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Alfa Chemistry provides customers with covalent bond modification services on the graphene surface. Covalent functionalization of graphene involves combining graphene with newly introduced groups in the form of covalent bonds to improve and enhance its performance.The large number of oxygen-containing groups on the surface of graphene oxide makes the functionalization of covalent bonds easier than on graphene. Covalent bond modification can improve the processability of graphene and bring new functions.
The sp2 carbon structure of graphene can directly react with free radical reagents such as diazonium salts. By selecting an appropriate reaction matrix, the required functional groups can be modified on the surface of various types of graphene. During the preparation of graphene oxide, a large number of functional groups such as hydroxyl, carboxyl, epoxy groups can be added to the surface and edges, which results in graphene oxide having higher chemical activity and lower cost than graphene. Therefore, using graphene oxide as a raw material to carry out organic chemical reactions through the oxygen-containing groups has gradually become the mainstream method of introducing target functional groups.
The common reactions are listed below.
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Fig 1. Covalent Bonding in Nanohybrid-ER. (Fu J.H, et al. 2019)
The methods for grafting organic polymers onto the surface of graphene or graphene oxide are generally divided into: "grafting from" and "grafting to". "Graft-from" mainly relies on the use of either “neat” graphene, or graphene in its oxidized form, graphite oxide (GO), upon which initiator sites are fixed from where the polymerization takes place. "Graft-to" refers to the synthesis of macromolecules, and then the functionalized groups on the macromolecules react with graphene or graphene oxide groups to form polymer modified graphene.
Fig 2. Two methods for covalent bonding of polymer and graphene.
| Modified Group | Modification Agent | Interaction Type | Property | Application |
| -C=C- | 4-Propargyloxydia-zobenzenetetra-fuoroborate | Diazotization | Water soluble | Biosensors |
| -OH | 2-Bromoisobutyryl bromide, NaN3, HC≡C-PS | Esterification | Good solubility | Polymer composites |
| -COOH | SOCl2 | Esterification | Conductive | Conducted membrane |
| -OH | N2H4, DNA | Addition esterification | Good solubility | Biosensors |
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