chemical reactions of single-layer graphene oxide, reveal reactivity of carboxylic groups , resultant stability of slgo sheets after treatment.

hydrazine reflux commonly used reducing slgo slg(r), titrations show around 20–30% of carboxylic groups lost, leaving significant number available chemical attachment. analysis of such slg(r) reveals system unstable. using room temperature stirring hcl (< 1.0 m) leads around 60% loss of cooh functionality. room temperature treatment of slgo carbodiimides leads collapse of individual sheets star-like clusters exhibited poor subsequent reactivity amines (c. 3–5% conversion of intermediate final amide). apparent conventional chemical treatment of carboxylic groups on slgo generates morphological changes of individual sheets leads reduction in chemical reactivity, may potentially limit use in composite synthesis. therefore, chemical reactions types have been explored. slgo has been grafted polyallylamine, cross-linked through epoxy groups. when filtered graphene oxide paper, these composites exhibit increased stiffness , strength relative unmodified graphene oxide paper.

full hydrogenation both sides of graphene sheet results in graphane, partial hydrogenation leads hydrogenated graphene. similarly, both-side fluorination of graphene (or chemical , mechanical exfoliation of graphite fluoride) leads fluorographene (graphene fluoride), while partial fluorination (generally halogenation) provides fluorinated (halogenated) graphene.