Chemical Functionalization of Graphene

Graphene is a two dimensional crystalline form of carbon, consisting only in sp2 hybridized carbon atoms arranged in a hexagonal mesh. The outstanding electronic properties, like the high electron and hole mobilieties, but also the mechanical properties, like the flexibility and strength of graphene allow a variety of possible applications.

In our current research the chemical reactivity of graphene is of central interest. Especially the attachment of carbon species to the graphene plane, as this could alter the electronic properties due to the change in hybridization of the graphene carbon atoms and also due to doping of attached molecules.

Surface potential measurements of functionalized graphite revealed a method to control the potential difference of graphite and a functionalized monolayer on top of the graphite. The difference is related to the Hammett constant of the functional groups attached to the graphite.

Scanning electron microscopy images of nitrobenzene(a) and methoxybenzene(b) functionalized graphite. Surface potential of nitrobenzene functionalized graphite (c) with corresponding profile (d) along the black line.

Difference in surface potential between functionalized and unfunctionalized regions with corresponding para substituted benzene rings correlated with their Hammett constant.

Further reading:

• A. Jacobsen, F.M. Koehler, W.J. Stark, K. Ensslin, Towards electron transport measurements in chemically modified graphene: effect of a solvent, New J. Phys.,12, 125007 (2010).
  DOI: 10.1088/1367-2630/12/12/125007
• F.M. Koehler, A. Jacobsen, K. Ensslin, C. Stampfer, W.J. Stark, Selective Chemical Modification of Graphene Surfaces: Distinction Between Single- and Bilayer Graphene, Small, 6(10), 1125-30 (2010).
  DOI: 10.1002/smll.200902370
  
• F.M. Koehler, N.A. Luechinger, D. Ziegler, E.K. Athanassiou, R.N. Grass, A. Rossi, C. Hierold, A. Stemmer, W.J. Stark, Permanent Pattern-Resolved Adjustment of the Surface Potential of Graphene-like Carbon through Chemical Functionalization, Angew. Chem. Int. Ed., 48(1), 224-7 (2009).
  DOI: 10.1002/anie.200804485